Metabolism of anesthetic agents: toxic implications

Postoperative elevation of serum transaminases following isoflurane anesthesia

Halogenated inhalational anesthetics have been implicated in hepatotoxicity. Halothane hepatitis results from the biotransformation of the drug to a metabolite that binds to liver proteins, which creates a hapten, which, in turn, causes an immunologic response in the liver. Case reports of hepatic injury resulting from isoflurane, which has a decreased biotransformation compared with that of halothane, have received much criticism. We describe a patient who had elevated liver enzymes and a positive trifluoroacetyl antibody titer following an anesthetic regimen that included isoflurane.

Choice of anesthetic alters the circulatory shock pattern as gauged by conscious rat endotoxemia

A standardized rat endotoxin shock model was used to assess the differential effects of four commonly used anesthetics upon hemodynamics before and during endotoxin shock. Forty-nine male Sprague-Dawley rats weighing 307 +/- 4 g were divided into five groups:freely-moving conscious, enflurane (2%), isoflurane (1.4%), pentobarbital (6 mg.kg-1.h-1 i.v.), and ketamine (45 mg.kg-1.h-1 i.v.). Anesthetic doses were chosen as 1.0 MAC equivalent. Anesthetized rats were intubated and ventilated with oxygen. The right carotid artery was cannulated with a thermocouple-catheter for aortic blood pressure, heart rate, and thermodilution cardiac output measurements. The right jugular vein was cannulated for measurement of central venous pressure and for i.v. injections. Data were collected over a 30-min baseline period and for 4 h after an i.v. bolus of endotoxin (40 mg.kg-1, LD100 within 24 h). Gross small intestinal pathology was rated on a 0-4 scale. Anesthetic effects were judged in terms of significant deviations from the awake data on each parameter. Despite differing patterns, total deviations were similar for enflurane, ketamine, and pentobarbital, although the latter drug was the least preferable due to particularly high systemic vascular resistance. Significantly less hemorrhagic small intestinal pathology occurred with enflurane. Ketamine offered no advantage over the inhalation anesthetics. Among the four anesthetics tested, results were closest to the awake pattern with isoflurane anesthesia, thus making it the logical choice for hemodynamic studies in experimental shock research.