PURPOSE:Central venous oxygen saturation (ScvO2) has been used as a surrogate marker for mixed venous oxygen saturation (SvO2) to help guide resuscitation in goal-directed therapy. The relationship between femoral (FvO2) and non-femoral venous oxygen saturation (ScvO2) in critically ill patients is unstudied. The purpose of this study was to compare paired samples of FvO2 and ScvO2 to test the hypothesis that these values can be used interchangeably in a critically ill population.
METHODS:This prospective observational study included critically ill patients who had femoral and non-femoral central venous catheters (CVCs) placed as part of their standard ICU care. Non-femoral catheters included those placed in the internal jugular or subclavian veins. Two sets of paired blood samples were drawn simultaneously from the femoral and non-femoral CVCs at times zero and thirty minutes. The blood samples were analyzed for oxygen saturation and lactate. Demographic and clinical parameters were also recorded for descriptive purposes.
RESULTS:30 patients were enrolled in this study. The mean age was 65±17 years and the mean APACHE and SOFA scores were 18.4 and 7.26 respectively. Data were compared by Wilcoxon analysis and by method of Bland-Altman. The mean FvO2 and ScvO2 were 72.2±12.4% and 75.5±11.5% respectively (p=0.06), with a mean bias of 3.22±12.13%. The mean serum lactate from the femoral and non-femoral CVCs was 2.54±2.8, and 2.51±2.9 respectively (p=0.07).
CONCLUSION:Our preliminary study revealed no significant difference between FvO2 and ScvO2 and between serum lactate obtained from femoral and non-femoral CVCs. However, a trend towards a significant difference between FvO2 and ScvO2 was shown. Moreover, the Bland-Altman analysis demonstrated that more than 50% of FvO2 and ScvO2 values diverged by more than 5%, which is a clinically relevant difference.
CLINICAL IMPLICATIONS:The inconsistent agreement between FvO2 and ScvO2 could lead to inappropriate interventions based on narrow resuscitation endpoints. These data need to be confirmed in a larger cohort of patients prior to using these values interchangeably.
DISCLOSURE:Danielle Davison, No Financial Disclosure Information; No Product/Research Disclosure Information