Thursday July 8, 2010

SfVO2? - Nah!

Background: 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.

Methods: We conducted a survey to assess the frequency of femoral line insertion during the initial treatment of patients who are critically ill. 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.

Results: 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).
  

Conclusions: This study revealed a significant difference between paired samples of Scvo₂ and Sfvo₂. More than 50% of Scvo₂ and Sfvo₂ values diverged by more than 5%. Sfvo₂ is not always a reliable substitute for Scvo₂ and should not routinely be used in protocols to help guide resuscitation.

Femoral-Based Central Venous Oxygen Saturation Is Not a Reliable Substitute for Subclavian/Internal Jugular-Based Central Venous Oxygen Saturation in Patients Who Are Critically Ill - Chest July 2010 138:76-83; also published ahead of print April 23, 2010.