Central venous oxygen saturation during cardiopulmonary bypass predicts 3-year survival

Abstract

Long-term survival after cardiac surgery is determined by a number of different risk factors. Central venous oxygen saturation (S(v)O(2)) measures the balance between oxygen delivery and demand. S(v)O(2) levels in the intensive care situation are reported to be associated with patient outcome. The present report explores the connection between S(v)O(2) during cardiopulmonary bypass (CPB) and survival after cardiac surgery. Retrospective analysis of one thousand consecutive cardiac surgical patients was undertaken. S(v)O(2) during CPB was monitored online. Registry data combining specific risk factors with S(v)O(2) were selected for Kaplan-Meier and Cox regression analysis to examine the influence on 30-day and 3-year survivals. Nine-hundred and thirty-two patient records were eligible for analysis. S(v)O(2) below 75% during CPB was associated with significantly shorter 30-day and 3-year survivals. Based on Kaplan-Meier statistics, the survival rate decreased by 3.1% (98.1-95.0), P = 0.011 and 6.1% (92.7-86.6), P = 0.003, respectively. The influence of S(v)O(2) on 3-year survival remained statistically significant after controlling for a series of risk factors in the Cox regression analysis. Patients with S(v)O(2) <75% carried a 2-fold (odds ratio 2.1) increased relative risk of shortened 3-year survival (P = 0.003). Other risk factors statistically significantly associated with 3-year survival were age, gender, duration of CPB, blood temperature, hypertension, haematocrit and type of surgical procedure. We report decreased 30-day and 3-year survival expectancy for patients experiencing S(v)O(2) lower than 75% during CPB.