Influence of glucose kinetics on plasma lactate concentration and energy expenditure in severely burned patients

Background: In critically ill patients, elevation in the plasma lactate con centration has traditionally been interpreted as indicating a deficiency in oxygen availability and is often an impetus to increase oxygen delivery cl inically. However, another possible basis for increased lactate concentrati ons may be simply a mass effect from increased pyruvate availability (i.e., accelerated glycolysis). Methods: In six hypermetabolic burned patients, the rates of glucose produc tion and oxidation were quantified using a tracer infusion of 6,6 d(2) gluc ose combined with indirect calorimetry. Measurements were obtained after a 9-hour fast and after a 3-hour infusion of unlabeled glucose at 30 mu mol/k g/min. No patient was overtly septic, hypoxic, or hypovolemic. Results: The infusion of glucose significantly increased the arterial gluco se concentration and rate of glucose oxidation, with a corresponding increa se in the arterial plasma concentration of lactate and pyruvate, Resting en ergy expenditure and oxygen consumption were not affected by the infusion o f glucose. Conclusions: These findings show that elevations in plasma lactate in sever ely injured patients may, in part, be related to increases in glucose flux and not entirely a reflection of any deficit in oxygen availability. Such f indings highlight a potential pitfall for interpreting plasma lactate conce ntrations as an index of tissue oxygen availability in hypermetabolic patie nts.