A retrospective study about the factors of early postoperative fluid balance of patients undergoing cardiopulmonary bypass

Abstract

Objective To explore the possible factors of early postoperative fluid balance and the influence of early postoperative fluid balance on the prognosis of patients undergoing cardiopulmonary bypass. Methods A retrospective study was conducted on the clinical data of 180 adult patients undergoing cardiopulmonary bypass from January 2012 to December 2015.All the patients were from Sun Yat-sen Memorial Hospital, Sun Yat-Sen University. The data were input and analyzed by SPSS 17.0 software. Results The early postoperative fluid balance of cardiovascular surgery with cardiopulmonary bypass was (540.94±135.86) ml. The value of the early postoperative fluid balance (the difference of the total input amount and the total output amount/body quality) in predicting the major clinical outcome was analyzed by ROC curve. The area under the ROC curve from fluid balance was 0.850 (95%CI 0.736-0.965, P<0.01) and it had the sensitivity of 80.0%, and the specificity was 84.6%. The result showed that the cut off values had a good prediction ability for outcome. The cut off values determined by the biggest Youden index were 28.63 ml/kg, indicated that patients may had better outcome when they had the fluid balance of 28.63 ml/kg. The level of early postoperative fluid balance of patients undergoing cardiopulmonary bypass was correlated with mechanical ventilation time, ICU length of stay, higher risk of acute kidney injury, mixed venous oxygen saturation and clinical outcome (P<0.05). Multivariate analysis indicated that European System for Cardiac Operative Risk Evaluation Ⅱ (EuroSCOREⅡ), other types of surgery, body mass index, early postoperative urine output and early postoperative drainage flow were independently associated with postoperative fluid balance of patients undergoing cardiopulmonary bypass. Conclusions Early postoperative fluid balance has a good prediction ability for prognosis of patients undergoing cardiopulmonary bypass. Compared with patients having lower level of fluid balance, the patients with a higher level would be more likely to have longer mechanical ventilation time, longer ICU length of stay, higher risk of acute kidney injury and lower level of mixed venous oxygen saturation. By analysis of ROC curves, the cut-off value for early postoperative fluid balance is 28.63 ml/kg, worse prognosis may be predicted if fluid balance is above 28.63 ml/kg. EuroSCOREⅡ, other types of surgery, body mass index, early postoperative urine output and early postoperative drainage flow are independently associated with the postoperative fluid balance of patients undergoing cardiopulmonary bypass. Key words: Cardiopulmonary bypass; Postoperative; Early period; Fluid balance; Prognosis; Influence factors