Background: Previous studies have shown that at the near steady state attained by slow insulin infusion, the local glycemia of subcutaneous fluid tracks the venous glucose concentration (i.e., it is not perturbed by the infusion of insulin). Here we test whether the subcutaneous glycemia near the site of injection of a bolus of insulin is perturbed by the injection in the minipig model without diabetes.
Methods: A bolus of short-acting diluted insulin was administered in the animal's flank while three to five continuous glucose monitoring systems measured the subcutaneous glucose concentrations at 0.5, 1, 2, and 3 cm ("near sensors") and at 10-15 cm ("far sensors") from the injection site.
Results: We found no statistically significant (P < 0.05) evidence that near and far sensors differ in response time, that is, the elapsed time to onset of signal drop or the elapsed time to minimum signal following insulin injection. We found mixed evidence that near and far sensors differ in the percentage drops at the glycemic minimum. The near versus far difference for near sensors at 0.5 and 3 cm from the injection site was statistically significant (P < 0.05): the average percentage drops for these near sensors were 3% and 11%, respectively, below those for far sensors. We did not find evidence of a difference for near sensors at 1 and 2 cm.
Conclusions: Because there is some evidence that insulin injection can cause a minor perturbation (about ≤10%) in the local glycemia, caution is warranted when co-locating glucose sensing and insulin injection sites.