Continuous blood glucose monitoring during surgery

AORN Journal, May, 2008 by George Allen

Anesthesis & Analgesia

January 2008

Maintaining tight control of blood glucose levels is reported to reduce mortality and is recommended as one procedure that may reduce the risk for surgical site infection. Protocols for tight control of blood glucose can be difficult to achieve in the surgical setting, however, especially with reliance on intermittent blood glucose testing. A continuous blood glucose monitoring system may facilitate blood glucose management.

Two types of continuous glucose monitoring systems are currently in use: a continuous subcutaneous glucose monitor and a continuous IV blood glucose monitor. The precision of both types of continuous glucose monitors has been questioned, however. One study reported that a continuous subcutaneous glucose monitor had a larger error than blood glucose measured by pinprick methods and could not be used in the clinical setting without computational model parameter fitting and semi-closed, or automated, feedback control systems. Such a system has been used as an artificial pancreas and was designed to measure blood glucose continuously. The goal of this study was to determine the reliability and accuracy of this continuous blood glucose monitoring method by comparing the blood glucose levels measured during surgery with coincident measurements from a conventional blood glucose assessment system.

Twenty-nine patients undergoing scheduled surgeries (eg, hepatectomy, pancreatico-duodenectomy, vascular surgery, off-pump coronary artery bypass grafting) were enrolled in the study. A 20-gauge IV catheter was inserted into a peripheral vein and connected to the continuous monitoring equipment, and blood was sampled continuously at a rate of 2 mL/hour. Additionally, a radial arterial catheter was inserted for intermittent blood glucose sampling, and samples were obtained every two hours during surgery following an established protocol of discarding 3 mL of blood before the actual blood sample was drawn. Common statistical techniques were used to analyze the data.

FINDINGS. One hundred points of paired blood glucose values were obtained. The blood glucose measurements obtained continuously agreed with the coincident intermittent measurements within 21%. Bias and upper and lower limits of agreements were -2.6, 23, and -28, respectively. The percentage error of the lower and upper limits of agreement was 21% and 18%, respectively.

CLINICAL IMPLICATIONS. The results of this study indicate that this continuous glucose monitoring device may be useful for following blood glucose level changes continuously and reducing the frequency of intermittent measurement. Perioperative nurses should understand that additional studies are required before this device is used widely and should be prepared to participate in such studies.

Yamashita K, Okabayashi T, Yokoyama T, et al. The accuracy of a continuous blood glucose monitor during surgery. Anesth Analg. 2008;106(1):160-163.

GEORGE ALLEN

PHD, RN, CNOR, CIC

DIRECTOR OF INFECTION CONTROL

DOWNSTATE MEDICAL CENTER

BROOKLYN, NY