The Use and Clinical Importance of a Substrate-Specific Electrode for Rapid Determination of Blood Lactate Concentrations

Objective. —To determine the validity and clinical importance of a newly developed amperometric, enzymatic, substrate-specific electrode for the rapid measurement of circulating lactate concentrations. Design. —A prospective multiexperiment study. Setting. —The critical care medicine research laboratory, intensive care unit (ICU), emergency department (ED), and general wards of a university-affiliated hospital. Patients. —A total of 1218 patients and control subjects were studied on one or more occasions. Interventions. —Blood lactate concentrations, descriptive data, physiological parameters, and outcome results were determined in various patient populations. Main Outcome Measures and Results. —Experiment 1: Lactate determinations performed with the new substrate-specific electrode were compared with two laboratory reference methods. Blood samples from 80 ICU patients and 165 ED patients formed the basis of this first experiment. There was excellent agreement between the test instrument and the two reference methods as reflected by bias (with reference method 1, 0.19 mmol/L; reference method 2, 0.09 mmol/L), precision (with reference method 1, ±0.47 mmol/L; reference method 2, ±0.34 mmol/L), and correlation data (with reference method 1, r =.92; reference method 2, r =.98). Experiment 2: The new test microchemistry instrument was used to analyze blood samples from 927 patients. The mean (SE) blood lactate concentrations in the various patient populations were 1.26 (0.04) mmol/L for control subjects (n=85), 1.52 (0.03) mmol/L for general ward patients (n=489; P P P P Conclusions. —Lactate determinations performed using the new test instrument are precise and accurate. Blood lactate concentrations greater than 4 mmol/L are unusual in normal and noncritically ill hospitalized patients and warrant concern. In hospitalized (non-ICU) nonhypotensive subjects, as well as in critically ill patients, a blood lactate concentration greater than 4 mmol/L may portend a poor prognosis. ( JAMA . 1994;272:1678-1685)