Central venous oxygen saturation for the diagnosis of low cardiac output in septic shock patients

Background Simple diagnostic tests are needed to screen septic patients for low cardiac output because intervention is recommended in these patients. We assessed the diagnostic value of central venous oxygen saturation in the superior vena cava (ScvO(2)) for detecting low cardiac output in patients with septic shock. Methods We conducted a prospective observational study in three general intensive care units (ICUs) of adult patients with septic shock, who were to have a catheter inserted for thermodilution measurement of cardiac index (CITD). Paired measurements of CITD and central venous oximetry values were obtained when the clinician first measured CITD. Results We included 56 patients with septic shock and a mean sequential organ failure assessment score of 12 (range 3-20). Baseline CITD was 3.5 l/min/m2 (1.0-6.2) and ScvO(2) of 70% (33-87). The best cut-off of ScvO(2) for CITD > 2.5 l/min/m2 (n=42) was a value >= 64% with positive and negative predictive values of 91% (95% confidence interval 79-98) and 91% (59-100), respectively. The diagnostic values were not improved by using instead central venous O-2 tension or the difference between arterial and central venous O-2 saturation. Conclusions This prospective, observational study found that a ScvO(2) measurement of >= 64% indicated CITD > 2.5 l/min/m2 in ICU patients with septic shock.