Combination of arterial lactate levels and venous-arterial CO(2) to arterial-venous O(2) content difference ratio as markers of resuscitation in patients with septic shock

PURPOSE: To evaluate the prognostic value of the Cv-aCO(2)/Da-vO(2) ratio combined with lactate levels during the early phases of resuscitation in septic shock. METHODS: Prospective observational study in a 60-bed mixed ICU. One hundred and thirty-five patients with septic shock were included. The resuscitation protocol targeted mean arterial pressure, pulse pressure variations or central venous pressure, mixed venous oxygen saturation, and lactate levels. Patients were classified into four groups according to lactate levels and Cv-aCO(2)/Da-vO(2) ratio at 6 h of resuscitation (T6): group 1, lactate ≥2.0 mmol/L and Cv-aCO(2)/Da-vO(2) >1.0; group 2, lactate ≥2.0 mmol/L and Cv-aCO(2)/Da-vO(2) ≤1.0; group 3, lactate <2.0 mmol/L and Cv-aCO(2)/Da-vO(2) >1.0; and group 4, lactate <2.0 mmol/L and Cv-aCO(2)/Da-vO(2) ≤1.0. RESULTS: Combination of hyperlactatemia and high Cv-aCO(2)/Da-vO(2) ratio was associated with the worst SOFA scores and lower survival rates at day 28 [log rank (Mantel–Cox) = 31.39, p < 0.0001]. Normalization of both variables was associated with the best outcomes. Patients with a high Cv-aCO(2)/Da-vO(2) ratio and lactate <2.0 mmol/L had similar outcomes to hyperlactatemic patients with low Cv-aCO(2)/Da-vO(2) ratio. The multivariate analysis revealed that Cv-aCO(2)/Da-vO(2) ratio at both T0 (RR 3.85; 95 % CI 1.60–9.27) and T6 (RR 3.97; 95 % CI 1.54–10.24) was an independent predictor for mortality at day 28, as well as lactate levels at T6 (RR 1.58; 95 % CI 1.13–2.22). CONCLUSION: Complementing lactate assessment with Cv-aCO(2)/Da-vO(2) ratio during early stages of resuscitation of septic shock can better identify patients at high risk of adverse outcomes. The Cv-aCO(2)/Da-vO(2) ratio may become a potential resuscitation goal in patients with septic shock. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00134-015-3720-6) contains supplementary material, which is available to authorized users.