Risk Factor Analysis of Hidden Blood Loss in Unilateral Biportal Endoscopy for Degenerative Lumbar Diseases

Risk Factor Analysis of Hidden Blood Loss in Unilateral Biportal Endoscopy for Degenerative Lumbar Diseases | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Risk Factor Analysis of Hidden Blood Loss in Unilateral Biportal Endoscopy for Degenerative Lumbar Diseases JunYi He, GeJin Wei, Lun Li, WanAn Qin, Bei Liu, Yanping Zeng, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6830206/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background To explore the risk factors associated with hidden blood loss (HBL) during unilateral biportal endoscopy (UBE) for degenerative lumbar diseases, this study provides a theoretical foundation for the precise prevention and management of HBL and related complications in clinical practice. Methods A retrospective analysis was conducted on 87 patients who underwent single-segment UBE surgery for lumbar degeneration from June 2022 to June 2023. Detailed records were maintained for demographic characteristics, laboratory indicators and surgical data. HBL was calculated via the Sehat formula (HBL = total blood loss (TBL) - visible blood loss (VBL)). Pearson and Spearman correlation analyses were initially employed to identify factors associated with HBL, followed by multivariate linear regression modelling to identify independent risk factors. Results The mean HBL was 227.40 ± 232.92 mL. HBL was positively correlated with surgical time, postoperative drainage volume, and TBL (P < 0.05) but negatively correlated with postoperative haemoglobin (Hb), haematocrit (Hct), and total protein (P < 0.05). Multivariate linear regression analysis revealed that surgical time (P = 0.049), preoperative platelet count (P = 0.002), postoperative platelet count (P = 0.016), preoperative Hct (P = 0.045), preoperative albumin (ALB) level (P = 0.011), and postoperative total protein level (P = 0.003) were independent risk factors for HBL. Conclusion HBL in UBE surgery for degenerative lumbar diseases is a significant concern that should not be overlooked. Prolonged surgical time, elevated preoperative platelets, low preoperative ALB levels, and low postoperative total protein levels may exacerbate HBL. These risk factors should be closely monitored during the perioperative period to optimize patient management, reduce postoperative complications, and improve overall prognosis. Unilateral biportal endoscopy Hidden blood loss Degenerative lumbar disease Risk factors Perioperative management Background In recent years, UBE has rapidly gained prominence in the field of spinal surgery and has emerged as one of the key minimally invasive surgical approaches for treating lumbar diseases. This technique is applicable for common spinal conditions such as disc herniation and stenosis [1]. UBE not only offers smaller incisions and less dissection of soft tissues but also demonstrates excellent clinical efficacy and a lower complication rate [2]. However, with the increasing popularity of UBE surgery, several potential issues have been identified, among which HBL has become a significant factor affecting postoperative recovery and prognosis. HBL is relatively common among surgical patients [3]. Despite the advantages of UBE, such as minimal invasiveness and reduced bleeding, the issue of HBL should not be ignored. Owing to continuous irrigation and blood seepage into soft tissues or dead spaces in the surgical pathway, spine surgeons may easily underestimate blood loss. If not properly managed, it can lead to postoperative anaemia, hypoproteinaemia, prolonged hospital stays, increased infection risks, and even improved surgical outcomes and long-term patient prognosis [4–5]. Therefore, accurate assessment and control of HBL are highly important for improving surgical safety and patient recovery quality. Currently, most research on surgical blood loss has focused on VBL in open surgeries, with extensive studies on risk factors and preventive measures for bleeding in open surgeries. However, research in the UBE field is relatively scarce. Given the significant differences in the operating environment and technical characteristics between UBE and open surgeries, the mechanisms and risk factors for HBL may also differ. There is a lack of systematic research on risk factors for HBL in UBE surgery, leaving clinicians with an insufficient theoretical basis and practical guidance for preventing and managing HBL in UBE surgeries. Therefore, we conducted a retrospective study on patients with lumbar degenerative diseases who underwent UBE surgery at our institution, aiming to identify risk factors that may exacerbate HBL during UBE surgery. This study is committed to precisely identifying independent risk factors for HBL in UBE patients, thereby providing a solid theoretical basis for developing effective preventive and therapeutic strategies in clinical practice. Materials and methods 2.1 Study Design To identify the risk factors for HBL in patients with lumbar degeneration who underwent UBE surgery, we conducted a retrospective clinical study. The study was approved by the Ethics Committee of the 923rd Hospital, and informed consent was obtained from all participants (923LL-KY-2022LW-001-01). From June 2022 to June 2023, 117 patients with lumbar degenerative disease were initially included. Among them, 30 were excluded for non-single-segment surgery, loss to follow-up, or other reasons. Ultimately, 87 patients with single-segment lumbar degeneration were enrolled in the study. The inclusion criteria were as follows: patients aged 18 years or older with lumbar degenerative disease (lumbar spinal stenosis, spondylolisthesis, and lumbar disc herniation), who had undergone UBE decompression for single-segment L4/5 or L5/S1 and who had complete laboratory data. The exclusion criteria were as follows: (1) age less than 18 years; (2) lumbar infection and tumors; (3) previous lumbar surgery; (4) accidental dural tear during surgery; (5) lumbar fracture; (6) hematologic diseases, coagulation disorders, and severe anemia; (7) use of antiplatelet drugs or anticoagulants; (8) autologous and allogeneic blood transfusion; and (9) scoliosis or other spinal deformities. 2.2 Data collection Patient data were extracted from our institution's electronic medical records system. We collected demographic characteristics and clinical information, including age, sex, body mass index (BMI), hypertension (defined as blood pressure ≥ 140/90 mmHg), diabetes (defined as fasting blood glucose ≥ 6.1 mmol/l), smoking history, alcohol history, surgical time, muscle thickness, subcutaneous fat thickness, hospital stay, diagnosis, number of surgical segments, American Society of Anesthesiologists (ASA) classification, ALB, and drainage volume. Additionally, we recorded the patients' blood volume, intraoperative blood loss, preoperative triglycerides (TGs), serum total cholesterol (TC), low-density lipoprotein (LDL), high-density lipoprotein (HDL), Hct, preoperative Hb, postoperative Hct (measured within 1 day after surgery), postoperative Hb (measured within 1 day after surgery), prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen, and platelets. Preoperative magnetic resonance imaging (MRI) was used to measure the distance from the lamina to the skin surface, the thickness of the paraspinal muscles, and the thickness of the subcutaneous fat. These measurements were obtained by two experienced participants on axial T2-weighted MR images [6]. During the investigation, two researchers were responsible for data and information extraction, and accuracy checks were performed by a third researcher. 2.3 Surgical procedure and HBL calculation The surgery was performed under general anaesthesia with the patient in the prone position. Under fluoroscopic guidance, two channels were first constructed. The skin and deep fascia were successively incised, and then a three-stage dilating cannula was inserted, converging at the junction of the spinous process and lamina. A high-speed burr was used to treat and grind the lower edge of the upper lamina. Laminectomy forceps were used to remove the lower edge of the lamina until the upper attachment of the ligamentum flavum was exposed. The LF was stripped from the upper edge of the lower lamina, and part of the upper edge of the lamina was removed with a rongeur to completely strip the LF. Part of the medial edge of the facet joint was removed with a rongeur until the outer edge of the ipsilateral nerve root was exposed. The nerve root was stripped with a nerve stripper to expose the protruding nucleus pulposus. A nerve root retractor was inserted, the nerve root was retracted to the midline, and nucleus pulposus forceps were inserted through the operating channel to remove the protruding nucleus pulposus. The nerve root was confirmed to be fully decompressed and mobile, and strict hemostasis was performed during the operation. Intravenous antibiotics were administered within 24 hours after surgery to prevent perioperative infection. A drainage tube was placed under the fascia after surgery and removed on the first or second day after surgery according to the daily drainage volume. Patients were closely monitored for signs and symptoms related to epidural hematoma after surgery, and computed tomography (CT) or magnetic resonance imaging (MRI) was performed if necessary. The electrolyte balance was carefully monitored after surgery. In this study, the formula proposed by Sehat et al. [7] was used to calculate HBL, that is, HBL = TBL - VBL. TBL was determined by calculating the patient's estimated blood volume (PBV) via the formula proposed by Nadler et al. [8] and combining it with the change in Hct. Specifically, the formula for calculating PBV is as follows: for males, PBV = 0.3669× height (m)³ + 0.03219× weight (kg) + 0.6041; for females, PBV = 0.3561× height (m)³ + 0.03308× weight (kg) + 0.1833. The formula for calculating TBL is TBL = PBV×(preoperative Hct - postoperative Hct)/average Hct, where the average Hct is the mean of the preoperative and postoperative Hct. VBL was obtained by adding the volume of blood and water mixture in the surgical suction bag and the volume of aspirated fluid from the gauze and then subtracting the volume of irrigation saline used during the operation [9]. 2.4 Statistical analysis All the statistical analyses were performed via SPSS version 22.0 (SPSS, Inc., Chicago, IL, USA). Pearson correlation analysis (for normal data/quantitative variables) or Spearman correlation analysis (for nonnormal data/qualitative variables) was used to assess risk factors related to HBL. Multivariate linear regression analysis was used to identify independent risk factors affecting HBL during the perioperative period. The factors included in the analysis were sex, age, BMI, hypertension, diabetes, smoking, alcohol consumption, surgical time, hospital stay, ASA grade, PBV, VBL, TBL, preoperative Hct, preoperative Hb, postoperative Hct, postoperative Hb, PT, APTT, TT, PLT, muscle relaxants, and level fusion. P < 0.05 was considered statistically significant. Results A retrospective analysis was conducted on 117 patients with single-segment lumbar degeneration who underwent UBE surgery. All demographic and baseline characteristics were systematically reviewed, and the specific data are shown in Table 1 . The study sample included 38 females and 49 males, with an average age of 48.7 ± 16.92 years. In terms of lumbar disease type distribution, 39 patients were diagnosed with lumbar disc herniation, and 45 were diagnosed with lumbar spinal stenosis. In terms of comorbidities, 13 patients had hypertension, and 5 had diabetes. The average surgical time was 170.78 ± 78.96 min. The preoperative mean Hct was 41.26 ± 4.64, and the mean Hb was 125.1 ± 11.6 g/L; the postoperative mean Hct was 37.48 ± 4.74, and the mean Hb decreased to 124.29 ± 17.58 g/L. The estimated blood volume (PBV) was 4.23 ± 0.79 L, the VBL reached 129.82 ± 77.56 ml, the HBL was 227.40 ± 232.92 ml, and the TBL was 407.21 ± 266.45 ml. Table 1 Demographic Information of the Patients Parameters Statistics Total number of patients (n) 87 Gender (n) Female 38 Male 49 Age (y) 48.70 ± 16.92 BMI (kg/m²) 24.70 ± 3.54 Hypertension (n) No 74 Yes 13 Diabetes (n) No 82 Yes 5 Smoking (n) No 63 Yes 24 Alcohol consumption (n) No 66 Yes 21 Disease group Lumbar disc herniation 39 Lumbar spinal stenosis 45 Fusion level (n) L3-L4 3 L4-L5 61 L5-S1 23 ASA classification (n) I 10 II 65 III 12 Surgical duration (min) 170.78 ± 78.96 PBV (mL) 4227.16 ± 791.76 Intraoperative blood loss (mL) 92.01 ± 75.96 TBL (mL) 407.21 ± 266.45 VBL (mL) 129.82 ± 77.56 HBL (mL) 277.40 ± 232.92 Preoperative Hb (g/L) 136.23 ± 17.41 Preoperative Hct 41.26 ± 4.64 Postoperative Hb (g/L) 124.29 ± 17.58 Postoperative Hct 37.48 ± 4.74 Muscle thickness (mm) 36.39 ± 6.03 Subcutaneous fat thickness (mm) 17.54 ± 8.08 Preoperative total protein 69.42 ± 8.61 Postoperative total protein 59.31 ± 4.21 Preoperative ALB (g/L) 44.05 ± 4.22 Preoperative D-dimer 410.23 ± 451.31 PT (s) 10.84 ± 0.68 APTT (s) 26.11 ± 3.47 Platelets (g/L) 246.45 ± 57.06 Preoperative fibrinogen (g/L) 2.87 ± 1.74 Postoperative D-dimer 1258.46 ± 1325.15 The results of the Pearson and Spearman correlation analyses are detailed in Tables 2 and 3 , respectively. These analyses demonstrated that surgical duration, postoperative drainage volume on the day of surgery, and TBL were positively correlated with HBL. Conversely, postoperative Hb levels, postoperative HCT, and postoperative total protein were negatively correlated with HBL (P < 0.05). To further pinpoint the independent risk factors for HBL, multivariate linear regression analysis was employed. The analysis revealed that surgical time (P = 0.049), preoperative platelet count (P = 0.002), postoperative platelet count (P = 0.016), preoperative Hct (P = 0.045), preoperative ALB level (P = 0.011), and postoperative total protein level (P = 0.003) were significant independent risk factors for HBL. For a comprehensive overview of the data, please refer to Table 4 . Table 2 Pearson Correlation Analysis Results for Hidden Blood Loss Parameters Pearson's r P-value Median Age (y) -0.80 0.463 BMI (kg/m²) 0.017 0.097 Surgical Duration (min) 0.247 0.021 PBV 0.179 0.097 Preoperative Hct 0.449 0.312 Preoperative Hb (g/L) 0.442 0.321 Preoperative ALB (g/L) 0.227 0.547 Muscle Thickness (mm) 0.044 0.687 Subcutaneous Fat Thickness -0.136 0.210 Intraoperative Blood Loss 0.162 0.134 Postoperative Drainage Volume on Day 1 0.323 0.002 TBL 0.945 0.000 Preoperative PT -0.020 0.854 Preoperative APTT 0.059 0.586 Preoperative Fibrinogen 0.080 0.462 Preoperative D-Dimer -0.104 0.338 Preoperative Hb 0.128 0.238 Preoperative HCT 0.179 0.097 Preoperative Platelets 0.127 0.243 Preoperative Total Protein 0.199 0.064 Postoperative Hb -0.220 0.041 Postoperative HCT -0.270 0.011 Postoperative Platelets -0.210 0.051 Postoperative Total Protein -0.355 0.001 Postoperative ALB -0.045 0.678 Postoperative D-Dimer -0.072 0.508 Table 3 Spearman Correlation Analysis Results for Hidden Blood Loss Parameter Sig. (2-tailed) P-value Gender -0.137 0.207 Smoking History -0.114 0.294 Alcohol Consumption -0.052 0.630 Disease Type -0.113 0.296 Surgical Segment 0.022 0.837 ASA Classification -0.086 0.430 Tranexamic Acid Use 0.060 0.583 Hypertension -0.054 0.620 Diabetes Mellitus -0.026 0.814 Table 4 Results of Multivariate Linear Regression Analysis for Hidden Blood Loss Coefficients Unstandardized SE Standardized t P β β Constant -1068.473 717.697 -1.489 0.142 Disease Type -72.406 45.570 -0.154 -1.589 0.118 Surgical Segment -35.142 47.583 -0.075 -0.739 0.463 Muscle Thickness -5.991 3.717 -0.155 -1.612 0.112 Subcutaneous Fat Thickness -2.809 3.277 -0.097 -0.857 0.395 Intraoperative Blood Loss -0.017 0.331 -0.006 -0.052 0.959 Postoperative Drainage Volume on Day 1 1.101 0.691 0.157 1.594 0.116 Hypertension -9.027 72.781 -0.014 -0.124 0.902 Diabetes Mellitus -62.397 100.583 -0.063 -0.620 0.537 Smoking -52.331 56.127 -0.101 -0.932 0.355 Alcohol Consumption -15.192 54.244 -0.028 -0.280 0.780 ASA Classification -30.336 52.442 -0.066 -0.578 0.565 Surgical Time 0.779 0.388 0.264 2.007 0.049* Tranexamic Acid -9.634 42.821 -0.020 -0.225 0.823 BMI 14.327 8.194 0.218 1.749 0.086 Preoperative PT 35.672 33.801 0.105 1.055 0.296 Preoperative APTT 7.346 6.961 0.109 1.055 0.296 Preoperative Fibrinogen -23.082 16.831 -0.173 -1.371 0.176 Preoperative D-Dimer -0.074 0.055 -0.143 -1.338 0.186 Preoperative HCT 14.501 7.087 0.289 2.046 0.045* Preoperative Platelets 2.440 0.755 0.598 3.233 0.002** Preoperative Total Protein -1.287 3.676 -0.048 -0.350 0.728 Preoperative ALB 21.206 8.024 0.384 2.643 0.011* Postoperative Platelets -2.287 0.918 -0.514 -2.492 0.016* Postoperative Total Protein -24.916 8.043 -0.450 -3.098 0.003** Postoperative ALB 18.543 11.624 0.253 1.595 0.116 Postoperative D-Dimer 0.007 0.018 0.038 0.371 0.712 Age 3.184 1.912 0.231 1.665 0.101 Gender -27.417 74.015 -0.059 -0.370 0.712 Note: * P < 0.05, ** P < 0.01 Discussion UBE spine surgery has emerged as an innovative ultraminimally invasive technique, offering significant advantages in the treatment of lumbar spine diseases. These advantages include minimal surgical trauma, rapid postoperative recovery, and minimal disruption to spinal stability. Since 2000, HBL has garnered increasing attention from spinal surgeons. HBL typically occurs via two primary pathways: blood infiltration into tissue compartments or dead spaces and hemolysis. Erskine et al. [10] suggested that 60% of HBL results from blood infiltration, whereas 40% is attributed to hemolytic reactions. Conversely, Sehat et al. [7] proposed a ratio of 2:1 for blood infiltration–related HBL versus hemolysis–related HBL. Studies have consistently indicated that HBL is frequently underestimated in clinical practice. It can significantly increase TBL, exacerbate postoperative Hb decline, and increase the need for blood transfusions. If not properly managed, HBL may lead to a range of perioperative complications, including delayed wound healing, increased risk of infection, and prolonged postoperative recovery time [11]. Wang et al. [12] reported that the average HBL during UBE spine surgery was 469.5 ± 195.3 ml, accounting for 57.6% of the TBL. Guo et al. [13] reported an average HBL volume of 361.4 ± 216.8 ml in patients who underwent UBE lumbar surgery. In our study, the average HBL was 277.40 ± 232.92 ml in patients undergoing UBE for lumbar spine diseases. Similar to previous studies on HBL in spine surgery [14], the volume of HBL during surgery was significantly greater than that of VBL, which was much greater than anticipated. However, the risk factors for HBL in UBE surgery remain unclear. This study aimed to identify potential risk factors for HBL in UBE spine surgery to enhance perioperative blood loss management, reduce perioperative complications, and ensure patient safety. We retrospectively analysed the clinical information of 117 patients who underwent UBE surgery and employed Pearson or Spearman correlation analysis and multiple linear regression to identify the risk factors for HBL. Pearson correlation analysis revealed that the preoperative ALB level was positively correlated with HBL (r = 0.425, p < 0.05). Xu et al. [15] demonstrated that in patients undergoing total joint arthroplasty (TJA), a 1 g/L decrease in the preoperative ALB level significantly increased the risk of perioperative blood transfusion (OR = 1.63). This finding may be related to unmonitored but actual anaemia caused by HBL. Multiple linear regression analysis further indicated that low preoperative serum ALB levels are an independent risk factor for perioperative HBL. This may be attributed to low ALB levels causing extravasation of tissue fluid, inducing tissue edema, and compromising the integrity of the microcirculation, thereby increasing hidden bleeding from surgical wounds or damaged tissues [16]. Experiments have shown that exogenous ALB can reduce capillary leakage (e.g., a 67% reduction in pulmonary leakage) [17], indirectly supporting the mechanism by which low ALB levels exacerbate bleeding. These findings also suggest that the preoperative nutritional status of patients may significantly impact perioperative blood loss. Previous studies have reported that in minimally invasive surgeries, male patients tend to have greater HBL than do female patients [18], and they are also more likely to require blood transfusions postoperatively [19]. Some studies have suggested that female patients have lower HBL than male patients do, possibly due to the relatively smaller amount of bone resection and smaller back muscles in females. Other studies attributed this difference to the advantages of male patients in terms of body mass index and blood volume. Additionally, the increased incidence of osteoporosis in females reduces the blood supply in the bone marrow cavity, thereby decreasing blood loss during surgery [20]. However, our study did not find a correlation between sex and HBL, which may be due to the small sample size. Further investigations with larger sample sizes are needed to confirm the exact mechanisms and results. Multiple linear regression analysis revealed that both preoperative and postoperative platelet counts are independent risk factors for HBL. The preoperative platelet count was positively correlated with HBL, likely because a higher preoperative platelet count reflects a hyperactive coagulation system. This hyperactivity can lead to platelet activation during tissue injury during surgery, promoting the formation of microthrombi. These microthrombi can obstruct the microcirculation, causing red blood cell rupture and Hb release, thereby exacerbating HBL [21]. Interestingly, the postoperative platelet count was negatively correlated with HBL, a finding that is consistent with the findings of several previous studies [22]. This may be because during HBL, blood components (including platelets) are retained in tissue spaces or destroyed. The postoperative decrease in platelet levels may reflect their extensive consumption in the hemostasis process. Wang et al. [12] reported that in UBE surgery, the higher the American Society of Anesthesiologists (ASA) classification is, the higher the HBL in patients. Moreover, some studies have shown that patients with ASA grade III HBL have significantly greater HBL than those with ASA grades I and II HBL [23]. This may be because, compared with ASA grade I patients, patients with ASA grades II to IV generally have poorer overall conditions and more comorbidities. In particular, some patients have poorer tolerance to surgery and anaesthesia, resulting in compromised coagulation system function compared with that of lower-grade patients, thereby increasing HBL [24]. However, our study did not reach the same conclusion, which may be because the majority of cases included in our study were ASA grades I and II, with very few ASA grade III cases. Further research is needed to confirm these results. Pearson or Spearman correlation analysis revealed that postoperative Hct was negatively correlated with HBL during UBE surgery. This may be related to the use of the Nadler formula to calculate HBL in this study [25]. This may also be because perioperative fluid administration can dilute the blood, leading to a decrease in Hct. However, this process may mask the actual loss of red blood cells, thereby contributing to HBL [26]. Multiple linear regression analysis revealed that surgical duration is an independent risk factor for HBL, a finding that is consistent with previous studies [27]. During UBE surgery, normal saline is typically used for irrigation to achieve a clear surgical field. Continuous irrigation with large amounts of fluid can flush out blood seeping from soft tissues and bone surfaces. A prolonged surgical duration is usually associated with more complex procedures and more extensive tissue exposure. Prolonged tissue traction may cause rupture of small blood vessels, and bleeding that is not promptly controlled during surgery can gradually accumulate as HBL. Surgeons should be vigilant about the possibility of excessive HBL during UBE surgery. The current study has several limitations. First, this was a retrospective study with a relatively small sample size. Future research should involve larger-scale prospective multicenter studies to validate our findings. Second, perioperative fluid administration was not strictly controlled, which may have affected the calculation of total perioperative blood loss. Third, the calculation of intraoperative blood loss was based on estimates by anesthesiologists, which may lack accuracy and introduce bias into the calculation of HBL. Finally, HBL is mostly estimated via the Gross formula, which is susceptible to errors from hemodilution due to intraoperative fluid administration and inaccuracies in drainage fluid collection. Additionally, considering that postoperative drainage may be affected by intraoperative irrigation, the calculations of VBL and HBL may have slight deviations, and the timing of drainage tube removal may also affect the HBL results. Therefore, high-quality observational and basic experimental studies are still needed to further investigate new risk factors for HBL in patients undergoing UBE treatment for lumbar spine diseases in the future. Conclusion This study demonstrates that patients undergoing UBE surgery for lumbar disc herniation or lumbar spinal stenosis experience varying degrees of HBL. HBL is correlated with TBL, VBL, drainage volume on the day of surgery, surgical duration, preoperative ALB, postoperative Hb, postoperative Hct, and postoperative total protein. Moreover, surgical duration, Hct, preoperative platelets, preoperative ALB, postoperative platelets, and postoperative total protein are independent risk factors for HBL in UBE surgery. Perioperative attention should be given to HBL and its risk factors, and appropriate management of these risk factors can help reduce the incidence of complications, hospital stay duration, healthcare costs, and financial burden on families for surgical patients. Abbreviations BMI body mass index Hct hematocrit ALB albumin PT prothrombin time APTT activated partial thromboplastin time TBL total blood loss PBV patient blood volume VBL visible blood loss HBL hidden blood loss ASA American Society of Anesthesiologists Hb hemoglobin MRI magnetic resonance imaging. Declarations Acknowledgements None. Authors’ contributions YPZ and CZC designed this study. JYH, GJW, LL and BL were involved in data collection. YPZ, GJW and WAQ analysed and interpreted the data. JYH and GJW performed the chart abstraction and revised the manuscript. JYH and YPZ were major contributors to the writing of the manuscript. All the authors read and approved the final manuscript. Funding None. Availability of data and material The datasets used and analysed during the current study are available from the corresponding author upon reasonable request. Ethics approval and consent to participate This research was approved by the Ethics Committee of the PLA Joint Logistic Support Force. All procedures adhered to the relevant guidelines and principles of the Declaration of Helsinki. All participants provided written informed consent for participation. Consent for publication Not applicable. Informed consent Informed consent was obtained from all participants in this research. Conflict of interest All the authors declare that they have no potential conflicts of interest. Clinical trial number Not applicable. References Liang J, Lian L, Liang S, et al. Efficacy and Complications of Unilateral Biportal Endoscopic Spinal Surgery for Lumbar Spinal Stenosis: A Meta-Analysis and Systematic Review. World Neurosurg 2022;159:e91-e102. 10.1016/j.wneu.2021.12.005 Park DY, Upfill-Brown A, Nora B, et al. Clinical outcomes and complications after biportal endoscopic spine surgery: a comprehensive systematic review and meta-analysis of 3673 cases. 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Quantification and influencing factors of perioperative hidden blood loss in patients undergoing laparoscopic ovarian cystectomy for benign ovarian tumours. J Obstet Gynaecol. 2022 Oct;42(7):3181-3186. Chon SB, Lee MJ, Oh WS, Park YJ, Kwon JM, Kim K. A simple and novel equation to estimate the degree of bleeding in haemorrhagic shock: mathematical derivation and preliminary in vivo validation. Korean J Physiol Pharmacol. 2022 May 1;26(3):195-205. Zhang R, Xing F, Yang Z, Lin G, Chu J. Analysis of risk factors for perioperative hidden blood loss in patients undergoing transforaminal lumbar interbody fusion. J Int Med Res. (2020) 48:300060520937848. 10.1177/0300060520937848 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6830206","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":469113161,"identity":"1fb25369-3cdf-4064-a132-0eef9c29335a","order_by":0,"name":"JunYi He","email":"","orcid":"","institution":"Guilin Medical College","correspondingAuthor":false,"prefix":"","firstName":"JunYi","middleName":"","lastName":"He","suffix":""},{"id":469113162,"identity":"03b2f445-fd43-42c2-826d-e1bbd36a152b","order_by":1,"name":"GeJin Wei","email":"","orcid":"","institution":"923rd Hospital of PLA joint Logistic Support Force","correspondingAuthor":false,"prefix":"","firstName":"GeJin","middleName":"","lastName":"Wei","suffix":""},{"id":469113164,"identity":"4a8362c9-695b-42a6-b786-a2b9366e9096","order_by":2,"name":"Lun Li","email":"","orcid":"","institution":"Guilin Medical College","correspondingAuthor":false,"prefix":"","firstName":"Lun","middleName":"","lastName":"Li","suffix":""},{"id":469113165,"identity":"d4dfd1b2-ab0d-4a63-b836-58469fc90798","order_by":3,"name":"WanAn Qin","email":"","orcid":"","institution":"923rd Hospital of PLA joint Logistic Support Force","correspondingAuthor":false,"prefix":"","firstName":"WanAn","middleName":"","lastName":"Qin","suffix":""},{"id":469113166,"identity":"2f95b680-60ed-4683-b723-7fa8b447a4f8","order_by":4,"name":"Bei Liu","email":"","orcid":"","institution":"923rd Hospital of PLA joint Logistic Support Force","correspondingAuthor":false,"prefix":"","firstName":"Bei","middleName":"","lastName":"Liu","suffix":""},{"id":469113167,"identity":"85574ab5-2112-4323-8371-7df2b1b99b81","order_by":5,"name":"Yanping Zeng","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAwklEQVRIiWNgGAWjYBACfvb+jw8+VNjI8bM3EKlFsueAseGMM2nGQAaRWgxmJJhJ87YdTtxwI4FYLQwJaZIzzhw2Nrj5eOMNhhqbaIJazBkOHLb4UJEuJ3k7rdiC4VhabgMhLZaNjY03Z5yxNua7nWMmwdhwmLAWg8PMDEC/MCc23DxDrJZjbExALc6JE27wEKlFsoeHGRrIQL8kEOMXfvk3jNCoPLzxxocaG8JaUBwpkUCKcogWUnWMglEwCkbByAAAADRE328YOSgAAAAASUVORK5CYII=","orcid":"","institution":"923rd Hospital of PLA joint Logistic Support Force","correspondingAuthor":true,"prefix":"","firstName":"Yanping","middleName":"","lastName":"Zeng","suffix":""},{"id":469113168,"identity":"265becc8-1345-4eb0-bd66-12dba7b8d4c6","order_by":6,"name":"ChangZhi Cheng","email":"","orcid":"","institution":"923rd Hospital of PLA joint Logistic Support Force","correspondingAuthor":false,"prefix":"","firstName":"ChangZhi","middleName":"","lastName":"Cheng","suffix":""}],"badges":[],"createdAt":"2025-06-05 14:38:26","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6830206/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6830206/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":87041114,"identity":"1319c625-691a-4e56-905c-01c0b10c2672","added_by":"auto","created_at":"2025-07-18 13:54:04","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":748912,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6830206/v1/2d37f515-f503-4336-9717-e637d9d8704a.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Risk Factor Analysis of Hidden Blood Loss in Unilateral Biportal Endoscopy for Degenerative Lumbar Diseases","fulltext":[{"header":"Background","content":"\u003cp\u003eIn recent years, UBE has rapidly gained prominence in the field of spinal surgery and has emerged as one of the key minimally invasive surgical approaches for treating lumbar diseases. This technique is applicable for common spinal conditions such as disc herniation and stenosis [1]. UBE not only offers smaller incisions and less dissection of soft tissues but also demonstrates excellent clinical efficacy and a lower complication rate [2]. However, with the increasing popularity of UBE surgery, several potential issues have been identified, among which HBL has become a significant factor affecting postoperative recovery and prognosis.\u003c/p\u003e \u003cp\u003eHBL is relatively common among surgical patients [3]. Despite the advantages of UBE, such as minimal invasiveness and reduced bleeding, the issue of HBL should not be ignored. Owing to continuous irrigation and blood seepage into soft tissues or dead spaces in the surgical pathway, spine surgeons may easily underestimate blood loss. If not properly managed, it can lead to postoperative anaemia, hypoproteinaemia, prolonged hospital stays, increased infection risks, and even improved surgical outcomes and long-term patient prognosis [4\u0026ndash;5]. Therefore, accurate assessment and control of HBL are highly important for improving surgical safety and patient recovery quality.\u003c/p\u003e \u003cp\u003eCurrently, most research on surgical blood loss has focused on VBL in open surgeries, with extensive studies on risk factors and preventive measures for bleeding in open surgeries. However, research in the UBE field is relatively scarce. Given the significant differences in the operating environment and technical characteristics between UBE and open surgeries, the mechanisms and risk factors for HBL may also differ. There is a lack of systematic research on risk factors for HBL in UBE surgery, leaving clinicians with an insufficient theoretical basis and practical guidance for preventing and managing HBL in UBE surgeries. Therefore, we conducted a retrospective study on patients with lumbar degenerative diseases who underwent UBE surgery at our institution, aiming to identify risk factors that may exacerbate HBL during UBE surgery. This study is committed to precisely identifying independent risk factors for HBL in UBE patients, thereby providing a solid theoretical basis for developing effective preventive and therapeutic strategies in clinical practice.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cp\u003e2.1 Study Design\u003c/p\u003e \u003cp\u003eTo identify the risk factors for HBL in patients with lumbar degeneration who underwent UBE surgery, we conducted a retrospective clinical study. The study was approved by the Ethics Committee of the 923rd Hospital, and informed consent was obtained from all participants (923LL-KY-2022LW-001-01). From June 2022 to June 2023, 117 patients with lumbar degenerative disease were initially included. Among them, 30 were excluded for non-single-segment surgery, loss to follow-up, or other reasons. Ultimately, 87 patients with single-segment lumbar degeneration were enrolled in the study. The inclusion criteria were as follows: patients aged 18 years or older with lumbar degenerative disease (lumbar spinal stenosis, spondylolisthesis, and lumbar disc herniation), who had undergone UBE decompression for single-segment L4/5 or L5/S1 and who had complete laboratory data. The exclusion criteria were as follows: (1) age less than 18 years; (2) lumbar infection and tumors; (3) previous lumbar surgery; (4) accidental dural tear during surgery; (5) lumbar fracture; (6) hematologic diseases, coagulation disorders, and severe anemia; (7) use of antiplatelet drugs or anticoagulants; (8) autologous and allogeneic blood transfusion; and (9) scoliosis or other spinal deformities.\u003c/p\u003e \u003cp\u003e2.2 Data collection\u003c/p\u003e \u003cp\u003ePatient data were extracted from our institution's electronic medical records system. We collected demographic characteristics and clinical information, including age, sex, body mass index (BMI), hypertension (defined as blood pressure\u0026thinsp;\u0026ge;\u0026thinsp;140/90 mmHg), diabetes (defined as fasting blood glucose\u0026thinsp;\u0026ge;\u0026thinsp;6.1 mmol/l), smoking history, alcohol history, surgical time, muscle thickness, subcutaneous fat thickness, hospital stay, diagnosis, number of surgical segments, American Society of Anesthesiologists (ASA) classification, ALB, and drainage volume. Additionally, we recorded the patients' blood volume, intraoperative blood loss, preoperative triglycerides (TGs), serum total cholesterol (TC), low-density lipoprotein (LDL), high-density lipoprotein (HDL), Hct, preoperative Hb, postoperative Hct (measured within 1 day after surgery), postoperative Hb (measured within 1 day after surgery), prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen, and platelets. Preoperative magnetic resonance imaging (MRI) was used to measure the distance from the lamina to the skin surface, the thickness of the paraspinal muscles, and the thickness of the subcutaneous fat. These measurements were obtained by two experienced participants on axial T2-weighted MR images [6]. During the investigation, two researchers were responsible for data and information extraction, and accuracy checks were performed by a third researcher.\u003c/p\u003e \u003cp\u003e2.3 Surgical procedure and HBL calculation\u003c/p\u003e \u003cp\u003eThe surgery was performed under general anaesthesia with the patient in the prone position. Under fluoroscopic guidance, two channels were first constructed. The skin and deep fascia were successively incised, and then a three-stage dilating cannula was inserted, converging at the junction of the spinous process and lamina. A high-speed burr was used to treat and grind the lower edge of the upper lamina. Laminectomy forceps were used to remove the lower edge of the lamina until the upper attachment of the ligamentum flavum was exposed. The LF was stripped from the upper edge of the lower lamina, and part of the upper edge of the lamina was removed with a rongeur to completely strip the LF. Part of the medial edge of the facet joint was removed with a rongeur until the outer edge of the ipsilateral nerve root was exposed. The nerve root was stripped with a nerve stripper to expose the protruding nucleus pulposus. A nerve root retractor was inserted, the nerve root was retracted to the midline, and nucleus pulposus forceps were inserted through the operating channel to remove the protruding nucleus pulposus. The nerve root was confirmed to be fully decompressed and mobile, and strict hemostasis was performed during the operation. Intravenous antibiotics were administered within 24 hours after surgery to prevent perioperative infection. A drainage tube was placed under the fascia after surgery and removed on the first or second day after surgery according to the daily drainage volume. Patients were closely monitored for signs and symptoms related to epidural hematoma after surgery, and computed tomography (CT) or magnetic resonance imaging (MRI) was performed if necessary. The electrolyte balance was carefully monitored after surgery.\u003c/p\u003e \u003cp\u003eIn this study, the formula proposed by Sehat et al. [7] was used to calculate HBL, that is, HBL\u0026thinsp;=\u0026thinsp;TBL - VBL. TBL was determined by calculating the patient's estimated blood volume (PBV) via the formula proposed by Nadler et al. [8] and combining it with the change in Hct. Specifically, the formula for calculating PBV is as follows: for males, PBV\u0026thinsp;=\u0026thinsp;0.3669\u0026times; height (m)\u0026sup3; + 0.03219\u0026times; weight (kg)\u0026thinsp;+\u0026thinsp;0.6041; for females, PBV\u0026thinsp;=\u0026thinsp;0.3561\u0026times; height (m)\u0026sup3; + 0.03308\u0026times; weight (kg)\u0026thinsp;+\u0026thinsp;0.1833. The formula for calculating TBL is TBL\u0026thinsp;=\u0026thinsp;PBV\u0026times;(preoperative Hct - postoperative Hct)/average Hct, where the average Hct is the mean of the preoperative and postoperative Hct. VBL was obtained by adding the volume of blood and water mixture in the surgical suction bag and the volume of aspirated fluid from the gauze and then subtracting the volume of irrigation saline used during the operation [9].\u003c/p\u003e \u003cp\u003e2.4 Statistical analysis\u003c/p\u003e \u003cp\u003eAll the statistical analyses were performed via SPSS version 22.0 (SPSS, Inc., Chicago, IL, USA). Pearson correlation analysis (for normal data/quantitative variables) or Spearman correlation analysis (for nonnormal data/qualitative variables) was used to assess risk factors related to HBL. Multivariate linear regression analysis was used to identify independent risk factors affecting HBL during the perioperative period. The factors included in the analysis were sex, age, BMI, hypertension, diabetes, smoking, alcohol consumption, surgical time, hospital stay, ASA grade, PBV, VBL, TBL, preoperative Hct, preoperative Hb, postoperative Hct, postoperative Hb, PT, APTT, TT, PLT, muscle relaxants, and level fusion. P\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered statistically significant.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eA retrospective analysis was conducted on 117 patients with single-segment lumbar degeneration who underwent UBE surgery. All demographic and baseline characteristics were systematically reviewed, and the specific data are shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The study sample included 38 females and 49 males, with an average age of 48.7\u0026thinsp;\u0026plusmn;\u0026thinsp;16.92 years. In terms of lumbar disease type distribution, 39 patients were diagnosed with lumbar disc herniation, and 45 were diagnosed with lumbar spinal stenosis. In terms of comorbidities, 13 patients had hypertension, and 5 had diabetes. The average surgical time was 170.78\u0026thinsp;\u0026plusmn;\u0026thinsp;78.96 min. The preoperative mean Hct was 41.26\u0026thinsp;\u0026plusmn;\u0026thinsp;4.64, and the mean Hb was 125.1\u0026thinsp;\u0026plusmn;\u0026thinsp;11.6 g/L; the postoperative mean Hct was 37.48\u0026thinsp;\u0026plusmn;\u0026thinsp;4.74, and the mean Hb decreased to 124.29\u0026thinsp;\u0026plusmn;\u0026thinsp;17.58 g/L. The estimated blood volume (PBV) was 4.23\u0026thinsp;\u0026plusmn;\u0026thinsp;0.79 L, the VBL reached 129.82\u0026thinsp;\u0026plusmn;\u0026thinsp;77.56 ml, the HBL was 227.40\u0026thinsp;\u0026plusmn;\u0026thinsp;232.92 ml, and the TBL was 407.21\u0026thinsp;\u0026plusmn;\u0026thinsp;266.45 ml.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDemographic Information of the Patients\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eStatistics\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTotal number of patients (n)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e87\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGender (n)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e38\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e49\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge (y)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e48.70\u0026thinsp;\u0026plusmn;\u0026thinsp;16.92\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBMI (kg/m\u0026sup2;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e24.70\u0026thinsp;\u0026plusmn;\u0026thinsp;3.54\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHypertension (n)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e74\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDiabetes (n)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e82\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSmoking (n)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e63\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e24\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAlcohol consumption (n)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e66\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e21\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDisease group\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLumbar disc herniation\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e39\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLumbar spinal stenosis\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e45\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFusion level (n)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eL3-L4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eL4-L5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e61\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eL5-S1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e23\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eASA classification (n)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eI\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eII\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e65\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIII\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSurgical duration (min)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e170.78\u0026thinsp;\u0026plusmn;\u0026thinsp;78.96\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePBV (mL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4227.16\u0026thinsp;\u0026plusmn;\u0026thinsp;791.76\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIntraoperative blood loss (mL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e92.01\u0026thinsp;\u0026plusmn;\u0026thinsp;75.96\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTBL (mL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e407.21\u0026thinsp;\u0026plusmn;\u0026thinsp;266.45\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVBL (mL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e129.82\u0026thinsp;\u0026plusmn;\u0026thinsp;77.56\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHBL (mL)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e277.40\u0026thinsp;\u0026plusmn;\u0026thinsp;232.92\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreoperative Hb (g/L)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e136.23\u0026thinsp;\u0026plusmn;\u0026thinsp;17.41\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreoperative Hct\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e41.26\u0026thinsp;\u0026plusmn;\u0026thinsp;4.64\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePostoperative Hb (g/L)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e124.29\u0026thinsp;\u0026plusmn;\u0026thinsp;17.58\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePostoperative Hct\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e37.48\u0026thinsp;\u0026plusmn;\u0026thinsp;4.74\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMuscle thickness (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e36.39\u0026thinsp;\u0026plusmn;\u0026thinsp;6.03\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSubcutaneous fat thickness (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e17.54\u0026thinsp;\u0026plusmn;\u0026thinsp;8.08\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreoperative total protein\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e69.42\u0026thinsp;\u0026plusmn;\u0026thinsp;8.61\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePostoperative total protein\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e59.31\u0026thinsp;\u0026plusmn;\u0026thinsp;4.21\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreoperative ALB (g/L)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e44.05\u0026thinsp;\u0026plusmn;\u0026thinsp;4.22\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreoperative D-dimer\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e410.23\u0026thinsp;\u0026plusmn;\u0026thinsp;451.31\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePT (s)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10.84\u0026thinsp;\u0026plusmn;\u0026thinsp;0.68\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAPTT (s)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e26.11\u0026thinsp;\u0026plusmn;\u0026thinsp;3.47\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePlatelets (g/L)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e246.45\u0026thinsp;\u0026plusmn;\u0026thinsp;57.06\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreoperative fibrinogen (g/L)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.87\u0026thinsp;\u0026plusmn;\u0026thinsp;1.74\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePostoperative D-dimer\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1258.46\u0026thinsp;\u0026plusmn;\u0026thinsp;1325.15\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe results of the Pearson and Spearman correlation analyses are detailed in Tables\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and \u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, respectively. These analyses demonstrated that surgical duration, postoperative drainage volume on the day of surgery, and TBL were positively correlated with HBL. Conversely, postoperative Hb levels, postoperative HCT, and postoperative total protein were negatively correlated with HBL (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05). To further pinpoint the independent risk factors for HBL, multivariate linear regression analysis was employed. The analysis revealed that surgical time (P\u0026thinsp;=\u0026thinsp;0.049), preoperative platelet count (P\u0026thinsp;=\u0026thinsp;0.002), postoperative platelet count (P\u0026thinsp;=\u0026thinsp;0.016), preoperative Hct (P\u0026thinsp;=\u0026thinsp;0.045), preoperative ALB level (P\u0026thinsp;=\u0026thinsp;0.011), and postoperative total protein level (P\u0026thinsp;=\u0026thinsp;0.003) were significant independent risk factors for HBL. For a comprehensive overview of the data, please refer to Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePearson Correlation Analysis Results for Hidden Blood Loss\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePearson's r\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eP-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMedian Age (y)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.463\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBMI (kg/m\u0026sup2;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.017\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.097\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSurgical Duration (min)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.247\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.021\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePBV\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.179\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.097\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreoperative Hct\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.449\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.312\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreoperative Hb (g/L)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.442\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.321\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreoperative ALB (g/L)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.227\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.547\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMuscle Thickness (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.044\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.687\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSubcutaneous Fat Thickness\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.136\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.210\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIntraoperative Blood Loss\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.162\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.134\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePostoperative Drainage Volume on Day 1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.323\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.002\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTBL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.945\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.000\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreoperative PT\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.020\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.854\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreoperative APTT\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.059\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.586\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreoperative Fibrinogen\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.080\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.462\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreoperative D-Dimer\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.104\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.338\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreoperative Hb\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.128\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.238\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreoperative HCT\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.179\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.097\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreoperative Platelets\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.127\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.243\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreoperative Total Protein\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.199\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.064\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePostoperative Hb\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.220\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.041\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePostoperative HCT\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.270\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.011\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePostoperative Platelets\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.210\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.051\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePostoperative Total Protein\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.355\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePostoperative ALB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.045\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.678\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePostoperative D-Dimer\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.072\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.508\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSpearman Correlation Analysis Results for Hidden Blood Loss\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSig. (2-tailed)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eP-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGender\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.137\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.207\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSmoking History\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.114\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.294\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAlcohol Consumption\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.052\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.630\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDisease Type\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.113\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.296\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSurgical Segment\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.022\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.837\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eASA Classification\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.086\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.430\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTranexamic Acid Use\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.060\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.583\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHypertension\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.054\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.620\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDiabetes Mellitus\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.026\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.814\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eResults of Multivariate Linear Regression Analysis for Hidden Blood Loss\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eCoefficients\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUnstandardized\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eSE\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eStandardized\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cem\u003et\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eβ\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eβ\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eConstant\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-1068.473\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e717.697\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-1.489\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.142\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDisease Type\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-72.406\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e45.570\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.154\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-1.589\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.118\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSurgical Segment\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-35.142\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e47.583\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.075\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-0.739\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.463\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMuscle Thickness\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-5.991\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3.717\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.155\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-1.612\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.112\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSubcutaneous Fat Thickness\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-2.809\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3.277\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.097\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-0.857\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.395\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIntraoperative Blood Loss\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.017\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.331\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.006\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-0.052\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.959\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePostoperative Drainage Volume on Day 1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.101\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.691\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.157\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.594\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.116\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHypertension\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-9.027\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e72.781\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.014\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-0.124\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.902\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDiabetes Mellitus\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-62.397\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e100.583\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.063\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-0.620\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.537\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSmoking\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-52.331\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e56.127\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.101\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-0.932\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.355\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAlcohol Consumption\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-15.192\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e54.244\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.028\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-0.280\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.780\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eASA Classification\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-30.336\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e52.442\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.066\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-0.578\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.565\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSurgical Time\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.779\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.388\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.264\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2.007\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.049*\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTranexamic Acid\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-9.634\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e42.821\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.020\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-0.225\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.823\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBMI\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e14.327\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e8.194\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.218\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.749\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.086\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreoperative PT\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e35.672\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e33.801\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.105\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.055\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.296\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreoperative APTT\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e7.346\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e6.961\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.109\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.055\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.296\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreoperative Fibrinogen\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-23.082\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e16.831\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.173\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-1.371\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.176\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreoperative D-Dimer\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-0.074\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.055\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.143\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-1.338\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.186\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreoperative HCT\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e14.501\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e7.087\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.289\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2.046\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.045*\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreoperative Platelets\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.440\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.755\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.598\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3.233\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.002**\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreoperative Total Protein\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-1.287\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3.676\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.048\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-0.350\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.728\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreoperative ALB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e21.206\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e8.024\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.384\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2.643\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.011*\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePostoperative Platelets\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-2.287\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.918\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.514\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-2.492\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.016*\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePostoperative Total Protein\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-24.916\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e8.043\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.450\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-3.098\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.003**\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePostoperative ALB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e18.543\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e11.624\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.253\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.595\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.116\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePostoperative D-Dimer\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.007\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.018\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.038\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.371\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.712\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3.184\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.912\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.231\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.665\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.101\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGender\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e-27.417\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e74.015\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-0.059\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-0.370\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.712\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"6\"\u003eNote: *\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05, **\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eUBE spine surgery has emerged as an innovative ultraminimally invasive technique, offering significant advantages in the treatment of lumbar spine diseases. These advantages include minimal surgical trauma, rapid postoperative recovery, and minimal disruption to spinal stability. Since 2000, HBL has garnered increasing attention from spinal surgeons. HBL typically occurs via two primary pathways: blood infiltration into tissue compartments or dead spaces and hemolysis. Erskine et al. [10] suggested that 60% of HBL results from blood infiltration, whereas 40% is attributed to hemolytic reactions. Conversely, Sehat et al. [7] proposed a ratio of 2:1 for blood infiltration\u0026ndash;related HBL versus hemolysis\u0026ndash;related HBL. Studies have consistently indicated that HBL is frequently underestimated in clinical practice. It can significantly increase TBL, exacerbate postoperative Hb decline, and increase the need for blood transfusions. If not properly managed, HBL may lead to a range of perioperative complications, including delayed wound healing, increased risk of infection, and prolonged postoperative recovery time [11].\u003c/p\u003e \u003cp\u003eWang et al. [12] reported that the average HBL during UBE spine surgery was 469.5\u0026thinsp;\u0026plusmn;\u0026thinsp;195.3 ml, accounting for 57.6% of the TBL. Guo et al. [13] reported an average HBL volume of 361.4\u0026thinsp;\u0026plusmn;\u0026thinsp;216.8 ml in patients who underwent UBE lumbar surgery. In our study, the average HBL was 277.40\u0026thinsp;\u0026plusmn;\u0026thinsp;232.92 ml in patients undergoing UBE for lumbar spine diseases. Similar to previous studies on HBL in spine surgery [14], the volume of HBL during surgery was significantly greater than that of VBL, which was much greater than anticipated. However, the risk factors for HBL in UBE surgery remain unclear. This study aimed to identify potential risk factors for HBL in UBE spine surgery to enhance perioperative blood loss management, reduce perioperative complications, and ensure patient safety. We retrospectively analysed the clinical information of 117 patients who underwent UBE surgery and employed Pearson or Spearman correlation analysis and multiple linear regression to identify the risk factors for HBL.\u003c/p\u003e \u003cp\u003ePearson correlation analysis revealed that the preoperative ALB level was positively correlated with HBL (r\u0026thinsp;=\u0026thinsp;0.425, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Xu et al. [15] demonstrated that in patients undergoing total joint arthroplasty (TJA), a 1 g/L decrease in the preoperative ALB level significantly increased the risk of perioperative blood transfusion (OR\u0026thinsp;=\u0026thinsp;1.63). This finding may be related to unmonitored but actual anaemia caused by HBL. Multiple linear regression analysis further indicated that low preoperative serum ALB levels are an independent risk factor for perioperative HBL. This may be attributed to low ALB levels causing extravasation of tissue fluid, inducing tissue edema, and compromising the integrity of the microcirculation, thereby increasing hidden bleeding from surgical wounds or damaged tissues [16]. Experiments have shown that exogenous ALB can reduce capillary leakage (e.g., a 67% reduction in pulmonary leakage) [17], indirectly supporting the mechanism by which low ALB levels exacerbate bleeding. These findings also suggest that the preoperative nutritional status of patients may significantly impact perioperative blood loss.\u003c/p\u003e \u003cp\u003ePrevious studies have reported that in minimally invasive surgeries, male patients tend to have greater HBL than do female patients [18], and they are also more likely to require blood transfusions postoperatively [19]. Some studies have suggested that female patients have lower HBL than male patients do, possibly due to the relatively smaller amount of bone resection and smaller back muscles in females. Other studies attributed this difference to the advantages of male patients in terms of body mass index and blood volume. Additionally, the increased incidence of osteoporosis in females reduces the blood supply in the bone marrow cavity, thereby decreasing blood loss during surgery [20]. However, our study did not find a correlation between sex and HBL, which may be due to the small sample size. Further investigations with larger sample sizes are needed to confirm the exact mechanisms and results.\u003c/p\u003e \u003cp\u003eMultiple linear regression analysis revealed that both preoperative and postoperative platelet counts are independent risk factors for HBL. The preoperative platelet count was positively correlated with HBL, likely because a higher preoperative platelet count reflects a hyperactive coagulation system. This hyperactivity can lead to platelet activation during tissue injury during surgery, promoting the formation of microthrombi. These microthrombi can obstruct the microcirculation, causing red blood cell rupture and Hb release, thereby exacerbating HBL [21]. Interestingly, the postoperative platelet count was negatively correlated with HBL, a finding that is consistent with the findings of several previous studies [22]. This may be because during HBL, blood components (including platelets) are retained in tissue spaces or destroyed. The postoperative decrease in platelet levels may reflect their extensive consumption in the hemostasis process.\u003c/p\u003e \u003cp\u003eWang et al. [12] reported that in UBE surgery, the higher the American Society of Anesthesiologists (ASA) classification is, the higher the HBL in patients. Moreover, some studies have shown that patients with ASA grade III HBL have significantly greater HBL than those with ASA grades I and II HBL [23]. This may be because, compared with ASA grade I patients, patients with ASA grades II to IV generally have poorer overall conditions and more comorbidities. In particular, some patients have poorer tolerance to surgery and anaesthesia, resulting in compromised coagulation system function compared with that of lower-grade patients, thereby increasing HBL [24]. However, our study did not reach the same conclusion, which may be because the majority of cases included in our study were ASA grades I and II, with very few ASA grade III cases. Further research is needed to confirm these results.\u003c/p\u003e \u003cp\u003ePearson or Spearman correlation analysis revealed that postoperative Hct was negatively correlated with HBL during UBE surgery. This may be related to the use of the Nadler formula to calculate HBL in this study [25]. This may also be because perioperative fluid administration can dilute the blood, leading to a decrease in Hct. However, this process may mask the actual loss of red blood cells, thereby contributing to HBL [26].\u003c/p\u003e \u003cp\u003eMultiple linear regression analysis revealed that surgical duration is an independent risk factor for HBL, a finding that is consistent with previous studies [27]. During UBE surgery, normal saline is typically used for irrigation to achieve a clear surgical field. Continuous irrigation with large amounts of fluid can flush out blood seeping from soft tissues and bone surfaces. A prolonged surgical duration is usually associated with more complex procedures and more extensive tissue exposure. Prolonged tissue traction may cause rupture of small blood vessels, and bleeding that is not promptly controlled during surgery can gradually accumulate as HBL. Surgeons should be vigilant about the possibility of excessive HBL during UBE surgery.\u003c/p\u003e \u003cp\u003eThe current study has several limitations. First, this was a retrospective study with a relatively small sample size. Future research should involve larger-scale prospective multicenter studies to validate our findings. Second, perioperative fluid administration was not strictly controlled, which may have affected the calculation of total perioperative blood loss. Third, the calculation of intraoperative blood loss was based on estimates by anesthesiologists, which may lack accuracy and introduce bias into the calculation of HBL. Finally, HBL is mostly estimated via the Gross formula, which is susceptible to errors from hemodilution due to intraoperative fluid administration and inaccuracies in drainage fluid collection. Additionally, considering that postoperative drainage may be affected by intraoperative irrigation, the calculations of VBL and HBL may have slight deviations, and the timing of drainage tube removal may also affect the HBL results. Therefore, high-quality observational and basic experimental studies are still needed to further investigate new risk factors for HBL in patients undergoing UBE treatment for lumbar spine diseases in the future.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis study demonstrates that patients undergoing UBE surgery for lumbar disc herniation or lumbar spinal stenosis experience varying degrees of HBL. HBL is correlated with TBL, VBL, drainage volume on the day of surgery, surgical duration, preoperative ALB, postoperative Hb, postoperative Hct, and postoperative total protein. Moreover, surgical duration, Hct, preoperative platelets, preoperative ALB, postoperative platelets, and postoperative total protein are independent risk factors for HBL in UBE surgery. Perioperative attention should be given to HBL and its risk factors, and appropriate management of these risk factors can help reduce the incidence of complications, hospital stay duration, healthcare costs, and financial burden on families for surgical patients.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eBMI\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003ebody mass index\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eHct\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003ehematocrit\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eALB\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003ealbumin\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003ePT\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eprothrombin time\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eAPTT\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eactivated partial thromboplastin time\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eTBL\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003etotal blood loss\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003ePBV\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003epatient blood volume\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eVBL\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003evisible blood loss\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eHBL\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003ehidden blood loss\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eASA\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eAmerican Society of Anesthesiologists\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eHb\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003ehemoglobin\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eMRI\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003emagnetic resonance imaging.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNone.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026rsquo; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eYPZ and CZC designed this study. JYH, GJW, LL and BL were involved in data collection. YPZ, GJW and WAQ analysed and interpreted the data. JYH and GJW performed the chart abstraction and revised the manuscript. JYH and YPZ were major contributors to the writing of the manuscript. All the authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNone.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and material\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used and analysed during the current study are available from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research was approved by the Ethics Committee of the PLA Joint Logistic Support Force. All procedures adhered to the relevant guidelines and principles of the Declaration of Helsinki. All participants provided written informed consent for participation.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eInformed consent\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eInformed consent was obtained from all participants in this research.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of\u0026nbsp;\u003c/strong\u003einterest\u003c/p\u003e\n\u003cp\u003eAll the authors declare that they have no potential conflicts of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical trial number\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eLiang J, Lian L, Liang S, et al. Efficacy and Complications of Unilateral Biportal Endoscopic Spinal Surgery for Lumbar Spinal Stenosis: A Meta-Analysis and Systematic Review. World Neurosurg 2022;159:e91-e102. 10.1016/j.wneu.2021.12.005\u003c/li\u003e\n\u003cli\u003ePark DY, Upfill-Brown A, Nora B, et al. Clinical outcomes and complications after biportal endoscopic spine surgery: a comprehensive systematic review and meta-analysis of 3673 cases. Eur Spine J 2023;32:2637-46. 10.1007/s00586-023-07701-9\u003c/li\u003e\n\u003cli\u003eElgafy H, Bransford RJ, McGuire RA, Dettori JR, Fischer D. Blood loss in major spine surgery: are there effective measures to decrease massive hemorrhage in major spine fusion surgery? Spine. 2010;35(9S):S47\u0026ndash;S56.\u003c/li\u003e\n\u003cli\u003eZhou Y, Fu X, Yang M, Ke S, Wang B, Li Z. Hidden blood loss and its possible risk factors in minimally invasive transforaminal lumbar interbody fusion. J Orthop Surg Res. 2020;15(1):1\u0026ndash;7.\u003c/li\u003e\n\u003cli\u003ePenninx BW, Pahor M, Cesari M, Corsi AM, Woodman RC, Bandinelli S, et al. Anemia is associated with disability and decreased physical performance and muscle strength in elderly individuals. J Am Geriatr Soc. 2004;52(5):719\u0026ndash;724.\u003c/li\u003e\n\u003cli\u003eZhou Y, Fu X, Yang M, Ke S, Wang B, Li Z. Hidden blood loss and its possible risk factors in minimally invasive transforaminal lumbar interbody fusion. J Orthop Surg Res. 2020 Sep 29;15(1):445.\u003c/li\u003e\n\u003cli\u003eSehat KR, Evans RL, Newman JH. Hidden blood loss following hip and knee arthroplasty. Correct management of blood loss should take hidden loss into account. J Bone Joint Surg. 2004;86:561\u0026ndash;565.\u003c/li\u003e\n\u003cli\u003eGross J.B. Estimating allowable blood loss: corrected for dilution. Anesthesiology. 1983;58:277\u0026ndash;280.\u003c/li\u003e\n\u003cli\u003eYu H., Liu M., Zhang X., Ma T., Yang J., Wu Y., Wang J., Li M., Wang J., Zeng M., Zhang L., Jin H., Liu X., Li S., Peng Y. The effect of tranexamic acid on intraoperative blood loss in patients undergoing brain meningioma resections: study protocol for a randomized controlled trial. PLoS One. 2023;18\u003c/li\u003e\n\u003cli\u003eErskine JG, Fraser C, Simpson R, et al. Blood loss with knee joint replacement. J Royal College Surgeons Edinburgh. 1981;26:295\u0026ndash;297.\u003c/li\u003e\n\u003cli\u003eFoss NB, Kehlet H. Hidden blood loss after surgery for hip fracture. J Bone Joint Surg Br. 2006;88(8):1053\u0026ndash;1059.\u003c/li\u003e\n\u003cli\u003eWang H, Wang K, Lv B, et al. Analysis of risk factors for perioperative hidden blood loss in unilateral biportal endoscopic spine surgery: a retrospective multicenter study. J Orthop Surg Res 2021;16:559.\u003c/li\u003e\n\u003cli\u003eGuo S, Tan H, Meng H, et al. Risk factors for hidden blood loss in unilateral biportal endoscopic lumbar spine surgery. Front Surg 2022;9:966197.\u003c/li\u003e\n\u003cli\u003eJiang HW, Chen CD, Zhan BS, Wang YL, Tang P, Jiang XS. Unilateral biportal endoscopic discectomy versus percutaneous endoscopic lumbar discectomy in the treatment of lumbar disc herniation: A retrospective study. J Orthop Surg Res. (2022) 17:30. 10.1186/s13018-022-02929-5\u003c/li\u003e\n\u003cli\u003eXu, S., Xiong, X., Li, T., Hu, P., \u0026amp; Mao, Q. (2024). Preoperative low serum albumin increases the rate of perioperative blood transfusion in patients undergoing total joint arthroplasty: propensity score matching. BMC musculoskeletal disorders, 25(1), 695.\u003c/li\u003e\n\u003cli\u003eWard, E. S., Gelinas, D., Dreesen, E., Van Santbergen, J., Andersen, J. T., Silvestri, N. J., Kiss, J. E., Sleep, D., Rader, D. J., Kastelein, J. J. P., Louagie, E., Vidarsson, G., \u0026amp; Spriet, I. (2022). Clinical Significance of Serum Albumin and Implications of FcRn Inhibitor Treatment in IgG-Mediated Autoimmune Disorders. Frontiers in immunology, 13, 892534.\u003c/li\u003e\n\u003cli\u003eAstapenko, D., Zrzavecky, M., Gorskaja, D., Hyspler, R., Ticha, A., Radochova, V., Lehmann, C., Malbrain, M. L. N. G., Cerny, V., \u0026amp; Hahn, R. G. (2024). Modulation of the capillary leakage by exogenous albumin in a rat model of endothelial glycocalyx damage. Clinical hemorheology and microcirculation, 86(4), 509\u0026ndash;517.\u003c/li\u003e\n\u003cli\u003eWang JQ, et al. Hidden blood loss and the influential factors after intramedullary nail fixation of extra-articular tibial fractures - a retrospective cohort study. Injury. 2020;51(6):1382\u0026ndash;1386.\u003c/li\u003e\n\u003cli\u003ePrasad N, et al. Blood loss in total knee arthroplasty: an analysis of risk factors. Int Orthop. 2007;31(1):39\u0026ndash;44.\u003c/li\u003e\n\u003cli\u003eXu D, Liu M, Lou W, Li M, Xiao J, Wu H, Zhuang Y, Chen J. Hidden blood loss and the influential factors after minimally invasive treatment of posterior pelvic ring injury with sacroiliac screw. Trials. 2024 May 6;25(1):305.\u003c/li\u003e\n\u003cli\u003eZhou S, A J, Xu X, Zhao H, Guo T, Hu P, Xu Z, Li Z, Hao Y. Comparison of surgical invasiveness and hidden blood loss between unilateral double portal endoscopic lumbar disc extraction and percutaneous endoscopic interlaminar discectomy for lumbar spinal stenosis. J Orthop Surg Res. 2024 Nov 21;19(1):778.\u003c/li\u003e\n\u003cli\u003eHaibier A, Yusufu A, Lin H, Kayierhan A, Abudukelimu Y, Abudurexiti T. Efficacy and Safety Study of Low-Molecular-Weight Heparin and Fondaparinux Sodium After Hip Arthroplasty: A Retrospective Cohort Study. Orthop Res Rev. 2023 Nov 24;15:253-261.\u003c/li\u003e\n\u003cli\u003eLei F, Li Z, He W, et al. Hidden blood loss and the risk factors after posterior lumbar fusion surgery: a retrospective study. Medicine (Baltimore) 2020;99:e20103.\u003c/li\u003e\n\u003cli\u003eWang H, Wang K, Lv B, Li W, Fan T, Zhao J, Kang M, Dong R, Qu Y. Analysis of risk factors for perioperative hidden blood loss in unilateral biportal endoscopic spine surgery: a retrospective multicenter study. J Orthop Surg Res. 2021 Sep 15;16(1):559.\u003c/li\u003e\n\u003cli\u003eZhou J, Ye M, Jiang W, Zhu X. Quantification and influencing factors of perioperative hidden blood loss in patients undergoing laparoscopic ovarian cystectomy for benign ovarian tumours. J Obstet Gynaecol. 2022 Oct;42(7):3181-3186.\u003c/li\u003e\n\u003cli\u003eChon SB, Lee MJ, Oh WS, Park YJ, Kwon JM, Kim K. A simple and novel equation to estimate the degree of bleeding in haemorrhagic shock: mathematical derivation and preliminary \u003cem\u003ein vivo\u003c/em\u003e validation. Korean J Physiol Pharmacol. 2022 May 1;26(3):195-205.\u003c/li\u003e\n\u003cli\u003eZhang R, Xing F, Yang Z, Lin G, Chu J. Analysis of risk factors for perioperative hidden blood loss in patients undergoing transforaminal lumbar interbody fusion. J Int Med Res. (2020) 48:300060520937848. 10.1177/0300060520937848\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Unilateral biportal endoscopy, Hidden blood loss, Degenerative lumbar disease, Risk factors, Perioperative management","lastPublishedDoi":"10.21203/rs.3.rs-6830206/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6830206/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eTo explore the risk factors associated with hidden blood loss (HBL) during unilateral biportal endoscopy (UBE) for degenerative lumbar diseases, this study provides a theoretical foundation for the precise prevention and management of HBL and related complications in clinical practice.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eA retrospective analysis was conducted on 87 patients who underwent single-segment UBE surgery for lumbar degeneration from June 2022 to June 2023. Detailed records were maintained for demographic characteristics, laboratory indicators and surgical data. HBL was calculated via the Sehat formula (HBL\u0026thinsp;=\u0026thinsp;total blood loss (TBL) - visible blood loss (VBL)). Pearson and Spearman correlation analyses were initially employed to identify factors associated with HBL, followed by multivariate linear regression modelling to identify independent risk factors.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eThe mean HBL was 227.40\u0026thinsp;\u0026plusmn;\u0026thinsp;232.92 mL. HBL was positively correlated with surgical time, postoperative drainage volume, and TBL (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05) but negatively correlated with postoperative haemoglobin (Hb), haematocrit (Hct), and total protein (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Multivariate linear regression analysis revealed that surgical time (P\u0026thinsp;=\u0026thinsp;0.049), preoperative platelet count (P\u0026thinsp;=\u0026thinsp;0.002), postoperative platelet count (P\u0026thinsp;=\u0026thinsp;0.016), preoperative Hct (P\u0026thinsp;=\u0026thinsp;0.045), preoperative albumin (ALB) level (P\u0026thinsp;=\u0026thinsp;0.011), and postoperative total protein level (P\u0026thinsp;=\u0026thinsp;0.003) were independent risk factors for HBL.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003eHBL in UBE surgery for degenerative lumbar diseases is a significant concern that should not be overlooked. Prolonged surgical time, elevated preoperative platelets, low preoperative ALB levels, and low postoperative total protein levels may exacerbate HBL. These risk factors should be closely monitored during the perioperative period to optimize patient management, reduce postoperative complications, and improve overall prognosis.\u003c/p\u003e","manuscriptTitle":"Risk Factor Analysis of Hidden Blood Loss in Unilateral Biportal Endoscopy for Degenerative Lumbar Diseases","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-12 04:42:08","doi":"10.21203/rs.3.rs-6830206/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"dba2b2e3-a1ea-4867-b240-58ec9da65272","owner":[],"postedDate":"June 12th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-07-18T13:53:52+00:00","versionOfRecord":[],"versionCreatedAt":"2025-06-12 04:42:08","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6830206","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6830206","identity":"rs-6830206","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}