Hepatic Circulation during Surgical Stress and Anesthesia with Halothane, Isoflurane, or Fentanyl

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Abstract
Hepatic blood flow and the oxygen supply I uptake relation were studied in 19 miniature pigs using labeled microspheres. Changes in hepatic arterial blood flow and portal blood flow, as well as total hepatic blood flow during halothane anesthesia were more closely associated with changes in mean arterial pressure (MAP) and cardiac output than during anesthesia with isoflurane or fentanyl. Halothane or isoflurane administered in concentrations that decreased MAP by approximately 30% were accompanied by decreases in hepatic oxygen delivery (DO2th) averaging 46% during halothane and 31% during isoflurane anesthesia and parallel decreases in hepatic blood flow. In concentrations that decreased MAP by 50%, halothane and isoflurane decreased DO2th 61 and 37%, respectively. DO2th was maintained (statistically insignificant, 23% increase) during both doses of fentanyl administered (20 μg/kg followed by 0.17 μg-kg −1 min−1, and 50 μg/kg followed by 0.42 μg-kg −1-min−1). Hepatic oxygen uptake increased 50% during fentanyl and was maintained at baseline levels during both doses of halothane and isoflurane anesthesia. Oxygen content in hepatic venous blood was maintained at baseline levels during fentanyl and isoflurane administration and was decreased by both concentrations of halothane anesthesia. The hepatic oxygen supply demand ratio was maintained at baseline levels after both doses of fentanyl and during isoflurane administered in a concentration that decreased blood pressure 30%; the ratio decreased during isoflurane administered in a concentration decreasing blood pressure by 50% and during both doses of halothane anesthesia. The data suggest that during surgical stress, anesthesia, using fentanyl or isoflurane in a concentration decreasing blood pressure by ≤30%, provides adequate hepatic oxygen supply, whereas anesthesia with isoflurane in a concentration decreasing blood pressure >30%, or with halothane in any concentration studied, results in inadequate hepatic oxygen supply.