The most common method of glucose measurement in many ICUs is point-of-care testing (glucometers). Considering the recommendations for strict glycemic control, accurate measurement of glucose level is essential. Accuracy of glucometers is influenced by various factors including mean arterial pressure, tissue perfusion and PaO2. The purpose of this study is to compare the blood glucose levels from various vascular compartments (arterial, venous and capillary), as determined by a glucometer, in critically ill patients.
All ICU patients in shock, defined as a systolic blood pressure of <90 mm Hg despite adequate volume resuscitation or requiring vasopressor therapy, were considered eligible for enrollment. Arterial, venous and capillary blood samples were obtained simultaneously. A total of 243 samples were obtained from 21 patients. Glucose determinations were made with a glucometer (ACCU-CHEK Comfort Curve, Roche) from each of the vascular compartments.
Mean blood glucose level measured in venous blood with a glucometer was 146.95 mg/dl with a median of 135 mg/dl and a range of 44 to 435 mg/dl. Glucose level in arterial sample was higher than in the venous sample by a mean of 8.25 mg/dl (5.88%) and a median of 5 mg/dl. The mean difference in glucose level between the capillary and arterial sample was 6.58% (10.55 mg/dl) and the mean difference between the capillary and the venous sample was 7.58% (12.58 mg/dl). The capillary sample had a consistently higher glucose level than the arterial or venous sample.
When glucose measurements are determined with a glucometer, the glucose level varies with the source of the blood sample. The difference between arterial sample and venous sample is minimal. If a capillary sample is used, then the difference in glucose level is increased.
Blood glucose levels in various vascular compartments, as determined by glucometer, differ and consistency in the source of the sample being tested is important.
Srinivas Chakravarthy, Grant monies (from sources other than industry) This study was supported by an award from The CHEST Foundation of the American College of Chest Physicians and Ortho Biotech Products, LP.; Grant monies (from industry related sources) The glucometer, chemistry strips and reagents were provided by Roche.