Central venous to mixed venous blood oxygen and lactate gradients are associated with outcome in critically ill patients

Abstract

Blood O(2) saturation and lactate concentration gradients from superior vena cava (SVC) to pulmonary artery (PA) occur in critically ill patients. These gradients (DeltaSO(2) and Delta[Lac]) may be positive or negative. We tested the hypothesis that positive DeltaSO(2) and Delta[Lac] are associated with improved survival in critically ill patients. 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. None. 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 SO(2), [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 DeltaSO(2) > or = 0 and Delta[Lac] > or = 0 than decedents (p < 0.01; p < 0.05 respectively). On the average, DeltaSO(2) and Delta[Lac] were positive in survivors and negative in decedents. Survival odds ratios for final measurements of DeltaSO(2) > or = 0 and Delta[Lac] > or = 0 were 19.22 and 7.70, respectively (p < 0.05). A strong association exists between positive DeltaSO(2) and Delta[Lac] and survival in critically ill patients. Whether therapy aimed at increasing DeltaSO(2) and Delta[Lac] results in improved ICU survival remains to be determined.