Table 3.

Factors controlling and interventions affecting hepatic blood flow (HBF)

Level	Flow	Regulation	Effect of intervention
Systemic50,98,99	Total HBF	↓ in HBF seen with: ▪ ↓ CO ▪ ↓ SVR (other than splanchnic) ▪ ↑ RAP > PVP	Inflow occlusion results in: ▪ MAP and ↓ CVP ▪ ↓ Blood loss Hepatic venous exclusion: ▪ Well tolerated ▪ ↓ CVP and CO ▪ MAP maintained >55 mmHg as a result of ↑ in SVR Infrahepatic caval clamping: ▪ Well tolerated ▪ ↓ Blood loss
Regional50,66,100,101	Total HBF	Total HBF (constant) = HAF + PVF (hepatic arterial buffer response)	Inflow occlusion followed by reperfusion results in ▪ ↓ SVR: ▪ Total HBF constant When preconditioning used: ▪ Total HBF Laparoscopic surgery: ▪ No difference in effect of inflow occlusion using laparoscopic or open surgery
	PVF	Passively drains splanchnic arterial bed so ↓ splanchnic flow results in ↓ PVF	Inflow occlusion followed by reperfusion results in: ▪ 29% ↓ in PVF on reperfusion lasting >30 min When preconditioning used: ▪ No change in PVF
	HAF	No auto-regulatory activity ↓ HAF with ↑ arterial resistance Arterial resistance ↑ with ↑ PVF (hepatic arterial buffer response)	Inflow occlusion followed by reperfusion results in: ▪ 8% ↑ in HAF on reperfusion lasting >30 min When preconditioning used: ▪ 200% ↑ in HAF
Micro50,66	HSF	Flow controlled by diameter of the sinusoids Sinusoidal diameter controlled by sinusoidal endothelial cells, hepatic stellate cells and Kupffer cells	Ischaemia and subsequent reperfusion create a mismatch in time and space of mediator release so that homeostasis of the mediators is lost
		Mediators released by above cells alter degree of contraction or relaxation of the cells, thus altering sinusoidal diameter and hence resistance to flow

CO, cardiac output; CVP, central venous pressure; HAF, hepatic artery flow; HSF, hepatic sinusoidal flow; MAP, mean arterial pressure; PVF, portal blood flow; PVP, portal blood pressure; RAP, right atrial pressure; SVR, systemic vascular resistance.