Are some anesthetic techniques free of hepatotoxic effects?

Are some anesthetic techniques free of hepatotoxic effects?

The most important factors in preserving hepatic func-tion are probably maintenance of hepatic blood flow and oxygenation.

When applicable and not contraindicated, spinal anes-thetics have been suggested as alternatives to general anes-thesia; however, even conduction anesthesia risks hepatic injury. Spinal anesthesia can reduce hepatic blood flow by as much as 30%. Although spinal anesthesia is not noted to cause massive hepatic necrosis, it may lead to transient elevations in liver transaminase levels. Careful delivery of anesthetic agents is as important as the actual choice of agents or technique. Except for halothane, halogenated anes-thetics can be employed. Other factors affect hepatic blood flow, and are important to consider as well. Excessive intrathoracic pressures may impede venous return and decrease hepatic blood supply. IPPV with positive end expi-ratory pressure (PEEP) will similarly affect hepatic blood supply and should be avoided if possible. Hyperventilation and hypocapnia increase hepatic arterial resistance and reduce blood flow to the liver, whereas hypercapnia will increase blood flow. Severe hypoxemia also decreases hepatic artery blood flow.

Concomitantly administered nonanesthetic drugs may affect blood supply to liver, and these should be considered. β-Blockers reduce hepatic blood supply and are often used in treatment of portal hypertension. α-Adrenergic agonists also reduce blood flow through the hepatic artery. Cimetidine, an H₂-receptor blocker, not only inhibits hepatic clearance of other drugs, but also reduces hepatic blood flow. A reasonable anesthetic plan for this patient would include maintenance of near preanesthetic blood pressure (which must be considered with the risk of addi-tional bleeding), the avoidance of hyperventilation and hypoxemia, and the avoidance of drugs that are associated with hepatotoxicity (e.g., halothane or acetaminophen).