Halothane Hepatotoxicity Research Articles

Drug-Induced Liver Injury in Children: Clinical Observations, Animal Models, and Regulatory Status.

Drug-induced liver injury in children (cDILI) accounts for about 1% of all reported adverse drug reactions throughout all age groups, less than 10% of all clinical DILI cases, and around 20% of all acute liver failure cases in children. The overall DILI susceptibility in children has been assumed to be lower than in adults. Nevertheless, controversial evidence is emerging about children's sensitivity to DILI, with children's relative susceptibility to DILI appearing to be highly drug-specific. The culprit drugs in cDILI are similar but not identical to DILI in adults (aDILI). This is demonstrated by recent findings that a drug frequently associated with aDILI (amoxicillin/clavulanate) was rarely associated with cDILI and that the drug basiliximab caused only cDILI but not aDILI. The fatality in reported cDILI studies ranged from 4% to 31%. According to the US Food and Drug Administration-approved drugs labels, valproic acid, dactinomycin, and ampicillin appear more likely to cause cDILI. In contrast, deferasirox, isoniazid, dantrolene, and levofloxacin appear more likely to cause aDILI. Animal models have been explored to mimic children's increased susceptibility to valproic acid hepatotoxicity or decreased susceptibility to acetaminophen or halothane hepatotoxicity. However, for most drugs, animal models are not readily available, and the underlying mechanisms for the differential reactions to DILI between children and adults remain highly hypothetical. Diagnosis tools for cDILI are not yet available. A critical need exists to fill the knowledge gaps in cDILI. This review article provides an overview of cDILI and specific drugs associated with cDILI.

A Mouse Model of Severe Halothane Hepatitis Based on Human Risk Factors

Halothane (2-bromo-2-chloro-1,1,1-trifluoro-ethane) is an inhaled anesthetic that induces severe, idiosyncratic liver injury, i.e., "halothane hepatitis," in approximately 1 in 20,000 human patients. We used known human risk factors (female sex, adult age, and genetics) as well as probable risk factors (fasting and inflammatory stress) to develop a murine model with characteristics of human halothane hepatitis. Female and male BALB/cJ mice treated with halothane developed dose-dependent liver injury within 24 h; however, the liver injury was severe only in females. Livers had extensive centrilobular necrosis, inflammatory cell infiltrate, and steatosis. Fasting rendered mice more sensitive to halothane hepatotoxicity, and 8-week-old female mice were more sensitive than males of the same age or than younger (4-week-old) females. C57BL/6 mice were insensitive to halothane, suggesting a strong genetic predisposition. In halothane-treated females, plasma concentration of tumor necrosis factor-alpha was greater than in males, and neutrophils were recruited to liver more rapidly and to a greater extent. Anti-CD18 serum attenuated halothane-induced liver injury in female mice, suggesting that neutrophil migration, activation, or both are required for injury. Coexposure of halothane-treated male mice to lipopolysaccharide to induce modest inflammatory stress converted their mild hepatotoxic response to a pronounced, female-like response. This is the first animal model of an idiosyncratic adverse drug reaction that is based on human risk factors and produces reproducible, severe hepatitis from halothane exposure with lesions characteristic of human halothane hepatitis. Moreover, these results suggest that a more robust innate immune response underlies the predisposition of female mice to halothane hepatitis.

Effect of polyI

Drug-induced liver injury (DILI) is a challenging problem in drug development and clinical practice. Patient susceptibility to DILI is multifactorial, making these reactions difficult to predict and prevent. Clinical observations have suggested that concurrent bacterial and viral infections represent an important risk factor in determining patient susceptibility to developing adverse drug reactions, although the underlying mechanism is not clear. In the present study, we employed the viral RNA mimetic (polyinosinic-polycytidylic acid [polyI:C]) to emulate viral infection and examined its effect on halothane-induced liver injury. Although pretreatment of mice with polyI:C attenuated halothane hepatotoxicity due to its inhibitory effect on halothane metabolism, posttreatment significantly exacerbated liver injury with hepatocellular apoptosis being significantly higher than that in mice treated with polyI:C alone or halothane alone. The pan-caspase inhibitor z-VAD-fmk suppressed liver injury induced by polyI:C/posthalothane cotreatment, suggesting that the increased hepatocyte apoptosis contributes to the exacerbation of liver injury. Posttreatment with polyI:C also caused activation of hepatic Kupffer cells (KCs) and natural killer (NK) cells and upregulated multiple proapoptotic factors, including tumor necrosis factor-alpha (TNF-alpha), NK receptor group 2, member D (NKG2D), and Fas ligand (FasL). These factors may play important roles in mediating polyI:C-induced hepatocyte apoptosis. This is the first study to provide evidence that concurrent viral infection can inhibit cytochrome (CYP)450 activities and activate the hepatic innate immune system to proapoptotic factors. DILI may be attenuated or exacerbated by pathogens depending on the time of infection.

Introduction of Sevoflurane, The Final Achievement of Burnell R. Brown MD, PhD, FFARCS (1933 - 1995)

Introduction In a videotaped interview for the Wood library Museum, Burnell R. Brown MD, PhD, FFARCS, reflected on his career filled with many significant achievements. He felt that he had done five things of significance to society: promoting the use of alpha blockers in pheochromocytoma, founding and nourishing the department at the University of Arizona, working out the pathophysiology of halothane hepatotoxicity, editing the Survey of Anesthesiology and the textbook General Anaesthesia, Fifth Edition, and introducing sevoflurane to the US market.** The purpose of this essay is to describe Dr. Brown’s role in the introduction of sevoflurane. This was his final achievement prior to his premature death at age 61 (August 8, 1995) from a highly anaplastic carcinoma of obscure origin. (Figure 1)

Experimental research on phospholipids variation of halothane on liver mitochondria.

AIM:To study the pathogenesis of hepatotoxicity of halothane.METHODS:The effect of different concentration of halothane and sevoflurane on mitochondrial membrane phospholipids composition of rat liver were analyzed using high performance liquid chromatography (HPLC) technology.RESULTS:Halothane at low concentration could degrade mitochondrial membrane major phospholipids and increase lysophosph-atidylcholine.CONCLUSION:The pathogenesis of halothane hepatotoxicity was the phospholipids variation on liver mitochondria.

Anaesthetic organ toxicity: is it really a problem?

The hepatotoxicity of halothane is now well known, but only became apparent after several years of use. The nephrotoxicity of methoxyflurane was not realized immediately, but once identified, led to its withdrawal from use. Therefore, when new agents that appear to offer significant advantages over established drugs become available, exhaustive testing and monitoring is necessary to ensure their safety. Sevoflurane, recently available in the UK and the USA but used for some time in Japan, has been subjected to considerable scrutiny.

Epidemic of liver disease caused by hydrochlorofluorocarbons used as ozone-sparing substitutes of chlorofluorocarbons

Hydrochlorofluorocarbons (HCFCs) are used increasingly in industry as substitutes for ozone-depleting chlorofluorocarbons (CFCs). Limited studies in animals indicate potential hepatotoxicity of some of these compounds. We investigated an epidemic of liver disease in nine industrial workers who had had repeated accidental exposure to a mixture of 1,1-dichloro-2,2,2-trifluoroethane (HCFC 123) and 1-chloro-1,2,2,2-tetrafluoroethane (HCFC 124). All nine exposed workers were affected to various degrees. Both compounds are metabolised in the same way as 1-bromo-1-chloro-2,2,2-trifluoroethane (halothane) to form reactive trifluoroacetyl halide intermediates, which have been implicated in the hepatotoxicity of halothane. We aimed to test whether HCFCs 123 and 124 can result in serious liver disease. For one severely affected worker liver biopsy and immunohistochemical stainings for the presence of trifluoroacetyl protein adducts were done. The serum of six affected workers and five controls was tested for autoantibodies that react with human liver cytochrome-P450 2E1 (P450 2E1) and P58 protein disulphide isomerase isoform (P58). The liver biopsy sample showed hepatocellular necrosis which was prominent in perivenular zone three and extended focally from portal tracts to portal tracts and centrilobular areas (bridging necrosis). Trifluoroacetyl-adducted proteins were detected in surviving hepatocytes. Autoantibodies against P450 2E1 or P58, previously associated with halothane hepatitis, were detected in the serum of five affected workers. Repeated exposure of human beings to HCFCs 123 and 124 can result in serious liver injury in a large proportion of the exposed population. Although the exact mechanism of hepatotoxicity of these agents is not known, the results suggest that trifluoroacetyl-altered liver proteins are involved. In view of the potentially widespread use of these compounds, there is an urgent need to develop safer alternatives.

Demonstration of a Cellular Immune Response in Halothane-Exposed Guinea Pigs

Halothane hepatitis is considered to be a result of an idiosyncratic autoimmune reaction brought about by the formation of neoantigens that have been generated by covalent binding of halothane biotransformation intermediates. The guinea pig is being examined as an animal model to investigate an immune-mediated mechanism for halothane hepatotoxicity. Male Hartley guinea pigs were exposed to 1% halothane/40% oxygen for 4 hr, three times with 40-day intervals. Kupffer cells and splenocytes were isolated from animals on various days after each halothane exposure. Splenocytes were cocultured in a lymphocyte transformation test with various concentrations of TFA(trifluoroacetylated)-antigens for 7 days and proliferation was measured by3H-thymidine incorporation. In a second experiment, Kupffer cells were cocultured with autologous as well as allogeneic splenocytes with or without concanavalin A to determine whole cell sensitization and accessory function by Kupffer cells from treated animals. A 4-fold increase in splenocyte proliferation occurred in response to TFA-guinea pig albumin. No significant increase in proliferation could be detected with TFA-lysine or guinea pig albumin. A 14-fold increase in splenocyte proliferation also occurred in response to Kupffer cells from halothane-exposed animals. Autologous splenocytes demonstrated more of a response from treated versus control animals, indicating possible involvement of major histocompatibility complex II antigens. These results indicate recognition of TFA-antigens and Kupffer cells as antigen-presenting cells in halothane-exposed guinea pigs. This study provides good evidence that a cellular immune response is involved in the guinea pig after halothane exposure.

Comparative Tolerability Profiles of the Inhaled Anaesthetics

Improved understanding of the structure/activity relationship of inhaled anaesthetics has resulted in the synthesis of fluorinated compounds which are more potent and less toxic than their unfluorinated antecedents. The toxic effects of inhaled anaesthetics on the liver and kidney are complex but, in general, are related to the extent to which individual inhaled agents are metabolised. Halothane hepatotoxicity is a rare, idiosyncratic reaction which typically occurs in obese women having more than one exposure to the drug within a short time interval. All currently available volatile anaesthetic drugs have depressant effects on the cardiovascular and respiratory systems; arrhythmias are more likely with halothane than with the fluorinated ethers. Cerebral blood flow tends to increase during inhalation anaesthesia, especially with halothane and in the presence of hypercarbia; isoflurane may be given sparingly during neurosurgical procedures whilst monitoring its end-tidal concentration. Although the volatile agents tend to cause uterine relaxation they may be given safely in low concentration to avoid awareness during Caesarean section. In general, young children require rather higher concentrations of volatile agents than adults and seem to be less susceptible to organ toxicity. Two relatively new volatile agents, sevoflurane and desflurane, offer some advantages over isoflurane but neither is an "ideal drug'. Sevoflurane interacts with soda-lime to produce a series of degradation products, the most important of which is compound A. Production is greatest during low-flow, closed circuit anaesthesia using high inspired concentrations of the drug. Compound A has nephrotoxic potential in rats but the clinical significance of the interaction between sevoflurane and soda-lime is unclear. Nitrous oxide when given for prolonged periods may cause irreversible bone marrow depression.

In vivo study of halothane hepatotoxicity in the rat using magnetic resonance imaging and 31P spectroscopy.

Using magnetic resonance imaging (MRI) and spectroscopy (MRS), in vivo halothane hepatotoxicity was assessed in male Wistar rats. With 1.5% halothane in 100 or 20% O 2, an edematous region, characterized by increased intensity on T 2 weighted images and an increase in regional tissue water content ( ρ water), was seen proximal to the hepatic portal vein in the liver. Both spin–lattice relaxation (T 1) and spin–spin relaxation (T 2) increased in this region, relative to distal regions of the liver. Similarly, a high signal intensity on proton density weighted images was observed in this area. As halothane anaesthesia progressed, a decrease in the adenosine triphosphate–inorganic phosphate ratio (ATP/P i) and an increase in the phosphomonoester–phosphodiester (PME/PDE) ratio was detected in the liver. In addition, intracellular pH decreased and intracellular free magnesium concentration [Mg 2+] increased with time of exposure. Excessive vacuolation, ribosomal disappearance from rough endoplasmic reticulum, mitochondrial swelling and fragmentation of smooth endoplasmic reticulum were observed by transmission electron microscopy (TEM) in samples from the edematous region of the liver.

Halothane hepatotoxicity and hepatic free radical metabolism in guinea pigs; the effects of vitamin E.

The aim of this study was to investigate the relation between halothane hepatotoxicity and hepatic free radical metabolism and to establish a possible protective role of vitamin E against halothane hepatotoxicity. Twenty-eight guinea pigs were used in the experiments. Halothane (1.5% v/v) in oxygen (100%) was given to the animals for 90 min over three days. Livers from animals were then taken and prepared for the assays. In the enzymatic study, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) activities were measured. As a peroxidation index, the malondialdehyde (MDA) concentration was determined. Also, electron spin resonance (ESR) analysis and electron microscopy (EM) were performed. Superoxide dismutase (1168.3 +/- 78.2 U.mg-1) and glutathione peroxidase (14.9 +/- 6.2 mIU.mg-1) activities were decreased, but catalase activity (1260.0 +/- 250.6 IU.mg-1) and malondialdehyde concentration (11.5 +/- 1.8 ppb) were increased in liver tissues exposed to halothane compared with control values (1382.2 +/- 91.8 U.mg-1 for SOD, 27.8 +/- 5.2 mIU.mg-1 for GSH-Px, 840.2 +/- 252.4 IU.mg-1 for CAT and 10.0 +/- 1.0 ppb for MDA). Electron spin resonance analysis revealed a peak of CF3CHCl. radical in the exposed tissue. Electron microscopy indicated ultrastructural changes in the hepatic cells of both halothane groups with and without vitamin E treatment. Halothane causes impairment in the hepatic antioxidant defense system and accelerates peroxidation reactions. As a result, some ultrastructural changes in hepatic tissues occur due to halothane treatment. Although vitamin E prevents peroxidative damage, it does not ameliorate ultrastructural changes caused by halothane treatment. This shows that halothane toxicity results not only from impaired hepatic antioxidant defense system but also from other, unknown causes.

Use of Halothane as a Model for Investigating Chemical-Induced Autoimmune Hepatotoxicity

Adverse drug reactions are usually unpredictable. The mechanisms by which these reactions occur are poorly understood but often involve the immune system. The volatile anesthetic halothane has evolved as a model drug for investigating chemical-induced autoimmune hepatotoxicity. It has been shown that during the biotransformation of halothane, adducts are formed with liver proteins which can be recognized as neoantigens. These adducts have been associated with the production of a humoral and cellular immune response in a guinea pig model of halothane hepatotoxicity. This model has been used to examine the various aspects of an autoimmune response and the authors' attempts to correlate the immune response to the liver injury.

Human hepatocytes express trifluoroacetylated neoantigens after in vitro exposure to halothane

Biotransformation of anaesthetic halothane by cytochrome P450-dependent monooxygenases resulted in the production of reactive intermediate trifluoroacetyl (TFA) halide, capable of covalently binding to hepatocyte proteins. TFA-modified liver proteins can act as antigens and are implicated in the pathogenesis of halothane hepatitis in humans. The aim of this study was to investigate the formation of TFA-neoantigens in halothane-treated primary cultures of adult human hepatocytes and to evaluate the usefulness of this in vitro model for studying immune-mediated halothane hepatotoxicity. Cultured human hepatocytes were incubated with halothane under constant temperature, atmosphere and anaesthetic concentration conditions. The results obtained show that halothane-treated hepatocytes isolated from seven different donors produced TFA-antigens as detected by immunocytochemical and western immunoblot analysis using rabbit anti-TFA antiserum. TFA-adducts were localized mainly in the endoplasmic reticulum and in small amounts on the plasma membrane of parenchymal cells. By immunoblotting, several neoantigens, with molecular masses from 42 to 100 kDa, were detected in halothane-exposed hepatocytes. These observations are consistent with the formation of TFA-adducts through metabolism of the anaesthetic and suggest that primary cultures of human hepatocytes represent a suitable in vitro model to study the pathogenesis of immune-mediated halothane hepatotoxicity.

Non-A, non-B fulminant hepatitis is also non-E and non-C.

to define the roles of the hepatitis C and E viruses (HCV and HEV) in non-A, non-B (NANB) fulminant hepatitis. we utilized the polymerase chain reaction to amplify HCV and HEV RNA sequences and assays to detect antibodies to HCV and HEV in the acute phase sera of eight presumed viral NANB and seven nonviral NANB fulminant hepatic failure (FHF) patients. none of the 15 patients had detectable HCV or HEV RNA or elevated HCV and IgM-HEV antibody titers in their acute phase sera. Three patients, all with features of autoimmune hepatitis, had raised IgG-HEV antibody titers. Due to the possibility of serologically undetectable hepatitis B virus (HBV) infection in fulminant hepatitis patients, we performed polymerase chain reaction amplification of HBV genomic DNA in acute phase sera of the presumed viral NANB FHF patients and subsequently found no evidence of HBV DNA. we did not find evidence implicating HCV or HEV in presumed viral NANB FHF or as agents contributing to or causing the liver failure in nonviral NANB FHF patients with autoimmune hepatitis, drug-induced hepatotoxicity, or halothane hepatotoxicity.

Effect of Halothane on Hypoxic Toxicity and Glutathione Status in Cultured Rat Hepatocytes

In hypoxic rats, halothane causes hepatotoxicity at oxygen levels that would cause minimal hepatotoxicity in the absence of halothane. Using a model that excludes systemic and extrahepatic effects of halothane, the authors tested the hypothesis that halothane hepatotoxicity in the whole-rat model is caused by a direct hepatotoxic effect of halothane, which is mediated by halothane-derived free radicals. Rat hepatocyte monolayer cultures were exposed to defined gas phases for 2 h. Three experimental variables were present or absent: hypoxia (1% O2), halothane (2%), and cytochrome P-450 induction (by phenobarbital). Two experimental outcomes were measured: aspartate aminotransferase release, a measure of cell death, and reduced glutathione, an endogenous free radical scavenger whose levels are decreased by physiologically significant free radical injury. As anticipated, hypoxia increased cell death. Cytochrome P-450 induction by itself increased cell death during hypoxia. However, halothane had no effect on cell death during hypoxia, with or without cytochrome P-450 induction. Halothane had no toxic effect, even when glutathione was depleted before the onset of hypoxia. Glutathione was decreased moderately by hypoxia alone. Neither halothane nor cytochrome P-450 induction had any effect on glutathione levels. Halothane was not toxic, and it did not generate a physiologically significant free radical insult during hypoxia in the isolated rat hepatocyte under the experimental conditions used in testing.

Covalent Binding of Oxidative Biotransformation Intermediates Is Associated with Halothane Hepatotoxicity in Guinea Pigs

In vivo covalent binding of halothane biotransformation-reactive intermediates to hepatic protein and lipid was examined in association with the subsequent development of hepatic necrosis in the guinea pig. Oxidative halothane biotransformation was inhibited by the use of deuterated halothane, whereas reductive metabolism was enhanced by low inspired oxygen concentrations. Male outbred Hartley guinea pigs (n = 8) were exposed to either 1% (v/v) halothane or deuterated halothane--with a fractional inspired O2 concentration (FIO2) of 0.40 or 0.10--for 4 h. Livers removed from half of the animals immediately after anesthesia were evaluated for organic fluorine bound to protein and lipid. The remaining animals were evaluated for a hepatotoxic response up to 96 h after exposure. Only guinea pigs that received 1% halothane at an FIO2 of 0.40 had centrilobular necrosis develop with significantly increased plasma alanine aminotransferase activities. All other treatment conditions significantly reduced oxidative halothane biotransformation, as indicated by decreased plasma trifluoroacetic acid concentrations. These reductions were associated with a significant decrease in organic fluorine bound to hepatic proteins. An FIO2 of 0.10 during halothane anesthesia significantly enhanced reductive biotransformation, as indicated by plasma fluoride ion concentrations. This was associated with a significant increase in organic fluoride bound to hepatic lipids. Centrilobular necrosis did not develop under these conditions. Thus, covalent binding to subcellular proteins by the trifluoroacetyl acid chloride intermediate generated by oxidative halothane biotransformation is implicated as a mechanism of centrilobular necrosis in guinea pigs. Binding to lipids by reductive pathway generated free radicals does not appear to be involved in production of the lesion.

Effects of Halothane and Hypoxia on Hepatic Oxygen Metabolism in the Dog

Hepatic oxygen delivery and consumption were assessed in mongrel dogs receiving 2MAC of halothane combined with graded hypoxic hypoxemia (21–8% oxygen). Hepatic blood flow was measured using electromagnetic flowmetry; hepatic oxygen delivery and consumption were calculated from measured hepatic blood flow and oxygen content in hepatic arterial, portal venous and hepatic venous blood. In hypoxia-halothane group, total hepatic blood flow decreased at mild hypoxia (15% O2) from control value, but recovered to control level at moderate hypoxia (10% O2), then again decreased at 8% O2. Oxygen supply to the liver was decreased with the augmentation of hypoxia in hypoxia-halothane and hypoxia-alone groups, and it was significantly lower in the hypoxia-halothane group at 15 and 12% O2. Hepatic oxygen consumption also decreased from air control values with the increment of hypoxia, but there was no significant difference between the groups. Arterial ketone body ratio, which indicates mitochondrial energy charge level, decreased with the development of hypoxia but there was no significant difference in this ratio between the groups. These results show that halothane aggravated oxygen supply to the liver at mild to moderate hypoxia (15–12% O2), but did not worsen it specifically at more serious hypoxia (10–8% O2) compared with hypoxia alone. Hepatic hypoxia itself could not thus be a main cause of halothane hepatotoxicity.

Halothane-Induced Liver Injury as a Consequence of Enhanced Microsomal Lipid Peroxidation in Guinea Pigs

We investigated the role of microsomal lipid peroxidation in halothane hepatotoxicity in guinea pigs. Animals were exposed to halothane, isoflurane or enflurane. Enhancement of microsomal lipid peroxidation was specific to halothane. The time-course of lipid peroxidation and hepatic damage following a single exposure to halothane was investigated by measuring the thiobarbituric acid (TBA)reactive products, serum transaminase activity, reduced glutathione (GSH) concentration and histopathological examination. Microsomal lipid peroxidation was enhanced most rapidly and preceded GSH depletion and hepatic injury. Metyrapone, an inhibitor of cytochrome P-450, and N-tert-butyl-alpha-phenylnitrone (BPN), a radical trapping agent, inhibited halothane-induced lipid peroxidation and the incidence and severity of liver injury. The metabolism of halothane was considered to be inhibited by metyrapone and the reactivity of radical intermediates was considered to be decreased by BPN. Microsomal lipid peroxidation was initiated by radical metabolites of halothane but did not result from GSH depletion. Inhibition of microsomal lipid peroxidation reduced the halothane hepatotoxicity. These results demonstrated that the halothane-induced liver injury was caused by microsomal lipid peroxidation in guinea pigs.

The role of oxidative biotransformation of halothane in the guinea pig model of halothane-associated hepatotoxicity.

The role of the oxidative pathway of halothane biotransformation in mediating the hepatotoxicity of halothane in the guinea pig was examined by utilizing the deuterated form of halothane (d-halothane), which is resistant to oxidative metabolism. Male outbred Hartley guinea pigs were exposed to either 1% v/v halothane or d-halothane, FIO2 = 0.21, for 4 h. Significant reductions in both oxidative and overall halothane biotransformation were observed with the use of d-halothane as indicated by decreased plasma levels of trifluoroacetic acid and bromide ion, respectively, immediately following exposure. Plasma fluoride ion, indicative of the reductive metabolism of halothane, was significantly increased with the use of d-halothane. These changes in metabolism were accompanied by a reduced hepatotoxic response as indicated by significantly decreased plasma ALT levels 24-96 h following exposure and a significantly lesser incidence of centrilobular necrosis. Thus, the oxidative biotransformation of halothane is implicated as a mechanism of injury in guinea pigs.

Effects of halothane and hypoxia on hepatic oxygen metabolism in the dog.

Hepatic oxygen delivery and consumption were assessed in mongrel dogs receiving 2MAC of halothane combined with graded hypoxic hypoxemia (21-8% oxygen). Hepatic blood flow was measured using electromagnetic flowmetry; hepatic oxygen delivery and consumption were calculated from measured hepatic blood flow and oxygen content in hepatic arterial, portal venous and hepatic venous blood. In hypoxia-halothane group, total hepatic blood flow decreased at mild hypoxia (15% O2) from control value, but recovered to control level at moderate hypoxia (10% O2), then again decreased at 8% O2. Oxygen supply to the liver was decreased with the augmentation of hypoxia in hypoxia-halothane and hypoxia-alone groups, and it was significantly lower in the hypoxia-halothane group at 15 and 12% O2. Hepatic oxygen consumption also decreased from air control values with the increment of hypoxia, but there was no significant difference between the groups. Arterial ketone body ratio, which indicates mitochondrial energy charge level, decreased with the development of hypoxia but there was no significant difference in this ratio between the groups. These results show that halothane aggravated oxygen supply to the liver at mild to moderate hypoxia (15-12% O2), but did not worsen it specifically at more serious hypoxia (10-8% O2) compared with hypoxia alone. Hepatic hypoxia itself could not thus be a main cause of halothane hepatotoxicity.