Splanchnic haemodynamic changes during acute hypoglycaemia in man

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.