Pilot study of the accuracy of bedside glucometry in the intensive care unit
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OBJECTIVE: To evaluate the accuracy of bedside glucometry among critically ill patients. DESIGN: Prospective audit, with sequential specimen collection. SETTING: Thirty-two-bed cardiovascular, neurosurgical, and medical-surgical intensive care unit in a single Canadian center. PATIENTS: Ten critically ill adults, who were sequentially followed during their intensive care unit stay. Eight had diabetes mellitus, and three were in shock. MEASUREMENTS AND MAIN RESULTS: Repeat arterial blood samples were obtained by the attending nurse, who withdrew a portion of the sample and performed reflectance glucometry at the bedside. The remainder was immediately sent in a vacuum-sealed plasma separation tube to the hospital laboratory, and analyzed using a conventional plasma glucose analyzer by a laboratory technologist. Sequential samples were taken at intervals of at least 12 hrs of one other. A total of 105 arterial glucose pairs were obtained. There was a significant correlation between the laboratory and glucometry determined glucose concentrations (intraclass correlation coefficient = 0.86, p <.0001). The overall average laboratory-glucometry glucose difference was -0.04 mmol/L (95% confidence interval [CI] -2.3-2.2 mmol/L). Five out of 105 values (4.8%) lay beyond these confidence bounds. The square of the Pearson correlation coefficient (r(2)) between the mean glucose level and the laboratory-glucometry glucose difference was not significant (0.01, 95% CI 0.005-0.04; p =.22), suggesting the absence of any trend between rising glucose concentration and the laboratory-glucometry difference. CONCLUSIONS: Bedside glucose testing of arterial whole blood samples may be an accurate alternative to laboratory plasma glucose measurement among critically ill adults, within approximately 2.3 mmol/L of certainty. Because previous studies have suggested that this bedside technique may be prone to a moderate degree of error among patients in shock as well as those with an abnormal blood pH or hematocrit, larger studies are needed to confirm our findings.