Venous-to-Arterial Carbon Dioxide Partial Pressure Difference: Predictor of Septic Patient Prognosis Depending on Central Venous Oxygen Saturation

This study aimed to assess the viability of using the venous-to-arterial carbon dioxide partial pressure difference (P(v-a)CO2) to predict clinical worsening of septic shock, depending on central venous oxygen saturation (ScvO(2)). The prospective, observational, multicentric study conducted in three intensive care units (ICUs) included all patients with a septic shock episode during the first 6 h, with 122 patients assessed. Clinical worsening was defined as an increase of sequential organ failure assessment (SOFA) scores >= 1 (Delta SOFA >= 1) within 2 days. To assess the ability of P(v-a)CO(2)to predict clinical worsening, univariate and multivariate analyses were performed according to Delta SOFA. A receiver-operating characteristic (ROC) analysis was used to confirm model predictions. Associations between P(v-a)CO(2)and mortality were explored using correlations. Using multivariate analyses, two independent factors associated with Delta SOFA at least 1 were identified: an averaged 6-h value of lactate concentration (Lac [1-6]) (odds ratios [ORs], 2.43 [95% confidence interval, CI, 1.20-4.89];P = 0.013) and an averaged 6-h value of P(v-a)CO2(P(v-a)CO2[1-6]) (OR, 1.49 [95% CI, 1.04-2.15];P = 0.029). ROC analysis confirmed that Lac [1-6] and P(v-a)CO2[1-6] were significantly associated with Delta SOFA at least 1, whereas ScvO(2)[1-6] was not. Finally, Delta SOFA at least 1 was associated with higher 28-day (76% vs. 10%,P = 0.001) and ICU (83% vs. 12%,P = 0.001) mortality rates, which were higher in patients with P(v-a)CO2[1-6] more than 5.8 mmHg (57% vs. 33%;P = 0.012). In conclusion, P(v-a)CO(2)may help predict outcomes for septic shock patients regardless of ScvO(2)values.