In Response

Abstract

The principal concern expressed by Pitkin et al.1 is the choice of point-of-care (POC) device used to monitor blood glucose concentrations in anesthetized patients and the potential risk of undetected severe hypoglycemia. In our protocol2 we used the AccuSoft Advantage (Roche Diagnostics, Hoffman-La Roche, Laval, Quebec, Canada), a POC device routinely used in operating rooms and previous studies assessing different glycemic control protocols.3,4 In this context, while some portable blood glucometers show falsely elevated values under hypoglycemic conditions,5 Accu-Cheks tend to display lower values during hypoglycemia and anemia, thereby presumably increasing the margin of safety in the hypoglycemic range.6 We agree with Rice et al. regarding the general limitations of such POC devices, originally designed for blood glucose self-monitoring at home and the apparent lack of “regulatory framework,” proper standardization, and evaluation in critical care.7 However, none of the patients enrolled in our protocol was “critically ill” according to the definition used by the Food and Drug Administration guidance (Food and Drug Administration. Draft guidance for industry and FDA staff: total product life cycle for portable invasive blood glucose monitoring systems. Rockville, MD: Center for Devices and Radiological Health, Oct 24, 2006. Available at: http://wwwfdagov/medicaldevices/deviceregulationandguidance/guidancedocuments/ucm079138htm), as referenced by Rice et al. Unfortunately, because of time constraints and the high frequency of blood glucose measurements, glucose–insulin therapy, as with any other algorithm aiming at tight blood glucose control in the acute care setting, depends on the results rapidly provided by POC devices rather than time-consuming central laboratory plasma glucose analysis. The relatively short 15- minute intervals between glucose measurements as dictated by our protocol and the fact that dextrose is being infused continuously, however, may be considered as an added safety feature of glucose–insulin therapy. In a recent randomized trial, completed before our investigation in patients undergoing liver surgery and designed to assess the cardioprotective effects of glucose and insulin administration while maintaining normoglycemia in 100 patients undergoing surgical coronary revascularization, we measured plasma glucose concentrations in approximately 500 arterial blood samples by using the Beckman Glucose Analyzer 2 (Beckman Instruments, Fullham, CA). We found no clinically important discrepancy between values obtained by the “gold standard” glucose-oxidase-based glucose analyzer3 and those provided by the Accu-Chek glucometer, particularly in the lower glycemic range (manuscript submitted for publication). Regardless of the protocol used or our belief in the potential benefits of strict glycemic control during and after surgery, thorough understanding of the patient's pathophysiology and the technology applied to maintain glucose homeostasis is mandatory to avoid the disastrous consequences of severe hypoglycemia.8,9 Thomas Schricker, MD, PhD George Carvalho, MD, MSc Hiroaki Sato, MD Department of Anaesthesia Royal Victoria Hospital McGill University Health Center Montreal, Quebec, Canada [email protected]