PHYSIOLOGICAL, SYMPTOMATIC AND HORMONAL RESPONSES TO ACUTE HYPOGLYCEMIA IN TYPE-1 DIABETIC-PATIENTS WITH AUTONOMIC NEUROPATHY

The effects of peripheral autonomic neuropathy on the symptomatic, phy siological, and hormonal responses to acute insulin-induced hypoglycae mia were studied in two groups of patients with Type 1 diabetes, match ed for age, duration of diabetes, and prevailing glycaemic control. A group of eight patients who gave a history of normal awareness of hypo glycaemia and had normal cardiovascular autonomic function tests were compared to a group of six patients who had symptoms of autonomic dysf unction and gross abnormalities of cardiovascular autonomic function t ests. An additional two patients with autonomic neuropathy who also ha d hypoglycaemia unawareness were studied. Acute hypoglycaemia was indu ced by intravenous infusion of insulin (2.5 mU kg(-1) min(-1)) and the onset of the acute autonomic reaction (R) was identified objectively by the sudden rise in heart rate and onset of sweating. Cognitive func tion and hypoglycaemia symptom scores were estimated serially, and pla sma counterregulatory hormones were measured. Acute autonomic activati on was observed to occur in all subjects in response to hypoglycaemia and commenced at similar venous plasma glucose concentrations in both groups (neuropathic patients: 1.6 +/- 0.2 mmol l(-1) vs non-neuropathi c patients 1.6 +/- 0.2 mmol l(-1), p = 0.9,). In the neuropathic patie nts plasma adrenaline responses were significantly lower at all time p oints from time R until time R + 30 min (MANOVA for repeated measures, F=19.4, p< 0.001). The total autonomic symptom score at R was slightl y lower in the neuropathic patients (12 (8-12) median (range)) but was not significantly different from the non-neuropathic patients (14 (10 -26), p = 0.10), and the total neuroglycopenic symptom scores we re ve ry similar (neuropathic group: 11 (6-21) vs non-neuropathic group: 11. 5 (6-22), p = 0.95). Although some of the autonomic responses were low er, but not significantly so, in the patients with autonomic neuropath y this study suggests that peripheral autonomic neuropathy is not the principal cause of hypoglycaemia unawareness in patients with Type 1 d iabetes.