1. Splanchnic haemodynamic changes were studied in seven healthy subjects during hypoglycaemia induced by the intravenous infusion of insulin. Superior mesenteric artery blood flow and cardiac output were examined non-invasively by a Doppler ultrasound technique.

2. Blood glucose concentration fell from 4.5 (0.14) mmol/l basally to 1.5 (0.09) mmol/l [mean (sem), P < 0.003] at the hypoglycaemic reaction (‘R’) and recovered to baseline by ‘R’ + 60 min. There was an associated rise in plasma glucagon, adrenaline and noradrenaline levels.

3. Superior mesenteric artery blood flow rose at ‘R’ from a basal value of 532 (38) ml/min to a peak of 803 (73) ml/min at ‘R’+10 min [mean (sem), P < 0.005] and remained significantly elevated until ‘R’ + 40 min. Resistance in this vessel fell by 33% at ‘R’+ 10 min (P < 0.005) and remained significantly low until ‘R’ + 40 min.

4. Cardiac output rose by 33% at ‘R’ (P < 0.004) and returned to normal by ‘R’ + 20 min. This was associated with a 24% rise in pulse rate (P 0.03), but no change in stroke volume or mean arterial pressure. Total peripheral resistance fell by 21% at ‘R’ (P 0.005) and had returned to normal by ‘R’ + 20 min.

5. The sustained rise in splanchnic blood flow during hypoglycaemic recovery may be of homoeostatic importance by providing metabolic fuel to the liver for gluconeogenesis.

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