Changes in central venous saturation after major surgery, and association with outcome

Despite recent interest in measurement of central venous oxygen saturation (ScvO₂), there are no published data describing the pattern of ScvO₂ changes after major general surgery or any relationship with outcome.

ScvO₂ and other biochemical, physiological and demographic data were prospectively measured for 8 hours after major surgery. Complications and deaths occurring within 28 days of enrolment were included in the data analysis. Independent predictors of complications were identified with the use of logistic regression analysis. Optimum cutoffs for ScvO₂ were identified by receiver operator characteristic analysis.

Data from 118 patients was analysed; 123 morbidity episodes occurred in 64 these patients. There were 12 deaths (10.2%). The mean ± SD age was 66.8 ± 11.4 years. Twenty patients (17%) underwent emergency surgery and 77 patients (66%) were male. The mean ± SD P-POSSUM (Portsmouth Physiologic and Operative Severity Score for the enUmeration of Mortality and morbidity) score was 38.6 ± 7.7, with a predicted mortality of 16.7 ± 17.6%. After multivariate analysis, the lowest cardiac index value (odds ratio (OR) 0.58 (95% confidence intervals 0.37 to 0.9); p = 0.018), lowest ScvO₂ value (OR 0.94 (0.89 to 0.98); p = 0.007) and P-POSSUM score (OR 1.09 (1.02 to 1.15); p = 0.008) were independently associated with post-operative complications. The optimal ScvO₂ cutoff value for morbidity prediction was 64.4%. In the first hour after surgery, significant reductions in ScvO₂ were observed, but there were no significant changes in CI or oxygen delivery index during the same period.

Significant fluctuations in ScvO₂ occur in the immediate post-operative period. These fluctuations are not always associated with changes in oxygen delivery, suggesting that oxygen consumption is also an important determinant of ScvO₂. Reductions in ScvO₂ are independently associated with post-operative complications.