The Prognostic Value of Central Venous-to-Arterial CO2 Difference/Arterial-Central Venous O2 Difference Ratio in Septic Shock Patients with Central Venous O2 Saturation ≥80%

ABSTRACT Background: It is a great challenge for physician to assess the relationship between O 2 delivery and O 2 consumption in septic shock patients with high ScvO 2 . Recently, the venous-to-arterial CO 2 difference/arterial-central venous O 2 difference ratio (P(v-a)CO 2 /C(a-v)O 2 ) has shown potential for reflecting anaerobic metabolism. Therefore, we evaluated the value of using the P(v-a)CO 2 /C(a-v)O 2 ratio to predict mortality and assess anaerobic metabolism in septic shock patients with high ScvO 2 (≥ 80%). Methods: This was a clinical investigation of septic shock patients on the P(v-a)CO 2 /C(a-v)O 2 ratio in the intensive care unit (ICU) department. The patients’ arterial and central venous blood gas levels were measured simultaneously at enrollment (T0) and 24 h (T24) after resuscitation. Results: A total of 61 patients with high ScvO 2 at T24 after resuscitation were selected for analysis. The ICU mortality rate in the septic shock patients was 20% (12/61). The nonsurvivors had a significantly higher P(v-a)CO 2 , P(v-a)CO 2 /C(a-v) O 2 ratio, arterial lactate level and lower lactate clearance at T24 after resuscitation. The P(v-a)CO 2 /C(a-v)O 2 ratio had the biggest the areas under the receiver operating characteristic (AUC) for predicting ICU mortality. For predicting ICU mortality, a threshold of P(v-a)CO 2 /C(a-v)O 2 ratio ≥1.6 was associated with a sensitivity of 83% and a specificity of 63%. Multivariate analysis showed P(v-a)CO 2 /C(a-v)O 2 ratio at both T0 (RR 5.597, P = 0.024) and T24 (RR 5.812, P = 0.031) was an independent predictor of ICU mortality. Including the ratio into the regression model showed a bigger AUC than without the ratio (0.886 vs. 0.833). Conclusions: The P(v-a)CO 2 /C(a-v)O 2 ratio is an independent predictor of ICU mortality in septic shock patients with high ScvO 2 after resuscitation. It is worthy of consideration to recruit microcirculation to correct the high ratio in high ScvO 2 case.