To the Editor:—
We read with interest the study by Bilotta et al. 1comparing intensive insulin therapy to conventional treatment in two cohorts of neurosurgical patients. When an arterial catheter was not available for glucose determination, capillary blood was measured with the HemoCue point-of-care device (HemoCue, Angelholm, Sweden). This was a wise choice, as this system has been shown to be accurate, even at low glucose concentrations.2What is not commonly appreciated is that most other point-of-care glucose measurement devices are not sufficiently accurate for critical care use, and that such devices originally approved and regulated for home self-monitoring by patients with diabetes have migrated into the hospital setting without further regulatory scrutiny. In fact, it has been specifically recommended that point-of-care devices designed for patient use at home, yet sometimes used in hospitals, should not be used in critically ill patients.3
Although their use of capillary blood for glucose determination is understandable, it should be pointed out that arterial blood glucose concentrations have been demonstrated to be a better representation of plasma glucose as compared with simultaneous capillary measurements.4,5This may be secondary to a variable time constant in the fingertip blood pool. Furthermore, hypotension, hypoxia, and acidosis, which are common problems in the critical care population, can significantly affect these capillary readings.6
Not all glucose measurements are equivalent, and care must be taken in their interpretation, especially at low concentrations.
*University of Florida College of Medicine, Gainesville, Florida. firstname.lastname@example.org