The accuracy of a continuous blood glucose monitor during surgery

BACKGROUND: Protocols for tight control of blood glucose can be difficult to achieve in the surgical setting, especially when relying upon intermittent blood glucose testing. A continuous blood glucose monitoring system can facilitate blood glucose management. In the present study, we compared blood glucose measured continuously (STG-22 (TM), Nikkiso, Tokyo, Japan), during surgery with coincident measurements obtained intermittently using a conventional laboratory glucometer (ABL (TM) 800FLEX (Radiometer Medical Aps, Bronshej, Den-mark). The goal of the study was to determine the reliability and accuracy of the continuous method during surgery. MATERIAL AND METHODS: Twenty-nine patients scheduled for routine surgery with general anesthesia were enrolled in this study. After anesthetic induction, a 20G IV catheter was inserted in a peripheral forearm vein and connected to the continuous blood glucose monitor. A radial arterial catheter was also inserted from which samples for blood glucose estimation were obtained by an anesthesiologist, following an established protocol of discarding 3 mL of blood before the actual blood sampling. Blood glucose was measured by ABL (TM) 800FLEX immediately after sampling. One hundred points of paired blood glucose values were obtained, which were compared using Bland and Altman analysis. RESULTS: Bias and upper and lower limits of agreement were -2.6, 23, and -28, respectively. The percentage error of the lower/upper limits of agreement was 21% and 18%, respectively. DISCUSSION AND CONCLUSIONS: The blood glucose measurements obtained continuously agreed with the coincident intermittent measurements within 21%. The STG-22 (TM) may still be useful for following changes continuously and reducing the frequency of intermittent measurement, but the need for testing samples with a reliable device is not eliminated.