Whole-blood glucose and lactate - Trilayer biosensors, drug interference, metabolism, and practice guidelines

Objective.-To assess the effects of 30 of the most commonly used critical c are drugs on measurements obtained with trilayer electrochemical biosensors on a reference analyzer (ABL625-GL), to determine metabolic changes in glu cose and lactate in vitro, and to formulate guidelines for whole-blood anal ysis of these 2 analytes. Design.-Serial measurements were taken of changes in glucose and lactate le vels caused by metabolism in whole blood in vitro over time. A parallel con trol study of drug interference with measurements of glucose and lactate in whole blood and of dose-response relationships in whole-blood samples and in plasma samples also was conducted. Results.-At room temperature, whole-blood metabolism decreased glucose leve ls -2.3% at 15 minutes, -4.6% at 30 minutes, and -6.4% at 45 minutes. Metab olism increased lactate levels 11.4% at 15 minutes, 20.6% at 30 minutes, an d 26.7% at 45 minutes in vitro. Paired differences between drug-spiked and control samples were calculated to determine interference (corrected for me tabolism). The threshold for determination of interference was +/-2 SD from within-day precision, equal to +/-0.18 and +/-0.10 mmol/L for glucose and lactate, respectively. Only mannitol (C6H14O6) interfered with glucose and lactate measurements. At a concentration of 24 mg/mL, mannitol decreased wh ole-blood glucose levels by an average of 0.711 mmol/L (12.8 mg/dL) and who le-blood lactate levels by 0.16 mmol/L (1.4 mg/dL). Mannitol interference w ith measurements may have resulted from suppression of hydrogen peroxide fo rmation in the enzymatic reactions in the biosensors, repartitioning of wat er between erythrocytes and plasma, or from other mechanisms. Conclusions.-Most critical care drugs had no significant effects on the tri layer electrochemical biosensors. Whole-blood analysis should be performed within 15 minutes for lactate and within 30 minutes for glucose because of metabolism in vitro. Mannitol effects on glucose measurements may be clinic ally significant in mannitol-induced acute renal failure and therefore shou ld be considered for appropriate diagnosis and treatment of critically ill patients.