It has been suggested that patients with insulin-dependent diabetes mellitus may be less aware of impending hypoglycaemia when lying than standing. We have studied the effect of posture and duration of hypoglycaemia on symptoms and physiological responses in 10 men with insulin-dependent diabetes. A standard tilting protocol was used (supine, 50 ~ 90 ~ headup, and return to supine, 5 min at each position). At one visit patients were tilted before, 10 min after and 40 min after achieving hypoglycaemia (blood glucose 2.5 mmol/1), and at another visit were tilted after euglycaemia (5.0 mmol/1) using a hyperinsulinaemic clamp. At each position, hormonal and physiological responses and symptoms (using visual analogue scales) were recorded. After 10 min of hypoglycaemia, adrenaline was significantly higher when 90 ~ headup compared with supine (mean [+SEM] 6.26 [+1.88] vs 1.68 [+0.4]nmol/1; p <0.05), and fell significantly (to 2.46 [+0.65] nmol/1; p < 0.05) when returned to supine; sweating, symptom score and blood pressure followed a similar pattern. After 40 min of hypoglycaemia a similar effect of standing was seen on sweating, adrenaline and blood pressure but symptoms did not increase. Five patients underwent two further periods of hypoglycaemia, remaining supine or standing throughout. Face skin blood flow (p < 0.05) and temperature (p = 0.05) decreased when standing was maintained compared with lying. In conclusion, standing increases awareness of early hypoglycaemia and modifies many of the physiological changes. This increase in awareness is lost if hypoglycaemia is prolonged. [Diabetologia (1994[Diabetologia ( ) 37: 1241[Diabetologia ( -1250] ] Key words Posture, insulin-dependent diabetes mellitus, hypoglycaemia, adrenaline, adaptation to hypoglycaemia.
It has been suggested that sudden death in the night of patients with insulin-dependent diabetes mellitus (IDDM) may be connected with unawareness of hypoglycaemia [1]. A possible explanation is that, in patients who are asleep and often alone, impending hypoglycaemia may go unnoticed. However, a further contributory factor may be posture itself; lying down may reduce the physiological response to and aware-