Central venous to mixed venous blood oxygen and lactate gradients are associated with outcome in critically ill patients
Blood O2 saturation and lactate concentration gradients from superior vena cava (SVC) to pulmonary artery (PA) occur in critically ill patients. These gradients (ΔSO2 and Δ[Lac]) may be positive or negative. We tested the hypothesis that positive ΔSO2 and Δ[Lac] are associated with improved survival in critically ill patients.
Design and setting
Multinational, prospective observational study conducted in six medical and surgical ICUs.
Consecutive sample of 106 adults requiring insertion of a pulmonary artery catheter (PAC). Average age was 59.5 ± 15.5 years, APACHE II score was 15.5 ± 6.7 (mean ± SD). Main outcome measure was 28-day mortality.
Measurements and results
We drew blood samples from the proximal and distal ports of PACs every 6 h from the time of PAC insertion (Initial measurement) until its removal (Final measurement). Samples were analyzed for SO2, [Lac], glucose concentration and blood gases. Hemodynamic measurements were obtained after blood samples. We monitored patients for 30.9 ± 11.0 h. Overall mortality rate was 25.5%. More survivors had mean and final ΔSO2 ≥ 0 and Δ[Lac] ≥ 0 than decedents (p < 0.01; p < 0.05 respectively). On the average, ΔSO2 and Δ[Lac] were positive in survivors and negative in decedents. Survival odds ratios for final measurements of ΔSO2 ≥ 0 and Δ[Lac] ≥ 0 were 19.22 and 7.70, respectively (p < 0.05).
A strong association exists between positive ΔSO2 and Δ[Lac] and survival in critically ill patients. Whether therapy aimed at increasing ΔSO2 and Δ[Lac] results in improved ICU survival remains to be determined.
KeywordsMixed venous Central venous Sepsis Myocardial metabolism Tissue oxygenation
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