Grip J, et al. - Researchers intended to develop as well as validate a feasible approach to analyze lactate kinetics in critically ill patients. A bolus dose of ¹³C-labeled lactate (20 μmol/kg body weight) was administered to 6 healthy volunteers, and 43 blood samples were collected over 2 h to assess the decay in labeled lactate. The rates of appearance (Ra) and clearance of lactate were assessed by applying non-compartmental modeling for data analysis. For healthy volunteers and ICU patients, the Ra and metabolic clearance were 12.8 ± 3.9 vs 22.7 ± 11.1 μmol/kg/min and 1.56 ± 0.39 vs 1.12 ± 0.43 L/min, respectively. The kinetics displayed by ICU patients with normal lactate levels were very similar to healthy volunteers. The same results were obtained when the number of samples was reduced from 43 to 14, as shown by simulations. The results on lactate kinetics generated using this protocol were found to be very similar to earlier published data employing other techniques. Overall, findings revealed the accuracy as well as the feasibility of this simple and user-friendly protocol using an isotopically labeled bolus dose of lactate for examining lactate kinetics in critically ill ICU patients.