Improved outcome of paracetamol-induced fulminant hepatic failure by late administration of acetylcysteine

A 7-year experience of severe acetaminophen-induced hepatotoxicity (1987-1993)

BACKGROUND & AIMS

Five hundred sixty patients admitted between January 1, 1987, and December 31, 1993, with severe acetaminophen-induced hepatotoxicity were studied. The aim of this study was to identify why severe acetaminophen-induced hepatotoxicity still occurs and to determine how known risk factors and advances in management have affected the pattern of illness and outcome.

METHODS

This was a retrospective study of the etiologic factors and the clinical course of all acetaminophen-related admissions.

RESULTS

The number of admissions increased from 58 in 1987 to 123 in 1993. During the corresponding period, overall survival improved from just < 50% to 78%. The percentage of admissions treated with N-acetylcysteine increased from 40% in 1987 to 83% in 1993. The frequency with which grade III or IV encephalopathy developed decreased from 62% in 1987 to 40% in 1993, and the percentage of these patients who developed cerebral edema decreased from 61% to 45% during the same period. There was an increase in both the number of patients transplanted and the survival of those managed medically.

CONCLUSIONS

Severe acetaminophen-induced hepatotoxicity remains a serious condition, but the increasing use of N-acetylcysteine, advances in medical management, and the increasing availability of transplantation have resulted in a significant improvement in survival rates.

[Acute liver failure caused by paracetamol: should treatment with N-acetylcysteine be prolonged?]

BACKGROUND

Some cases of paracetamol-induced acute hepatic failure may require liver transplantation but the present shortage of graft urges the search for an alternate therapeutic approach.

CASE REPORT

A 17 year-old girl was admitted for sleepingness and vomiting after about 15 hours of voluntary but denied absorption of paracetamol. Plasma paracetamol concentration was 120 mg/l; factors VII+X level were 55% and factor V 106%. The patient was given IV N-acetylcysteine, 150 mg/kg/30 min, then 50 mg/kg/4 hours. Further decrease in facteur VII level led to pursue administration of N-acetylcysteine (total dose: 350 mg/kg/2 hours). While indication of liver transplantation was considered, clinical and laboratory findings definitely improved.

CONCLUSIONS

N-acetylcysteine may be effective even if administered late. Repeated determination of factor VII could be a good means for managing such a severe condition.

Hepatic disorders. Features and appropriate management

The spectrum of liver disease is extremely wide, with many of the underlying disorders having acute and chronic presentations. Most of the underlying pathogenetic mechanisms are accounted for by autoimmune disease, viral infection and toxic insult. The management strategy of any liver disease is a combination of treating the symptoms and complications that arise, as well as drug therapies relevant to the specific underlying diagnosis. Encephalopathy, ascites, spontaneous bacterial peritonitis, variceal bleeding and pruritus are the main complications at which drug therapy is directed, although in some cases it represents only 1 aspect of the overall management. Drug therapy per se is largely ineffective in acute liver failure with the possible exception of acetylcysteine, but many drugs are used in the management of the constituent components of this complex medical emergency. Treatments for specific liver conditions are expanding, especially in the areas of autoimmune and viral disease. The increasing availability and success of liver transplantation has tended to change the emphasis of management, and it is often not appropriate to exhaust the treatment options before referring the patient for transplantation. A comprehensive review of all liver disease is beyond the scope of this article, but hopefully the important principles of management and commonly occurring clinical decisions are discussed.

Protection against acetaminophen-induced liver injury in vivo by an iron chelator, deferoxamine

BACKGROUND

Recent data indicate that iron ions play a major role in lipid peroxidation, a hepatotoxic effect of acetaminophen (APAP).

METHODS

We investigated whether an iron chelator, deferoxamine (DFO), can protect against APAP-induced liver injury in vivo in rats.

RESULTS

DFO diminished the increase in serum alanine aminotransferase (ALAT) in a dose-dependent manner after APAP administration and also reduced mortality. Administration of 750 mg/kg APAP resulted in an increased ALAT (11,666 +/- 4633) after 8 h, and the mortality at 24 h was 88%. Pretreatment with 200 mg/kg DFO for 1 h significantly reduced ALAT (to 3406 +/- 894) and mortality (38%). DFO also attenuated histopathologic changes. Treatment with DFO depressed malondialdehyde formation by APAP without inhibiting glutathione depletion in the liver or reducing covalent binding of [3H]APAP to liver proteins.

CONCLUSIONS

These results indicate that the protective effect of DFO against APAP-induced liver injury may be attributable not to changes in APAP metabolism but to the chelation of iron, which can catalyze the generation of active oxygen species, in hepatocytes.

Effects of N-acetylcysteine and dithiothreitol on glutathione and protein thiol replenishment during acetaminophen-induced toxicity in isolated mouse hepatocytes

Isolated mouse hepatocytes were incubated with 1.0 mM acetaminophen (AA) for 1.5 h to initiate glutathione (GSH) and protein thiol (PSH) depletion and cell injury. Cells were subsequently washed to remove non-covalently bound AA and resuspended in medium containing N-acetylcysteine (NAC, 2.0 mM) or dithiothreitol (DTT, 1.5 mM). The effects of these agents on the replenishment of GSH and total PSH content were related to the development of cytotoxicity. When cells exposed to AA were resuspended in medium containing NAC or DTT, both agents replenished GSH and total PSH content to levels observed in untreated cells but only DTT was able to attenuate cytotoxicity. Addition of the GSH synthesis inhibitor, buthionine sulfoximine (BSO, 1.0 mM, 1.5 h), to cells in incubation medium containing AA, enhanced GSH and total PSH depletion and potentiated cytotoxicity. Resuspension of these cells in medium containing NAC did not alter the potentiating effects of BSO; GSH and PSH levels were not replenished and no cytoprotective effects were observed. However, when cells exposed to AA and BSO were resuspended in medium containing DTT, PSH content was replenished but GSH levels were not restored. In addition, DTT was able to delay the development of cytotoxicity. It appears that DTT, unlike NAC, has a GSH-independent mechanism of PSH replenishment. These observations suggest that while replenishment of GSH and total PSH content does not result in cytoprotection, the regeneration of critical PSH by DTT may play an important role in the maintenance of proper cell structure and/or function.

The influence of N-acetylcysteine on the measurement of prothrombin time and activated partial thromboplastin time in healthy subjects

The purpose of the study was to evaluate whether the infusion of N-acetylcysteine decreased the measurement of prothrombin time and activated partial thromboplastin time (APTT) in healthy persons. N-acetylcysteine was administered intraveneously 10 mg kg-1 as a loading dose and then at a rate of 10 mg kg-1 h-1 for 32 h in six male subjects. The intrinsic, extrinsic and common pathway of coagulation were monitored with activated partial thromboplastin time (APTT), and prothrombin time, respectively. In addition, the extrinsic coagulation pathway was monitored with the clotting activity of single factors II, VII, and X. No effect on the intrinsic coagulation pathway was observed. There was a significant and rapid decrease in prothrombin time. Coagulation factors II, VII and X, the three components of prothrombin time, decreased significantly to different degrees. We conclude that infusion of N-acetylcysteine intraveneously decreases the prothrombin time in healthy subjects. Thus, one should not make conclusions which are too far-reaching based on prothrombin time alone in patients who have been treated recently with N-acetylcysteine intraveneously.

Acetylcysteine as a cytoprotective antioxidant in patients with severe sepsis: potential new use for an old drug

OBJECTIVE

To stimulate debate regarding a potential new use for acetylcysteine as a cellular antioxidant in severely septic patients with systemic inflammatory response syndrome (SIRS).

DATA SOURCES

A MEDLINE review of published animal, human, and laboratory studies relating to the cytopathogenic effects of active radicals in SIRS and the protective effects of acetylcysteine and glutathione.

STUDY SELECTION

Few studies were available so all studies pertinent to the objective were reviewed.

DATA EXTRACTION

Clinical and basic science data from the available trials of the effects of acetylcysteine on active radical production or active radical cell injury were extrapolated to predict the effect of acetylcysteine on human sepsis.

DATA SYNTHESIS

Severe sepsis is a major cause of SIRS. Much of the cellular injury associated with SIRS is mediated by active radicals produced by inflammatory cells that overwhelm endogenous antioxidants. Reduced glutathione is a crucial intracellular antioxidant that becomes depleted during SIRS. Regeneration of glutathione can be achieved by acetylcysteine, which unlike glutathione itself penetrates cells. In animal models of sepsis and lung injury, acetylcysteine mitigates the cytopathologic effects of SIRS. In humans, clinical benefit has been demonstrated in the SIRS of established fulminant hepatic failure.

CONCLUSIONS

The data do not as yet lead to any firm conclusions regarding the value of acetylcysteine in the management of SIRS in severe sepsis. The animal and human studies are, however, sufficiently encouraging to warrant formal trials to test the hypothesis that acetylcysteine therapy has a cytoprotective effect in sepsis.

Serious paracetamol poisoning and the results of liver transplantation

Paracetamol poisoning is the most common cause of fulminant liver failure in the United Kingdom. An accurate assessment of prognosis at the time of referral will allow the appropriate application of liver transplantation in this setting. The outcome of 92 patients consecutively admitted to a specialist liver unit with severe poisoning has been examined. In patients who did not have a transplant, a fatal outcome was seen for 26/82 (32%), and was associated with late presentation, coma grade, prothrombin time prolongation, metabolic acidosis, and renal dysfunction. Cerebral oedema, and sepsis were responsible for most deaths. Prognostic criteria defined at King's College Hospital seemed to predict the outcome of patients who did not have a transplant managed on the Birmingham liver unit. Seventeen patients were listed for transplantation, 10 had liver transplantation, and seven of 10 survived. Seven were listed but not transplanted, and one of seven survived. Psychological rehabilitation of patients who had a transplant has not proved difficult. These results suggest a role for liver transplantation in the management of selected patients with paracetamol poisoning.

Liver disease

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Paracetamol (acetaminophen) poisoning

Paracetamol poisoning caused by intentional overdose remains a common cause of morbidity. In this article the mechanism of toxicity and the clinical effects and treatment of poisoning, including specific antidotal therapy, are reviewed. Areas for further research directed at reducing morbidity and mortality from paracetamol poisoning are considered.

High volume plasma exchange in fulminant hepatic failure

We investigated the effect of repeated high volume plasma exchange with fresh donor plasma in 11 patients with fulminant hepatic failure, all initially in stage 3 or 4 encephalopathy. A daily exchange of a volume equal to the extracellular volume (20% of body weight) on three consecutive days was intended. We obtained an average of 2.6 exchanges each with a mean volume equal to 16% of the body weight. Five patients (46%, 95% confidence limits 17%-77%) survived, all with acetaminophen induced liver failure. Four of the 6 non-survivors showed a temporary improvement in cerebral function. Two of the patients woke up completely. The 6 non-survivors maintained a stable condition with a systolic blood pressure > 110 mm Hg for a mean of 6.9 days after initiating plasma exchange. Plasma exchange may be considered in acute liver failure in patients with residual liver function before transplantation is finally decided. In addition, plasmapheresis may be used to keep patients with definite liver failure clinically stable until a transplant can be performed.

Hepatotoxicity from paracetamol self-poisoning in western Sydney: a continuing challenge

OBJECTIVE

To determine the annual incidence of admissions for paracetamol overdosage in the years 1985 to 1990, morbidity and mortality rates, predictors of poor prognosis and the most appropriate use of N-acetylcysteine (NAC).

DESIGN

A retrospective review of case records of all patients with a discharge diagnosis of paracetamol overdosage.

SETTING

A 900-bed tertiary referral teaching hospital in western Sydney with a busy accident and emergency department.

PATIENTS

306 patient records were reviewed and details of the overdose and admission were recorded.

INTERVENTIONS

NAC infusion in patients with possible paracetamol hepatotoxicity.

MAIN OUTCOME MEASURES

Blood paracetamol levels; elevated alanine aminotransferase levels; prolonged prothrombin time; severe liver injury; and NAC side effects.

RESULTS

Annual admission rate was constant at circa 55 per annum. Female to male ratio was 2:1. Predictors of liver injury included paracetamol dose over 10 g, presentation more than 10 hours after the overdose and chronic ingestion of more than 80 g alcohol per day. There were no deaths. Fifty-five patients (18%) had toxic paracetamol levels, 51% received treatment with NAC, including 40% of those with non-toxic levels, and 11% of those treated with NAC experienced side effects.

CONCLUSION

Paracetamol overdosage continues to be a significant cause of hospital admissions in western Sydney. Severe hepatic damage occurs infrequently and the prognosis for liver injury, when it occurs, is good. Treatment with NAC should be reserved for patients with definite indications for the drug.

Does hypothermia protect against the development of hepatitis in paracetamol overdose?

A 24-year-old female presented in hospital following self-poisoning with a dose of greater than 30 g of paracetamol (acetaminophen), taken both as co-proxamol (dextropropoxyphene and paracetamol) and paracetamol. She arrived in hospital more than 18 h after ingestion of the drug. On admission, she was profoundly hypothermic, with a rectal temperature of 19 degrees C. Her paracetamol level was 943 mumol.l-1 which, when related to the time of ingestion, implied a very high risk of hepatocellular damage as well as fulminant liver failure, even if she was treated with the antioxidant n-acetylcysteine. The patient's condition was stabilised by initial resuscitation with fluids, vasoactive drugs, and active rewarming. N-acetylcysteine therapy was begun promptly. This patient's liver function tests remained entirely normal in spite of the delay in presentation and she made a rapid and complete recovery. This remarkable clinical course indicates a possible role for therapeutically induced hypothermia in the management of severe paracetamol overdose, particularly in the group of patients who seek medical attention some hours after ingestion of the drug and who therefore remain at high risk, despite treatment with n-acetylcysteine.

Effects of vasopressor agents and epoprostenol on systemic hemodynamics and oxygen transport in fulminant hepatic failure

Hypotension is a serious complication in patients with fulminant hepatic failure, because it is associated with tissue hypoxia and a further compromise to end-organ function. In this study we investigated the effects of epinephrine and norepinephrine on hemodynamics and oxygen transport variables in 30 patients with fulminant hepatic failure. All had a mean arterial pressure of less than 60 mm Hg, despite adequate intravascular filling pressures. Both epinephrine (n = 15) and norepinephrine (n = 15) improved mean arterial pressure (p less than 0.001 epinephrine and norepinephrine), although this was not associated with a rise in oxygen delivery. Oxygen consumption fell (p less than 0.05 epinephrine, p less than 0.001 norepinephrine) because of a lower oxygen extraction ratio (p less than 0.01 epinephrine and norepinephrine). The addition of epoprostenol, a microcirculatory vasodilator, in 10 patients from each group led to an increase in oxygen consumption (p less than 0.001 epinephrine and norepinephrine) because of a rise in oxygen delivery (p less than 0.05 epinephrine, p less than 0.01 norepinephrine) and oxygen extraction ratio (p less than 0.01 epinephrine, p less than 0.001 norepinephrine), without a fall in mean arterial pressure. The fall in oxygen consumption after the institution of vasopressor therapy could exacerbate tissue hypoxia and thus contribute to further organ damage in an already susceptible patient. In patients with fulminant hepatic failure who are given vasopressor support, the addition of epoprostenol may prevent the development of tissue hypoxia.

S-adenosylmethionine protects against acetaminophen hepatotoxicity in two mouse models

Because S-adenosylmethionine promotes synthesis of hepatic glutathione in chronic liver disease and is well tolerated in man, we investigated its use as an antidote to acetaminophen hepatotoxicity in two mouse models. In C57Bl6 mice, deaths were abolished by S-adenosylmethionine given within 1 hr of 3.3 mmol/kg body wt acetaminophen (0 of 32 vs. 13 of 49, p less than 0.005) and reduced if given 2 to 5 hours after acetaminophen administration (4 of 42 vs. 13 of 49, p less than 0.01). Mixed disulfate/tosylate salt of S-adenosylmethionine abolished mortality in C3H mice given 2 mmol/kg body wt acetaminophen (0 of 24 vs. 4 of 18; p less than 0.05). In both mouse models, S-adenosylmethionine reduced depletion of plasma (median = 20.8 mumol/L vs. 14.6 mumol/L) and liver glutathione (198% vs. 100%; p less than 0.05), liver damage and release of AST after acetaminophen administration. Pretreatment with buthionine sulfoximine, which inhibits glutathione synthesis, abolished the beneficial effect of S-adenosylmethionine on survival and plasma glutathione level. S-adenosylmethionine reduces acetaminophen hepatotoxicity by metabolism of the active moiety to glutathione. This benefit may last as long as 5 hr after acetaminophen ingestion.

Coagulation factor V and VIII/V ratio as predictors of outcome in paracetamol induced fulminant hepatic failure: relation to other prognostic indicators

The value of coagulation factor V and VIII/V levels as prognostic indicators was assessed in 27 patients with fulminant hepatic failure and compared with other predictive indices. Admission factor V levels were significantly reduced in 22 patients with paracetamol induced hepatic failure compared with a healthy control group (median 9.5% v 103%, respectively; p less than 0.001) and with lower values in non-A non-B hepatitis (median 2.7%). Values in the seven patients who died after paracetamol overdose, considered together with the four who underwent liver transplantation (group median 5.1%), were significantly lower than in the 11 who survived (median 11.8%; p less than 0.01). Median admission factor VIII was higher in those who died or received a transplant than in those who survived (298% v 162%; p less than 0.05), with both results higher than in healthy volunteers (median 104%; p less than 0.01) but lower than in non-A non-B hepatitis (median 340%). The ratio of factor VIII/V on admission was less than 30 in all patients who survived paracetamol overdose (median 17) with corresponding values greater than 30 in 10 of 11 of those who died (median 39). A factor V result less than or equal to 10% on admission predicted an adverse outcome in 10 of 11 fatal cases, a 91% sensitivity which was greater than for the previously defined indicator of an arterial blood pH less than 7.30 on admission (sensitivity 82%). Prothrombin time at admission or on day 4 did not usefully predict outcome in our series. Predictive accuracy was 73% and 82% for factor V and admission acidosis respectively and 95% for factor V in conjunction with admission coma grade III or IV and factor VIII (ratio > 30). These criteria may be useful in selecting patients with paracetamol induced fulminant hepatic failure for transplantation.

Anaphylactoid reaction to intravenous acetylcysteine associated with electrocardiographic abnormalities

OBJECTIVE

To review the potential for anaphylactoid reactions to intravenously administered acetylcysteine when used in the treatment of acetaminophen overdose. This case is unique in that electrocardiographic changes, including ST segment depression and T-wave inversion were associated with the episode and complicated the diagnosis.

DATA SOURCES

Reference articles and letters are identified in the text.

DATA SYNTHESIS

Intravenous administration of acetylcysteine has been used in the treatment of acetaminophen overdose. This route may be considered in some clinical situations where oral therapy is complicated. Anaphylactoid reactions, including cutaneous eruptions, flushing, chest pain, tachycardia, and fever have been reported in up to three percent of patients receiving intravenous acetylcysteine. The nature of these reactions and evidence concerning their etiology suggest a histamine-release phenomenon. Response to intervention with antihistamines and the safety of further acetylcysteine administration are discussed.

CONCLUSIONS

This case illustrates a variant anaphylactoid reaction to intravenously administered acetylcysteine and emphasizes the need for practitioners to consider the potential for these reactions prior to initiation of therapy and indicates appropriate treatment of these reactions.

Hepatobiliary disease: medical emergencies

Medical emergencies involving the liver and biliary tract are common clinical problems. If it is already known that the patient has cirrhosis it may be an easy matter to identify the cause of complications such as gastro-intestinal bleeding or coma, but it must be borne in mind that oesophageal varices are not the only cause of such bleeding in cirrhotics and that hepatic encephalopathy is not the only cause of coma. Bacterial infection should always be considered as a possible cause of deterioration in the clinical picture; it may be a complication of pre-existing acute or chronic liver or biliary tract disease or a cause of hepatobiliary disease; prompt administration of appropriate antibiotics may save the patient's life. If there is any suspicion of biliary obstruction in a patient with signs of bacteraemia the biliary tree should be drained without delay. The key to the management of hepatobiliary emergencies lies in prompt and appropriate supportive therapy, and then in a correct diagnosis which may allow specific treatment to be administered. However, it is often difficult to establish the cause, and the resources of a specialist centre may be needed. Prompt referral is indicated when a patient is clearly very ill and shows no signs of rapid improvement.

Intravenous acetylcysteine in paracetamol induced fulminant hepatic failure: a prospective controlled trial

OBJECTIVE

To see whether intravenous acetylcysteine would improve outcome in patients with fulminant hepatic failure after paracetamol overdose.

DESIGN

A prospective randomised controlled study.

SETTING

The Institute of Liver Studies, King's College Hospital, London.

PATIENTS

50 consecutive patients (21 male) aged 16-60 with fulminant hepatic failure after paracetamol overdose who had not previously received acetylcysteine.

INTERVENTIONS

Conventional intensive liver care plus either acetylcysteine (25 patients) in the same dose regimen as used early after a paracetamol overdose, except that the infusion was continued until recovery from encephalopathy or death, or an equivalent volume of 5% dextrose (25 patients).

MAIN OUTCOME MEASURES

Survival; incidence of cerebral oedema, renal failure, and hypotension requiring inotropic support; liver function as assessed by prolongation of the prothrombin time; and degree of encephalopathy.

RESULTS

The rate of survival was significantly higher in the acetylcysteine treated group than in the controls (48% (12/25 patients) v 20% (5/25); p = 0.037, 95% confidence interval for difference in proportions surviving 3% to 53%). Acetylcysteine treated patients had a lower incidence of cerebral oedema (40% (10/25) v 68% (17/25); p = 0.047, 95% confidence interval for difference in incidence 2% to 54%), and fewer developed hypotension requiring inotropic support (48% (12/25) v 80% (20/25); p = 0.018, 95% confidence interval 7% to 57%). Rates of deterioration and recovery of liver function, however, were similar in the two groups. No adverse reactions to acetylcysteine were seen.

CONCLUSIONS

Acetylcysteine is safe and effective in fulminant hepatic failure after paracetamol overdose.

Use of N-acetylcysteine in clinical toxicology

The major use of N-acetylcysteine in clinical toxicology is in the treatment of acetaminophen (paracetamol) overdosage. The hepatorenal toxicity of acetaminophen is mediated by a reactive metabolite normally detoxified by reduced glutathione. If glutathione is depleted, covalent binding to macromolecules and/or oxidation of thiol enzymes can lead to cell death. Oral or intravenous N-acetylcysteine or oral D,L-methionine mitigates acetaminophen-induced hepatorenal damage if given within 10 hours, but becomes less effective thereafter. In vivo, N-acetylcysteine forms L-cysteine, cystine, L-methionine, glutathione, and mixed disulfides; L-methionine also forms cysteine, thus giving rise to glutathione and other products. Oral therapy with N-acetylcysteine or methionine for acetaminophen poisoning is contraindicated in the presence of coma or vomiting, or if activated charcoal has been given by mouth. Nausea, vomiting, and diarrhea may also occur as a result of oral N-acetylcysteine administration. Anaphylactoid reactions including angioedema, bronchospasm, flushing, hypotension, nausea/vomiting, rash, tachycardia, and respiratory distress may occur 15-60 minutes into N-acetylcysteine infusion (20 hours intravenous regimen) in up to 10% of patients. Following accidental intravenous overdosage, the adverse reactions of N-acetylcysteine are similar but more severe; fatalities have occurred. A reduction in the loading dose of N-acetylcysteine may reduce the risk of adverse reactions while maintaining efficacy. Administration of N-acetylcysteine for a longer period might provide enhanced protection for patients in whom acetaminophen absorption or elimination is delayed. N-acetylcysteine may also have a role in the treatment of toxicity from carbon tetrachloride, chloroform, 1,2-dichloropropane, and other compounds. The possible use of N-acetylcysteine and other agents in the prevention of the neuropsychiatric sequelae of acute carbon monoxide poisoning is an important area for future research.

Liver transplantation after paracetamol overdose

OBJECTIVE

To evaluate the role of liver transplantation after paracetamol overdose.

DESIGN

Prospective study of consecutive candidates for transplantation and performance of transplantation over 18 months.

SETTING

Liver unit, King's College Hospital, London.

MAIN OUTCOME MEASURES

Fulfilment of indicators of poor prognosis, selection for transplantation, transplantation, survival.

RESULTS

30 of 37 patients considered to have a reasonable prognosis with intensive medical care survived. Of 14 of 29 patients considered to have a very poor prognosis and registered for urgent liver transplantation, six received liver transplants, four of whom survived, while seven died and one survived without a transplant. Three of 15 patients with poor prognostic indicators but not selected for transplantation survived.

CONCLUSION

Liver transplantation will have a definite but limited role in the management of fulminant hepatic failure induced by paracetamol.

Improvement by acetylcysteine of hemodynamics and oxygen transport in fulminant hepatic failure

BACKGROUND

When administered early after an overdose of acetaminophen, intravenous acetylcysteine prevents hepatic necrosis by replenishing reduced stores of glutathione. How acetylcysteine improves the survival of patients with established liver damage induced by acetaminophen, however, is unknown. This study was undertaken to determine whether the beneficial effect of acetylcysteine under such circumstances could be due to enhancement of oxygen delivery and consumption.

METHODS

We studied the effect of acetylcysteine on systemic hemodynamics and oxygen transport in 12 patients with acetaminophen-induced fulminant hepatic failure and 8 patients with acute liver failure from other causes. The acetylcysteine was given in a dose of 150 mg per kilogram of body weight in 250 ml of 5 percent dextrose over a period of 15 minutes and then in a dose of 50 mg per kilogram in 500 ml of 5 percent dextrose over a period of 4 hours; measurements were made before treatment began and after 30 minutes of the regimen.

RESULTS

In the patients with acetaminophen-induced liver failure, the infusion of acetylcysteine resulted in an increase in mean oxygen delivery from 856 to 975 ml per minute per square meter of body-surface area (P = 0.0036), due to an increase in the cardiac index from 5.6 to 6.7 liters per minute per square meter (P = 0.0021). Mean arterial pressure rose from 88 to 95 mm Hg (P = 0.0054) despite a decrease in systemic vascular resistance from 1296 to 1113 dyn.sec.cm-5 per square meter (P = 0.027). There was an increase in oxygen consumption from 127 to 184 ml per minute per square meter (P = 0.0007) associated with an increase in the oxygen-extraction ratio from 16 to 21 percent (P = 0.022). The effects in the patients with acute liver failure from other causes were similar.

CONCLUSIONS

The increase in oxygen delivery and consumption in response to acetylcysteine may account for its beneficial effect on survival in patients with fulminant hepatic failure induced by acetaminophen.

Delayed calcium channel blockade with diltiazem reduces paracetamol hepatotoxicity in mice

1. Diltiazem (30 mg kg-1 body weight, intraperitoneally) given to mice 9 h after paracetamol (450 mg kg-1, orally) reduced liver damage, as judged by plasma aspartate aminotransferase activity (median 186, range 6-602 IU 1(-1), n = 18 vs 466, range 23-3872 IU 1(-1) in 18 saline-treated controls; P less than 0.05) with comparable reductions in mortality (14% vs 33%, respectively; NS). 2. Regenerative activity, as judged by mitotic figures in tissue removed at 30 h after paracetamol, was significantly higher in mice treated at 9 h with diltiazem (median 0.83 per high power field vs 0.1 in saline-treated controls; P less than 0.05). 3. Diltiazem administered earlier or later than 9 h showed reduced efficacy and in some cases potentiated toxicity, as did nifedipine (40 mg kg-1 in divided doses up to 9 h).