Rest reduces venous lactate levels significantly in patients in outpatient clinic

Lactate is produced in the human body during physical activity and elimination takes time with a half-life of approximately 18 min. We, therefore, investigated the potential impact of resting time (RT) duration on lactate concentration in our outpatient venipuncture clinic for all lactate requests during a 4½-year period. All samples drawn for venous lactate analysis during a 4½-year period in our hospital outpatient venipuncture clinics were included in this study. RT was reported electronically at each visit. Results from a total of 831 samples were obtained for further analysis. We found varying lactate concentrations across resting time <15min (median 1.6 mmol/L, IQR[1.2-2.1] mmol/L), between <15 min and >30 min (median 1.4 mmol/L, IQR[1.0-1.9] mmol/L) and for >30 min (median 1.3 mmol/L, IQR[1.0-1.7] mmol/L). There was a significant difference between <15 min versus 15-30 min (p = 0.015), which gives a 17.7% higher lactate from 15-30 min to <15 min. There was a significant 28.3% increase in mean lactate concentration from >30min to <15min (p < 0.0001) when corrected for age. We found that lactate concentration was dependent on RT in the outpatient clinic. The difference was clinically significant. Based on the results of this study, we, therefore, conclude that a 15 min waiting time before venipuncture for lactate sampling in an outpatient clinic is of clinical importance.