Diabetic autonomic neuropathy: What are the risks?

This paper considers the risks related to each of the complications of diabetic autonomic neuropathy. Gastroparesia induces its own functional disorders in the digestive tract but is also probably involved in an undetermined proportion of unstable diabetes. Neural bladder, in its aspect of hypoactive, hypocontractile and hypoaesthesic bladder, makes patients prone to urinary chronic retention and repeated urinary infections or even kidney disease. In patients with hypoglycaemia unawareness, the responsibility of autonomic neuropathy may he suspected in those with severe cardiac autonomic neuropathy (CAN) or selective autonomic neuropathy characterised only by a defect in adrenergic contraregulation of hypoglycaemia. CAN is the best-known and most frequent complication of dysautonomia; Several longitudinal studies have clearly shown that CAN is associated with excessive mortality. Various functional disorders may account for the increased frequency of cardiovascular events. In particular, a reduction of left ventricle ejection fraction, inadaptability of haemodynamic response to exercise, alterations of the nycthemeral pattern of blood pressure variations, ventricle repolarisation and ventilatory function have been associated with CAN. Though the relationship between CAN and silent myocardial ischaemia is not clearly established, CAN seems to increase the frequency of major cardiac events, particularly in patients with silent myocardial ischaemia. Vascular neuropathy, by altering peripheral vasomotricity, may contribute to foot ulcer. The statistical association between CAN and retinopathy and kidney disease suggests that CAN might contribute to worsening microangiopathic complications or at least be considered as a marker of these complications. Finally, several arguments suggest an association between CAN and insulin resistance. Thus CAN might be involved in the poor prognosis of kidney disease or insulin resistance. From a practical point of view, the risks related to diabetic dysautonomia, which range from simple discomfort to severe complications, should lead to systematic detection of dysautonomia. In any event, detection by standardised tests analysing heart rate variations should he widely performed, and the presence of CAN should lead to a specific cardiovascular assessment.