Comparison between arterial and capillary blood glucose monitoring in patients with shock

The accuracy of bedside glucometry using capillary blood is contentious in patients admitted to intensive care units. We aimed to compare the accuracy of capillary bedside glucometry with arterial samples in critically ill patients with shock through a prospective case-control study.

Study group consisted of 100 patients with shock on vasopressor support and control group had 100 normotensive patients. Arterial and capillary samples were taken simultaneously and were tested immediately at the bedside. Results of the paired measurements were analyzed as a scatter plot by Bland and Altman method and were expressed as a correlation coefficient. Values were considered to disagree significantly when the difference exceeded 20%.

Mean arterial and capillary sugars (mg/dl) in study and control groups were 164.7±70 and 157.4±68.9, and 167.1±62.2 and 167.5±61, respectively. On Bland-Altman analysis, 6% in study group and 5% in control group were out of range (acceptable limit<5%). Correlation between capillary and arterial values was less in the study group (r=0.917, p<0.001 vs r=0.979, p<0.001). In addition, the disagreement between capillary and arterial values was more than 20% in 18% of the patients in the study group vs 3% in control group (p=0.015) (ISO standard<5%).

Capillary blood glucose monitoring is reliable only in a selected group of ICU patients. Hence, caution must be exercised especially in patients with shock in whom arterial blood may be preferred.