The Effect of Body Mass Index on Vasopressor Use, Block Dynamics, and Hemodynamic Responses in Urological Surgery Undergoing Spinal Anesthesia

The Effect of Body Mass Index on Vasopressor Use, Block Dynamics, and Hemodynamic Responses in Urological Surgery Undergoing Spinal Anesthesia | 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 The Effect of Body Mass Index on Vasopressor Use, Block Dynamics, and Hemodynamic Responses in Urological Surgery Undergoing Spinal Anesthesia Fadime Tosun, Ufuk Karbaş, Bedreddin Kalyenci, Zeliha Bozkurt, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8673299/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 While the effects of body mass index (BMI) on intrathecal local anesthetic spread and hemodynamic responses during spinal anesthesia are well-defined in obstetric surgery, studies directly examining this relationship in urological surgeries where spinal anesthesia is commonly performed are limited. Therefore, this study aimed to evaluate the effect of BMI on vasopressor requirements and block characteristics after spinal anesthesia. Methods This prospective, observational study included 120 patients undergoing elective urological surgery under spinal anesthesia. Patients were divided into two groups according to BMI: BMI < 27.5 kg/m² (Group L) and BMI ≥ 27.5 kg/m² (Group H). The groups were compared in terms of demographic data, surgical duration, spinal block characteristics, hemodynamic changes, and ephedrine use. Results Three patients were excluded from the analysis due to spinal anesthesia failure, and a total of 117 patients were evaluated (Group L: n = 60; Group H: n = 57). Total intraoperative ephedrine requirement was significantly higher in Group H (p < 0.001). The maximum sensory block level was significantly more cephalic in Group H compared to Group L (T7.42 ± 2.63 vs T8.97 ± 1.99, p < 0.001). No significant differences were found between the groups in terms of time to reach maximum block, time to two-segment sensory block regression, time to reach motor block 3, and motor block recovery time (p > 0.05). Although basal systolic arterial pressure was higher in Group H (p = 0.019), hemodynamic parameters after spinal anesthesia were similar between the groups. Conclusions In the high BMI patient group, a significant effect was observed on vasopressor requirement, block level, and surgical duration during spinal anesthesia procedures. These findings highlight the need for comprehensive preoperative planning, determination of appropriate anesthesia strategies, and careful hemodynamic monitoring in obese patients. Body mass index ephedrine sensory block hemodynamic response Figures Figure 1 Figure 2 Background Due to the rapid increase in obesity prevalence, it has become a significant public health problem on a global scale today [ 1 ]. Accordingly, the increasing rate of obesity in the operating room makes it important to investigate the effect of obesity on spinal anesthesia [ 2 , 3 ]. In spinal anesthesia applications, the level and duration of sensory and motor block are affected by numerous factors, including patient characteristics such as age, gender, height, weight and body mass index (BMI), as well as the dose, temperature and pharmacological properties of the intrathecally administered local anesthetic agent, cerebrospinal fluid (CSF) volume and spinal anatomy [ 3 – 5 ]. However, the literature reports inconsistent and sometimes contradictory results regarding the effects of these variables on spinal anesthesia [ 6 , 7 ]. Most of the information on regional anesthesia in obese patients in the current literature has been obtained from obstetric surgeries [ 2 , 8 , 9 ]. This makes the generalizability of obstetric data to different surgical groups debatable. This is because pregnancy-related anatomical landmarks can become blurred, lung volumes decrease, and the aorta and inferior vena cava can be compressed, leading to dilation of the epidural veins and reduction of the epidural space [ 2 ]. Although spinal anesthesia is commonly used in urological surgeries, studies directly examining anesthetic outcomes related to BMI are quite limited. However, it is thought that the findings obtained from lower abdominal and orthopedic surgeries performed under spinal anesthesia may be partially applicable to urological surgeries due to similar pharmacodynamic and physiological mechanisms. However, this assumption needs to be supported by data specific to the urological patient population [ 3 , 4 , 10 ]. It is suggested that pathophysiological changes in obese individuals, such as increased intra- abdominal pressure, epidural venous distension, and relative decrease in CSF volume, may affect the cephalic spread of intrathecal local anesthetics [ 2 , 7 ]. These mechanisms may be associated with higher block levels and significant hemodynamic changes. However, the literature lacks clear results regarding the effect of obesity on the incidence of hypotension and vasopressor requirements after spinal anesthesia. This uncertainty makes it difficult to determine the optimal spinal anesthesia management in obese patients. The aim of this study is to comparatively evaluate the vasopressor requirements, sensory and motor block characteristics, hemodynamic and responsiveness of spinal anesthesia administered during urological surgery in patients grouped according to BMI. The study aims to fill the existing knowledge gap regarding spinal anesthesia applications in obese patients and contribute to the development of individualized anesthesia strategies to improve patient safety in clinical practice. Methods Study Design and Ethical Approval This study was planned as a prospective, observational study. Ethical approval was obtained from the Non-Interventional Clinical Research Ethics Committee of Adıyaman University Faculty of Medicine with decision number 2022/4–20 dated 20/04/2022. The research was conducted in accordance with the principles of the Helsinki Declaration. All subjects were informed about the purpose and methods of the study and their written informed consent was obtained. The primary outcome of the study was the total intraoperative vasopressor requirement, defined as the cumulative dose of intravenous ephedrine (mg) administered to treat hypotension during surgery. Secondary outcomes included: Maximum sensory block level, defined as the highest thoracic dermatome reached after spinal anesthesia. Hemodynamic responses, defined as noninvasive systolic arterial pressure (SBP), diastolic arterial pressure (DBP), and heart rate (HR) measured at baseline and at 5- minute intervals after spinal anesthesia. Two-segment sensory regression time, defined as the time (minutes) from the maximal sensory block level to regression of two dermatomes. Time to reach maximum sensory block, defined as the time (minutes) from intrathecal injection to the highest sensory level achieved. Time to achieve complete motor block, defined as the time (minutes) required to reach Bromage score 3. Motor block recovery time, defined as the time (minutes) to the return of the first detectable motor activity. Patient Selection and Grouping A total of 120 patients aged 18 years or older, classified as American Society of Anesthesiologists (ASA) physical status I–II and scheduled for elective urological surgery, were included in the study. Patients who declined to participate, those with contraindications to spinal anesthesia, those who required conversion to general anesthesia intraoperatively, patients with height 190 cm, and those with a body mass index (BMI) < 18.5 kg/m² were excluded in order to minimize the potential impact of extreme anthropometric variations on spinal block characteristics. Body mass index was calculated as body weight divided by the square of height (kg/m²) [ 11 ]. In the present study, a BMI cutoff value of 27.5 kg/m² was selected based on World Health Organization obesity criteria [ 12 ] and prior evidence demonstrating that BMI may exert clinically relevant effects on intrathecal local anesthetic spread and cerebrospinal fluid dynamics [ 4 , 10 ]. Accordingly, patients with BMI < 27.5 kg/m² were assigned to Group L (normal weight), whereas those with BMI ≥ 27.5 kg/m² were classified as Group H (obese). A total of 60 patients were planned for inclusion in each group. The enrollment and allocation process is presented in the STROBE flow diagram (Fig. 1 ). Anesthesia Procedure Spinal anesthesia was administered to all patients in a sitting position under aseptic conditions. Dural puncture was performed in the L4–5 intervertebral space, midline, using a 25-gauge spinal needle. Following successful puncture, 3 ml of 0.5% hyperbaric bupivacaine (Bupivon Spinal Heavy 0.5%®, Onfarma, Samsun, Turkey) was injected intrathecally at a rate of approximately 1 ml/4–5 seconds. Barbotage was not applied in any case. Spinal anesthesia was limited to a maximum of three attempts; patients who did not achieve successful anesthesia in three attempts were excluded from the study. Block Assessment Following spinal anesthesia, patients were immediately placed in the supine position. Sensory block level was assessed every 2 minutes using a pinprick test, and motor block level was assessed using the modified Bromage scale (0: hip, knee, and foot free movement; 1: knee and foot movements present, no straight leg raises; 2: no knee flexion; 3: no foot and knee movement). For each patient, the maximum sensory block level (thoracic level), time to reach the maximum sensory block level, time to reach Bromage level 3 motor block, time to two-segment sensory block regression, motor block recovery time, surgical duration, and total ephedrine dose administered were recorded. Hemodynamic Monitoring and Fluid Management Systolic (SBP) and diastolic arterial pressures (DBP) and heart rate (HR) were recorded using non-invasive methods, as baseline values before spinal anesthesia and every 5 minutes after the block. Ringer's lactate solution was administered at a maintenance dose of 8 ml/kg during the first 10 minutes of spinal anesthesia and 4 ml/kg/hour during surgery. Intraoperative hypotension and ephedrine administration were managed based on a standard protocol based on predefined mean arterial pressure thresholds. The protocol defines hypotension as a drop in systolic arterial pressure below 90 mmHg or a decrease of more than 30% from baseline, and recommends a response with a 5 mg intravenous bolus of ephedrine. This minimizes inter-operator variability and performance bias, ensuring consistency and reliability in the treatment approach. Postoperative Monitoring Sensory and motor block levels of patients admitted to the recovery room were evaluated and recorded every 10 minutes. Sample Size Data from the study by Nani et al. [ 13 ] were used to determine the sample size for our study. When the data from the groups were compared using the G*power 3.1.9.7 program, the effect size was calculated as 0.48 [ 14 ]. The number of patients to be included in the study was calculated as 108, with at least 54 in each group, with a 5% margin of error (α = 0.05) and 80% power (power (1- β) = 0.80). However, considering the possibility of exclusion of 5–10% of patients, and taking into account possible protocol exclusion, failed spinal block, or conversion to intraoperative general anesthesia, it was decided to include 60 patients in each group. Statistical Analysis Descriptive statistics of the data included mean, standard deviation, median, minimum, maximum, frequency, and ratio values. The distribution of variables was measured using the Kolmogorov-Smirnov and Shapiro-Wilk tests. The independent samples t-test was used for the analysis of quantitative independent data with a normal distribution. The Mann-Whitney U test was used for the analysis of quantitative independent data with a non-normal distribution. The chi-square test was used for the analysis of qualitative independent data, and the Fischer test was used when the chi-square test conditions were not met. The relationship between two variables was assessed appliying Pearson’s correlation analysis. Multivariable linear regression analysis was performed for multivariate analyses. All statistical analyses were conducted using SPSS 18.0. Results were evaluated using two-sided tests with a 95% confidence interval. Results The study was planned with 60 patients in each group. However, in Group H, general anesthesia was applied in three cases where spinal anesthesia was unsuccessful, and these patients were excluded from the study and analysis. The total number of patients accepted into the study was determined to be 117; 60 of these were patients with BMI < 2 7.5 kg/m² (Group L) and 57 were patients with BMI ≥ 27.5 kg/m² (Group H) (Fig. 1 ). The baseline demographic and surgical characteristics of the groups are summarized in Table 1 . Patients in Group H were significantly older than those in Group L (46.38 ± 14.19 vs. 38.08 ± 13.95 years, p = 0.002). Body weight and BMI values were significantly higher in Group H, as expected (p < 0.001 for both). No significant difference was observed between the groups in terms of height (p = 0.457). Surgical duration was significantly longer in Group H compared to Group L (46.50 ± 21.58 minutes vs 37.40 ± 10.69 minutes, p = 0.004). Gender distribution and type of surgical procedure were not comparable between the groups (p > 0.05). Table 1 Demographic characteristics and surgical data Group L (mean ± sd) (n = 60) Group H (mean ± sd) (n = 57) p Age(year) 38.08 ± 13.95 46.38 ± 14.19 0.002 t Weight (kg) 68.95 ± 11.37 97.13 ± 13.96 < 0.001 t Height(cm) 168.67 ± 8.74 169.87 ± 8.88 0.457 t BMI (kg/m 2 ) 24.14 ± 2.91 33.80 ± 5.50 0.05 t Surgery duration (min) 37.4 ± 10.69 46.50 ± 21.58 0.004 t Type of Surgery (Upper Urinary/Lower Urinary) 48/12 42/18 0.292 c Min;minute t Independent sample t test c Chi-square test p < 0.05 is taken as statistically significant The incidence of failed spinal and postdural headaches did not differ significantly between the groups (p = 0.079 and p = 0.55, respectively) (Table 2 ). Table 2 Intraoperative and postoperative complications Group L (n = 60) Group H (n = 57) p Failed Spinal Anaesthesia + 0 3 0.079 c - 60 57 Postdural puncture headache + 2 1 0.55 c - 58 59 c Chi-square test p < 0.05 is taken as statistically significant The block characteristics related to spinal anesthesia are presented in Table 3 . Ephedrine use was significantly higher in Group H compared to Group L (p < 0.001). The maximum sensory block level was observed at significantly higher dermatomal levels in Group H (7.42 ± 2.63 vs 8.97 ± 1.99, p < 0.001). There were no significant differences between the groups in terms of sensory block regression time (two levels), time to reach maximum block, motor block development time, and motor block recovery time (p > 0.05). Table 3 Spinal block characteristics Group L (mean ± sd) (n = 60) Group H (mean ± sd) (n = 57) p Ephedrine (mg) 0.33 ± 1.81 3.75 ± 4.93 < 0.001 t Maximum sensory block level (thoracic dermatome) 8.97 ± 1.99 7.42 ± 2.63 < 0.001 m Time until maximum sensory block is reached (min) 5.18 ± 1.53 5.05 ± 1.24 0.602 m Sensory block regression time (2 levels) (min) 57.43 ± 12.88 59.65 ± 13.58 0.482m Time to reach motor block 3 (min) 7.78 ± 2.19 7.33 ± 2.46 0.292 m Motor block start-up time (min) 175.08 ± 20.22 167.83 ± 33.41 0.153 m t Independent sample test / m Mann-whitney u test p 0.05). Basal systolic arterial pressure was significantly higher in Group H compared to Group L (146.53 ± 17.87 vs 139.02 ± 16.70 mmHg, p = 0.019). Following spinal anesthesia, systolic and diastolic arterial pressure values measured between 5 and 30 minutes did not show a significant difference between the groups (p > 0.05). While there were significant differences between the groups in terms of age and surgical duration, a multivariable analysis was performed to evaluate the independent effect of BMI on intraoperative ephedrine requirements. Multivariable linear regression analysis demonstrated that BMI was independently associated with a significant increase in the amount of ephedrine required during surgery (B = 3.015, 95% CI: 1.633–4.396, p < 0.001). Age showed a weak but statistically significant association with ephedrine use (B = 0.048, 95% CI: 0.001–0.096, p = 0.046). In contrast, surgical duration was not significantly associated with intraoperative ephedrine requirements (B = 0.006, 95% CI: −0.034–0.045, p = 0.78) (Table 4 ). Table 4 Multivariable linear regression analysis for intraoperative ephedrine use B (SE) p 95% CI for B (multivariable) BMI group (H vs L) 3.015 (0.698) < 0.001 1.633 to 4.396 Age 0.048 (0.024) 0.046 0.001 to 0.096 Surgery duration 0.006(0.02) 0.780 0.034 to 0.045 Dependent variable: intraoperative ephedrine use (dose/amount as recorded). B indicates the unstandardized regression coefficient; SE indicates standard error; CI indicates confidence interval. P < 0.05 was considered statistically significant Discussion This study demonstrates that body mass index is an important determinant of both spinal block characteristics and vasopressor requirement in patients undergoing urological surgery under spinal anesthesia. Unlike most previous studies that primarily focused on obstetric populations, our work provides evidence from a non-obstetric surgical group, thereby improving the generalizability of current knowledge. In this study, it was found that the mean age of patients in Group H was significantly higher. This finding is consistent with epidemiological data reporting that the prevalence of obesity increases with age and supports the consistency of the demographic distribution of our study with the literature [ 11 ]. In addition, while the longer surgical time in Group H shows the intraoperative technical difficulties of obesity, the existence of studies in the literature that did not find a significant difference in surgical time between obese and non-obese patients suggests that the effect of obesity on surgical time may be heterogeneous [ 4 , 15 ]. Although numerical differences were observed between groups in terms of the incidence of spinal anesthesia failure and postdural puncture headache (PDPH), these differences did not reach statistical significance. Literature highlights findings suggesting that obesity can lead to technical difficulties in spinal anesthesia procedures; in this context, mechanisms such as obesity reducing the capacity to highlight anatomical landmarks, making the needle advancement process more difficult, and altering cerebrospinal fluid (CSF) flow dynamics have been proposed [ 2 , 16 ]. These factors may potentially increase the incidence of spinal anesthesia failure and PDPH. However, it is thought that when performed by experienced anesthesiologists, the impact of these difficulties on adverse outcomes can be significantly reduced. On the other hand, there are inconsistent findings in the literature regarding the relationship between BMI and the incidence of PDPH. For example, although two separate studies (including 464 and 315 female participants) showed that BMI had no significant effect on the development of PDPH [ 17 , 18 ], the study by Peralta et al. suggested that obesity may be protective against the development of PDPH. This suggestion was explained by the assumption that obesity could limit CSF leakage by increasing intraabdominal fat tissue, thereby increasing epidural pressure and reducing the intrathecal–epidural pressure gradient [ 19 ]. In the retrospective study by Azzi et al., the incidence of PDPH was examined in patients who underwent regional anesthesia for a total of 10,051 surgical procedures, and it was found that the frequency of PDPH was higher in patients with low BMI [ 20 ]. Franz et al. and Hashemi et al. found an inverse and significant relationship between BMI and PDPH [ 21 , 22 ]. This finding suggests that BMI may play a potential risk factor for the development of PDPH, however, the clinical significance of this relationship requires further evaluation. Additionally, this study aimed to reduce the risk of PDPH based on needle type; all patients received a standard 25G Quincke spinal needle. Although baseline systolic arterial pressure was higher in obese patients, the overall hemodynamic course after spinal anesthesia was comparable between groups. This may reflect early recognition and treatment of hypotension according to a standardized protocol. Nevertheless, the significantly higher vasopressor requirement in the obese group indicates that hemodynamic instability may be more likely if preventive strategies are not applied. Similarly, to Elmeliegy et al., Nani et al. reported that more pronounced hemodynamic changes may develop in obese patients and that the need for vasopressors increases to maintain stable hemodynamics, and these findings are consistent with the results of our study [ 13 , 23 ]. In contrast, studies by Kim et al. and Ngaka et al. reported no statistically significant difference between obese and non-obese groups in terms of ephedrine consumption and hypotension [ 9 , 10 ]. It is thought that these differences in the literature may be related to the doses of local anesthetics used, the characteristics of the patient populations (e.g., pregnancy status), and methodological heterogeneity in the study designs [ 8 , 9 , 24 ]. Another important finding is that obese patients achieved significantly higher sensory block levels. This has direct clinical implications, as excessive cephalad spread increases the risk of high spinal block and cardiorespiratory compromise. Taivainen et al. showed that higher thoracic sensory block levels were achieved in obese patients after isobaric bupivacaine administered at the L3-4 or L4-5 level of the spinal space [ 7 ]. Similarly, Hogan et al. demonstrated with magnetic resonance imaging that CSF volume is related to body posture and intraabdominal pressure, and that these changes can significantly affect the cranial spread of intrathecal drugs [ 25 ]. However, it is thought that anatomical and physiological changes associated with obesity, such as increased intra-abdominal pressure, epidural venous distension, and decreased CSF volume, contribute to the sensory block level reaching more cephalic dermatomes by altering the distribution of local anesthetics in the CSF [ 7 , 25 ]. Although data on the maximum sensory block level are heterogeneous in the literature, Elmeliegy et al. reported that the maximum sensory block level was T5 in patients with low BMI, while it increased to T3 in patients with high BMI [ 23 ]. In contrast, Kim et al. reported that the highest sensory block level was T7 in both obese and non-obese groups [ 10 ]. Furthermore, a retrospective cohort study of 5,015 female patients found that high spinal block was significantly different in the obese group [ 8 ]. In this study, the maximum sensory block level was determined as T8.97 ± 1.99 in Group L and T7.42 ± 2.63 in Group H, and this difference was found to be statistically significant. Therefore, careful dose selection, patient positioning, and close monitoring are particularly important in this population. Despite higher block levels, the temporal profile of spinal anesthesia was similar between groups, suggesting that BMI primarily affects block height rather than block duration. Hosseinzadeh et al. reported that the time to reach the maximum sensory block level was shorter in obese patients compared with non-obese individuals [ 4 ]. In contrast, Elmeliegy et al. demonstrated that patients with higher BMI exhibited a prolonged sensory block regression time, whereas the time to achieve a Bromage score of 3 and the regression time of motor block were shorter [ 23 ]. In the present study, although the temporal profile of spinal anesthesia tended to be slightly shorter in the obese group, these differences did not reach statistical significance. Comparative evaluations of the intrathecal spread and sensory block levels of local anesthetic solutions with different baricities have demonstrated that a decrease in intrathecal solution baricity is associated with a significant increase in cephalad spread and maximum sensory block level. In parallel, it has been reported that ephedrine requirements are 1.83-fold and 3.0-fold higher with isobaric and hypobaric solutions, respectively, compared with hyperbaric solutions [ 26 ]. To minimize the potential confounding effects of these variables on block height, the same dose and baricity of the local anesthetic were used in both groups in the present study. This approach was intended to more precisely isolate and reflect BMI-related differences in the observed outcomes. Clinical implications In patients with elevated body mass index, spinal anesthesia should be managed with anticipation of higher sensory block levels and increased vasopressor requirements. Early availability of vasopressors, vigilant hemodynamic monitoring, and individualized anesthetic strategies may reduce the risk of hypotension-related complications in this population. Limitations This study has some limitations. Firstly, although the local anesthetic dose and application technique used in spinal anesthesia procedures were standardized, technical factors such as operator experience, small variations in patient position during the procedure, and subjective differences in determining the spinal range could not be fully controlled. These variables may have potential effects on intrathecal drug delivery and block characteristics. Secondly, although initially planned for 60 patients in both groups, the sample size of Group H was relatively reduced due to the exclusion of three patients from the study because of spinal anesthesia failure in the high BMI group. This may have limited the statistical power of the study, particularly in terms of rare complications (such as spinal anesthesia failure and PDPH), and may have contributed to the failure of the observed numerical differences between the groups to reach statistical significance. Furthermore, the study was conducted in a single center and encompassed a specific surgical patient population. Therefore, the generalizability of the findings to different surgical procedures, different patient profiles, and multicenter applications may be limited. Conclusion The clinical significance of this study lies in demonstrating that body mass index is not merely a demographic characteristic but an important factor influencing intraoperative hemodynamic management during spinal anesthesia. The more cephalad spread of maximum sensory block and the increased vasopressor requirement observed in obese patients suggest that this population may require more meticulous anesthetic management. Declarations Ethics approval and consent to participate This study was designed as a prospective observational study. Ethical approval was obtained from the Non-Interventional Clinical Research Ethics Committee of Adıyaman University Faculty of Medicine (Decision No: 2022/4-20, Date: 20 April 2022). The study was conducted in accordance with the principles of the Declaration of Helsinki. Written informed consent was obtained from all participants prior to enrollment. Consent for publication Not applicable. Availability of data and materials The datasets generated and/or analyzed during the current study are available from the corresponding author upon reasonable request. Competing interests The authors declare that they have no conflict of interest relevant to this study. Funding This study did not receive any specific funding from public, commercial, or not-for-profit funding agencies. Authors’ contributions FT and BK conceived and designed the study. FT, BK and DY collected the data. UK performed the statistical analysis. FT and UK interpreted the data and drafted the manuscript. 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Effect of body mass index on anesthesia characteristics and vasopressor requirements during spinal anesthesia for elective cesarean section. Open J Anesthesiol. 2020;10:141–52. 10.4236/ojanes.2020.104014 . Harten JM, Boyne I, Hannah P, Varveris D, Brown A. Effects of a height- and weight-adjusted dose of local anaesthetic for spinal anaesthesia for elective Caesarean section. Anaesthesia. 2005;60(4):348–53. 10.1111/j.1365-2044.2005.04113.x . Hogan QH, Prost R, Kulier A, Taylor ML, Liu S, Mark L. Magnetic resonance imaging of cerebrospinal fluid volume and the influence of body habitus and abdominal pressure. Anesthesiology. 1996;84(6):1341–9. 10.1097/00000542-199606000-00010 . Loubert C, Hallworth S, Fernando R, Columb M, Patel N, Sarang K, et al. Does the baricity of bupivacaine influence intrathecal spread in the prolonged sitting position before elective cesarean delivery? A prospective randomized controlled study. Anesth Analg. 2011;113(4):811–7. 10.1213/ANE.0b013e3182288bf2 . 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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-8673299","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":592033769,"identity":"9628fb04-757d-4928-8cf9-9c635a495bde","order_by":0,"name":"Fadime Tosun","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA6klEQVRIiWNgGAWjYBAC9gYGgwNQNuMDIMHDR0gLzwGwFgMQmxlE8rARo4UBqoVNAkwS1MJ+eOOhGxV/5ORn5B6r/JpjJ8PGwPzw0Q18WnjSCg7nnDEwNriRl3Zbdlsy0GFsxsY5eLTYM+QYHM5tM0jcIJFjdltyGzNQCw+bND4tPPxvgFr+GSTOn5FjViy5rZ4ILRIgWxoMEhtu5Jgxftx2mBgtz4B+OWZsbHDmjbE047bjPGzMBPzCw5+8+XNOjZycfHuO4cef26rt+dmbHz7GpwUFMPOASWKVgwDjD1JUj4JRMApGwYgBAKihROuF3djNAAAAAElFTkSuQmCC","orcid":"","institution":"Adıyaman University","correspondingAuthor":true,"prefix":"","firstName":"Fadime","middleName":"","lastName":"Tosun","suffix":""},{"id":592033771,"identity":"e1788c77-9f15-4e61-ae0a-fcf981e079d2","order_by":1,"name":"Ufuk Karbaş","email":"","orcid":"","institution":"Adıyaman University","correspondingAuthor":false,"prefix":"","firstName":"Ufuk","middleName":"","lastName":"Karbaş","suffix":""},{"id":592033773,"identity":"0998aa6c-5c8e-4b0e-9c3a-25062fb6d7ac","order_by":2,"name":"Bedreddin Kalyenci","email":"","orcid":"","institution":"Adıyaman University","correspondingAuthor":false,"prefix":"","firstName":"Bedreddin","middleName":"","lastName":"Kalyenci","suffix":""},{"id":592033774,"identity":"36343e59-e44c-4f6f-aa54-b24128508f77","order_by":3,"name":"Zeliha Bozkurt","email":"","orcid":"","institution":"Adıyaman University","correspondingAuthor":false,"prefix":"","firstName":"Zeliha","middleName":"","lastName":"Bozkurt","suffix":""},{"id":592033775,"identity":"7229f322-2c2c-42e2-9ceb-323f2a6e9e1d","order_by":4,"name":"Damla Yılmaz","email":"","orcid":"","institution":"Adıyaman University","correspondingAuthor":false,"prefix":"","firstName":"Damla","middleName":"","lastName":"Yılmaz","suffix":""}],"badges":[],"createdAt":"2026-01-22 21:38:16","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8673299/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8673299/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":102839721,"identity":"864c115e-8da5-4260-af5c-bb78420f4b4e","added_by":"auto","created_at":"2026-02-17 11:47:33","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":177480,"visible":true,"origin":"","legend":"\u003cp\u003eSTROBE flow diagram of patient enrollment, allocation, follow-up, and analysis.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8673299/v1/d805e332e0ced200438cbda0.png"},{"id":102963938,"identity":"025f9b38-8f56-4ccc-8f21-68c166d45eba","added_by":"auto","created_at":"2026-02-19 04:20:54","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":61107,"visible":true,"origin":"","legend":"\u003cp\u003eHemodynamic parameters of the groups (* p = 0.019)\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8673299/v1/2fb6212dda6b42004227e23e.png"},{"id":104290398,"identity":"041267b4-0ca7-4200-a231-3c25e90a5248","added_by":"auto","created_at":"2026-03-10 06:42:37","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":808718,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8673299/v1/d2a8b72b-06c4-4743-8d23-7abdecc96fbc.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"The Effect of Body Mass Index on Vasopressor Use, Block Dynamics, and Hemodynamic Responses in Urological Surgery Undergoing Spinal Anesthesia","fulltext":[{"header":"Background","content":"\u003cp\u003eDue to the rapid increase in obesity prevalence, it has become a significant public health problem on a global scale today [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Accordingly, the increasing rate of obesity in the operating room makes it important to investigate the effect of obesity on spinal anesthesia [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. In spinal anesthesia applications, the level and duration of sensory and motor block are affected by numerous factors, including patient characteristics such as age, gender, height, weight and body mass index (BMI), as well as the dose, temperature and pharmacological properties of the intrathecally administered local anesthetic agent, cerebrospinal fluid (CSF) volume and spinal anatomy [\u003cspan additionalcitationids=\"CR4\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. However, the literature reports inconsistent and sometimes contradictory results regarding the effects of these variables on spinal anesthesia [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Most of the information on regional anesthesia in obese patients in the current literature has been obtained from obstetric surgeries [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. This makes the generalizability of obstetric data to different surgical groups debatable. This is because pregnancy-related anatomical landmarks can become blurred, lung volumes decrease, and the aorta and inferior vena cava can be compressed, leading to dilation of the epidural veins and reduction of the epidural space [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Although spinal anesthesia is commonly used in urological surgeries, studies directly examining anesthetic outcomes related to BMI are quite limited. However, it is thought that the findings obtained from lower abdominal and orthopedic surgeries performed under spinal anesthesia may be partially applicable to urological surgeries due to similar pharmacodynamic and physiological mechanisms. However, this assumption needs to be supported by data specific to the urological patient population [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIt is suggested that pathophysiological changes in obese individuals, such as increased intra- abdominal pressure, epidural venous distension, and relative decrease in CSF volume, may affect the cephalic spread of intrathecal local anesthetics [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. These mechanisms may be associated with higher block levels and significant hemodynamic changes. However, the literature lacks clear results regarding the effect of obesity on the incidence of hypotension and vasopressor requirements after spinal anesthesia. This uncertainty makes it difficult to determine the optimal spinal anesthesia management in obese patients.\u003c/p\u003e \u003cp\u003eThe aim of this study is to comparatively evaluate the vasopressor requirements, sensory and motor block characteristics, hemodynamic and responsiveness of spinal anesthesia administered during urological surgery in patients grouped according to BMI. The study aims to fill the existing knowledge gap regarding spinal anesthesia applications in obese patients and contribute to the development of individualized anesthesia strategies to improve patient safety in clinical practice.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy Design and Ethical Approval\u003c/h2\u003e \u003cp\u003eThis study was planned as a prospective, observational study. Ethical approval was obtained from the Non-Interventional Clinical Research Ethics Committee of Adıyaman University Faculty of Medicine with decision number 2022/4\u0026ndash;20 dated 20/04/2022. The research was conducted in accordance with the principles of the Helsinki Declaration. All subjects were informed about the purpose and methods of the study and their written informed consent was obtained.\u003c/p\u003e \u003cp\u003eThe primary outcome of the study was the total intraoperative vasopressor requirement, defined as the cumulative dose of intravenous ephedrine (mg) administered to treat hypotension during surgery.\u003c/p\u003e \u003cp\u003eSecondary outcomes included:\u003c/p\u003e \u003cp\u003eMaximum sensory block level, defined as the highest thoracic dermatome reached after spinal anesthesia.\u003c/p\u003e \u003cp\u003eHemodynamic responses, defined as noninvasive systolic arterial pressure (SBP), diastolic arterial pressure (DBP), and heart rate (HR) measured at baseline and at 5- minute intervals after spinal anesthesia.\u003c/p\u003e \u003cp\u003eTwo-segment sensory regression time, defined as the time (minutes) from the maximal sensory block level to regression of two dermatomes.\u003c/p\u003e \u003cp\u003eTime to reach maximum sensory block, defined as the time (minutes) from intrathecal injection to the highest sensory level achieved.\u003c/p\u003e \u003cp\u003eTime to achieve complete motor block, defined as the time (minutes) required to reach Bromage score 3.\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eMotor block recovery time, defined as the time (minutes) to the return of the first detectable motor activity.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003ePatient Selection and Grouping\u003c/h3\u003e\n\u003cp\u003eA total of 120 patients aged 18 years or older, classified as American Society of Anesthesiologists (ASA) physical status I\u0026ndash;II and scheduled for elective urological surgery, were included in the study. Patients who declined to participate, those with contraindications to spinal anesthesia, those who required conversion to general anesthesia intraoperatively, patients with height\u0026thinsp;\u0026lt;\u0026thinsp;150 cm or \u0026gt;\u0026thinsp;190 cm, and those with a body mass index (BMI)\u0026thinsp;\u0026lt;\u0026thinsp;18.5 kg/m\u0026sup2; were excluded in order to minimize the potential impact of extreme anthropometric variations on spinal block characteristics.\u003c/p\u003e \u003cp\u003eBody mass index was calculated as body weight divided by the square of height (kg/m\u0026sup2;) [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. In the present study, a BMI cutoff value of 27.5 kg/m\u0026sup2; was selected based on World Health Organization obesity criteria [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] and prior evidence demonstrating that BMI may exert clinically relevant effects on intrathecal local anesthetic spread and cerebrospinal fluid dynamics [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Accordingly, patients with BMI\u0026thinsp;\u0026lt;\u0026thinsp;27.5 kg/m\u0026sup2; were assigned to Group L (normal weight), whereas those with BMI\u0026thinsp;\u0026ge;\u0026thinsp;27.5 kg/m\u0026sup2; were classified as Group H (obese). A total of 60 patients were planned for inclusion in each group. The enrollment and allocation process is presented in the STROBE flow diagram (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\n\u003ch3\u003eAnesthesia Procedure\u003c/h3\u003e\n\u003cp\u003eSpinal anesthesia was administered to all patients in a sitting position under aseptic conditions. Dural puncture was performed in the L4\u0026ndash;5 intervertebral space, midline, using a 25-gauge spinal needle. Following successful puncture, 3 ml of 0.5% hyperbaric bupivacaine (Bupivon Spinal Heavy 0.5%\u0026reg;, Onfarma, Samsun, Turkey) was injected intrathecally at a rate of approximately 1 ml/4\u0026ndash;5 seconds. Barbotage was not applied in any case. Spinal anesthesia was limited to a maximum of three attempts; patients who did not achieve successful anesthesia in three attempts were excluded from the study.\u003c/p\u003e\n\u003ch3\u003eBlock Assessment\u003c/h3\u003e\n\u003cp\u003eFollowing spinal anesthesia, patients were immediately placed in the supine position. Sensory block level was assessed every 2 minutes using a pinprick test, and motor block level was assessed using the modified Bromage scale (0: hip, knee, and foot free movement; 1: knee and foot movements present, no straight leg raises; 2: no knee flexion; 3: no foot and knee movement).\u003c/p\u003e \u003cp\u003eFor each patient, the maximum sensory block level (thoracic level), time to reach the maximum sensory block level, time to reach Bromage level 3 motor block, time to two-segment sensory block regression, motor block recovery time, surgical duration, and total ephedrine dose administered were recorded.\u003c/p\u003e\n\u003ch3\u003eHemodynamic Monitoring and Fluid Management\u003c/h3\u003e\n\u003cp\u003eSystolic (SBP) and diastolic arterial pressures (DBP) and heart rate (HR) were recorded using non-invasive methods, as baseline values before spinal anesthesia and every 5 minutes after the block. Ringer's lactate solution was administered at a maintenance dose of 8 ml/kg during the first 10 minutes of spinal anesthesia and 4 ml/kg/hour during surgery.\u003c/p\u003e \u003cp\u003eIntraoperative hypotension and ephedrine administration were managed based on a standard protocol based on predefined mean arterial pressure thresholds. The protocol defines hypotension as a drop in systolic arterial pressure below 90 mmHg or a decrease of more than 30% from baseline, and recommends a response with a 5 mg intravenous bolus of ephedrine. This minimizes inter-operator variability and performance bias, ensuring consistency and reliability in the treatment approach.\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003ePostoperative Monitoring\u003c/h2\u003e \u003cp\u003eSensory and motor block levels of patients admitted to the recovery room were evaluated and recorded every 10 minutes.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eSample Size\u003c/h3\u003e\n\u003cp\u003eData from the study by Nani et al. [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] were used to determine the sample size for our study. When the data from the groups were compared using the G*power 3.1.9.7 program, the effect size was calculated as 0.48 [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. The number of patients to be included in the study was calculated as 108, with at least 54 in each group, with a 5% margin of error (α\u0026thinsp;=\u0026thinsp;0.05) and 80% power (power (1- β)\u0026thinsp;=\u0026thinsp;0.80). However, considering the possibility of exclusion of 5\u0026ndash;10% of patients, and taking into account possible protocol exclusion, failed spinal block, or conversion to intraoperative general anesthesia, it was decided to include 60 patients in each group.\u003c/p\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003eStatistical Analysis\u003c/h2\u003e \u003cp\u003eDescriptive statistics of the data included mean, standard deviation, median, minimum, maximum, frequency, and ratio values. The distribution of variables was measured using the Kolmogorov-Smirnov and Shapiro-Wilk tests. The independent samples t-test was used for the analysis of quantitative independent data with a normal distribution. The Mann-Whitney U test was used for the analysis of quantitative independent data with a non-normal distribution. The chi-square test was used for the analysis of qualitative independent data, and the Fischer test was used when the chi-square test conditions were not met. The relationship between two variables was assessed appliying Pearson\u0026rsquo;s correlation analysis. Multivariable linear regression analysis was performed for multivariate analyses. All statistical analyses were conducted using SPSS 18.0. Results were evaluated using two-sided tests with a 95% confidence interval.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eThe study was planned with 60 patients in each group. However, in Group H, general anesthesia was applied in three cases where spinal anesthesia was unsuccessful, and these patients were excluded from the study and analysis. The total number of patients accepted into the study was determined to be 117; 60 of these were patients with BMI\u0026thinsp;\u0026lt;\u0026thinsp;2 7.5 kg/m\u0026sup2; (Group L) and 57 were patients with BMI\u0026thinsp;\u0026ge;\u0026thinsp;27.5 kg/m\u0026sup2; (Group H) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe baseline demographic and surgical characteristics of the groups are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Patients in Group H were significantly older than those in Group L (46.38\u0026thinsp;\u0026plusmn;\u0026thinsp;14.19 vs. 38.08\u003c/p\u003e \u003cp\u003e\u0026plusmn;\u0026thinsp;13.95 years, p\u0026thinsp;=\u0026thinsp;0.002). Body weight and BMI values were significantly higher in Group H, as expected (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001 for both). No significant difference was observed between the groups in terms of height (p\u0026thinsp;=\u0026thinsp;0.457). Surgical duration was significantly longer in Group H compared to Group L (46.50\u0026thinsp;\u0026plusmn;\u0026thinsp;21.58 minutes vs 37.40\u0026thinsp;\u0026plusmn;\u0026thinsp;10.69 minutes, p\u0026thinsp;=\u0026thinsp;0.004). Gender distribution and type of surgical procedure were not comparable between the groups (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\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 characteristics and surgical data\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\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 \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGroup L\u003c/p\u003e \u003cp\u003e(mean\u0026thinsp;\u0026plusmn;\u0026thinsp;sd) (n\u0026thinsp;=\u0026thinsp;60)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eGroup H\u003c/p\u003e \u003cp\u003e(mean\u0026thinsp;\u0026plusmn;\u0026thinsp;sd) (n\u0026thinsp;=\u0026thinsp;57)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ep\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge(year)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e38.08\u0026thinsp;\u0026plusmn;\u0026thinsp;13.95\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e46.38\u0026thinsp;\u0026plusmn;\u0026thinsp;14.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.002\u003csup\u003et\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWeight (kg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e68.95\u0026thinsp;\u0026plusmn;\u0026thinsp;11.37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e97.13\u0026thinsp;\u0026plusmn;\u0026thinsp;13.96\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003csup\u003et\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHeight(cm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e168.67\u0026thinsp;\u0026plusmn;\u0026thinsp;8.74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e169.87\u0026thinsp;\u0026plusmn;\u0026thinsp;8.88\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.457\u003csup\u003et\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBMI (kg/m\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e24.14\u0026thinsp;\u0026plusmn;\u0026thinsp;2.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e33.80\u0026thinsp;\u0026plusmn;\u0026thinsp;5.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003csup\u003et\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGender (male/female)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e47/13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e46/14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026gt;\u0026thinsp;0.05\u003csup\u003et\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSurgery duration (min)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e37.4\u0026thinsp;\u0026plusmn;\u0026thinsp;10.69\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e46.50\u0026thinsp;\u0026plusmn;\u0026thinsp;21.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.004\u003csup\u003et\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eType of Surgery\u003c/p\u003e \u003cp\u003e(Upper Urinary/Lower Urinary)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e48/12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e42/18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.292\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003eMin;minute\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003e\u003csup\u003et\u003c/sup\u003e Independent sample t test\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003e\u003csup\u003ec\u003c/sup\u003e Chi-square test\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.05 is taken as statistically significant\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe incidence of failed spinal and postdural headaches did not differ significantly between the groups (p\u0026thinsp;=\u0026thinsp;0.079 and p\u0026thinsp;=\u0026thinsp;0.55, respectively) (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\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\u003eIntraoperative and postoperative complications\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\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 \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=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eGroup L (n\u0026thinsp;=\u0026thinsp;60)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eGroup H (n\u0026thinsp;=\u0026thinsp;57)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003ep\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eFailed Spinal\u003c/p\u003e \u003cp\u003eAnaesthesia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.079\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e57\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePostdural\u003c/p\u003e \u003cp\u003epuncture headache\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e+\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.55\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e59\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003e\u003csup\u003ec\u003c/sup\u003e Chi-square test\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.05 is taken as statistically significant\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe block characteristics related to spinal anesthesia are presented in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. Ephedrine use was significantly higher in Group H compared to Group L (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The maximum sensory block level was observed at significantly higher dermatomal levels in Group H (7.42\u0026thinsp;\u0026plusmn;\u0026thinsp;2.63 vs 8.97\u0026thinsp;\u0026plusmn;\u0026thinsp;1.99, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). There were no significant differences between the groups in terms of sensory block regression time (two levels), time to reach maximum block, motor block development time, and motor block recovery time (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\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\u003eSpinal block characteristics\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGroup L (mean\u0026thinsp;\u0026plusmn;\u0026thinsp;sd) (n\u0026thinsp;=\u0026thinsp;60)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eGroup H\u003c/p\u003e \u003cp\u003e(mean\u0026thinsp;\u0026plusmn;\u0026thinsp;sd) (n\u0026thinsp;=\u0026thinsp;57)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ep\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEphedrine (mg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e0.33\u0026thinsp;\u0026plusmn;\u0026thinsp;1.81\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e3.75\u0026thinsp;\u0026plusmn;\u0026thinsp;4.93\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003csup\u003et\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMaximum sensory\u003c/p\u003e \u003cp\u003eblock level (thoracic\u003c/p\u003e \u003cp\u003edermatome)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e8.97\u0026thinsp;\u0026plusmn;\u0026thinsp;1.99\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e7.42\u0026thinsp;\u0026plusmn;\u0026thinsp;2.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003csup\u003em\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTime until maximum\u003c/p\u003e \u003cp\u003esensory block is\u003c/p\u003e \u003cp\u003ereached (min)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e5.18\u0026thinsp;\u0026plusmn;\u0026thinsp;1.53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e5.05\u0026thinsp;\u0026plusmn;\u0026thinsp;1.24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.602\u003csup\u003em\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSensory block\u003c/p\u003e \u003cp\u003eregression time (2\u003c/p\u003e \u003cp\u003elevels) (min)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e57.43\u0026thinsp;\u0026plusmn;\u0026thinsp;12.88\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e59.65\u0026thinsp;\u0026plusmn;\u0026thinsp;13.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.482m\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTime to reach motor\u003c/p\u003e \u003cp\u003eblock 3 (min)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e7.78\u0026thinsp;\u0026plusmn;\u0026thinsp;2.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e7.33\u0026thinsp;\u0026plusmn;\u0026thinsp;2.46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.292\u003csup\u003em\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMotor block start-up\u003c/p\u003e \u003cp\u003etime (min)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e175.08\u0026thinsp;\u0026plusmn;\u0026thinsp;20.22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e167.83\u0026thinsp;\u0026plusmn;\u0026thinsp;33.41\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.153\u003csup\u003em\u003c/sup\u003e\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=\"BlockQuote\"\u003e \u003cp\u003e \u003csup\u003et\u003c/sup\u003eIndependent sample test / \u003csup\u003em\u003c/sup\u003e Mann-whitney u test\u003c/p\u003e \u003cp\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.05 is taken as statistically significant\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003eHemodynamic parameters are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e Heart rate trends were similar between the two groups throughout the perioperative period (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). Basal systolic arterial pressure was significantly higher in Group H compared to Group L (146.53\u0026thinsp;\u0026plusmn;\u0026thinsp;17.87 vs 139.02\u0026thinsp;\u0026plusmn;\u0026thinsp;16.70 mmHg, p\u0026thinsp;=\u0026thinsp;0.019). Following spinal anesthesia, systolic and diastolic arterial pressure values measured between 5 and 30 minutes did not show a significant difference between the groups (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eWhile there were significant differences between the groups in terms of age and surgical duration, a multivariable analysis was performed to evaluate the independent effect of BMI on intraoperative ephedrine requirements. Multivariable linear regression analysis demonstrated that BMI was independently associated with a significant increase in the amount of ephedrine required during surgery (B\u0026thinsp;=\u0026thinsp;3.015, 95% CI: 1.633\u0026ndash;4.396, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Age showed a weak but statistically significant association with ephedrine use (B\u0026thinsp;=\u0026thinsp;0.048, 95% CI: 0.001\u0026ndash;0.096, p\u0026thinsp;=\u0026thinsp;0.046). In contrast, surgical duration was not significantly associated with intraoperative ephedrine requirements (B\u0026thinsp;=\u0026thinsp;0.006, 95% CI: \u0026minus;0.034\u0026ndash;0.045, p\u0026thinsp;=\u0026thinsp;0.78) (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\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\u003eMultivariable linear regression analysis for intraoperative ephedrine use\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\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=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eB (SE)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ep\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e95% CI for B (multivariable)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBMI group (H vs L)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3.015 (0.698)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.633 to 4.396\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\u003e0.048 (0.024)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.046\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.001 to 0.096\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSurgery duration\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.006(0.02)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.780\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.034 to 0.045\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\u003eDependent variable: intraoperative ephedrine use (dose/amount as recorded).\u003c/p\u003e \u003cp\u003eB indicates the unstandardized regression coefficient; SE indicates standard error; CI indicates confidence interval. P\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered statistically significant\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis study demonstrates that body mass index is an important determinant of both spinal block characteristics and vasopressor requirement in patients undergoing urological surgery under spinal anesthesia. Unlike most previous studies that primarily focused on obstetric populations, our work provides evidence from a non-obstetric surgical group, thereby improving the generalizability of current knowledge.\u003c/p\u003e \u003cp\u003eIn this study, it was found that the mean age of patients in Group H was significantly higher. This finding is consistent with epidemiological data reporting that the prevalence of obesity increases with age and supports the consistency of the demographic distribution of our study with the literature [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. In addition, while the longer surgical time in Group H shows the intraoperative technical difficulties of obesity, the existence of studies in the literature that did not find a significant difference in surgical time between obese and non-obese patients suggests that the effect of obesity on surgical time may be heterogeneous [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAlthough numerical differences were observed between groups in terms of the incidence of spinal anesthesia failure and postdural puncture headache (PDPH), these differences did not reach statistical significance. Literature highlights findings suggesting that obesity can lead to technical difficulties in spinal anesthesia procedures; in this context, mechanisms such as obesity reducing the capacity to highlight anatomical landmarks, making the needle advancement process more difficult, and altering cerebrospinal fluid (CSF) flow dynamics have been proposed [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. These factors may potentially increase the incidence of spinal anesthesia failure and PDPH. However, it is thought that when performed by experienced anesthesiologists, the impact of these difficulties on adverse outcomes can be significantly reduced. On the other hand, there are inconsistent findings in the literature regarding the relationship between BMI and the incidence of PDPH. For example, although two separate studies (including 464 and 315 female participants) showed that BMI had no significant effect on the development of PDPH [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e], the study by Peralta et al. suggested that obesity may be protective against the development of PDPH. This suggestion was explained by the assumption that obesity could limit CSF leakage by increasing intraabdominal fat tissue, thereby increasing epidural pressure and reducing the intrathecal\u0026ndash;epidural pressure gradient [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. In the retrospective study by Azzi et al., the incidence of PDPH was examined in patients who underwent regional anesthesia for a total of 10,051 surgical procedures, and it was found that the frequency of PDPH was higher in patients with low BMI [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Franz et al. and Hashemi et al. found an inverse and significant relationship between BMI and PDPH [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. This finding suggests that BMI may play a potential risk factor for the development of PDPH, however, the clinical significance of this relationship requires further evaluation. Additionally, this study aimed to reduce the risk of PDPH based on needle type; all patients received a standard 25G Quincke spinal needle.\u003c/p\u003e \u003cp\u003eAlthough baseline systolic arterial pressure was higher in obese patients, the overall hemodynamic course after spinal anesthesia was comparable between groups. This may reflect early recognition and treatment of hypotension according to a standardized protocol. Nevertheless, the significantly higher vasopressor requirement in the obese group indicates that hemodynamic instability may be more likely if preventive strategies are not applied. Similarly, to Elmeliegy et al., Nani et al. reported that more pronounced hemodynamic changes may develop in obese patients and that the need for vasopressors increases to maintain stable hemodynamics, and these findings are consistent with the results of our study [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. In contrast, studies by Kim et al. and Ngaka et al. reported no statistically significant difference between obese and non-obese groups in terms of ephedrine consumption and hypotension [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. It is thought that these differences in the literature may be related to the doses of local anesthetics used, the characteristics of the patient populations (e.g., pregnancy status), and methodological heterogeneity in the study designs [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAnother important finding is that obese patients achieved significantly higher sensory block levels. This has direct clinical implications, as excessive cephalad spread increases the risk of high spinal block and cardiorespiratory compromise. Taivainen et al. showed that higher thoracic sensory block levels were achieved in obese patients after isobaric bupivacaine administered at the L3-4 or L4-5 level of the spinal space [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Similarly, Hogan et al. demonstrated with magnetic resonance imaging that CSF volume is related to body posture and intraabdominal pressure, and that these changes can significantly affect the cranial spread of intrathecal drugs [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. However, it is thought that anatomical and physiological changes associated with obesity, such as increased intra-abdominal pressure, epidural venous distension, and decreased CSF volume, contribute to the sensory block level reaching more cephalic dermatomes by altering the distribution of local anesthetics in the CSF [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. Although data on the maximum sensory block level are heterogeneous in the literature, Elmeliegy et al. reported that the maximum sensory block level was T5 in patients with low BMI, while it increased to T3 in patients with high BMI [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. In contrast, Kim et al. reported that the highest sensory block level was T7 in both obese and non-obese groups [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Furthermore, a retrospective cohort study of 5,015 female patients found that high spinal block was significantly different in the obese group [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. In this study, the maximum sensory block level was determined as T8.97\u0026thinsp;\u0026plusmn;\u0026thinsp;1.99 in Group L and T7.42\u0026thinsp;\u0026plusmn;\u0026thinsp;2.63 in Group H, and this difference was found to be statistically significant. Therefore, careful dose selection, patient positioning, and close monitoring are particularly important in this population.\u003c/p\u003e \u003cp\u003eDespite higher block levels, the temporal profile of spinal anesthesia was similar between groups, suggesting that BMI primarily affects block height rather than block duration. Hosseinzadeh et al. reported that the time to reach the maximum sensory block level was shorter in obese patients compared with non-obese individuals [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. In contrast, Elmeliegy et al. demonstrated that patients with higher BMI exhibited a prolonged sensory block regression time, whereas the time to achieve a Bromage score of 3 and the regression time of motor block were shorter [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. In the present study, although the temporal profile of spinal anesthesia tended to be slightly shorter in the obese group, these differences did not reach statistical significance.\u003c/p\u003e \u003cp\u003eComparative evaluations of the intrathecal spread and sensory block levels of local anesthetic solutions with different baricities have demonstrated that a decrease in intrathecal solution baricity is associated with a significant increase in cephalad spread and maximum sensory block level. In parallel, it has been reported that ephedrine requirements are 1.83-fold and 3.0-fold higher with isobaric and hypobaric solutions, respectively, compared with hyperbaric solutions [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. To minimize the potential confounding effects of these variables on block height, the same dose and baricity of the local anesthetic were used in both groups in the present study. This approach was intended to more precisely isolate and reflect BMI-related differences in the observed outcomes.\u003c/p\u003e \u003cp\u003eClinical implications\u003c/p\u003e \u003cp\u003eIn patients with elevated body mass index, spinal anesthesia should be managed with anticipation of higher sensory block levels and increased vasopressor requirements. Early availability of vasopressors, vigilant hemodynamic monitoring, and individualized anesthetic strategies may reduce the risk of hypotension-related complications in this population.\u003c/p\u003e \u003cp\u003eLimitations\u003c/p\u003e \u003cp\u003eThis study has some limitations. Firstly, although the local anesthetic dose and application technique used in spinal anesthesia procedures were standardized, technical factors such as operator experience, small variations in patient position during the procedure, and subjective differences in determining the spinal range could not be fully controlled. These variables may have potential effects on intrathecal drug delivery and block characteristics.\u003c/p\u003e \u003cp\u003eSecondly, although initially planned for 60 patients in both groups, the sample size of Group H was relatively reduced due to the exclusion of three patients from the study because of spinal anesthesia failure in the high BMI group. This may have limited the statistical power of the study, particularly in terms of rare complications (such as spinal anesthesia failure and PDPH), and may have contributed to the failure of the observed numerical differences between the groups to reach statistical significance.\u003c/p\u003e \u003cp\u003eFurthermore, the study was conducted in a single center and encompassed a specific surgical patient population. Therefore, the generalizability of the findings to different surgical procedures, different patient profiles, and multicenter applications may be limited.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThe clinical significance of this study lies in demonstrating that body mass index is not merely a demographic characteristic but an important factor influencing intraoperative hemodynamic management during spinal anesthesia. The more cephalad spread of maximum sensory block and the increased vasopressor requirement observed in obese patients suggest that this population may require more meticulous anesthetic management.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eEthics approval and consent to participate\u003c/p\u003e\n\u003cp\u003eThis study was designed as a prospective observational study. Ethical approval was obtained from the Non-Interventional Clinical Research Ethics Committee of Adıyaman University Faculty of Medicine (Decision No: 2022/4-20, Date: 20 April 2022). The study was conducted in accordance with the principles of the Declaration of Helsinki. Written informed consent was obtained from all participants prior to enrollment.\u003c/p\u003e\n\u003cp\u003eConsent for publication\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003eAvailability of data and materials\u003c/p\u003e\n\u003cp\u003eThe datasets generated and/or analyzed during the current study are available from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003eCompeting interests\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no conflict of interest relevant to this study.\u003c/p\u003e\n\u003cp\u003eFunding\u003c/p\u003e\n\u003cp\u003eThis study did not receive any specific funding from public, commercial, or not-for-profit funding agencies.\u003c/p\u003e\n\u003cp\u003eAuthors’ contributions\u003c/p\u003e\n\u003cp\u003eFT and BK conceived and designed the study. FT, BK and DY collected the data.\u003c/p\u003e\n\u003cp\u003eUK performed the statistical analysis. FT and UK interpreted the data and drafted the manuscript.\u003c/p\u003e\n\u003cp\u003eBK, ZB and DY contributed to data interpretation and critically revised the manuscript for important intellectual content. All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003eAcknowledgements\u003c/p\u003e\n\u003cp\u003eThe authors would like to thank the operating room staff of Adıyaman Training and Research Hospital for their assistance during data collection.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eNCD Risk Factor Collaboration. Worldwide trends in underweight and obesity from 1990 to 2022: a pooled analysis of 3663 population-representative studies with 222 million children, adolescents, and adults. 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Anesth Analg. 2011;113(4):811\u0026ndash;7. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1213/ANE.0b013e3182288bf2\u003c/span\u003e\u003cspan address=\"10.1213/ANE.0b013e3182288bf2\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"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":"Body mass index, ephedrine, sensory block, hemodynamic response","lastPublishedDoi":"10.21203/rs.3.rs-8673299/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8673299/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eWhile the effects of body mass index (BMI) on intrathecal local anesthetic spread and hemodynamic responses during spinal anesthesia are well-defined in obstetric surgery, studies directly examining this relationship in urological surgeries where spinal anesthesia is commonly performed are limited. Therefore, this study aimed to evaluate the effect of BMI on vasopressor requirements and block characteristics after spinal anesthesia.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eThis prospective, observational study included 120 patients undergoing elective urological surgery under spinal anesthesia. Patients were divided into two groups according to BMI: BMI\u0026thinsp;\u0026lt;\u0026thinsp;27.5 kg/m\u0026sup2; (Group L) and BMI\u0026thinsp;\u0026ge;\u0026thinsp;27.5 kg/m\u0026sup2; (Group H). The groups were compared in terms of demographic data, surgical duration, spinal block characteristics, hemodynamic changes, and ephedrine use.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eThree patients were excluded from the analysis due to spinal anesthesia failure, and a total of 117 patients were evaluated (Group L: n\u0026thinsp;=\u0026thinsp;60; Group H: n\u0026thinsp;=\u0026thinsp;57). Total intraoperative ephedrine requirement was significantly higher in Group H (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The maximum sensory block level was significantly more cephalic in Group H compared to Group L (T7.42\u0026thinsp;\u0026plusmn;\u0026thinsp;2.63 vs T8.97\u0026thinsp;\u0026plusmn;\u0026thinsp;1.99, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). No significant differences were found between the groups in terms of time to reach maximum block, time to two-segment sensory block regression, time to reach motor block 3, and motor block recovery time (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). Although basal systolic arterial pressure was higher in Group H (p\u0026thinsp;=\u0026thinsp;0.019), hemodynamic parameters after spinal anesthesia were similar between the groups.\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eIn the high BMI patient group, a significant effect was observed on vasopressor requirement, block level, and surgical duration during spinal anesthesia procedures. These findings highlight the need for comprehensive preoperative planning, determination of appropriate anesthesia strategies, and careful hemodynamic monitoring in obese patients.\u003c/p\u003e","manuscriptTitle":"The Effect of Body Mass Index on Vasopressor Use, Block Dynamics, and Hemodynamic Responses in Urological Surgery Undergoing Spinal Anesthesia","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-17 11:47:17","doi":"10.21203/rs.3.rs-8673299/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":"24c81529-513f-42be-9db2-f79d1895ab36","owner":[],"postedDate":"February 17th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-03-10T06:42:03+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-17 11:47:17","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8673299","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8673299","identity":"rs-8673299","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}