Mild hyperlactatemia in stable septic patients is due to impaired lactate clearance rather than overproduction

A prospective study was conducted on 34 stable septic patients to determine whether mild hyperlactatemia is a marker of lactate overproduction or an indicator of lactate underutilization during sepsis. Plasma lactate clearance and lactate production were evaluated by modeling the lactate kinetic induced by an infusion of 1 mmol/kg L-lactate over 15 min. The patients were divided in two groups depending on their blood lactate: less than or equal to 1.5 mmol/L (n = 20, lactate = 1.2 +/- 0.2 mmol/L) or greater than or equal to 2 mmol/L (n = 10, lactate = 2.6 +/- 0.6 mmol/L). The hyperlactatemic patients had a lower lactate clearance (473 +/- 102 ml/kg/h) than those with normal blood lactate (1,002 +/- 284 ml/kg/h, p < 0.001), whereas lactate production in the two groups was similar (1,194 +/- 230 and 1,181 +/- 325 mu mol/kg/h, p = 0.90). A second analysis including all the patients confirmed that the blood lactate concentration was closely linked to the reciprocal of lactate clearance (r(2) = 0.73, p < 0.001) but not to lactate production (r(2) = 0.03, p = 0.29). We conclude that a mild hyperlactatemia occurring in a stable septic patient is mainly due to a defect in lactate utilization.