Central venous oxygen saturation (Scvo2) has been used as a surrogate marker for mixed venous oxygen saturation (Svo2). Femoral venous oxygen saturation (Sfvo2) is sometimes used as a substitute for Scvo2. The purpose of this study is to test the hypothesis that these values can be used interchangeably in a population of patients who are critically ill.
We conducted a survey to assess the frequency of femoral line insertion during the initial treatment of patients who are critically ill. Scvo2 vs Sfvo2 Study: Patients with femoral and nonfemoral central venous catheters (CVCs) were included in this prospective study. Two sets of paired blood samples were drawn simultaneously from the femoral and nonfemoral CVCs. Blood samples were analyzed for oxygen saturation and lactate.
One hundred and fifty physicians responded to the survey. More than one-third of the physicians insert a femoral line at least 10% of the time during the initial treatment of patients who were critically ill. Scvo2 vs Sfvo2 Study: Thirty-nine patients were enrolled. The mean Scvo2 and Sfvo2 were 73.1% ± 11.6% and 69.1% ± 12.9%, respectively (P = .002), with a mean bias of 4.0% ± 11.2% (95% limits of agreement: −18.4% to 26.4%). The mean serum lactate from the nonfemoral and femoral CVCs was 2.84 ± 4.0 and 2.72 ± 3.2, respectively (P = .15).
This study revealed a significant difference between paired samples of Scvo2 and Sfvo2. More than 50% of Scvo2 and Sfvo2 values diverged by > 5%. Sfvo2 is not always a reliable substitute for Scvo2 and should not routinely be used in protocols to help guide resuscitation.