EFFECT OF PROPOFOL INFUSION ON SPLANCHNIC HEMODYNAMICS AND LIVER OXYGEN-CONSUMPTION IN THE RAT - A DOSE-RESPONSE STUDY

Background. Propofol has been used for the maintenance of anesthesia. The effects of propofol infusion on splanchnic hemodynamics and liver oxygen consumption, however, have not been reported. In the current in vestigation, the authors studied the effects of a continuous infusion of propofol on systemic and splanchnic hemodynamics using a new method to measure liver oxygen consumption in awake control and anesthetized rats. Methods. Cannulas were inserted into the left ventricle, femora l artery, portal vein, and hepatic vein during ether anesthesia, and t he rats were allowed to awaken and recover for 3-4 h before study. Ani mals were infused for 30 min with either saline (controls) or propofol at a rate of 300, 600, 900, or 1,200 mug . kg-1 . min-1. Cardiac outp ut and organ blood flows were measured using radiolabelled microsphere s, and blood samples from the femoral artery, portal vein, and hepatic vein were used to determine liver oxygen consumption. Results: Mean a rterial pressure decreased in a dose-dependent manner with a 25% reduc tion at the highest infusion rate. Systemic vascular resistance simila rly decreased, whereas cardiac output remained unchanged at all the in fusion rates. Hepatic arterial blood flow increased in a dose-dependen t fashion over the dose range studied, to a maximum increase of 120%. Portal tributary blood flow increased by 30% at the highest infusion r ate. Total liver blood flow increased in a dose-dependent manner to a maximum of 38%. Total oxygen delivery to the liver by the hepatic arte ry and portal vein increased in a dose-dependent fashion. Liver oxygen consumption increased in a dose-dependent fashion to a maximum increa se of 51% at an infusion rate of 1,200 mug . kg-1 . min-1. The percent of oxygen extracted by the liver was not altered by propofol infusion , and hepatic venous oxygen saturation did not decrease at any dose st udied. Coronary and renal blood flows were not altered. Arterial Pa(CO 2) increased from 31 +/- 2 mmHg in awake control rats to 41 +/- 2 mmHg in spontaneously breathing rats infused with 1,200 mug . kg-1 . min-1 propofol. Conclusions: The maintenance of anesthesia using an infusio n of propofol resulted in an increase in liver oxygen consumption that was fully compensated for by an increase in oxygen delivery to the li ver. Splanchnic hemodynamics and liver oxygenation are not adversely a ffected during maintenance of anesthesia with propofol in the normal r at.