Preoperative fluid removal volume in patients on dialysis undergoing cardiovascular surgery

Preoperative fluid removal volume in patients on dialysis undergoing cardiovascular surgery | 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 Preoperative fluid removal volume in patients on dialysis undergoing cardiovascular surgery Hiroshi Noguchi, Daisuke Miura, Mariko Baba, Shinichiro Kusaba, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8264468/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 6 You are reading this latest preprint version Abstract Background In patients on dialysis who are scheduled for surgery, the volume of fluid removed preoperatively may influence intraoperative circulatory stability and can affect perioperative complications. However, no clear standards for approaches to preoperative fluid removal have been established. In this study, we investigated the association between preoperative fluid removal volume and early postoperative mortality and complications in patients undergoing dialysis who underwent cardiovascular surgery. Methods We included patients placed on dialysis who underwent cardiovascular surgery between January 1, 2012, and December 31, 2021. Their clinical data were retrieved from electronic medical records. The primary outcome was early postoperative mortality. Secondary outcomes were postoperative complications, postoperative continuous renal replacement therapy (CRRT), and duration of mechanical ventilation. Statistical comparisons were performed using the Wilcoxon rank-sum test and Fisher’s exact test. The optimal cut-off values for fluid removal volume were determined using receiver operating characteristic (ROC) analysis. The patients were classified into two groups based on their preoperative fluid removal volumes (≥ 2,000 mL or < 2,000 ml). Statistical significance was set at p < 0.05. Results In this cohort of 50 patients, the proportion of male patients and the median age were 76.0% and 69.0 years (IQR: 63–73.8), respectively. The preoperative fluid removal volume was significantly associated with early postoperative mortality (p = 0.029), postoperative complications (p = 0.042), and prolonged postoperative mechanical ventilation (p = 0.014). ROC analysis identified 2,250 mL as the optimal cut-off value (sensitivity, 83.3%; specificity, 84.1%). Patients with volumes of ≥ 2,000 mL had a significantly higher early postoperative mortality rate (p = 0.018). Greater fluid removal volumes were associated with increased early postoperative mortality in those with hypotension during preoperative dialysis (p = 0.026). Conclusions Excessive preoperative fluid removal (> 2,000 mL) is associated with increased risks of early postoperative mortality, particularly in patients with hypotension during preoperative hemodialysis. These findings highlight the importance of individualized fluid management through multidisciplinary collaboration. cardiovascular surgery dialysis mortality preoperative fluid removal Figures Figure 1 Figure 2 Figure 3 Figure 4 Background The prevalence of end-stage kidney disease requiring maintenance dialysis is increasing globally, driven by population aging and the increasing prevalence of diabetes, hypertension, and atherosclerosis [ 1 ]. Consequently, patients referred for cardiovascular surgery, due to the high incidence of coronary artery disease and valvular heart disease, are more frequently dependent on dialysis [ 2 , 3 ]. The risk of perioperative morbidity and mortality is significantly higher in these patients than in the general population. Cardiac events, such as myocardial infarction and heart failure, are major causes of death in patients who are dependent on dialysis, with rates reported as 10–20 times higher than those for individuals who are not dependent on dialysis [ 3 , 4 ]. Pre-existing cardiovascular disease, vascular calcification, and rapid progression of valvular lesions contribute to this vulnerability [ 2 , 5 ]. Perioperative fluid management is a critical challenge in patients on dialysis who are undergoing cardiac surgery, as poor volume control exacerbates cardiovascular stress. Additionally, excessive ultrafiltration before surgery may result in hypovolemia, intradialytic hypotension (IDH), and poor perfusion [ 6 ]. IDH has been associated with dialysis intolerance and myocardial ischemia, but its association with early postoperative mortality is controversial [ 7 ]. The preoperative ultrafiltration volume is usually determined by dialysis physicians based on dry weight, cardiothoracic ratio, and laboratory parameters. However, no clear standards for optimal fluid removal before surgery have been established [ 8 , 9 ]. Patients with excessive interdialytic weight gain tend to require higher ultrafiltration rates (UFRs), which increase the risk of IDH and cardiovascular instability [ 6 , 7 ]. Several studies have reported worse postoperative outcomes after cardiac surgery in patients who are on dialysis than in those who are not [ 10 ]. However, these studies have been limited by small sample sizes, and clear predictors of mortality and complications in this population have not been established. In this retrospective study, with a view to guiding perioperative strategies to improve outcomes in this high-risk population, we aimed to evaluate the impact of the volume of preoperative fluid removed and of IDH on early postoperative mortality and complications in patients on dialysis who underwent cardiovascular surgery. Methods Study design and data collection This study was approved by the Ethics Committee (Saga Prefectural Medical Center Koseikan, Certification Number: 22-03-01-01). We used the opt-out method for obtaining consent for participation. To this end, we ensured that information about the research was widely disseminated and that opportunities to decline were guaranteed. This retrospective observational single-center study included consecutive patients who had undergone cardiovascular surgery in our department between January 1, 2012, and December 31, 2021, and who underwent hemodialysis or peritoneal dialysis before surgery. We excluded the data of patients whose preoperative fluid removal volumes were unknown and those who had discontinued hemodialysis before surgery. All demographic and perioperative variables were obtained from the medical records. These data included the following: (a) patient characteristics: age, sex, height, weight, comorbidities, preoperative left ventricular ejection fraction, and preoperative blood test data; (b) dialysis-related variables: preoperative dry weight, preoperative fluid removal volume, duration of dialysis, and IDH; (c) surgical and anesthetic data: diagnosis, procedure, anesthesia time, operative time, cardiopulmonary bypass (CPB) time, intraoperative fluid volume, blood transfusion volume, blood loss volume, total balance, hypotension during surgery, norepinephrine dose, dopamine dose, dobutamine dose, PaO2/FiO2 ratio, and others; (d) postoperative outcomes: complications (such as cerebral infarction, hyperkalemia, mediastinitis, pneumonia, arrhythmia, seizures, and gastrointestinal disorders), mortality (overall and early postoperative death, defined as death within 90 days), and durations of mechanical ventilation, continuous renal replacement therapy (CCRT), and intensive care unit stay. Data analysis We investigated the relationships of preoperative fluid removal volume with complications, CRRT, duration of mechanical ventilation, and mortality. Continuous variables are reported as mean ± standard deviation or median with interquartile range (IQR). The Wilcoxon rank-sum and Fisher’s exact tests were used to compare continuous and categorical variables, respectively. Receiver operating characteristic (ROC) curve analysis was performed to determine the preoperative fluid removal volume cut-off value associated with early mortality. The sensitivity and specificity of this volume were also determined. The patients were stratified into two groups based on this volume for subsequent analyses. Subgroup analyses were performed for patients with IDH before surgery, using the same threshold. Statistical significance was set at p < 0.05. Results Study population Of the 54 patients on dialysis who underwent elective cardiovascular surgery at our institution between January 1, 2012, and December 31, 2021, four were excluded (2 lacked data on preoperative fluid removal volume, and 2 were weaned from dialysis) (Fig. 1 ). The data of the remaining 50 patients were used for statistical analysis. The preoperative diagnoses and surgical procedures are provided in Tables 1 and 2 . Table 1 Classification by preoperative diagnosis Preoperative Diagnosis Cases Angina pectoris, myocardial infarction 19 Aortic valve stenosis 17 Aortic valve regurgitation 7 Mitral valve regurgitation 4 Infective endocarditis 1 Tricuspid valve regurgitation 1 Aortic dissection 1 Table 2 Classification by surgical procedure Surgical procedure Cases Aortic valve replacement 12 Off-pump CABG 12 On-pump CABG 6 Aortic valve replacement་On-pump CABG 10 Mitral valve replacement་Tricuspid valve plasty 3 Aortic valve replacement + Mitral valve replacement 2 Aortic valve replacement་Tricuspid valve plasty 1 Mitral valve replacement 1 Mitral valve plasty་Tricuspid annuloplasty 1 Tricuspid annuloplasty་On-pump CABG 1 Descending aortic dissection repair 1 CABG, coronary artery bypass graft Patient characteristics In our study population, the proportion of male patients and the median age were 76.0% and 69.0 years (IQR: 63–73.8), respectively. The median durations of surgery and CPB were 329.5 min (IQR: 277.3–373.0) and 154.5 min (IQR: 78.0–188.5), respectively. The median preoperative fluid removal volume was 1,600.0 ml (IQR: 1,000.0–2,175.0). The proportion of patients demonstrating hypotension during preoperative dialysis was 60.0% (Table 3 ). Table 3 Patient background factors included in this study Population Median (IQR or %) Age (years) 69.0 (63.0–73.8) Height (cm) 161.0 (154.3–167.0) Weight (kg) 57.5 (46.9–61.9) Male/Female (N) 38.0/12.0 (76/24) Preoperative ejection fraction (%) 60.0 (46.0–66.0) Amount of fluid removed preoperatively (ml) 1600.0 (1000.0–2175.0) Preoperative hypotension during dialysis (N) 30 (60) Dialysis history (years) 5.0 (3.0–12.8) Duration of surgery (min) 329.5 (277.3–373.0) Anesthesia time (min) 438.5 (365.5–490.5) Aortic occlusion time (min) 83.5 (0.0–115.3) Cardiopulmonary bypass time (min) 154.5 (78.0–188.5) Total fluid and blood transfusion volume (ml) 3155.0 (2460.5–4394.3) Self-collected blood return volume (ml) 1003.5 (737.3–1433.0) Intraoperative hypotension (case) * 36/14 (72.0/28.0) Postoperative hemoglobin (g/dl) 10.2 (9.7, 10.9) Postoperative complications (N) 37.0 (74.0) Postoperative continuous renal replacement therapy (N) 24.0 (48.0) Duration of mechanical ventilation (days) 3.0 (3.0–6.5) For cases not using cardiopulmonary bypass or aortic occlusion, the cardiopulmonary bypass and aortic occlusion times were recorded as 0 min. *Intraoperative hypotension was defined as systolic blood pressure of 80 mmHg or lower sustained for 5 min or longer before cardiopulmonary bypass. For off-pump coronary artery bypass graft, intraoperative hypotension was defined as systolic blood pressure of 80 mmHg or lower sustained for 5 min or longer before bypass initiation. Association between preoperative fluid removal and outcomes We found a significant relationship between early postoperative death and preoperative fluid removal volume (p = 0.029). A large preoperative fluid removal volume was associated with increased incidences of postoperative complications and longer durations of mechanical ventilation (p = 0.042 and p = 0.014, respectively) (Fig. 2 ). ROC curve analysis ROC analysis identified the preoperative fluid removal volume cut-off value for early postoperative mortality as 2,250 mL (area under the ROC curve, AUC: 0.78, sensitivity: 83.3%; specificity: 84.1%) (Fig. 3 ). Stratified analysis using the 2,000-ml threshold The patients were grouped based on their preoperative fluid removal volume for clinical interpretability: those with preoperative fluid removal volume of ≥ 2,000 ml (n = 18) and < 2,000 ml (n = 32). The early postoperative mortality rate was significantly lower in the < 2,000 ml group (p = 0.018) (Table 4 ). Table 4 Association of preoperative fluid removal volume with early postoperative mortality Amount of preoperative fluid removal No early postoperative mortality (N = 44) Early postoperative mortality (N = 6) < 2,000 31 1 (3.1%) ≤ 2,000 13 5 (27.8%) Subgroup analysis: patients with hypotension during preoperative dialysis The early mortality rate was significantly higher for patients with IDH (n = 30) who had fluid removal volumes of ≥ 2,000 mL than for those with volumes < 2,000 mL (p = 0.026) (Table 5 , Fig. 4 ). Table 5 Association of preoperative fluid removal volume with early postoperative mortality in cases of hypotension during dialysis Amount of preoperative fluid removal (in cases of hypotension during dialysis with preoperative fluid removal) No early postoperative mortality (N = 24) Early postoperative mortality (N = 6) 2,000 mL) in patients on dialysis before they undergo cardiovascular surgery was significantly associated with increased early postoperative mortality. This association was particularly pronounced in patients who experienced hypotension during preoperative dialysis. Removal of a greater preoperative fluid volume was also associated with increased postoperative complications and a longer duration of mechanical ventilation. These findings are consistent with previously reported high perioperative mortality rates of patients on dialysis, particularly those undergoing valve surgeries (8–10% for coronary artery bypass graft [CABG] and up to 20% for valve surgeries) [ 11 , 12 ]. Consistent with these previously reported rates, 6 of our 50 patients (12%) suffered early mortality, with rates of 16% and 10% for valve surgery and CABG, respectively. Removal of a large volume of fluid preoperatively may reduce intravascular volume and cause hemodynamic instability. This can necessitate large intraoperative fluid and transfusion volumes, which can contribute to pulmonary edema and the need for prolonged mechanical ventilation. Previous studies have also reported associations of excessive UFRs and large interdialytic weight gains with increased mortality [ 13 , 14 ]. Intraoperative crystalloid infusion exceeding 3 L has been associated with prolonged intensive care unit stay and ventilation [ 15 ]. Chronic dialysis induces persistent inflammatory responses, oxidative stress, endothelial dysfunction, and vascular remodeling. These pathophysiologic changes reduce vascular smooth muscle reactivity and increase the risk of vasodilation. They also increase the susceptibility of patients placed on dialysis to vasoplegic syndrome (VPS) during CPB. Dialysis-dependence has been reported as an independent predictor of VPS (odds ratio, 1.47; 95% confidence interval, 1.17–1.86) [ 16 ]. VPS is characterized by low systemic vascular resistance, high cardiac output, and refractory hypotension that is unresponsive to vasopressors. Maintaining perfusion after VPS development often requires aggressive fluid and blood administration and multiple vasoactive agents. This compensatory volume loading may further aggravate pulmonary and tissue edema and can create a vicious cycle of hemodynamic instability and poor oxygenation. VPS is associated with adverse outcomes, including mortality, extended intensive care unit stay, and prolonged ventilation [ 17 ]. However, previous studies have not consistently reported a direct relationship between elevated UFR and mortality in the non-surgical population [ 18 , 19 ]. This discrepancy may be ascribed to differences in patient populations, surgical stress, or dialysis protocols. Few previous studies have specifically addressed preoperative ultrafiltration in the context of cardiac surgery, highlighting the novelty of our findings. Current guidelines recommend avoiding excessive dehydration before anesthesia induction, due to the high risk of hypotension [ 20 ]. Fluid removal exceeding 6% of body weight has been associated with adverse outcomes [ 21 ]; rather, a preoperative target of dry weight + 1 kg has been proposed to optimize perioperative stability [ 11 ]. Our findings support these recommendations and highlight the need for individualized, multidisciplinary adjustment of fluid removal strategies. IDH occurs when the plasma refilling rate is exceeded by the ultrafiltration volume during dialysis, resulting in a reduction of circulating blood volume. IDH is also influenced by dialysis-related cardiovascular impairment and autonomic dysfunction [ 22 , 23 ]. In this study patients with preoperative IDH who underwent high-volume fluid removal preoperatively had high early mortality. This finding underscores the need to reconsider fluid removal targets for patients with IDH. Limitations This study had some limitations. First, it was a retrospective single-center study. Second, some data were missing from the medical records. Third, as a retrospective study, the findings cannot establish causality between fluid removal volume and outcomes. Variations in dry weight determination, patient physiology, and comorbidities may have influenced the results. Conclusion Excessive preoperative fluid removal (> 2,000 ml), particularly in the presence of IDH, is associated with increased early postoperative mortality and complications in patients on dialysis undergoing cardiovascular surgery. These findings highlight the importance of individualized fluid management in close collaboration with dialysis teams to optimize the preoperative volume status and improve the surgical outcomes. Abbreviations CPB, cardiopulmonary bypass IDH, intradialytic hypotension IQR, interquartile range ROC, receiver operating characteristic UFR, ultrafiltration rate VPS, vasoplegic syndrome Declarations Ethics approval and consent to participate This study was conducted in accordance with the Declaration of Helsinki and was approved by the Ethics Committee of Saga Prefectural Medical Center Koseikan (Certification Number: 22-03-01-01). In accordance with the “Ethical Rules of the Saga Prefectural Medical Center Koseikan, a Local Independent Administrative Institution,” the committee determined that obtaining consent solely through the opt-out method was sufficient. These ethical rules comply with the “Ethical Guidelines for Life Science and Medical Research Involving Human Subjects” (Joint Notice No. 1 of the Ministry of Education, Culture, Sports, Science and Technology, the Ministry of Health, Labour and Welfare, and the Ministry of Economy, Trade and Industry, dated March 23, 2021). We ensured that information about the research was made publicly available on hospital websites, and opportunities to decline participation were fully ensured. Consent for publication Not applicable. Availability of data and materials The data of this study were generated at Saga Prefectural Medical Center Koseikan. Derived data supporting the results of this study can be obtained upon request from the corresponding author, Hiroshi Noguchi. Competing interests The authors declare that they have no competing interests. Funding Not applicable. Authors' contributions DM : Supervision, Methodology, Writing – original draft, Writing – review & editing. MB: Conceptualization, Investigation. SK: Conceptualization, Investigation. YS: Formal analysis, Writing – review & editing. All authors read and approved the final manuscript. Acknowledgements We thank Dr. Daisuke Miura for the warm guidance and encouragement offered over many hours regarding research methodology and paper writing. We also thank Drs. Mariko Baba and Shinichiro Kusaba for valuable advice based on their expertise in cardiovascular anesthesia. We are grateful to Professor Yoshiro Sakaguchi who provided valuable advice on research methodology and paper writing. Meeting presentation A summary of this paper was presented at the 27th Academic Meeting of the Japanese Society of Cardiovascular Anesthesiology (Kyoto Prefecture, September 2022). References Mourad F, Cleve N, Nowak J, Wendt D, Sander A, Demircioglu E, et al. Long-term single-center outcomes of patients with chronic renal dialysis undergoing cardiac surgery. Ann Thorac Surg. 2020;109:1442–8. Foley RN, Parfrey PS, Sarnak MJ. Clinical epidemiology of cardiovascular disease in chronic renal disease. Am J Kidney Dis. 1998;32 Suppl 3:S112–9. Goodkin DA, Young EW, Kurokawa K, Prütz KG, Levin NW. Mortality among hemodialysis patients in Europe, Japan, and the United States: Case-mix effects. Am J Kidney Dis. 2004;44 Suppl 2:16–21. Rocco MV, Yan G, Heyka RJ, Benz R, Cheung AK, HEMO Study Group. Risk factors for hypertension in chronic hemodialysis patients: Baseline data from the HEMO study. Am J Nephrol. 2001;21:280–8. 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Supplementary Files SupplementaryMaterial.xlsx Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 14 Jan, 2026 Reviewers invited by journal 07 Jan, 2026 Editor assigned by journal 05 Jan, 2026 Editor invited by journal 10 Dec, 2025 Submission checks completed at journal 09 Dec, 2025 First submitted to journal 09 Dec, 2025 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. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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07:45:54","extension":"html","order_by":25,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":85796,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8264468/v1/50e51a63a561f329aa4d9bf9.html"},{"id":100012703,"identity":"a04ca971-0eab-43e0-99e9-acc2543d8ce5","added_by":"auto","created_at":"2026-01-12 06:16:16","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":11823,"visible":true,"origin":"","legend":"\u003cp\u003eFlowchart for this study\u003c/p\u003e","description":"","filename":"Binder11.png","url":"https://assets-eu.researchsquare.com/files/rs-8264468/v1/52407ebfa48e373d877362d8.png"},{"id":100012704,"identity":"5fd8e695-2c65-42c3-8690-6b0014a6a6d5","added_by":"auto","created_at":"2026-01-12 06:16:16","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":95726,"visible":true,"origin":"","legend":"\u003cp\u003eResults of univariate analysis of primary and secondary endpoints\u003c/p\u003e","description":"","filename":"Binder12.png","url":"https://assets-eu.researchsquare.com/files/rs-8264468/v1/84096f28dbd593d390a9665d.png"},{"id":100361764,"identity":"c6669d1e-e67b-44a4-b01a-96f62b09cb9f","added_by":"auto","created_at":"2026-01-16 07:45:41","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":78795,"visible":true,"origin":"","legend":"\u003cp\u003eResults of receiver operating characteristic curve analysis for primary endpoints\u003c/p\u003e","description":"","filename":"Binder13.png","url":"https://assets-eu.researchsquare.com/files/rs-8264468/v1/69e346e5710b86931c144dc7.png"},{"id":100012709,"identity":"af74ca2b-5dde-4adf-bc96-f9ce3ee65996","added_by":"auto","created_at":"2026-01-12 06:16:16","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":92297,"visible":true,"origin":"","legend":"\u003cp\u003eAssociation between early postoperative mortality, preoperative fluid removal, and dialysis-related hypotension cases\u003c/p\u003e","description":"","filename":"Binder14.png","url":"https://assets-eu.researchsquare.com/files/rs-8264468/v1/13d9a79791b706b147bdf07b.png"},{"id":100380959,"identity":"bb2c2c5d-0460-4532-8dff-e5ac361c857b","added_by":"auto","created_at":"2026-01-16 10:36:41","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1031617,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8264468/v1/ea69c6b8-59f7-498f-a6be-76a8013d9c6b.pdf"},{"id":100012708,"identity":"61eed9bc-cfc5-4833-95b5-7c3c051a9bbd","added_by":"auto","created_at":"2026-01-12 06:16:16","extension":"xlsx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":33705,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryMaterial.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-8264468/v1/8d971b0f193ff02a0a54451a.xlsx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Preoperative fluid removal volume in patients on dialysis undergoing cardiovascular surgery","fulltext":[{"header":"Background","content":"\u003cp\u003eThe prevalence of end-stage kidney disease requiring maintenance dialysis is increasing globally, driven by population aging and the increasing prevalence of diabetes, hypertension, and atherosclerosis [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Consequently, patients referred for cardiovascular surgery, due to the high incidence of coronary artery disease and valvular heart disease, are more frequently dependent on dialysis [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. The risk of perioperative morbidity and mortality is significantly higher in these patients than in the general population. Cardiac events, such as myocardial infarction and heart failure, are major causes of death in patients who are dependent on dialysis, with rates reported as 10\u0026ndash;20 times higher than those for individuals who are not dependent on dialysis [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Pre-existing cardiovascular disease, vascular calcification, and rapid progression of valvular lesions contribute to this vulnerability [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e \u003cp\u003ePerioperative fluid management is a critical challenge in patients on dialysis who are undergoing cardiac surgery, as poor volume control exacerbates cardiovascular stress. Additionally, excessive ultrafiltration before surgery may result in hypovolemia, intradialytic hypotension (IDH), and poor perfusion [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. IDH has been associated with dialysis intolerance and myocardial ischemia, but its association with early postoperative mortality is controversial [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe preoperative ultrafiltration volume is usually determined by dialysis physicians based on dry weight, cardiothoracic ratio, and laboratory parameters. However, no clear standards for optimal fluid removal before surgery have been established [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Patients with excessive interdialytic weight gain tend to require higher ultrafiltration rates (UFRs), which increase the risk of IDH and cardiovascular instability [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eSeveral studies have reported worse postoperative outcomes after cardiac surgery in patients who are on dialysis than in those who are not [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. However, these studies have been limited by small sample sizes, and clear predictors of mortality and complications in this population have not been established.\u003c/p\u003e \u003cp\u003eIn this retrospective study, with a view to guiding perioperative strategies to improve outcomes in this high-risk population, we aimed to evaluate the impact of the volume of preoperative fluid removed and of IDH on early postoperative mortality and complications in patients on dialysis who underwent cardiovascular surgery.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy design and data collection\u003c/h2\u003e \u003cp\u003e This study was approved by the Ethics Committee (Saga Prefectural Medical Center Koseikan, Certification Number: 22-03-01-01). We used the opt-out method for obtaining consent for participation. To this end, we ensured that information about the research was widely disseminated and that opportunities to decline were guaranteed.\u003c/p\u003e \u003cp\u003eThis retrospective observational single-center study included consecutive patients who had undergone cardiovascular surgery in our department between January 1, 2012, and December 31, 2021, and who underwent hemodialysis or peritoneal dialysis before surgery. We excluded the data of patients whose preoperative fluid removal volumes were unknown and those who had discontinued hemodialysis before surgery.\u003c/p\u003e \u003cp\u003eAll demographic and perioperative variables were obtained from the medical records. These data included the following: (a) patient characteristics: age, sex, height, weight, comorbidities, preoperative left ventricular ejection fraction, and preoperative blood test data; (b) dialysis-related variables: preoperative dry weight, preoperative fluid removal volume, duration of dialysis, and IDH; (c) surgical and anesthetic data: diagnosis, procedure, anesthesia time, operative time, cardiopulmonary bypass (CPB) time, intraoperative fluid volume, blood transfusion volume, blood loss volume, total balance, hypotension during surgery, norepinephrine dose, dopamine dose, dobutamine dose, PaO2/FiO2 ratio, and others; (d) postoperative outcomes: complications (such as cerebral infarction, hyperkalemia, mediastinitis, pneumonia, arrhythmia, seizures, and gastrointestinal disorders), mortality (overall and early postoperative death, defined as death within 90 days), and durations of mechanical ventilation, continuous renal replacement therapy (CCRT), and intensive care unit stay.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eData analysis\u003c/h2\u003e \u003cp\u003eWe investigated the relationships of preoperative fluid removal volume with complications, CRRT, duration of mechanical ventilation, and mortality. Continuous variables are reported as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation or median with interquartile range (IQR). The Wilcoxon rank-sum and Fisher\u0026rsquo;s exact tests were used to compare continuous and categorical variables, respectively. Receiver operating characteristic (ROC) curve analysis was performed to determine the preoperative fluid removal volume cut-off value associated with early mortality. The sensitivity and specificity of this volume were also determined. The patients were stratified into two groups based on this volume for subsequent analyses. Subgroup analyses were performed for patients with IDH before surgery, using the same threshold. Statistical significance was set at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eStudy population\u003c/h2\u003e \u003cp\u003eOf the 54 patients on dialysis who underwent elective cardiovascular surgery at our institution between January 1, 2012, and December 31, 2021, four were excluded (2 lacked data on preoperative fluid removal volume, and 2 were weaned from dialysis) (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The data of the remaining 50 patients were used for statistical analysis. The preoperative diagnoses and surgical procedures are provided in Tables\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and \u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\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\u003eClassification by preoperative diagnosis\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=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreoperative Diagnosis\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCases\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAngina pectoris, myocardial infarction\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e19\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAortic valve stenosis\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAortic valve regurgitation\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMitral valve regurgitation\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eInfective endocarditis\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTricuspid valve regurgitation\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAortic dissection\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1\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=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eClassification by surgical procedure\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=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSurgical procedure\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCases\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAortic valve replacement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOff-pump CABG\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOn-pump CABG\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAortic valve replacement་On-pump CABG\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMitral valve replacement་Tricuspid valve plasty\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAortic valve replacement\u0026thinsp;+\u0026thinsp;Mitral valve replacement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAortic valve replacement་Tricuspid valve plasty\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMitral valve replacement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMitral valve plasty་Tricuspid annuloplasty\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTricuspid annuloplasty་On-pump CABG\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDescending aortic dissection repair\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"2\"\u003eCABG, coronary artery bypass graft\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003ePatient characteristics\u003c/h3\u003e\n\u003cp\u003eIn our study population, the proportion of male patients and the median age were 76.0% and 69.0 years (IQR: 63\u0026ndash;73.8), respectively. The median durations of surgery and CPB were 329.5 min (IQR: 277.3\u0026ndash;373.0) and 154.5 min (IQR: 78.0\u0026ndash;188.5), respectively. The median preoperative fluid removal volume was 1,600.0 ml (IQR: 1,000.0\u0026ndash;2,175.0). The proportion of patients demonstrating hypotension during preoperative dialysis was 60.0% (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\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\u003ePatient background factors included in this study\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\u003ePopulation\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMedian (IQR or %)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge (years)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e69.0 (63.0\u0026ndash;73.8)\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\u003e161.0 (154.3\u0026ndash;167.0)\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\u003e57.5 (46.9\u0026ndash;61.9)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMale/Female (N)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e38.0/12.0 (76/24)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreoperative ejection fraction (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e60.0 (46.0\u0026ndash;66.0)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAmount of fluid removed preoperatively (ml)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1600.0 (1000.0\u0026ndash;2175.0)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreoperative hypotension during dialysis (N)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e30 (60)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDialysis history (years)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5.0 (3.0\u0026ndash;12.8)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDuration of surgery (min)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e329.5 (277.3\u0026ndash;373.0)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAnesthesia time (min)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e438.5 (365.5\u0026ndash;490.5)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAortic occlusion time (min)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e83.5 (0.0\u0026ndash;115.3)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCardiopulmonary bypass time (min)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e154.5 (78.0\u0026ndash;188.5)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTotal fluid and blood transfusion volume (ml)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3155.0 (2460.5\u0026ndash;4394.3)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSelf-collected blood return volume (ml)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1003.5 (737.3\u0026ndash;1433.0)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIntraoperative hypotension (case) *\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e36/14 (72.0/28.0)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePostoperative hemoglobin (g/dl)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10.2 (9.7, 10.9)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePostoperative complications (N)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e37.0 (74.0)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePostoperative continuous renal replacement therapy (N)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e24.0 (48.0)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDuration of mechanical ventilation (days)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.0 (3.0\u0026ndash;6.5)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"2\"\u003eFor cases not using cardiopulmonary bypass or aortic occlusion, the cardiopulmonary bypass and aortic occlusion times were recorded as 0 min.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"2\"\u003e*Intraoperative hypotension was defined as systolic blood pressure of 80 mmHg or lower sustained for 5 min or longer before cardiopulmonary bypass. For off-pump coronary artery bypass graft, intraoperative hypotension was defined as systolic blood pressure of 80 mmHg or lower sustained for 5 min or longer before bypass initiation.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eAssociation between preoperative fluid removal and outcomes\u003c/h2\u003e \u003cp\u003eWe found a significant relationship between early postoperative death and preoperative fluid removal volume (p\u0026thinsp;=\u0026thinsp;0.029). A large preoperative fluid removal volume was associated with increased incidences of postoperative complications and longer durations of mechanical ventilation (p\u0026thinsp;=\u0026thinsp;0.042 and p\u0026thinsp;=\u0026thinsp;0.014, respectively) (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eROC curve analysis\u003c/h3\u003e\n\u003cp\u003eROC analysis identified the preoperative fluid removal volume cut-off value for early postoperative mortality as 2,250 mL (area under the ROC curve, AUC: 0.78, sensitivity: 83.3%; specificity: 84.1%) (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\n\u003ch3\u003eStratified analysis using the 2,000-ml threshold\u003c/h3\u003e\n\u003cp\u003eThe patients were grouped based on their preoperative fluid removal volume for clinical interpretability: those with preoperative fluid removal volume of \u0026ge;\u0026thinsp;2,000 ml (n\u0026thinsp;=\u0026thinsp;18) and \u0026lt;\u0026thinsp;2,000 ml (n\u0026thinsp;=\u0026thinsp;32). The early postoperative mortality rate was significantly lower in the \u0026lt;\u0026thinsp;2,000 ml group (p\u0026thinsp;=\u0026thinsp;0.018) (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\u003eAssociation of preoperative fluid removal volume with early postoperative mortality\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\u003eAmount of preoperative fluid removal\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNo early postoperative mortality\u003c/p\u003e \u003cp\u003e(N\u0026thinsp;=\u0026thinsp;44)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eEarly postoperative mortality\u003c/p\u003e \u003cp\u003e(N\u0026thinsp;=\u0026thinsp;6)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;2,000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1 (3.1%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026le;\u0026thinsp;2,000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5 (27.8%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eSubgroup analysis: patients with hypotension during preoperative dialysis\u003c/h2\u003e \u003cp\u003eThe early mortality rate was significantly higher for patients with IDH (n\u0026thinsp;=\u0026thinsp;30) who had fluid removal volumes of \u0026ge;\u0026thinsp;2,000 mL than for those with volumes\u0026thinsp;\u0026lt;\u0026thinsp;2,000 mL (p\u0026thinsp;=\u0026thinsp;0.026) (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eAssociation of preoperative fluid removal volume with early postoperative mortality in cases of hypotension during dialysis\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\u003eAmount of preoperative fluid removal (in cases of hypotension during dialysis with preoperative fluid removal)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNo early postoperative mortality\u003c/p\u003e \u003cp\u003e(N\u0026thinsp;=\u0026thinsp;24)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eEarly postoperative mortality\u003c/p\u003e \u003cp\u003e(N\u0026thinsp;=\u0026thinsp;6)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;2,000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1 (5.6%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026le;\u0026thinsp;2,000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5 (41.7%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis study demonstrated that removal of a greater volume of fluid (\u0026gt;\u0026thinsp;2,000 mL) in patients on dialysis before they undergo cardiovascular surgery was significantly associated with increased early postoperative mortality. This association was particularly pronounced in patients who experienced hypotension during preoperative dialysis. Removal of a greater preoperative fluid volume was also associated with increased postoperative complications and a longer duration of mechanical ventilation.\u003c/p\u003e \u003cp\u003eThese findings are consistent with previously reported high perioperative mortality rates of patients on dialysis, particularly those undergoing valve surgeries (8\u0026ndash;10% for coronary artery bypass graft [CABG] and up to 20% for valve surgeries) [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Consistent with these previously reported rates, 6 of our 50 patients (12%) suffered early mortality, with rates of 16% and 10% for valve surgery and CABG, respectively.\u003c/p\u003e \u003cp\u003eRemoval of a large volume of fluid preoperatively may reduce intravascular volume and cause hemodynamic instability. This can necessitate large intraoperative fluid and transfusion volumes, which can contribute to pulmonary edema and the need for prolonged mechanical ventilation. Previous studies have also reported associations of excessive UFRs and large interdialytic weight gains with increased mortality [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Intraoperative crystalloid infusion exceeding 3 L has been associated with prolonged intensive care unit stay and ventilation [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eChronic dialysis induces persistent inflammatory responses, oxidative stress, endothelial dysfunction, and vascular remodeling. These pathophysiologic changes reduce vascular smooth muscle reactivity and increase the risk of vasodilation. They also increase the susceptibility of patients placed on dialysis to vasoplegic syndrome (VPS) during CPB. Dialysis-dependence has been reported as an independent predictor of VPS (odds ratio, 1.47; 95% confidence interval, 1.17\u0026ndash;1.86) [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. VPS is characterized by low systemic vascular resistance, high cardiac output, and refractory hypotension that is unresponsive to vasopressors.\u003c/p\u003e \u003cp\u003eMaintaining perfusion after VPS development often requires aggressive fluid and blood administration and multiple vasoactive agents. This compensatory volume loading may further aggravate pulmonary and tissue edema and can create a vicious cycle of hemodynamic instability and poor oxygenation. VPS is associated with adverse outcomes, including mortality, extended intensive care unit stay, and prolonged ventilation [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eHowever, previous studies have not consistently reported a direct relationship between elevated UFR and mortality in the non-surgical population [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. This discrepancy may be ascribed to differences in patient populations, surgical stress, or dialysis protocols. Few previous studies have specifically addressed preoperative ultrafiltration in the context of cardiac surgery, highlighting the novelty of our findings.\u003c/p\u003e \u003cp\u003eCurrent guidelines recommend avoiding excessive dehydration before anesthesia induction, due to the high risk of hypotension [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Fluid removal exceeding 6% of body weight has been associated with adverse outcomes [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]; rather, a preoperative target of dry weight\u0026thinsp;+\u0026thinsp;1 kg has been proposed to optimize perioperative stability [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Our findings support these recommendations and highlight the need for individualized, multidisciplinary adjustment of fluid removal strategies.\u003c/p\u003e \u003cp\u003eIDH occurs when the plasma refilling rate is exceeded by the ultrafiltration volume during dialysis, resulting in a reduction of circulating blood volume. IDH is also influenced by dialysis-related cardiovascular impairment and autonomic dysfunction [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. In this study patients with preoperative IDH who underwent high-volume fluid removal preoperatively had high early mortality. This finding underscores the need to reconsider fluid removal targets for patients with IDH.\u003c/p\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eLimitations\u003c/h2\u003e \u003cp\u003eThis study had some limitations. First, it was a retrospective single-center study. Second, some data were missing from the medical records. Third, as a retrospective study, the findings cannot establish causality between fluid removal volume and outcomes. Variations in dry weight determination, patient physiology, and comorbidities may have influenced the results.\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eExcessive preoperative fluid removal (\u0026gt;\u0026thinsp;2,000 ml), particularly in the presence of IDH, is associated with increased early postoperative mortality and complications in patients on dialysis undergoing cardiovascular surgery. These findings highlight the importance of individualized fluid management in close collaboration with dialysis teams to optimize the preoperative volume status and improve the surgical outcomes.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eCPB, cardiopulmonary bypass\u003c/p\u003e\n\u003cp\u003eIDH, intradialytic hypotension\u003c/p\u003e\n\u003cp\u003eIQR, interquartile range\u003c/p\u003e\n\u003cp\u003eROC, receiver operating characteristic\u003c/p\u003e\n\u003cp\u003eUFR, ultrafiltration rate\u003c/p\u003e\n\u003cp\u003eVPS, vasoplegic syndrome\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was conducted in accordance with the Declaration of Helsinki and\u0026nbsp;was approved by the Ethics Committee of\u0026nbsp;Saga Prefectural Medical Center Koseikan (Certification Number: 22-03-01-01). In accordance with the \u0026ldquo;Ethical Rules of the Saga Prefectural Medical Center Koseikan, a Local Independent Administrative Institution,\u0026rdquo; the committee determined that obtaining consent solely through the opt-out method was sufficient. These ethical rules comply with the \u0026ldquo;Ethical Guidelines for Life Science and Medical Research Involving Human Subjects\u0026rdquo; (Joint Notice No. 1 of the Ministry of Education, Culture, Sports, Science and Technology, the Ministry of Health, Labour and Welfare, and the Ministry of Economy, Trade and Industry, dated March 23, 2021).\u0026nbsp;We ensured that information about the research was made publicly available on hospital websites, and opportunities to decline participation were fully ensured.\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\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data of this study were generated at Saga Prefectural Medical Center Koseikan. Derived data supporting the results of this study can be obtained upon request from the corresponding author, Hiroshi Noguchi.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDM\u003c/strong\u003e: Supervision,\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eMethodology, Writing \u0026ndash; original draft, Writing \u0026ndash; review \u0026amp; editing. \u003cstrong\u003eMB:\u003c/strong\u003e Conceptualization, Investigation. \u003cstrong\u003eSK:\u0026nbsp;\u003c/strong\u003eConceptualization, Investigation. \u003cstrong\u003eYS:\u003c/strong\u003e Formal analysis, Writing \u0026ndash; review \u0026amp; editing. All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe thank Dr. Daisuke Miura for the warm guidance and encouragement offered over many hours regarding research methodology and paper writing. We also thank Drs. Mariko Baba and Shinichiro Kusaba for valuable advice based on their expertise in cardiovascular anesthesia. We are grateful to Professor Yoshiro Sakaguchi who provided valuable advice on research methodology and paper writing.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMeeting presentation\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA summary of this paper was presented at the 27th Academic Meeting of the Japanese Society of Cardiovascular Anesthesiology (Kyoto Prefecture, September 2022).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eMourad F, Cleve N, Nowak J, Wendt D, Sander A, Demircioglu E, et al. Long-term single-center outcomes of patients with chronic renal dialysis undergoing cardiac surgery. Ann Thorac Surg. 2020;109:1442\u0026ndash;8.\u003c/li\u003e\n \u003cli\u003eFoley RN, Parfrey PS, Sarnak MJ. Clinical epidemiology of cardiovascular disease in chronic renal disease. Am J Kidney Dis. 1998;32 Suppl 3:S112\u0026ndash;9.\u003c/li\u003e\n \u003cli\u003eGoodkin DA, Young EW, Kurokawa K, Pr\u0026uuml;tz KG, Levin NW. Mortality among hemodialysis patients in Europe, Japan, and the United States: Case-mix effects. Am J Kidney Dis. 2004;44 Suppl 2:16\u0026ndash;21.\u003c/li\u003e\n \u003cli\u003eRocco MV, Yan G, Heyka RJ, Benz R, Cheung AK, HEMO Study Group. Risk factors for hypertension in chronic hemodialysis patients: Baseline data from the HEMO study. Am J Nephrol. 2001;21:280\u0026ndash;8.\u003c/li\u003e\n \u003cli\u003eIfudu O, Uribarri J, Rajwani I, Vlacich V, Reydel K, Delosreyes G, et al. Relation between interdialytic weight gain, body weight and nutrition in hemodialysis patients. Am J Nephrol. 2002;22:363\u0026ndash;8.\u003c/li\u003e\n \u003cli\u003eSharpe N. Left ventricular remodeling: Pathophysiology and treatment. Heart Fail Monit. 2003;4:55\u0026ndash;61.\u003c/li\u003e\n \u003cli\u003eTisl\u0026eacute;r A, Ak\u0026oacute;csi K, Borb\u0026aacute;s B, Fazakas L, Ferenczi S, G\u0026ouml;r\u0026ouml;gh S, et al. The effect of frequent or occasional dialysis-associated hypotension on survival of patients on maintenance haemodialysis. Nephrol Dial Transplant. 2003;18:2601\u0026ndash;5.\u003c/li\u003e\n \u003cli\u003eFrenken M, Krian A. Cardiovascular operations in patients with dialysis-dependent renal failure. Ann Thorac Surg. 1999;68:887\u0026ndash;93.\u003c/li\u003e\n \u003cli\u003eHorai T, Fukui T, Tabata M, Takanashi S. Early and mid-term results of off-pump coronary artery bypass grafting in patients with end stage renal disease: Surgical outcomes after achievement of complete revascularization. Interact Cardiovasc Thorac Surg. 2008;7:218\u0026ndash;21.\u003c/li\u003e\n \u003cli\u003eDiegeler A, Hirsch R, Schneider F, Schilling LO, Falk V, Rauch T, et al. Neuromonitoring and neurocognitive outcome in off-pump versus conventional coronary bypass operation. Ann Thorac Surg. 2000;69:1162\u0026ndash;6.\u003c/li\u003e\n \u003cli\u003eNakai K, Yamamoto S, Tomooka H, Inoue M, Kohara C, Shukuri T, et al. Cardiac surgery in dialysis patients: Perioperative protocol and complications. Nihon Toseki igakkai zasshi. 2020;53:61\u0026ndash;9\u003c/li\u003e\n \u003cli\u003eTakami Y. Blood purification in perioperative management of cardiac surgery. J Jpn Soc Acute Blood Purif. 2016;7:3\u0026ndash;9.\u003c/li\u003e\n \u003cli\u003eMovilli E, Gaggia P, Zubani R, Camerini C, Vizzardi V, Parrinello G, et al. Association between high ultrafiltration rates and mortality in uraemic patients on regular haemodialysis. A 5-year prospective observational multicentre study. Nephrol Dial Transplant. 2007;22:3547\u0026ndash;52.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003e.\u0026nbsp;\u003c/strong\u003eFielding-Singh V, Roshanov PS, Morris AM, Chertow GM. Perioperative management of the patient receiving maintenance hemodialysis. Anesthesiology. 2025;143:1030\u0026ndash;48.\u003c/li\u003e\n \u003cli\u003eAdesanya A, Rosero E, Timaran C, Clagett P, Johnston WE. Intraoperative fluid restriction predicts improved outcomes in major vascular surgery. Vasc Endovasc Surg. 2008;42:531\u0026ndash;6.\u003c/li\u003e\n \u003cli\u003eRatnani I, Ochani RK, Shaikh A, Jatoi HN. Vasoplegia: A review. Methodist deBakey Cardiovasc J. 2023;19:38\u0026ndash;47.\u003c/li\u003e\n \u003cli\u003eBusse LW, Barker N, Petersen C. Vasoplegic syndrome following cardiothoracic surgery-review of pathophysiology and update of treatment options. Crit Care. 2020;24:36.\u003c/li\u003e\n \u003cli\u003eFernandez-Prado R, Pe\u0026ntilde;a-Esparragoza JK, Santos-S\u0026aacute;nchez-Rey B, Pereira M, Avello A, Gom\u0026aacute;-Garc\u0026eacute;s E, et al. Ultrafiltration rate adjusted to body weight and mortality in hemodialysis patients. Nefrologia. 2021;41:426\u0026ndash;35.\u003c/li\u003e\n \u003cli\u003eSlinin Y, Babu M, Ishani A. Ultrafiltration rate in conventional hemodialysis: Where are the limits and what are the consequences? Semin Dial. 2018;31:544\u0026ndash;50.\u003c/li\u003e\n \u003cli\u003e20. Hirata S, Nitta K, Inaba M, Shoji T, Fujii H, Kobayashi S, et al. Japanese Society for Dialysis Therapy guidelines for management of cardiovascular diseases in patients on chronic hemodialysis. J Dial Soc. 2011;44:337\u0026ndash;425.\u003c/li\u003e\n \u003cli\u003eNakai S, Iseki K, Itami N, Ogata S, Kazama JJ, Kimata N, et al. Overview of Regular Dialysis Treatment in Japan (as of 31 December 2009). J Jpn Soc Dial Ther. 2011;43:1\u0026ndash;36.\u003c/li\u003e\n \u003cli\u003eTsukui H, Iwasa S, Yamazaki K. Comprehensive treatment strategy aiming to improve the results of open heart surgery in dialysis patients. J Jpn Soc Acute Blood Purif. 2016;7:141\u0026ndash;6.\u003c/li\u003e\n \u003cli\u003eKamio M, Harada K, Watanabe T, Waki H, Kanno M, Kakinuma Y, et al. A case in which left ventricular stenosis was suggested to be involved in decreased blood pressure accompanied by chest pain during dialysis. Heart. 2021;53:177\u0026ndash;82.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"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":"bmc-nephrology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bnep","sideBox":"Learn more about [BMC Nephrology](http://bmcnephrol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bnep/default.aspx","title":"BMC Nephrology","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"cardiovascular surgery, dialysis, mortality, preoperative fluid removal","lastPublishedDoi":"10.21203/rs.3.rs-8264468/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8264468/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cb\u003eBackground\u003c/b\u003e\u003c/p\u003e \u003cp\u003eIn patients on dialysis who are scheduled for surgery, the volume of fluid removed preoperatively may influence intraoperative circulatory stability and can affect perioperative complications. However, no clear standards for approaches to preoperative fluid removal have been established. In this study, we investigated the association between preoperative fluid removal volume and early postoperative mortality and complications in patients undergoing dialysis who underwent cardiovascular surgery.\u003c/p\u003e\u003cp\u003e\u003cb\u003eMethods\u003c/b\u003e\u003c/p\u003e \u003cp\u003eWe included patients placed on dialysis who underwent cardiovascular surgery between January 1, 2012, and December 31, 2021. Their clinical data were retrieved from electronic medical records. The primary outcome was early postoperative mortality. Secondary outcomes were postoperative complications, postoperative continuous renal replacement therapy (CRRT), and duration of mechanical ventilation. Statistical comparisons were performed using the Wilcoxon rank-sum test and Fisher\u0026rsquo;s exact test. The optimal cut-off values for fluid removal volume were determined using receiver operating characteristic (ROC) analysis. The patients were classified into two groups based on their preoperative fluid removal volumes (\u0026ge;\u0026thinsp;2,000 mL or \u0026lt;\u0026thinsp;2,000 ml). Statistical significance was set at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e\u003cp\u003e\u003cb\u003eResults\u003c/b\u003e\u003c/p\u003e \u003cp\u003eIn this cohort of 50 patients, the proportion of male patients and the median age were 76.0% and 69.0 years (IQR: 63\u0026ndash;73.8), respectively. The preoperative fluid removal volume was significantly associated with early postoperative mortality (p\u0026thinsp;=\u0026thinsp;0.029), postoperative complications (p\u0026thinsp;=\u0026thinsp;0.042), and prolonged postoperative mechanical ventilation (p\u0026thinsp;=\u0026thinsp;0.014). ROC analysis identified 2,250 mL as the optimal cut-off value (sensitivity, 83.3%; specificity, 84.1%). Patients with volumes of \u0026ge;\u0026thinsp;2,000 mL had a significantly higher early postoperative mortality rate (p\u0026thinsp;=\u0026thinsp;0.018). Greater fluid removal volumes were associated with increased early postoperative mortality in those with hypotension during preoperative dialysis (p\u0026thinsp;=\u0026thinsp;0.026).\u003c/p\u003e\u003cp\u003e\u003cb\u003eConclusions\u003c/b\u003e\u003c/p\u003e \u003cp\u003eExcessive preoperative fluid removal (\u0026gt;\u0026thinsp;2,000 mL) is associated with increased risks of early postoperative mortality, particularly in patients with hypotension during preoperative hemodialysis. These findings highlight the importance of individualized fluid management through multidisciplinary collaboration.\u003c/p\u003e","manuscriptTitle":"Preoperative fluid removal volume in patients on dialysis undergoing cardiovascular surgery","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-12 06:16:11","doi":"10.21203/rs.3.rs-8264468/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"166277166144920527413793762048730541069","date":"2026-01-14T07:51:23+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-01-07T11:24:59+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-01-05T10:00:32+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-12-10T09:12:05+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-12-09T22:28:09+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Nephrology","date":"2025-12-09T22:23:21+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-nephrology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bnep","sideBox":"Learn more about [BMC Nephrology](http://bmcnephrol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bnep/default.aspx","title":"BMC Nephrology","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"6bf8d24b-027e-4aa2-a101-5690c65242f1","owner":[],"postedDate":"January 12th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-01-12T06:16:11+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-12 06:16:11","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8264468","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8264468","identity":"rs-8264468","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}