Preserved arterial flow secures hepatic oxygenation during haemorrhage in the pig

1. This study examined the extent of liver perfusion and its oxygenation du ring progressive haemorrhage. We examined hepatic arterial flow and hepatic oxygenation following the reduced portal flow during haemorrhage in 18 pig s. The hepatic surface oxygenation was assessed by near-infrared spectrosco py and the hepatic metabolism of oxygen, lactate and catecholamines determi ned the adequacy of the hepatic flow 2. Stepwise haemorrhage until circulatory collapse resulted in proportional reductions in cardiac output and in arterial, central venous and pulmonary wedge pressures. While heart rate increased, pulmonary arterial pressure r emained stable. In addition, renal blood flow decreased, renal vascular res istance increased and there was elevated noradrenaline spillover. Further, renal surface oxygenation was lowered from the onset of haemorrhage. 3. Similarly, the portal blood flow was reduced in response to haemorrhage, and, as for the renal flow, the reduced splanchnic blood flow was associat ed with an elevated noradrenaline spill-over. In contrast, hepatic arterial blood flow was only slightly reduced by haemorrhage, and surface oxygenati on did not change. The hepatic oxygen uptake was maintained until the blood loss represented more than 30 % of the estimated blood volume. At 30 % red uced blood volume, hepatic catecholamine uptake was reduced, and the lactat e uptake approached zero. 4. Subsequent reduction of cardiac output and portal blood flow elicited a selective dilatation of the hepatic arterial vascular bed. Due to this dila tation liver blood flow and hepatic cell oxygenation and metabolism were pr eserved prior to circulatory collapse.