Suspending basal insulin during exercise in children with type 1 diabetes can effectively control hypoglycemia. Strategies for preventing hypoglycemia during exercise in children with type 1 diabetes have not been well studied. The Diabetes Research in Children Network (DirecNet) Study Group conducted a study to determine whether stopping basal insulin could reduce the frequency of hypoglycemia occurring during exercise.
Using a randomized crossover design, 49 children 8–17 years of age with type 1 diabetes on insulin pump therapy were studied during structured exercise sessions on 2 days. On day 1, basal insulin was stopped during exercise, and on day 2 it was continued. Each exercise session, performed from 4:00–5:00 P.M., consisted of four 15-min treadmill cycles at a target heart rate of 140 bpm (interspersed with three 5-min rest breaks over 75 min), followed by a 45-min observation period. Frequently sampled glucose concentrations (measured in the DirecNet Central Laboratory) were measured before, during, and after the exercise.
The results showed that hypoglycemia ( 70 mg/dl) during exercise occurred less frequently when the basal insulin was discontinued than when it was continued (16 vs. 43%; P = 0.003). Hyperglycemia (increase from baseline of 20% to 200 mg/dl) 45 min after the completion of exercise was more frequent without basal insulin (27 vs. 4%; P = 0.002). There were no cases of abnormal blood ketone levels.
In the present study, we demonstrated that stopping the basal insulin infusion at the start of a prolonged period of moderate aerobic exercise in the late afternoon was an effective strategy for reducing the risk of hypoglycemia during the exercise period. While this maneuver did not completely eliminate the risk of hypoglycemia, a fall in glucose that required treatment was infrequently observed if the pre-exercise plasma glucose level was >130 mg/dl. Moreover, the response to treatment of hypoglycemia with oral carbohydrate was more effective under basal-stopped conditions, since none of the subjects required more than one treatment with carbohydrate snacks compared with approximately one-third of the subjects during the basal-continued visit. Discontinuation of basal infusion was associated with a modest increased risk of hyperglycemia (12 vs. 4%, P = 0.11) during exercise, but blood ketone levels remained suppressed.
Because of its complexity, trial and error remains the principal method of regulating plasma glucose levels during exercise. However, the results of the present study can be used to guide recommendations for managing youth receiving insulin pump treatment during similar late-afternoon exercise. The plasma glucose should be checked before exercise, and 15–30 g of carbohydrate should be taken if the glucose is <130 mg/dl, or a small correction bolus should be given if the glucose is >200 mg/dl. Although in most patients the pump can then be safely suspended or disconnected for up to 2 h, glucose levels should be measured every 60–90 min during and after exercise and insulin administered when needed. The child and parents can also be informed that if hypoglycemia develops during exercise, it will be easier and more consistently treated with 15–30 g carbohydrate if the basal insulin infusion has been temporarily interrupted.
The ability to suspend or reduce basal insulin during increased physical activity is another example of the flexibility of insulin pump therapy that distinguishes it from multiple daily injection regimens that use long-acting insulin analogs for basal insulin replacement.
Diabetes Care 29:2200-2204, 2006
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