Effect Of Propofol Infusion On Rabbit Hepatic Blood Flow And Oxygen Supply-demand

Backgroud and Objective: Propofol is a intravenous anesthetic agent with extensive clinical application, and it can induce arterial blood pressure decreased. Whether propofol reduce the perfusion of liver, a splanchnic organ which is sensitive to ischemia, is still unclear. In recent years, investigators had some controversial results about the effects of propofol on portal venous and hepatic arterial blood flows. However, there were no enough evidences to determine the effects of propofol on hepatic blood flow (HBF). More important, the effects of propofol infusion on hepatic oxygen supply-demand had rarely been reported . So the purpose of our study is to evaluate the effects of a continuous infusion of propofol on HBF and oxyen supply-demand.Methods: Thirty mature male rabbits weighed (1.6-2.4) kg were randomly allocated into three groups: high dose propofol (HP), smalldose propofol (SP) and control group (C). Rabbits who had abnomal t-emprature or had been administrated any drugs in recent two months were excluded. Inhibited food and water for 8h, the rabbits were anesthetized and intubated with 3% pentobarbitalum natricum (45mg·kg^-1 iv) before mechanically ventilation. Tidal volume was maintained at 10ml·kg^-1, respiratory rate was 40 bpm and I:E ratio was 1:2. ECG, urinary volum and rectal temperature were monitored. The right common carotid artery and jugular vein were cannulated by direct puncture for BP and CVP monitoring. Through the median laparotomy, portal vein and hepatic artery were isolated for continuous detection of blood flows utilizing two electromagnetic flowmeters. Catheters were inserted into portal vein and hepatic vein via a mesen-teric vein and the right femoral vein, respectively, for pressure monitoring and collection of blood samples. After achieving steady circulation, the rabbits recieved propofol infusion at a rate of 1.2 mg·kg^-1min^-1 and 0.4 mg·kg^-1min^-1 in Hp group and in SP group, respectively. In C group propofol was replaced by same volume of 0.9% normal saline. Portal venous and hepatic arterial blood flows were measured before and 10,20,30,40,50,60,70,80,90min after infusion treatment. Blood samples each 0.5ml were obtained before and 30,50,70,90min after infusion from the common carotid artery, portal vein and hepatic vein, for analysis of the Hb, SO₂ , PO₂ and PCO₂ concentrations. Then hepatic oxygen delivery (hDO₂) (blood flow xHbxSO2 xl-34), oxygen consumption (hDO2 - HBF x Hb x ShvO2x1.34) and oxygen extraction were calculated.Results: There were no significant differences in body weight, duration of operation, infusion volume, blood loss volume and urinary volume. At 30-90min after infusion , HBF was significantly higherthan the baseline value before infusion in HP group, and it also higher than the control value in C group. HDO2 and I1VO2 in HP group increased greatly at 30-90min after infusion, compared with those in C group. Nevertheless, there was no significant variation in the hDCV hVC>2 ratio and ERO2 after administration of high dose propofol. MAP, portal vein and hepatic vein vascular resistance (PVR and HVR) decreased markedly at 40-90min after infusion in HP group as compared with those in C group. Although increased at 60-70min after infusion, HBF in SP group was not higher than that in C group. There were no differences in variation of hDO2, hVO2, ERO2, PVR, HVR and MAP between SP group and C group. There were no significant correlation between HBF and MAP in all groups.Conclusion: High dose propofol improve liver blood perfusion and oxygen delivery, and it can also make hepatic oxygen consumption increased. However, the hepatic oxygen supply/demand ratio was persevered. Small dose propofol have no significant effects on HBF and hepatic oxygen supply-demand. We suggest that it is not suitable for the patients who have disorders of oxygen supply-demand or have liver dysfunction to receive high dose propofol.