Adjust Insulin Pump after Exercise to Avoid Nocturnal Hypoglycemia

Nearly half of diabetic kids who exercise for an hour in the afternoon will have blood glucose levels below 60 mg/dL later that night, according to research published in 2005 by the Diabetes Research in Children Network. 

Dr. H. Peter Chase, a coauthor on the current study stated that, "Exercise is important for all people, but particularly those with diabetes. Unfortunately, exercise is the number-one known factor associated with severe hypoglycemia."

Dr. Chase and colleagues at the University of Colorado, Aurora, studied 16 young diabetic patients, mean age 13.3 years, on insulin pumps. The average total daily insulin dose was 0.76 units/kg with 0.40 units/kg as basal insulin.

The subjects were monitored overnight on three occasions after a 60-minute exercise session. In random order on the three occasions they either had their basal insulin rate decreased by 20% from 9 p.m. to 3 a.m., or they received 2.5 mg terbutaline, or they had no intervention. The researchers measured each child's blood glucose every 30 minutes.

On the control night, the mean blood glucose nadir was 128 mg/dL. With the basal insulin reduction it was 172 mg/dl, and with terbutaline it was 189 mg/dL. Terbutaline was also associated with a higher mean maximum blood glucose reading: 331 mg/dL, vs 305 mg/dL with basal infusion reduction.

Blood glucose readings lower than 70 mg/dL, indicating hypoglycemic episodes, occurred in 2 of the 16 children during the control night, 1 of 16 during basal rate reduction, and none with bedtime terbutaline.

"A basal insulin rate reduction was safe and effective in raising post-exercise nocturnal blood glucose nadir and in reducing hypoglycemia in children with Type 1 diabetes mellitus," the investigators conclude in their report.

"This study shows that with thinking ahead and appropriate insulin reduction (with use of a pump or injections), the likelihood of hypoglycemia can be greatly reduced," Dr. Chase added.

He and his associates do point out that basal insulin reduction is not an option for patients with Type 1 diabetes using multiple daily insulin injections. For them, some further research is needed.

The Journal of Pediatrics, published online July 21, 2010