To assess the effects of 30 of the most commonly used critical care drugs on measurements obtained with trilayer electrochemical biosensors on a reference analyzer (ABL625-GL), to determine metabolic changes in glucose and lactate in vitro, and to formulate guidelines for whole-blood analysis of these 2 analytes.
Serial measurements were taken of changes in glucose and lactate levels caused by metabolism in whole blood in vitro over time. A parallel control 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.
At room temperature, whole-blood metabolism decreased glucose levels -2.3% at 15 minutes, -4.6% at 30 minutes, and -6.4% at 45 minutes. Metabolism increased lactate levels 11.4% at 15 minutes, 20.6% at 30 minutes, and 26.7% at 45 minutes in vitro. Paired differences between drug-spiked and control samples were calculated to determine interference (corrected for metabolism). 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 (C(6)H(14)O(6)) interfered with glucose and lactate measurements. At a concentration of 24 mg/mL, mannitol decreased whole-blood glucose levels by an average of 0.711 mmol/L (12.8 mg/dL) and whole-blood lactate levels by 0.16 mmol/L (1.4 mg/dL). Mannitol interference with measurements may have resulted from suppression of hydrogen peroxide formation in the enzymatic reactions in the biosensors, repartitioning of water between erythrocytes and plasma, or from other mechanisms.
Most critical care drugs had no significant effects on the trilayer 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 clinically significant in mannitol-induced acute renal failure and therefore should be considered for appropriate diagnosis and treatment of critically ill patients.