Acetaminophen overdose. 662 cases with evaluation of oral acetylcysteine treatment

Novel acetylcysteine regimens for treatment of paracetamol overdose

Paracetamol (acetaminophen) overdose remains the leading cause of death or transplantation due to acute liver failure in many parts of the world. Acetylcysteine has long been recognized as an effective antidote, via oral or intravenous administration, minimizing the risk and severity of acute liver injury if administered sufficiently early after a paracetamol overdose. Despite this, its mechanisms of action remain obscure, and there is uncertainty regarding the optimal dose and duration of treatment. The intravenous infusion protocol was originally developed as a three-step loading regimen; it causes very high early peak plasma concentrations of acetylcysteine whereas the later maintenance infusion is associated with much lower concentrations. This pharmacokinetic profile is associated with two particular concerns: a high rate of occurrence of adverse effects that occur after the initial loading infusion, and the possibility that the maintenance phase of treatment might deliver too low a dose of acetylcysteine for optimum protection against liver injury. Recently described novel administration regimens offer different rates of intravenous acetylcysteine administration in both the loading and maintenance phases. These alternative regimens appear to be well tolerated in small patient groups, but too few clinical data are available to evaluate their comparative efficacy in preventing paracetamol-induced liver injury.

Low rates of hepatotoxicity among Asian patients with paracetamol overdose: a review of 1024 cases

Background

The metabolism of paracetamol in Asians is thought to differ from Westerners. Detailed clinical features of paracetamol -induced hepatotoxicity among Asians remains largely unreported.

Methods

A retrospective review of adult cases with paracetamol overdose over a five-year duration was performed in two of the largest public institutions in this country. Prevalence and predictive factors for hepatotoxicity were determined.

Results

Data on 1024 patients (median age 23 years, 82.0% female, ethnic groups: Malays 40.8%, Chinese 20.9% , Indian 33.2%) were obtained from January 2005 to December 2009. The median amount of paracetamol ingestion was 10.0 (IQR 5.0 - 15.0) g and the median serum paracetamol level was 274.80 (IQR 70.0 - 640.0) μmol/L at presentation. 75 (7.3%) patients developed hepatotoxicity. 23/ 55 (41.8%) patients who had ingested > 10 g of paracetamol and had a delayed (> 24 hour) administration of N-acetyl cystine (NAC) developed hepatotoxicity. No patients developed acute liver failure nor suffered any mortality (0%). Independent predictors for hepatotoxicity were identified as Malay (OR 2.22, 95% CI = 1.13-4.37) and Chinese (OR 3.26, 95% CI = 1.55-6.84) ethnicity, paracetamol dose > 10 g (OR 2.61, 95% CI = 1.53-4.46), prolonged duration of time from paracetamol ingestion to hospital presentation (> 24 hours OR 10.71, 95% CI = 3.46-33.15) and prolonged duration of time from paracetamol ingestion to NAC administration (> 24 hours OR 9.02, 95% CI = 2.97-27.45).

Conclusions

Paracetamol-induced hepatotoxicity rates in a multi-ethnic Asian population was low at 7.3%. Mortality and morbidity were non-existent despite high doses of paracetamol ingestion and delayed presentations to hospital.

An analysis of N-acetylcysteine treatment for acetaminophen overdose using a systems model of drug-induced liver injury

N-acetylcysteine (NAC) is the treatment of choice for acetaminophen poisoning; standard 72-h oral or 21-h intravenous protocols are most frequently used. There is controversy regarding which protocol is optimal and whether the full treatment course is always necessary. It would be challenging to address these questions in a clinical trial. We used DILIsym, a mechanistic simulation of drug-induced liver injury, to investigate optimal NAC treatment after a single acetaminophen overdose for an average patient and a sample population (n = 957). For patients presenting within 24 h of ingestion, we found that the oral NAC protocol preserves more hepatocytes than the 21-h intravenous protocol. In various modeled scenarios, we found that the 21-h NAC infusion is often too short, whereas the full 72-h oral course is often unnecessary. We found that there is generally a good correlation between the time taken to reach peak serum alanine aminotransferase (ALT) and the time taken to clear N-acetyl-p-benzoquinone imine (NAPQI) from the liver. We also found that the most frequently used treatment nomograms underestimate the risk for patients presenting within 8 h of overdose ingestion. V(max) for acetaminophen bioactivation to NAPQI was the most important variable in the model in determining interpatient differences in susceptibility. In conclusion, DILIsym predicts that the oral NAC treatment protocol, or an intravenous protocol with identical dosing, is superior to the 21-h intravenous protocol and ALT is the optimal available biomarker for discontinuation of the therapy. The modeling also suggests that modification of the current treatment nomograms should be considered.

Mitogen-activated protein kinase phosphatase (Mkp)-1 protects mice against acetaminophen-induced hepatic injury

c-Jun N-terminal kinase (JNK) activation promotes hepatocyte death during acetaminophen overdose, a common cause of drug-induced liver failure. While mitogen-activated protein kinase (MAPK) phosphatase (Mkp)-1 is a critical negative regulator of JNK MAPK, little is known about the role of Mkp-1 during hepatotoxicity. In this study, we evaluated the role of Mkp-1 during acute acetaminophen toxicity. Mkp-1⁺/⁺ and Mkp-1⁻/⁻ mice were dosed ip with vehicle or acetaminophen at 300 mg/kg (for mechanistic studies) or 400 mg/kg (for survival studies). Tissues were collected 1-6 hr post 300 mg/kg dosing to assess glutathione levels, organ damage, and MAPK activation. Mkp-1⁻/⁻ mice exhibited more rapid plasma clearance of acetaminophen than did Mkp-1⁺/⁺ mice, indicated by a quicker decline of plasma acetaminophen level. Moreover, Mkp-1⁻/⁻ mice suffered more severe liver injury, indicated by higher plasma alanine transaminase activity and more extensive centrilobular apoptosis and necrosis. Hepatic JNK activity in Mkp-1⁻/⁻ mice was higher than in Mkp-1⁺/⁺ mice. Finally, Mkp-1⁻/⁻ mice displayed a lower overall survival rate and shorter median survival time after dosing with 400 mg/kg acetaminophen. The more severe phenotype exhibited by Mkp-1⁻/⁻ mice indicates that Mkp-1 plays a protective role during acute acetaminophen overdose, potentially through regulation of JNK.

Acetaminophen and acetylcysteine dose and duration: past, present and future

Acetylcysteine has been utilized successfully in the treatment of acetaminophen overdose since the 1970s. Although prospective trials as to efficacy and safety of acetylcysteine were conducted, there were no randomized controlled trials. This commentary addresses the reasons for this, and the background to choice of dose of acetylcysteine utilized in the oral and IV dosing regimens. Nomograms to predict possible hepatotoxicity based upon time of ingestion of acetaminophen were developed from a relatively arbitrary definition of toxicity as an aspartate aminotransferase/alanine aminotransferase (ALT/AST) greater than 1000 IU/L. While these have proved generally useful, patients still continue to develop hepatic damage after acetaminophen overdose, particularly if they present late after ingestion. The optimum management of these patients remains unclear, and one area of uncertainty is the dose and duration of acetylcysteine in various circumstances. This article discusses the issues that need to be elucidated to better target changes in acetylcysteine dose. The potential for measurements of other markers to improve treatment selection is the subject of further research.

Reliability of the reported ingested dose of acetaminophen for predicting the risk of toxicity in acetaminophen overdose patients

PURPOSE

The present study examines the relationship between the dose of acetaminophen reported to have been ingested by patients and the occurrence of serum acetaminophen levels above the 'possible toxicity' line in patients presenting at the hospital after acetaminophen overdose. The prognostic value of patient-reported dosage cut-offs of 8, 10 and 12 g was determined.

METHODS

This retrospective cohort study included patients admitted to the emergency department or hospital within 24 hours of acetaminophen ingestion. Serum acetaminophen concentrations were considered to be the gold standard, and specificity, sensitivity and positive/negative predictive values were calculated from the reported ingested dose, to predict toxicity using the Rumack-Matthew nomogram (i.e. the 'possible toxicity' treatment line) and standard equations.

RESULTS

Of 305 patients identified, 291 met the study inclusion criteria, and 121 (41.6%) had serum acetaminophen concentrations above the 'possible toxicity' treatment line. The range of patient-reported acetaminophen ingested was 1-75 g, with 185 patients (63.6%) reporting ≥8 g. One hundred eighteen patients (97.5%) who reported ingesting ≥8 g had serum acetaminophen concentrations above the '150-line', compared with only three patients (2.5%) who reported ingesting <8 g (p < 0.001). The positive predictive value of a patient-reported dose ≥8 g for predicting serum acetaminophen concentrations above the 'possible toxicity' treatment line was 63.78%, with a negative predictive value of 97.17%. The sensitivity of patient-reported doses ≥8 g was high (97.52%) but with low specificity (60.59%). The sensitivity of patient-reported doses ≥10 g also was high (89.26%) with low specificity (65.29%), whereas the sensitivity of ≥12 g dose was low (61.16%) with high specificity (86.47%).

CONCLUSIONS

Patient-reported doses of acetaminophen are good risk indicators for acetaminophen overdose patients in Malaysia. Patient-reported ingestion of ≥8 g (as a cut-off dose) had a higher sensitivity than ≥10 g or ≥12 g. The results of this study have important implications for toxicity risk evaluations in areas with poor serum acetaminophen assay availability.

Toxicology in the ICU: Part 2: specific toxins

This is the second of a three-part series that reviews the generalized care of poisoned patients in the ICU. This article focuses on specific agents grouped into categories, including analgesics, anticoagulants, cardiovascular drugs, dissociative agents, carbon monoxide, cyanide, methemoglobinemia, cholinergic agents, psychoactive medications, sedative-hypnotics, amphetamine-like drugs, toxic alcohols, and withdrawal states. The first article discussed the general approach to the toxicology patient, including laboratory testing; the third article will cover natural toxins.

An analysis of the length of hospital stay after acetaminophen overdose

BACKGROUND

Acetaminophen is one of the most commonly encountered medications in self-poisoning, with a high rate of morbidity. The prevalence and characteristics of acetaminophen intoxication associated with long hospital stay in patients are not well defined.

OBJECTIVES

This study aims to identify the clinical and demographic factors associated with the length of in-hospital stay (LOS), and to evaluate the effect of early treatment of acetaminophen overdose patients (≤8 hours) by intravenous N-acetylcysteine (IV-NAC) on hospital stay.

METHODS

This is a retrospective cohort study of hospital admissions for acetaminophen overdose conducted over a period of 5 years from 1 January 2004 to 31 December 2008. Patients were divided into two groups: LS group patients had a long hospital stay (> median hours stay in hospital) and SS group patients had a short hospital stay (≤ median hours stay in hospital). Variables were abstracted from medical records for comparison between the two groups. A total of 20 variables were identified for comparison. Parametric and non-parametric tests were used to test differences between groups depending on the normality of the data. SPSS 15 was used for data analysis.

RESULTS

Of the 305 patients, 11 factors were identified in the univariate analysis as associated with LS. Three independent factors were found to be significant predictors of LS in the multivariate analysis. The factors associated with LS were seen among patients with a history of abdominal pain after ingestion of acetaminophen (p = 0.04), who were on IV-NAC administration (p < 0.001) and had an acutely depressed mood (p = 0.003). Late time to NAC infusion of more than 8 hours was associated with LS rather than SS (96 patients [57%] and 6 [24%], respectively; p = 0.003).

CONCLUSION

Patients with long hospital stay have different clinical characteristics compared to patients with short hospital stay. We identified time to IV-NAC administration is a potentially modifiable factor that may lead to prolonged hospital stay. When risk assessment indicates that NAC is required, it is highly recommended that NAC be started in the first hours of admission to reduce the LOS.

Evaluation of a Simplified N-Acetylcysteine Dosing Regimen for the Treatment of Acetaminophen Toxicity

BACKGROUND:

Acetaminophen overdose is the most common pharmaceutical poisoning in the US. The labeled dosing regimen for Acetadote, the only intravenous N-acetylcysteine (IV-NAC) product approved by the Food and Drug Administration (FDA) for treatment of acetaminophen toxicity, is a complex 3-step process that produces frequent medication errors. We have been using an off-label, uncomplicated dosing regimen consisting of a standard preparation of IV-NAC 30 g in 1 L of 5% dextrose in water, with a 150-mg/kg loading dose administered over 1 hour followed by an infusion of 14 mg/kg/h for 20 hours.

OBJECTIVE:

To evaluate the frequency of medication errors, resolution of hepatotoxicity, and tolerability of the protocol used in our institution for treatment of acetaminophen toxicity.

METHODS:

This single-center, retrospective chart review evaluated patients receiving IV-NAC for acetaminophen toxicity from August 2006 to August 2008. Charts were reviewed for prescribing practices, dosing errors, and clinical outcomes.

RESULTS:

Among 70 patients who met inclusion criteria, 35 medication errors occurred, including 22 administration errors and 13 protocol initiation errors. The frequency of administration errors was 13.5 errors per 100 administration interventions. Loading dose errors were most common with 11 rate-related and 8 dose-related errors. Interruptions longer than 60 minutes occurred in only 3 patients. No adverse outcomes were associated with medication errors. The mean (SD) duration of therapy was 25.6 hours (n = 60 pts. [17.8], range 1-76.5), and mean length of stay was 2.99 days ([3.82], range 0.1-25.7). All patients with hepatotoxicity (aspartate aminotransferase >1000 units/L) due to acute acetaminophen toxicity had resolution of the toxicity and were successfully discharged.

CONCLUSIONS:

This single intravenous bag protocol is effective and well tolerated, and there is infrequent interruption of therapy. The overall rate of administration errors is similar to that in reports on the FDA regimen; thus, our protocol may be an acceptable alternative.

Toxicology today: what you need to know now

Clinicians are frequently confronted with toxicological emergencies and challenged with the task of correctly identifying the possible agents involved and providing appropriate treatments. In this review article, we describe the epidemiology of overdoses, provide a practical approach to the recognition and diagnosis of classic toxidromes, and discuss the initial management strategies that should be considered in all overdoses. In addition, we evaluate some of the most common agents involved in poisonings and present their respective treatments. Recognition of toxidromes with knowledge of indications for antidotes and their limitations for treating overdoses is crucial for the acute care of poisoned patients.

Fulminant hepatitis after 10 days of acetaminophen treatment at recommended dosage in an infant

Acetaminophen is considered a safe drug for children, although hepatotoxicity may develop after overdosing. Reports of liver failure after repeated therapeutic doses of the drug have been rare. Here we describe the case of an infant who developed acute liver failure after administration of acetaminophen for 10 days at a total dose of 720 mg/day (72 mg/kg per day). The patient had high levels of aspartate aminotransferase (11 735 U/L) and alanine aminotransferase (6611 U/L) accompanied by encephalopathy and an increased ammonium level (266 μg/dL). Intravenous N-acetylcysteine therapy resulted in rapid improvement of the child's clinical condition and laboratory test results. Health care providers should be aware that multiple doses of acetaminophen in infants may lead to acute hepatic failure. N-acetylcysteine therapy should be initiated in cases of drug-induced acute liver failure.

Impact of serum acetaminophen concentration on changes in serum potassium, creatinine and urea concentrations among patients with acetaminophen overdose

BACKGROUND

Acetaminophen overdose may be accompanied by electrolyte disturbances. The basis for electrolyte change appears to be due to increased fractional urinary electrolyte excretion.

PURPOSE

This study investigated the impact of serum acetaminophen concentration on changes in serum potassium, creatinine and urea concentrations in patients with acetaminophen overdose.

METHODS

This was a retrospective cohort study which included patients admitted to the emergency department and hospital within 24 h of acetaminophen ingestion. The study was conducted over a period of 5 years from 1 January 2004 to 31 December 2008. Data are presented as mean ± SD and as medians (interquartile range) and groups were compared using independent two-tailed Student t-test. Statistical Package for Social Sciences (SPSS) 15 was used for data analysis.

RESULTS

Two hundred and eighty-three patients were studied (44 males and 239 females), mean age 23 ± 7.5 years. Patients who had a serum acetaminophen concentration above a 'possible toxicity' treatment line were associated with an elevation in serum creatinine concentration (p=0.044) and a reduction in the serum potassium concentration (p<0.001) but were not associated with a reduction in serum urea concentration (p>0.99). During the study period, 63.3% (179 patients) had serum potassium concentrations less than the normal concentration (3.5 mmol/l) and 31.4% (89 patients) had serum urea concentrations less than the normal concentration (2.5 mmol/l). The serum creatinine concentration in all patients was within the normal range.

CONCLUSIONS

Acetaminophen appears to cause a concentration-dependent reduction of potassium concentrations and an elevation of creatinine concentrations of short duration (<24 h) after overdose.

Assessing the impact of vomiting episodes on outcome after acetaminophen poisoning

Identifying indices of poor prognosis at first presentation after acetaminophen poisoning is the key to both improving clinical care and determining targets for intervention. This study intended to document the prevalence, clinical characteristics and predictors of vomiting and to investigate the relationship between episodes of vomiting at first hospital presentation and outcome in acetaminophen poisoning. This retrospective cohort study included patients who attended the emergency department and were admitted within 24 hr of acetaminophen ingestion. The study was conducted over a period of 5 years from 1 January 2004 to 31 December 2008. Parametric and non-parametric tests were used to test differences between groups depending on the normality of the data. SPSS 15 was used for data analysis. Data from 291 patients were included. Vomiting was present in 65.3% of patients with acetaminophen poisoning at the time of first presentation. Multiple logistic regression showed that significant risk factors for vomiting were present among patients who reported an ingested dose of acetaminophen ≥10 g (p < 0.001) and a latency time of more than 8 hr (p = 0.030). Overall, an increasing trend in prothrombin time (p = 0.03), serum bilirubin (p < 0.001), serum creatinine (p = 0.005), serum potassium (p < 0.001), length of hospital stay (p < 0.001) and the prevalence of patients who had a serum acetaminophen level above a 'possible toxicity' treatment line (p = 0.001) were associated with an increased number of episodes of vomiting. In conclusion, vomiting was common among patients with acetaminophen poisoning. This study suggests that an increase in episodes of vomiting at first presentation appears to be an important risk marker of subsequent nephrotoxicity and hepatotoxicity.

Effects of delay in infusion of N-acetylcysteine on appearance of adverse drug reactions after acetaminophen overdose: a retrospective study

PURPOSE

To investigate the relationship between different types of adverse drug reaction (ADR) and late time to N-acetylcysteine (NAC) infusion in patients presenting to the hospital with acetaminophen overdose.

METHODS

This is a retrospective study of patients admitted to the hospital for acute acetaminophen overdose over a period of 5 years (1 January 2004 to 31 December 2008). The primary outcome of interest was the relationship between ADR, if any, and late time to NAC infusion. Parametric and non-parametric tests were used to test differences between groups depending on the normality of the data. SPSS 15 was used for data analysis.

RESULTS

Of 305 patients with acetaminophen overdose, 146 (47.9%) were treated with intravenous NAC and 139 (45.6%) were included in this study. Different types of ADR were observed in 94 (67.6%) patients. Late time to NAC infusion was significantly associated with cutaneous anaphylactoid reactions when compared to patients without this type of ADR (p  <  0.001). However, there were no significant differences in time to NAC infusion between patients with and without the following ADR: gastrointestinal reactions (p = 0.11), respiratory reactions (p = 0.77), central nervous reactions (p = 0.64), and cardiovascular reactions (p = 0.63).

CONCLUSION

Late time to NAC infusion is a risk factor for developing cutaneous anaphylactoid reactions, suggesting, rather than proving, that early NAC infusion (≤ 8 hours) may be protective against this type of ADR.

A cross-sectional observation of the factors associated with deliberate self-poisoning with acetaminophen: impact of gender differences and psychiatric intervention

OBJECTIVES

The objectives of this study were to determine the risk factors and life stressors that are prevalent among the acetaminophen deliberate self-poisoning (DSP) cases, to identify gender differences in the associated factors, and to determine the prevalence of psychiatric diagnosis and the patterns and types of psychotherapeutic interventions provided by psychiatrists.

METHODS

This is a cross-sectional study, a retrospective descriptive case review of hospital admissions for acetaminophen DSP.

RESULTS

There were 177 incidences of DSP during the study period. The mean age of the cases was 23.1 +/- 7.3 years and 84.1% of them were females. The risk factors were more significantly associated with males: chronic ethanol intake (p = 0.04), higher reported dose ingested (p = 0.01), higher latency time (p = 0.04) and longer hospital stay (p = 0.03). The most commonly reported psychotherapeutic interventions used by psychiatrists were psychoeducation of the patient, followed by referral to a psychiatric clinic, family psychoeducation and psychotropic medication. Sertraline (SSRI) was the most frequently prescribed antidepressant.

CONCLUSIONS

Males have been shown to use more toxic doses and to delay treatment due to high latency time. Most DSP patients have different life stressors and psychiatric diagnoses that may be associated with varying degrees of suicidal intent. All patients presenting following DSP need to be carefully screened for psychiatric illness. Randomized controlled studies need to be conducted on DSP patients with psychiatric illness to determine which treatments are effective.

A multicenter comparison of the safety of oral versus intravenous acetylcysteine for treatment of acetaminophen overdose

Oral and intravenous (IV) N-acetylcysteine (NAC) are used for the treatment of acetaminophen poisoning. The objective of this multicenter study was to compare the safety of these two routes of administration.

METHODS

We conducted a multicenter chart review of all patients treated with NAC for acetaminophen poisoning. The primary safety outcome was the percentage of patients with NAC-related adverse events.

RESULTS

A total of 503 subjects were included in the safety analysis (306 IV-only, 145 oral-only, and 52 both routes). There were no serious adverse events related to NAC for either route. Nausea and vomiting were the most common related adverse events and were more common with oral treatment (23 vs. 9%). Anaphylactoid reactions were more common with IV administration (6 vs. 2%).

CONCLUSIONS

IV and oral NAC are generally mild adverse drug reactions.

Association between gastrointestinal manifestations following acetaminophen poisoning and outcome in 291 acetaminophen poisoning patients

BACKGROUND

Acetaminophen poisoning is a common clinical problem, and early identification of patients with more severe poisoning is key to improving outcomes.

PURPOSES

This study intends to document prevalence, clinical characteristics, and predictors of gastrointestinal (GI) manifestations and to assess the impact of these manifestations on outcome in patients with acetaminophen poisoning.

METHODS

This is a retrospective cohort study of hospital admissions for acute acetaminophen poisoning conducted over a period of 5 years from 1 January 2004 to 31 December 2008. Parametric and non-parametric tests were used to test differences between groups depending on the normality of the data. Statistical Package for Social Sciences (SPSS) 15 was used for data analysis.

RESULTS

Two hundred and ninety-one patients were studied; their mean age was 23.01 +/- 7.4 years and 76.6% had GI manifestations. Multiple logistic regression showed that significant risk factors for GI manifestations were present among patients who reported acetaminophen dose ingested >or=10 g (p < 0.001), and latency time more than 8 hours (p = 0.030). GI manifestations at first admission predicted poorer outcomes in terms of estimated acetaminophen levels to be a possible toxic (p < 0.001), elevated bilirubin levels (p = 0.002), prolonged prothrombin time (PT; p = 0.002), elevated creatinine level (p = 0.028), declination of potassium level (p < 0.001), and prolonged hospital stay (p < 0.001).

CONCLUSIONS

GI manifestations were common among patients with acetaminophen poisoning. This study suggests that the presence of GI manifestations at first presentation appears to be an important risk marker of subsequent hepatotoxicity and nephrotoxicity.

Mechanisms of acetaminophen-induced liver necrosis

Although considered safe at therapeutic doses, at higher doses, acetaminophen produces a centrilobular hepatic necrosis that can be fatal. Acetaminophen poisoning accounts for approximately one-half of all cases of acute liver failure in the United States and Great Britain today. The mechanism occurs by a complex sequence of events. These events include: (1) CYP metabolism to a reactive metabolite which depletes glutathione and covalently binds to proteins; (2) loss of glutathione with an increased formation of reactive oxygen and nitrogen species in hepatocytes undergoing necrotic changes; (3) increased oxidative stress, associated with alterations in calcium homeostasis and initiation of signal transduction responses, causing mitochondrial permeability transition; (4) mitochondrial permeability transition occurring with additional oxidative stress, loss of mitochondrial membrane potential, and loss of the ability of the mitochondria to synthesize ATP; and (5) loss of ATP which leads to necrosis. Associated with these essential events there appear to be a number of inflammatory mediators such as certain cytokines and chemokines that can modify the toxicity. Some have been shown to alter oxidative stress, but the relationship of these modulators to other critical mechanistic events has not been well delineated. In addition, existing data support the involvement of cytokines, chemokines, and growth factors in the initiation of regenerative processes leading to the reestablishment of hepatic structure and function.

Signal transduction pathways involved in drug-induced liver injury

Hepatocyte death following drug intake is the critical event in the clinical manifestation of drug-induced liver injury (DILI). Traditionally, hepatocyte death caused by drugs had been attributed to overwhelming oxidative stress and mitochondria dysfunction caused by reactive metabolites formed during drug metabolism. However, recent studies have also shown that signal transduction pathways activated/inhibited during oxidative stress play a key role in DILI. In acetaminophen (APAP)-induced liver injury, hepatocyte death requires the sustained activation of c-Jun kinase (JNK), a kinase important in mediating apoptotic and necrotic death. Inhibition of JNK using chemical inhibitors or knocking down JNK can prevent hepatocyte death even in the presence of extensive glutathione (GSH) depletion, covalent binding, and oxidative stress. Once activated, JNK translocates to mitochondria, to induce mitochondria permeability transition and trigger hepatocyte death. Mitochondria are central targets where prodeath kinases such as JNK, prosurvival death proteins such as bcl-xl, and oxidative damage converge to determine hepatocyte survival. The importance of mitochondria in DILI is also observed in the Mn-SOD heterozygous (+/-) model, where mice with less mitochondrial Mn-SOD are sensitized to liver injury caused by certain drugs. An extensive body of research is accumulating suggesting a central role of mitochondria in DILI. Drugs can also cause redox changes that inhibit important prosurvival pathways such as NF-kappaB. The inhibition of NF-kappaB by subtoxic doses of APAP sensitizes hepatocyte to the cytotoxic actions of tumor necrosis factor (TNF). Many drugs will induce liver injury if simultaneously treated with LPS, which promotes inflammation and cytokine release. Drugs may be sensitizing hepatocytes to the cytotoxic effects of cytokines such as TNF, or vice versa. Overall many signaling pathways are important in regulating DILI, and represent potential therapeutic targets to reduce liver injury caused by drugs.

Pharmacokinetics of acetaminophen-protein adducts in adults with acetaminophen overdose and acute liver failure

Acetaminophen (APAP)-induced liver toxicity occurs with formation of APAP-protein adducts. These adducts are formed by hepatic metabolism of APAP to N-acetyl-p-benzoquinone imine, which covalently binds to hepatic proteins as 3-(cystein-S-yl)-APAP adducts. Adducts are released into blood during hepatocyte lysis. We previously showed that adducts could be quantified by high-performance liquid chromatography with electrochemical detection following proteolytic hydrolysis, and that the concentration of adducts in serum of overdose patients correlated with toxicity. The following study examined the pharmacokinetic profile and clinical associations of adducts in 53 adults with acute APAP overdose resulting in acute liver failure. A population pharmacokinetic analysis using nonlinear mixed effects (statistical regression type) models was conducted; individual empiric Bayesian estimates were determined for the elimination rate constant and elimination half-life. Correlations between clinical and laboratory data were examined relative to adduct concentrations using nonparametric statistical approaches. Peak concentrations of APAP-protein adducts correlated with peak aminotransferase concentrations (r = 0.779) in adults with APAP-related acute liver failure. Adducts did not correlate with bilirubin, creatinine, and APAP concentration at admission, international normalized ratio for prothrombin time, or reported APAP dose. After N-acetylcysteine therapy, adducts exhibited first-order disappearance. The mean elimination rate constant and elimination half-life were 0.42 +/- 0.09 days(-1) and 1.72 +/- 0.34 days, respectively, and estimates from the population model were in strong agreement with these data. Adducts were detected in some patient samples 12 days post-ingestion. The persistence and specificity of APAP-protein adducts as correlates of toxicity support their use as specific biomarkers of APAP toxicity in patients with acute liver injury.

Comparison of the 20-hour intravenous and 72-hour oral acetylcysteine protocols for the treatment of acute acetaminophen poisoning

STUDY OBJECTIVE

To compare outcomes after acute acetaminophen poisoning in 2 large cohorts of patients treated with either the 20-hour intravenous or 72-hour oral acetylcysteine protocol.

METHODS

We conducted a retrospective cohort study with historical control comparing patients treated with one of 2 acetylcysteine regimens. Data for the 20-hour group were obtained from a medical record review of patients on whom the 20-hour intravenous protocol was initiated in Canadian hospitals from 1980 to 2005. The 72-hour group consisted of a historical cohort of patients treated in US hospitals with the 72-hour oral protocol from 1976 to 1985. The primary outcome was hepatotoxicity (aminotransferase levels >1,000 IU/L).

RESULTS

Of the 4,048 patients analyzed, 2,086 were in the 20-hour group and 1,962 were in the 72-hour group. The incidence of hepatotoxicity was 13.9% in the 20-hour group and 15.8% in the 72-hour group (-1.9% absolute difference; 95% confidence interval [CI] -4.2 to 0.3). The relative risk of hepatotoxicity was lower in the 20-hour group when acetylcysteine was initiated within 12 hours of ingestion. The relative risk was lower in the 72-hour group when acetylcysteine was initiated later than 18 hours after ingestion. There was no significant risk difference between groups when acetylcysteine treatment was started 12 to 18 hours after ingestion. One patient in the 20-hour group received a liver transplant and died because of acetaminophen toxicity compared with no liver transplants and 3 deaths in the 72-hour group. Anaphylactoid reactions to intravenous acetylcysteine were reported in 148 of 2,086 patients (7.1%; 95% CI 6.1% to 8.3%). This study is limited by comparison of 2 separate data sets from different countries and study years.

CONCLUSION

The risk of hepatotoxicity differed between the 20-hour and 72-hour protocols according to the time to initiation of acetylcysteine. It favored the 20-hour protocol for patients presenting early and favored the 72-hour protocol for patients presenting late after acute acetaminophen overdose.

Acetaminophen hepatotoxicity and acute liver failure

Acetaminophen-induced hepatotoxicity is a common consequence of acetaminophen overdose and may lead to acute liver failure (ALF). Currently acetaminophen is the most common cause of ALF in both United States and United Kingdom, with a trend to increasing incidence in the United States. N-acetylcysteine is the most effective drug to prevent progression to liver failure with acetaminophen hepatotoxicity. Liver transplantation is the only definitive therapy that will significantly increase the chances of survival for advanced ALF. This communication reviews current information regarding causes and management of acetaminophen-induced hepatotoxicity and ALF.

Managing acute acetaminophen poisoning with oral versus intravenous N-acetylcysteine: a provider-perspective cost analysis

BACKGROUND

Acetaminophen (APAP) overdose, which can lead to hepatotoxicity, is the most commonly reported poisoning in the United States and has the highest rate of mortality, with more than 100,000 exposures and 300 deaths reported annually (1) . The treatment of choice, N-acetylcysteine (NAC), is effective in both oral (PO) and intravenous (IV) formulations. The main difference in therapies, other than administration route, is time to complete delivery--72 hours for PO NAC versus 21 hours for IV NAC, according to full prescribing information. This distinction is the primary basis for variation in management costs for hospitalized patients receiving these products.

OBJECTIVES

To quantify and compare full treatment costs from the provider perspective to manage acute APAP poisoning with either PO or IV NAC in a standard treatment regimen.

METHODS

A cost model was developed and populated with published data comprising probabilities of potential clinical outcomes and the costs of resources consumed during patient care.

RESULTS

For patients who present <10 hours post-ingestion, the estimated total cost of care with PO NAC in the treatment regimen is $5,817 (ICU patients) or $3,850, (ward patients) compared with $3,765 and $2,768 for similar care with IV NAC. Potential cost savings equal - $2,052 (-35%) or -$1,083 (-28%), respectively, in favor of IV NAC. Similar potential savings were estimated for patients presenting 10-24 hours post-ingestion.

CONCLUSION

IV NAC is the less costly therapeutic option for APAP poisonings, based on simulation modeling and retrospective data. The current economic evaluation is restricted by the absence of comparative data from head-to-head, matched-cohort studies and the limitations common to retrospective APAP toxicology datasets. Additional research could refine these results.

Too toxic

Firm up on the facts and considerations associated with acetaminophen toxicity.

Acetaminophen is cardioprotective against H2O2-induced injury in vivo

Here we report our ongoing investigation of the cardiovascular effects of acetaminophen, with emphasis on oxidation-induced canine myocardial dysfunction. The objective of the current study was to investigate whether acetaminophen could attenuate exogenous H(2)O(2)-mediated myocardial dysfunction in vivo. Respiratory, metabolic, and hemodynamic indices such as left ventricular function (LVDP and +/-dP/dt(max)), and percent ectopy were measured in anesthetized, open-chest dogs during intravenous administration of 0.88 mM, 2.2 mM, 6.6 mM H(2)O(2). Following 6.6 mM H(2)O(2), tissue from the left ventricle was harvested for electron microscopy. Left ventricular function did not vary significantly between vehicle and acetaminophen groups under baseline conditions. Acetaminophen-treated dogs regained a significantly greater fraction of baseline function after high concentrations of H(2)O(2) than vehicle-treated dogs. Moreover, the incidence of H(2)O(2)-induced ventricular arrhythmias was significantly reduced in the acetaminophen-treated group. Percent ectopy following 6.6 mM concentrations of H(2)O(2) was 1 +/- 0.3 vs. 0.3 +/- 0.1 (P < 0.05) for vehicle- and acetaminophen-treated dogs, respectively. Additionally, electron micrograph images of left ventricular tissue confirmed preservation of tissue ultrastructure in acetaminophen-treated hearts when compared to vehicle. We conclude that, in the canine myocardium, acetaminophen is both functionally cardioprotective and antiarrhythmic against H(2)O(2)-induced oxidative injury.

Lower incidence of anaphylactoid reactions to N-acetylcysteine in patients with high acetaminophen concentrations after overdose

BACKGROUND

Mechanisms responsible for anaphylactoid reactions to N-acetylcysteine (NAC) are poorly understood, and acetaminophen itself may play an important role. The present study examined the relationship between serum acetaminophen concentrations and risk of anaphylactoid reactions.

METHODS

Prospective study of adverse reactions to NAC administered according to standardized clinical protocols in patients who present to hospital after acute acetaminophen overdose. Subgroups were defined by serum acetaminophen concentrations 0 to 100 mg/L, 101 to 150 mg/L, 151 to 200 mg/L, 201 to 300 mg/L, and >300 mg/L.

RESULTS

There were 362 patients, and anaphylactoid reactions occurred in 14.9%. Anaphylactoid reactions occurred less commonly in patients with high serum acetaminophen concentrations (p = 0.046 by Cochran-Armitage trend test) and high equivalent 4 h acetaminophen concentrations (p = 0.004).

DISCUSSION

High serum acetaminophen concentrations were associated with fewer anaphylactoid reactions, suggesting that these might in some way be protective. The biological basis needs further exploration so as to allow a better understanding of the mechanisms responsible for adverse reactions to NAC treatment.

Clinical policy: critical issues in the management of patients presenting to the emergency department with acetaminophen overdose

This clinical policy focuses on critical issues concerning the management of patients presenting to the emergency department (ED) with acetaminophen overdose. The subcommittee reviewed the medical literature relevant to the questions posed. The critical questions are: 1. What are the indications for N-acetylcysteine (NAC) in the acetaminophen overdose patient with a known time of acute ingestion who can be risk stratified by th Rumack-Matthew nomogram? 2. What are the indications for NAC in the acetaminophen overdose patient who cannot be risk stratified by the Rumack-Matthew nomogram? Recommendations are provided on the basis of the strength of evidence of the literature. Level A recommendations represent patient management principles that reflect a high degree of clinical certainty; Level B recommendations represent patient management principles that reflect moderate clinical certainty; and Level C recommendations represent other patient management strategies that are based on preliminary, inconclusive, or conflicting evidence, or based on committee consensus. This guideline is intended for physicians working in EDs.

Frequency of medication errors with intravenous acetylcysteine for acetaminophen overdose

BACKGROUND

Acetadote, an intravenous preparation of acetylcysteine, became commercially available in the US in June 2004 for the treatment of acetaminophen poisoning. The dosing regimen is complex, consisting of a loading dose followed by 2 maintenance doses, each with different infusion rates.

OBJECTIVE

To analyze the frequency of medication errors related to the complex dosing regimen for intravenous acetylcysteine.

METHODS

A retrospective chart review of a regional poison center's records was performed for all patients treated with intravenous acetylcysteine from August 1, 2006, to August 31, 2007. Data collected included acetylcysteine dose, infusion rate, interruptions in therapy, unnecessary administration, and medical outcome. Records that revealed medication errors were further examined for the time and location of the errors.

RESULTS

There were 221 acetaminophen overdose cases treated with intravenous acetylcysteine that met inclusion criteria. Of these, 84 medication errors occurred in 74 (33%) patients. The frequency and types of errors were 1.4% incorrect dose, 5% incorrect infusion rate, 18.6% more than 1 hour of interruption in therapy, and 13.1% unnecessary administration. The frequency and types of medication errors in pediatric patients were similar to those in the total patient population. Errors occurred most frequently in the emergency department compared with intensive care units or general medical floors. In addition, errors occurred most frequently on third shift, compared with first or second shift. Evaluation of medical outcomes in cases involving acetaminophen only found that medication errors did not have an impact on coded outcomes.

CONCLUSIONS

Medication administration errors occur frequently with intravenous acetylcysteine. Awareness of this problem, coupled with increased vigilance in identifying factors associated with errors, should decrease medication errors with intravenous acetylcysteine therapy for acetaminophen poisoning.

Sorbent-based artificial liver devices: principles of operation, chemical effects and clinical results

Devices for support of patients with liver failure are of two types: bioartificial livers and artificial livers. Bioartificial livers include hepatocytes in bioreactors to provide both excretory and synthetic liver functions. Artificial livers use nonliving components to remove toxins of liver failure, supply nutrients and macromolecules. Current artificial liver devices use columns or suspensions of sorbents (including adsorbents and absorbents) to selectively remove toxins and regenerate dialysate, albumin-containing dialysate, plasma filtrate or plasma. This article reviews three artificial liver devices. Liver Dialysis uses a suspension of charcoal and cation exchangers to regenerate dialysate. MARS uses charcoal and an anion exchanger to regenerate dialysate with albumin. Prometheus uses neutral and anion exchange resins to regenerate a plasma filtrate containing albumin and small globulins. We review the operating principles, chemical effects, clinical effects and complications of use of each type of artificial liver. These devices clearly improve the clinical condition of patients with acute or acute-on-chronic liver failure. Further randomized outcome studies are necessary to prove clinical outcome benefit of the artificial liver support devices, and define what types of patients appear most amenable to therapy.

Acute ethanol coingestion confers a lower risk of hepatotoxicity after deliberate acetaminophen overdose

OBJECTIVES

Little is known about the clinical significance of acute ethanol coingestion around the time of acetaminophen (paracetamol) overdose. This study prospectively examined the effect of acute ethanol coingestion on risk of hepatotoxicity among patients admitted to hospital for N-acetylcysteine (NAC) therapy after deliberate acetaminophen overdose.

METHODS

This was a prospective observational study and included sequential patients who presented within 24 hours of acute acetaminophen ingestion and required NAC therapy. Significant hepatotoxicity was defined by alanine transaminase > 1,000 U/L or the international normalized ratio > 1.3 after a standardized intravenous administration of 300 mg/kg NAC.

RESULTS

There were 362 patients, including 178 (49.2%) who coingested ethanol acutely. The prevalence of hepatotoxicity was 5.1% (95% CI = 2.6% to 9.5%) in those who ingested ethanol, compared to 15.2% (95% CI = 10.7% to 21.2%) in those who did not (p = 0.0027 by chi-square proportional test). Acute ethanol intake conferred a lower risk of hepatotoxicity in patients who had acetaminophen concentrations above or below the "200-line" and was independent of the interval between ingestion and assessment.

CONCLUSIONS

Acute ethanol intake is associated with a lower risk of hepatotoxicity after acetaminophen overdose. This apparent protective effect cannot be explained solely by lower exposure to acetaminophen in this group, nor differences in the interval between ingestion and initiation of treatment. Further work is required to establish mechanisms by which ethanol might confer protection against hepatotoxicity, so as to identify novel strategies for reducing risk after acute acetaminophen ingestion.

Comparison of S-adenosyl-L-methionine (SAMe) and N-acetylcysteine (NAC) protective effects on hepatic damage when administered after acetaminophen overdose

In the clinical setting, antidotes are generally administered after the occurrence of a drug overdose. Therefore, the most pertinent evaluation of any new agent should model human exposure. This study tested whether acetaminophen (APAP) hepatotoxicity was reversed when S-adenosyl-L-methionine (SAMe) was administered after APAP exposure, similar to what occurs in clinical situations. Comparisons were made for potency between SAMe and N-acetylcysteine (NAC), the current treatment for APAP toxicity. Male C57BL/6 mice were fasted overnight and divided into groups: control (VEH), SAMe treated (SAMe), APAP treated (APAP), N-acetylcysteine treated (NAC), SAMe or NAC administered 1h after APAP (SAMe+APAP) and (NAC+APAP), respectively. Mice were injected intraperitoneal (i.p.) with water (VEH) or 250 mg/kg APAP (15 ml/kg). One hour later, mice were injected (i.p.) with 1.25 mmol/kg SAMe (SAMe+APAP) or NAC (NAC+APAP). Hepatotoxicity was evaluated 4h after APAP or VEH treatment. APAP induced centrilobular necrosis, increased liver weight and alanine transaminase (ALT) levels, depressed total hepatic glutathione (GSH), increased protein carbonyls and 4-hydroxynonenal (4-HNE) adducted proteins. Treatment with SAMe 1h after APAP overdose (SAMe+APAP) was hepatoprotective and was comparable to NAC+APAP. Treatment with SAMe or NAC 1h after APAP was sufficient to return total hepatic glutathione (GSH) to levels comparable to the VEH group. Western blot showed reversal of APAP mediated effects in the SAMe+APAP and NAC+APAP groups. In summary, SAMe was protective when given 1h after APAP and was comparable to NAC.

Clinical policy: critical issues in the management of patients presenting to the emergency department with acetaminophen overdose

This clinical policy focuses on critical issues concerning the management of patients presenting to the emergency department (ED) with acetaminophen overdose. The subcommittee reviewed the medical literature relevant to the questions posed. The critical questions are: 1. What are the indications for N-acetylcysteine (NAC) in the acetaminophen overdose patient with a known time of acute ingestion who can be risk stratified by the Rumack-Matthew nomogram? 2. What are the indications for NAC in the acetaminophen overdose patient who cannot be risk stratified by the Rumack-Matthew nomogram? Recommendations are provided on the basis of the strength of evidence of the literature. Level A recommendations represent patient management principles that reflect a high degree of clinical certainty; Level B recommendations represent patient management principles that reflect moderate clinical certainty; and Level C recommendations represent other patient management strategies that are based on preliminary, inconclusive, or conflicting evidence, or based on committee consensus. This guideline is intended for physicians working in EDs.

Acetaminophen hepatotoxicity

Acetaminophen is a commonly used antipyretic and analgesic agent. It is safe when taken at therapeutic doses; however, overdose can lead to serious and even fatal hepatotoxicity. The initial metabolic and biochemical events leading to toxicity have been well described, but the precise mechanism of cell injury and death is unknown. Prompt recognition of overdose, aggressive management, and administration of N-acetylcysteine can minimize hepatotoxicity and prevent liver failure and death. Liver transplantation can be lifesaving for those who develop acute liver failure.

A randomized trial to determine the change in alanine aminotransferase during 10 days of paracetamol (acetaminophen) administration in subjects who consume moderate amounts of alcohol

BACKGROUND

Previous studies have suggested that therapeutic doses of paracetamol (acetaminophen) are safe in alcoholic patients when administered for up to 3 days. However, 14 days of therapeutic doses of paracetamol has been associated with an increase in serum transaminases.

AIM

To determine the effect of 10 days of the maximal therapeutic dose of paracetamol on serum alanine aminotransferase (ALT) activity in subjects who consume 1 to 3 alcoholic beverages per day.

METHODS

This was a randomized, double blind, placebo-controlled trial. Subjects took 4 g of paracetamol (or placebo) daily for 10 days. Serum aspartate aminotransferase (AST), ALT, bilirubin and INR were measured at baseline, day 4 and day 11. Symptoms potentially related to liver injury were also recorded.

RESULTS

Paracetamol and placebo groups had no change from baseline values at day 4, but the paracetamol group had an increase in mean ALT at day 11 of 8.7 IU/L. No subject developed symptoms of liver injury or met predefined criteria for hepatotoxicity or liver failure.

CONCLUSION

Therapeutic dosing of paracetamol administered for 10 days appears to elevate serum ALT in moderate drinkers, but does not produce clinically evident liver injury.

Stability of acetylcysteine solution repackaged in oral syringes and associated cost savings

PURPOSE

The physical and chemical stability of repackaged acetylcysteine 600 mg/3 mL solution in oral syringes stored under refrigeration or at room temperature was studied for six months; a cost analysis was also conducted.

METHODS

Acetylcysteine 20% solution for inhalation was repackaged undiluted as 600 mg/3 mL in capped oral syringes and stored either under refrigeration or at room temperature exposed to fluorescent light. Four samples for each storage condition were analyzed in duplicate on day zero, weekly for the first month, and then every two weeks during months 2-6. Physical stability was assessed, and the chemical stability of acetylcysteine was evaluated by high-performance liquid chromatography.

RESULTS

Acetylcysteine solution in syringes was physically stable during the entire six-month study period. When stored at room temperature, acetylcysteine retained 99% of the original concentration at three months and 95% at six months after preparation of the syringes. Loss of acetylcysteine was <2% at six months when stored under refrigeration. Packaging acetylcysteine in batches of 100 syringes instead of preparing individual syringes reduced wastage to zero syringes, saving an estimated $247 in drug costs. The estimated pharmacy time savings was 30 hours ($702).

CONCLUSION

Acetylcysteine 20% solution repackaged as 600 mg/3 mL in oral syringes is both physically and chemically stable under refrigeration or at room temperature under normal fluorescent lighting for six months. The total loss of acetylcysteine was approximately 5% at room temperature under fluorescent lighting and <2% under refrigeration. Repackaging the solution in syringes in bulk rather than in single doses demonstrated a measurable cost saving.

Comparison of oral and i.v. acetylcysteine in the treatment of acetaminophen poisoning

PURPOSE

The efficacy, safety, and cost issues that should be considered when deciding on the appropriate route of acetylcysteine for the treatment of patients with acetaminophen poisoning are reviewed.

SUMMARY

Oral and i.v. acetylcysteine appear to be equally effective when given within 8-10 hours of acetaminophen overdose. Anaphylactoid reactions to i.v. acetylcysteine have generally been reported in 3-6% of acetaminophen-poisoned patients. Dosing errors and hyponatremia have occurred in pediatric patients receiving i.v. acetylcysteine. Several investigators found an increased rate of anaphylactoid reactions in patients treated with i.v. acetylcysteine whose pretreatment serum acetaminophen levels were nontoxic. Compounding i.v. acetylcysteine from the oral preparation is less expensive than using premade i.v. solution. State pharmacy laws dictate whether extemporaneous compounding of acetylcysteine from the oral formulation is allowed. Oral acetylcysteine administration has resulted in minimal anaphylactoid reactions and is safer than i.v. acetylcysteine. Oral therapy should preferentially be considered in patients with asthma or atopic histories. The most important factors to consider when selecting the route of acetylcysteine administration include individual susceptibility, the severity of acetaminophen toxicity, and the time interval between acetaminophen ingestion and initiation of acetylcysteine therapy.

CONCLUSION

Oral acetylcysteine administered within 8-10 hours of acetaminophen overdose prevents liver toxicity in the majority of patients who tolerate it and have no contraindications to therapy. I.V. acetylcysteine should be administered when patients are treated more than 10 hours postingestion of acetaminophen overdose or have underlying conditions preventing oral treatment. Anaphylactoid reactions are rare and occur more frequently in patients treated with the i.v. preparation.

Capillary electrophoresis and the clinical laboratory

Over the past 15 years, CE as an analytical tool has shown great promise in replacing many conventional clinical laboratory methods, such as electrophoresis and HPLC. CE's appeal was that it was fast, used very small amounts of sample and reagents, was extremely versatile, and was able to separate large and small analytes, whether neutral or charged. Because of this versatility, numerous methods have been developed for analytes that are of clinical interest. Other than molecular diagnostic and forensic laboratories CE has not been able to make a major impact in the United States. In contrast, in Europe and Japan an increasing number of clinical laboratories are using CE. Now that automated multicapillary instruments are commercially available along with cost-effective test kits, CE may yet be accepted as an instrument that will be routinely used in the clinical laboratories. This review will focus on areas where CE has the potential to have the greatest impact on the clinical laboratory. These include analyses of proteins found in serum and urine, hemoglobin (A1c and variants), carbohydrate-deficient transferrin, forensic and therapeutic drug screening, and molecular diagnostics.

Cardioprotective effect of cold-blood cardioplegia enriched with N-acetylcysteine during coronary artery bypass grafting

BACKGROUND

Cold-blood cardioplegia is a well-known method in coronary artery bypass graft surgery, and several authors have used various agents in the enrichment of cold-blood cardioplegia to decrease ischemia-reperfusion injury seen during surgery. N-acetylcysteine, which can increase glutathione levels, is one of the agents added to cardioplegic solutions to decrease myocardial injury. This study was planned to assess the efficiency of N-acetylcysteine-enriched cold-blood cardioplegia on early reperfusion injury in patients with ischemic heart disease undergoing coronary artery bypass grafting, using measurements of cardiac troponin I and malondialdehyde release.

METHODS

Thirty patients (11 women and 19 men) with left ventricular ejection fraction greater than 0.40 scheduled for coronary artery bypass grafting were randomly divided into two groups. We used cold-blood cardioplegia enriched with N-acetylcysteine (50 mg per kilogram of body weight) in the first group and cold-blood cardioplegia alone in the second group. Hemodynamic variables and clinical properties of the patients were preoperatively and postoperatively evaluated. Enzyme releases were measured in the early hours after the operation.

RESULTS

In the N-acetylcysteine-enriched group cardiac troponin I levels were lower than in the N-acetylcysteine-free group, and this difference was statistically significant. Cardiac troponin I levels increased in both groups in the 6th and 12th hours postoperatively, but there was a statistically significant difference between the two groups. Malondialdehyde levels were significantly higher in the N-acetylcysteine-free group after the 6th, 12th, 24th, and 48th hours postoperatively when compared with the N-acetylcysteine-enriched group.

CONCLUSIONS

N-acetylcysteine-supplemented cold-blood cardioplegia minimizes myocardial injury in the early hours after and during the cardiac surgery.

Formal heparin anticoagulation protocol improves safety of charcoal-based liver-assist treatments

Extracorporeal devices have had limited effectiveness in liver failure due to consequences of inadequate anticoagulation. The purpose of this study was to evaluate an anticoagulation protocol developed for Liver Dialysis Unit (LDU) treatments. Twelve patients underwent 19 LDU treatments for acetaminophen overdose (n = 1), subacute liver failure (n = 1), and refractory encephalopathy in cirrhosis (n = 10). The initial 6 patients (group 1) were treated according to the manufacturer's recommendations. The subsequent 6 patients (group 2) were treated using a formal heparin anticoagulation protocol that included 2000 units in prime solution and 30 units/kg induction, activated clotting time (ACT) measurements, and heparin administered by dose-response curve to maintain 300-second ACT. Protamine reversal was used. Treatments were well tolerated and equally effective in both groups. Adequate (ACT > or = 250 seconds) and therapeutic (ACT 250-350 seconds) anticoagulation was maintained more consistently in group 2 (90.9% vs 50.0%, p < 0.0001; and 77.4% vs 45.8%, p < 0.001). There was less consumption of fibrinogen (12.1% vs 43.3%, p < 0.005) and platelets (13.8% vs 29.9%, p < 0.05) and a trend for less blood product used (8.3 vs 15.8 units/patient, p = 0.13) and fewer complications (16.7% vs 66.7%, p = 0.15) in group 2. Anticoagulation using ACT monitoring, heparin dose-response curves, and a target ACT of 300 seconds improves the safety of LDU treatments.