Severe hypoglycaemia and cardiovascular autonomic dysfunction in type I diabetic children treated with intensified...

To assess the relationship between severe hypoglycaemias and autonomic dysfunction, five cardiovascular tests (resting heart rate, hyperventilatory arrhythmia, standing/lying heart rate ratio, orthostatic decrease in blood pressure, and increase in blood pressure during sustained handgrip) were performed in a 1-yr prospective study of 34 insulin-dependent diabetic children treated with intensified conventional insulin therapy (ICIT). There were twelve severe episodes in 7 diabetic children, and the remaining 27 patients had no severe hypoglycaemia. The hypoglycaemic group had a longer duration of diabetes than the nonhypoglycaemic group (5.4 SD 2.5 years vs. 2.8 SD 2.2 years, p less than 0.02). The hyperventilatory arrhythmia in the hypoglycaemic group in comparison with the nonhypoglycaemic group was significantly decreased (before ICIT: 16.1 SD 3/min vs. 24.4 SD 5/min, p less than 0.01; 1 yr thereafter: 17.3 SD 3/min vs. 26.0 SD 5/min, p less than 0.01). The hypoglycaemic group showed a pronounced orthostatic decrease in blood pressure compared to the nonhypoglycaemic group (before ICIT: 13.2 SD 4 mmHg vs. 6.0 SD 4 mmHg, p less than 0.01; 1 yr thereafter: 12.3 SD 4 mmHg vs. 5.6 SD 4 mmHg, p less than 0.01). Three or more abnormal cardiovascular test results were found in patients of the hypoglycaemic group who showed abnormal hyperventilatory arrhythmia and abnormal orthostatic decrease in blood pressure simultaneously, whereas such a coexistence was not found in the nonhypoglycaemic group. These observations may support the view that diabetic children and adolescents with autonomic dysfunction are susceptible to severe hypoglycaemia during ICIT.