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Global indices of tissue perfusion include lactate and central venous oxygen saturation (SvcO2). The mixed venous-arterial pCO2 difference (ΔCO2m) cannot serve as a marker of tissue hypoxia. It is a marker of venous flow adequacy to remove the total CO2 produced by peripheral tissues . Substitution of a central for a mixed venous- arterial pCO2 difference is acceptable . The objective was to assess the relationship between ΔCO2 and SOFA score variation in patients with severe sepsis and septic shock. Lactate and ScO2 were also evaluated.
Prospective observational study in patients with severe sepsis and septic shock admitted to an adult tertiary ICU. The management of sepsis was carried out as proposed by Surviving Sepsis Campaign guidelines. The earliest simultaneous measurement of lactate, SvcO2, and ΔCO2 were obtained when clinically indicated (T0) and after 8 to 12 hours (T8-12). The SOFA score was determined at T0 and after 24 hours (T24) and ΔSOFA (T24-T0) was calculated. The patients were classified according to their parameters at T0 (ΔCO2 ≥6 vs <6, lactate ≥28 mg/dl vs <28 mg/dl, SvcO2 ≥70% vs <70%) and their trends after 8 to 12 hours (adequate vs not adequate). Those groups were compared regarding their ΔSOFA score. The Student's t test was used for analysis and results were considered significant if P < 0.05.
Forty-three patients were included with mean of 60.2 ± 18.6 years, time from intensive care admission to T0 10.3 ± 9.3 hours and duration of organ dysfunction before enrollment 21.4 ± 15.6 hours. APACHE II, SOFA T0, and SOFA T24 scores were 18.8 ± 6.5, 7.9 ± 3.8, and 8.0 ± 4.3, respectively. ΔCO2 at T0 (P = 0.60) and its trend (P = 0.36) are not related to ΔSOFA. The analysis of SvcO2 also showed no significant finding. Patients with high (≥28 mg/dl) blood lactate concentration at T0 (P = 0.03) and not adequate in blood lactate concentration at T8-12 (P = 0.04) had an increase in SOFA score.
Patients with hyperlactatemia in the beginning of admission, which persists with increased levels of lactate, evolve to a worsening of SOFA score in 24 hours. ΔCO2 and SvcO2 and its trends are unrelated to the SOFA score in 24 hours.