PHYSIOLOGICAL AND SYMPTOMATIC RESPONSES TO POSTURAL CHANGE IN NONDIABETIC SUBJECTS DURING HYPOGLYCEMIA

1. Insulin-induced hypoglycaemia is characterized by an autonomic dist urbance which produces some of the symptoms of hypoglycaemia. How an a dditional autonomic stress like postural change may alter physiologica l responses and symptoms of hypoglycaemia is not known. In 10 healthy male subjects (mean age 24 years) we observed physiological and sympto matic responses to postural change during acute (20 min) and prolonged (60 min) hyperinsulinaemic (60 m-units min(-1)m(-2)) hypoglycaemia (2 .5 mmol/l) and euglycaemia (4.5 mmol/l), and placebo control (saline). 2. In all studies standing increased plasma catecholamines (adrenalin e, P<0.001; noradrenaline, P<0.0001), blood pressure (P<0.0001) and he art rate (P<0.0001). Catecholamine responses to standing were augmente d by acute hypoglycaemia (adrenaline, P<0.005; noradrenaline, P<0.01), but less so by prolonged hypoglycaemia (adrenaline, P<0.05; noradrena line, P<0.05). Supine heart rate was higher before standing during pro longed hypoglycaemia (P<0.05), but did not increase as much on standin g when compared with acute hypoglycaemia and prolonged euglycaemia. 3. During acute hypoglycaemia, autonomic symptoms increased on standing, but during prolonged hypoglycaemia, in the presence of generally high er symptom scores, standing had no effect. Autonomic symptoms, with th e exception of hunger, tended to decrease with time (P<0.05) during pr olonged hypoglycaemia. 4. To conclude, posture does modify the catecho lamine and symptomatic responses to hypoglycaemia, but this effect is dependent on the duration of hypoglycaemia. Hypoglycaemia and hyperins ulinaemia had little or no effect on the cardiovascular responses to c hanging posture.