Effect of continuous venovenous hemofiltration with dialysis on lactate clearance in critically ill patients

Objective: To evaluate the effect of continuous venovenous hemofiltration with dialysis on lactate elimination by critically ill patients. Design: Prospective, clinical study, Setting: Surgical intensive care unit of a university hospital. Patients: Ten critically ill patients with acute renal failure and stable blood lactate concentrations. Interventions: Two-stage investigation: a) measurement of lactate concentrations in samples of serum and ultradiafiltrate from patients receiving continuous venovenous hemofiltration with dialysis to calculate lactate clearance by the hemofilter; b) evaluation of total plasma lactate clearance by infusing sodium L-lactate (1 mmol/kg of body weight) over 15 mins. Measurements and Main Results: Arterial lactate concentra tion was determined before, during, and after the infusion, Lactate elimination variables were calculated from the plasma curve using model independent and model-dependent estimates (by software). At the end of the infusion, median blood lactate concentration increased from 1.4 mmol/L (range 0.8 to 2.6) to 4.8 mmol/L (range 2.4 to 5.7) and returned to 1.6 mmol/L (range 0.9 to 3.4) 60 mins later. The median total plasma lactate clearance was 1379 mL/min (range 753.7 to 1880.7) and the median filter lactate clearance was 24.2 mL/min (range 7.1 to 35.6). Thus, filter lactate clearance accounted for <3% Of total lactate clearance. Conclusions: Continuous venovenous hemofiltration with dialysis cannot mask lactate overproduction, and its blood concentration remains a reliable marker of tissue oxygenation in patients receiving this renal replacement technique.