INFLUENCE OF BLOOD-SAMPLE OXYGEN-TENSION ON BLOOD-GLUCOSE CONCENTRATION MEASURED USING AN ENZYME-ELECTRODE METHOD

Objective: To determine the accuracy of a bedside glucometer with an e nzyme-electrode sensor based on enzyme oxidation by glucose oxidase. D esign: Prospective, cross sectional clinical study. Setting: Operating room in a public hospital. Patients: Fifty-four patients undergoing s urgical procedures for a derivation (n = 17) and a validation (n = 37) study. interventions: Arterial blood samples were obtained via a 2-ga uge cannula inserted into each patient's radial artery. Measurements a nd Main Results: Glucose measurements and arterial blood gas analyses were concurrently performed, using 48 blood samples for the derivation study and 45 blood samples for the Validation study of this technique . Blood glucose concentrations were measured with both a bedside gluco meter using an enzyme-electrode method and a laboratory glucometer bas ed on the colorimetric method. The bedside glucometer consistently und erestimated the glucose concentrations and the underestimation was rel ated to the sample oxygen tension but not to hematocrit, plasma protei n, creatinine, uric acid, or bilirubin. The present investigation used the following correction formula: (corrected glucose value) = (glucos e concentration obtained by a bedside glucometer) + 0.1 x (sample oxyg en tension) + 16. The corrected data were in agreement with the labora tory-determined glucose values (i.e., the mean difference and precisio n were 0.4 and 7.1 mg/dL, respectively). A validation study confirmed the generalization of the present correction formula which facilitates a more accurate estimation of brood glucose concentrations. Conclusio ns: Brood glucose values measured using a bedside glucometer in this s tudy were influenced by the sample oxygen tension. We used a correctiv e equation which improved the accuracy of estimating blood glucose val ues to a clinically acceptable range.