Exogenous L-lactate clearance in adult horses

Objective: To determine endogenous production of L-lactate and the clearance of exogenous sodium L-lactate (ExLC) in healthy adult horses. Design: A sodium L-lactate solution (1 mmol/kg body weight qs to 500 mL final volume in 0.9% NaCl) was adminstered IV over 15 minutes. Blood samples for L-lactate concentration [LAC] measurement were collected immediately prior to infusion, at 5, 10, and 15 minutes during infusion and at 1 minute intervals for 15 minutes, at 30, 45, 60, 120, and 180 minutes postinfusion. Disposition modeling and pharmacokinetic analysis was performed using proprietary software. Setting: University Teaching Hospital. Animals: Six clinically healthy adult horses. Measurements and Main Results: Median (range) baseline [LAC] was 0.43 (0.20-0.72) mmol/L for samples obtained every 3 hours over the 24 hours prior to ExLC and demonstrated variability primarily associated with horse. Median [LAC] immediately prior to ExLC was 0.43 (0.35-0.52) mmol/L. A 2-compartment model was used to specify the pharmacokinetic parameters. Median (range) ExLC was 1.05 (0.073-1.75) L·h^-1·kg^-1 and t_1/2 β was 29.54 (20.8-38.6) min. Median lactate production based on basal [LAC] immediately prior to ExLC was was 0.49 (0.31-0.93) mmol·h^-1·kg^-1. Conclusions: ExLC in healthy adult horses is greater than that of hyperlactemic human patients but similar to normolactemic-sick human patients examined using the same model, supporting development of species, and disease specific ExLC parameters.