A Risk Quantification Instrument for Acute Acetaminophen Overdose Patients Treated With N-Acetylcysteine

The Evolution of Circulating Biomarkers for Use in Acetaminophen/Paracetamol-Induced Liver Injury in Humans: A Scoping Review

Acetaminophen (APAP) is a widely used drug, but overdose can cause severe acute liver injury. The first reports of APAP hepatotoxicity in humans were published in 1966, shortly after the development of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) as the first biomarkers of liver injury as opposed to liver function. Thus, the field of liver injury biomarkers has evolved alongside the growth in APAP hepatotoxicity incidence. Numerous biomarkers have been proposed for use in the management of APAP overdose patients in the intervening years. Here, we comprehensively review the development of these markers from the 1960s to the present day and briefly discuss possible future directions.

Acetaminophen Poisoning

Acetaminophen is a common medication taken in deliberate self-poisoning and unintentional overdose. It is the commonest cause of severe acute liver injury in Western countries. The optimal management of most acetaminophen poisonings is usually straightforward. Patients who present early should be offered activated charcoal and those at risk of acute liver injury should receive acetylcysteine. This approach ensures survival in most. The acetaminophen nomogram is used to assess the need for treatment in acute immediate-release overdoses with a known time of ingestion. However, scenarios that require different management pathways include modified-release, large/massive, and repeated supratherapeutic ingestions.

Adducts Post Acetaminophen Overdose Treated with a 12-Hour vs 20-Hour Acetylcysteine Infusion

INTRODUCTION

Acetaminophen protein adducts in the circulation are a specific biomarker of acetaminophen oxidation, and may be a more sensitive measure of impending hepatic injury following overdose than alanine transaminase (ALT). We performed an exploratory analytical substudy of adducts during a clinical trial (NACSTOP) of abbreviated (12-hour) versus control (20-hour) acetylcysteine to identify any signal of diminished antidotal effectiveness with shortened therapy.

METHODS

We measured adducts at 0, 12, and 20 hours from a convenience sample of subjects enrolled in the cluster-controlled NACSTOP trial evaluating a 12-hour ("abbreviated"; 200 mg/kg over 4 hours, 50 mg/kg over 8 hours) vs 20-hour acetylcysteine regimen ("control"; 200 mg/kg over 4 hours, 100 mg/kg over 16 hours). Adducts were assayed using high-performance liquid chromatography/mass spectrometry.

RESULTS

Median ALT 20 hours after the initiation of acetylcysteine was 12 U/L (IQR 8,14) in the abbreviated 12-hour regimen group (N = 8), compared with the control group 16 U/L (IQR 11,21; N = 21) (p = 0.46). Adduct concentrations were similarly low in both groups: abbreviated [(0.005 μmol/L, IQR (0,0.14)] and control [(0.005 μmol/L, IQR (0,0.05)] (p = 0.61).

CONCLUSIONS

There were minimal to no acetaminophen protein adducts detected. These findings further support discontinuing acetylcysteine when acetaminophen concentrations are low and liver function tests normal after 12 hours of treatment.

Fomepizole as an Adjunctive Treatment in Severe Acetaminophen Toxicity

A 33-year-old male presented to the emergency department with a chief complaint of abdominal pain after taking #50 500 mg acetaminophen tablets over the preceding two days. He was tachycardic and tachypneic, and the initial labs were notable for acetaminophen level, 337 mg/L; AST, 137 IU/L; ALT, 194 IU/L; ABG pH, 7.24; and lactate, 4.1 mmol/L. The patient was started on IV N-Acetylcysteine (NAC) as well as given a single dose of 15 mg/kg fomepizole. The patient did remarkably well, with a peak AST of 198 IU/L, peak ALT of 301 IU/L, and peak INR of 3.1. Biochemical and animal data support fomepizole having hepatoprotective effects in acetaminophen poisoning. To our knowledge, this is the first human case of an intentional dual NAC/fomepizole regimen for severe acetaminophen toxicity.

Liquid Chromatography-Tandem Mass Spectrometry Analysis of Acetaminophen Covalent Binding to Glutathione S-Transferases

Acetaminophen (APAP)-induced hepatotoxicity is the most common cause of acute liver failure in the Western world. APAP is bioactivated to N-acetyl p-benzoquinone imine (NAPQI), a reactive metabolite, which can subsequently covalently bind to glutathione and protein thiols. In this study, we have used liquid chromatography-tandem mass spectrometry (LC-MS/MS) to characterize NAPQI binding to human glutathione S-transferases (GSTs) in vitro. GSTs play a crucial role in the detoxification of reactive metabolites and therefore are interesting target proteins to study in the context of APAP covalent binding. Recombinantly-expressed and purified GSTs were used to assess NAPQI binding in vitro. APAP biotransformation to NAPQI was achieved using rat liver microsomes or human cytochrome P450 Supersomes in the presence of GSTA1, M1, M2, or P1. Resulting adducts were analyzed using bottom-up proteomics, with or without LC fractionation prior to LC-MS/MS analysis on a quadrupole-time-of-flight instrument with data-dependent acquisition (DDA). Targeted methods using multiple reaction monitoring (MRM) on a triple quadrupole platform were also developed by quantitatively labeling all available cysteine residues with a labeling reagent yielding isomerically-modified peptides following enzymatic digestion. Seven modified cysteine sites were confirmed, including Cys112 in GSTA1, Cys78 in GSTM1, Cys115 and 174 in GSTM2, as well as Cys15, 48, and 170 in GSTP1. Most modified peptides could be detected using both untargeted (DDA) and targeted (MRM) approaches, however the latter yielded better detection sensitivity with higher signal-to-noise and two sites were uniquely found by MRM.

The NACSTOP Trial: A Multicenter, Cluster-Controlled Trial of Early Cessation of Acetylcysteine in Acetaminophen Overdose

Historically, intravenous acetylcysteine has been delivered at a fixed dose and duration of 300 mg/kg over 20 to 21 hours to nearly every patient deemed to be at any risk for hepatotoxicity following acetaminophen overdose. We investigated a 12-hour treatment regimen for selected low-risk patients. This was a multicenter, open-label, cluster-controlled trial at six metropolitan emergency departments. We enrolled subjects following single or staggered acetaminophen overdose with normal serum alanine transaminase (ALT) and creatinine on presentation and at 12 hours, and less than 20 mg/L acetaminophen at 12 hours. Patients were allocated to intervention (250 mg/kg over 12-hour) or control (300 mg/kg over 20-hour) regimens by site. The primary outcome was incidence of "hepatic injury" 20 hours following initiation of acetylcysteine treatment, defined as ALT doubling and peak ALT greater than 100 IU/L, indicating the need for further antidotal treatment. Secondary outcomes included incidence of hepatotoxicity (ALT > 1,000 IU/L), peak international normalized ratio (INR), and adverse drug reactions. Of the 449 acetaminophen overdoses receiving acetylcysteine, 100 were recruited to the study. Time to acetylcysteine (median 7 hours [interquartile ratio 6,12] versus 7 hours [6,10]) and initial acetaminophen (124 mg/L [58,171] versus 146 mg/L [66,204]) were similar between intervention and control groups. There was no difference in ALT (18 IU/L [13,22] versus 16 IU/L [13,21]) or INR (1.2 versus 1.2) 20 hours after starting acetylcysteine between groups. No patients developed hepatic injury or hepatotoxicity in either group (odds ratio 1.0 [95% confidence interval 0.02, 50]). No patients represented with liver injury, none died, and 96 of 96 were well at 14-day telephone follow-up. Conclusion: Discontinuing acetylcysteine based on laboratory testing after 12 hours of treatment is feasible and likely safe in selected patients at very low risk of liver injury from acetaminophen overdose.

Performance of an emergency department observation unit protocol in reducing length of stay for acetaminophen overdose: a retrospective study

Introduction

Acetaminophen is one of the most common causes of poisoning among developed countries. The emergency department observation unit (EDOU) has been increasingly used in the management of various conditions to reduce hospitalisation but its efficacy in not well studied in management of poisoned patients. In this study, we aim to study the effectiveness of our EDOU in the management of acetaminophen overdosed patients.

Results

Medical records of patients admitted from the emergency department from 2012 to 2016 for acetaminophen overdose were reviewed. One hundred ninety-five patients presenting with acetaminophen overdose were admitted to the EDOU while 184 were admitted to the general ward. Of these, 27 patients admitted to EDOU did not meet the admission criteria for it while 71 patients who met EDOU criteria were admitted to the ward instead. For patients who fulfilled EDOU admission criteria, median length of stay for EDOU patients was 23 h (IQR 19–24) while that for those admitted to the ward was 66 h (IQR 62.5–88.3).

Conclusion

The EDOU is a safe alternative to hospitalisation for patients presenting with acetaminophen poisoning. It is also associated with a shorter length of stay for such patients. Further studies need to be done to assess the cost-effectiveness of EDOU for management of patients presenting with acetaminophen overdose.

Absolute quantitation of acetaminophen-modified human serum albumin in acute liver failure patients by liquid chromatography/tandem mass spectrometry

RATIONALE

Acetaminophen (APAP) is a well-known analgesic, deemed a very safe over-the-counter medication. However, it is also the main cause of acute liver failure (ALF) in the Western world, via the formation of its reactive metabolite, N-acetyl p-benzoquinone imine (NAPQI), and its covalent attachment to liver proteins. The aim of this study was to develop a sensitive and robust quantitative assay to monitor APAP-protein binding to human serum albumin (HSA) in patient samples.

METHODS

A combination of isotope dilution, peptic digestion and solid-phase extraction coupled to liquid chromatography/multiple reaction monitoring (LC/MRM) was employed. An external calibration curve with surrogate modified protein spiked into blank serum was used for absolute quantitation. Samples were analyzed by LC/MRM to measure the modified active site peptide of HSA. The LC/MRM assay was validated and successfully applied to serum samples from patients suffering from APAP-induced ALF.

RESULTS

Accuracy ranged from 83.8-113.3%, within-run coefficient of variation (CV) ranged from 0.3-6.9%, and total CVs from 1.6-10.6%. Patient samples ranged from 0.12-3.91 nmol/mL NAPQI-HSA; in-between the assay dynamic range of 0.11-50.13 nmol/mL serum. In vivo median concentrations were found to be 0.62 nmol/mL and 0.91 nmol/mL for non-spontaneous survivors (n = 25) and individuals with irreversible liver damage (n = 10), respectively (p-value = 0.028), demonstrating significant potential as a biomarker for ALF outcome.

CONCLUSIONS

A fast and sensitive assay was developed to accurately quantify NAPQI-HSA as a biomarker for APAP-related covalent binding in human serum.

Accuracy of the paracetamol-aminotransferase product to predict hepatotoxicity in paracetamol overdose treated with a 2-bag acetylcysteine regimen

INTRODUCTION

Paracetamol concentration is a highly accurate risk predictor for hepatotoxicity following overdose with known time of ingestion. However, the paracetamol-aminotransferase multiplication product can be used as a risk predictor independent of timing or ingestion type. Validated in patients treated with the traditional, "three-bag" intravenous acetylcysteine regimen, we evaluated the accuracy of the multiplication product in paracetamol overdose treated with a two-bag acetylcysteine regimen.

METHODS

We examined consecutive patients treated with the two-bag regimen from five emergency departments over a two-year period. We assessed the predictive accuracy of initial multiplication product for the primary outcome of hepatotoxicity (peak alanine aminotransferase ≥1000IU/L), as well as for acute liver injury (ALI), defined peak alanine aminotransferase ≥2× baseline and above 50IU/L).

RESULTS

Of 447 paracetamol overdoses treated with the two-bag acetylcysteine regimen, 32 (7%) developed hepatotoxicity and 73 (16%) ALI. The pre-specified cut-off points of 1500 mg/L × IU/L (sensitivity 100% [95% CI 82%, 100%], specificity 62% [56%, 67%]) and 10,000 mg/L × IU/L (sensitivity 70% [47%, 87%], specificity of 97% [95%, 99%]) were highly accurate for predicting hepatotoxicity. There were few cases of hepatotoxicity irrespective of the product when acetylcysteine was administered within eight hours of overdose, when the product was largely determined by a high paracetamol concentration but normal aminotransferase.

CONCLUSIONS

The multiplication product accurately predicts hepatotoxicity when using a two-bag acetylcysteine regimen, especially in patients treated more than eight hours post-overdose. Further studies are needed to assess the product as a method to adjust for exposure severity when testing efficacy of modified acetylcysteine regimens.

The 100 most influential publications in paracetamol poisoning treatment: a bibliometric analysis of human studies

BACKGROUND

Analysis of the most influential publications within paracetamol poisoning treatment can be helpful in recognizing main and novel treatment issues within the field of toxicology. The current study was performed to recognize and describe the most highly cited articles related to paracetamol poisoning treatment.

METHODS

The 100 most highly cited articles in paracetamol poisoning treatment were identified from the Scopus database in November 2015. All eligible articles were read for basic information, including total number of citations, average citations per year, authors' names, journal name, impact factors, document types and countries of authors of publications.

RESULTS

The median number of citations was 75 (interquartile range 56-137). These publications were published between 1974 and 2013. The average number of years since publication was 17.6 years, and 45 of the publications were from the 2000s. A significant, modest positive correlation was found between years since publication and the number of citations among the top 100 cited articles (r = 0.316; p = 0.001). A total of 55 journals published these 100 most cited articles. Nine documents were published in Clinical Toxicology, whereas eight documents were published in Annals of Emergency Medicine. Citations per year since publication for the top 100 most-cited articles ranged from 1.5 to 42.6 and had a mean of 8.5 citations per year and a median of 5.9 with an interquartile range of 3.75-10.35. In relation to the origin of the research publications, they were from 8 countries. The USA had the largest number of articles, 47, followed by the UK and Australia with 38 and nine articles respectively.

CONCLUSIONS

This study is the first bibliometric assessment of the top 100 cited articles in toxicology literature. Interest in paracetamol poisoning as a serious clinical problem continues to grow. Research published in high-impact journals and from high income countries is most likely to be cited in published paracetamol research.

Outcomes of Patients With Premature Discontinuation of the 21-h Intravenous N-Acetylcysteine Protocol After Acute Acetaminophen Overdose

BACKGROUND

The minimum recommended treatment duration for i.v. N-acetylcysteine (NAC) after an acute, single acetaminophen (APAP) overdose is 21 h. Some have questioned whether shorter courses may be sufficient in carefully selected cases.

OBJECTIVE

We sought to describe the incidence of hepatotoxicity in a cohort of acute APAP overdose patients who received <21 h of i.v. NAC for any reason.

METHODS

We performed a secondary analysis of a large multicenter retrospective cohort of patients hospitalized for APAP poisoning. We selected patients with a potentially toxic serum APAP concentration measured between 4 and 24 h post ingestion, in whom i.v. NAC was initiated but discontinued before completing the full 21-h course. We further characterized outcomes in these patients as a function of two novel risk-prediction tools, the psi (ψ) parameter and APAP × aminotransferase (AT) product. The ψ parameter is an estimate of the cellular burden of injury based on the area under the concentration-time curve before treatment, and calculated with respect to the APAP concentration and time to initiation of NAC.

RESULTS

Fifty-nine patients met inclusion criteria. Intravenous NAC was initiated a median of 11.3 h post ingestion and administered for a median of 11.0 h. Hepatotoxicity (aspartate aminotransferase [AST] or alanine aminotransferase [ALT] > 1,000 IU/L) occurred in one patient (1.7%; 95% confidence interval 0.04-9.1), and eight additional patients developed hepatic injury (AST or ALT > 100 IU/L). No fatalities occurred. A multiplication product of APAP and AT (APAP × AT) that falls below 10,000 μmol/L/IU-L, or pretreatment ψ < 5 mmol/L-h suggested a low risk of hepatic injury.

CONCLUSIONS

In this retrospective analysis of patients treated with < 21 h of i.v. NAC for acute APAP overdose, the incidence of hepatotoxicity and coagulopathy was low, despite delays to NAC treatment.

Nomogram line crossing after acetaminophen combination product overdose

BACKGROUND

The Rumack-Matthew nomogram predicts the risk of hepatotoxicity following acute acetaminophen overdose based on a serum concentration obtained ≥ 4-hour post-ingestion. Some patients with low-risk concentrations at 4 hours may have subsequent values indicating increased risk (above the nomogram treatment line), especially if coingestants that slow gastrointestinal motility are involved. The treatment line currently used to identify low risk patients in the United States, Canada, and Australia begins at 150 mcg/mL (993 μmol/L) and intersects at 18.75 mcg/mL (124.1 μmol/L) 16 hours post-ingestion.

OBJECTIVE

To determine the incidence of nomogram line crossing after acute overdose of acetaminophen combination products containing an opioid or antihistamine.

METHODS

This was a prospective cohort study of hospitalized patients reported to a regional poison center (RPC) after acute overdose of a combination product containing an opioid or antihistamine. If a 4-hour acetaminophen concentration was detectable but below the nomogram treatment line, the RPC recommended repeat concentrations. Patients were entered into the study if at least one subsequent concentration was available. During follow-up calls hospital providers were queried regarding clinical features, treatment, and indicators of liver injury.

RESULTS

Over a 4-year period 76 patients met entry criteria. 5/76 (6.6%) had measureable acetaminophen concentrations below the treatment line at or close to 4-hour post-ingestion followed by values above the line obtained at 6.5-12.5 hours. Four of the five were treated with acetylcysteine and none developed hepatotoxicity. Four of the five had clinical features reported to the RPC suggesting toxicity from the opioid or antihistamine component.

CONCLUSION

After acute overdose of acetaminophen combination products, patients with detectable but non-toxic 4-hour acetaminophen concentrations should have repeat concentrations obtained in a time frame that would allow providers to initiate acetylcysteine treatment, if needed, without undue delay.

A descriptive analysis of aspartate and alanine aminotransferase rise and fall following acetaminophen overdose

CONTEXT

Risk prediction following acetaminophen (paracetamol, APAP) overdose is based on serum APAP, aspartate aminotransferase (AST), and alanine aminotransferase (ALT) levels. One recently proposed risk stratification tool, the APAPxAT multiplication product, uses either AST or ALT, whichever is higher, yet their interrelation is not well known following APAP-induced hepatic injury.

OBJECTIVE

To describe the kinetics of AST and ALT release into and disappearance from the circulation following APAP overdose.

MATERIALS AND METHODS

An observational case series of adult patients with peak AST or ALT > 100 IU/L attributable to APAP toxicity. Cases were identified by electronic search of hospital laboratory database and by discharge diagnosis corroborated by structured explicit medical record review.

RESULTS

Of 68 cases identified (mean age (SD): 39 (18) years, 63% female, and 21% ethanol co-ingested), 28 (41%) developed hepatotoxicity (peak AST or ALT > 1000 IU/L), 28 (41%) coagulopathy (international normalized ratio or INR > 2), and 21 (31%) both. Three patients (4%) were transferred for liver transplantation and ultimately six (8.8%) died. Serum AST and ALT activity rose in a closely aligned 1:1 AST:ALT ratio, but fell at distinctly different rates: AST activity fell with a half-life (interquartile range [IQR]) of 15.1 (12.2, 19.4) hours, and ALT 39.6 (32.9, 47.6) hours. Using an aminotransferase falling to below 50% of peak as the basis for discontinuing acetylcysteine would have resulted in antidotal treatment being stopped 24 (IQR: 9.6, 40) hours earlier (and in no cases later) using AST rather than ALT. Only six patients had an AST:ALT ratio greater than 2:1 at the time of acetylcysteine administration; of these six, four died and one survivor developed coagulopathy.

DISCUSSION

AST and ALT release into the circulation appears tightly linked and numerically similar, except in the sickest patients. Once the aminotransferases peak, AST returns to baseline more quickly.

CONCLUSION

Either AST or ALT can be used for early risk stratification tools when only one is known. Any criterion for N-AC discontinuation should be based on the decline of AST rather than ALT, with a potential benefit measured in days.

Performance of a multi-disciplinary emergency department observation protocol for acetaminophen overdose

The availability of 20-h N-acetylcysteine (NAC) infusion for low-risk acetaminophen (APAP) overdose enabled our center to implement an Emergency Department observation unit (OU) protocol as an alternative to hospitalization. Our objective was to evaluate our early experience with this protocol. This retrospective cohort study included all patients treated for low-risk APAP overdose in our academic hospital between 2006 and 2011. Cases were identified using OU and pharmacy records. Successful OU discharge was defined as disposition with no inpatient admission. Differences in medians with 95 % confidence intervals were used for comparisons. One hundred ninety-six patients received NAC for APAP overdose with a mean age of 35 years (SD 14); 73 % were white, and 43 % were male. Twenty (10 %) received care in the OU; 3/20(15 %) met criteria for inclusion in the OU protocol and 13/20(65 %) were discharged successfully. Out of the 196 patients, 10 met criteria for inclusion in the OU protocol but instead received care in the inpatient setting. The median total length of stay from presentation to ED discharge was 41 h for all patients treated in the OU, compared to 68 h for ten patients who met criteria for inclusion in the OU protocol but who were admitted (difference 27 h, 95 % CI 18-72 h). ED observation for APAP overdose can be a viable alternative to inpatient admission. Most patients were successfully discharged from the OU. This evaluation identified both over- and under-utilization of the OU. OU treatment resulted in shorter median length of stay than inpatient admission.

Antidote removal during haemodialysis for massive acetaminophen overdose

CONTEXT

Haemodialysis is sometimes used for patients with massive acetaminophen overdose when signs of "mitochondrial paralysis" (lactic acidosis, altered mental status, hypothermia and hyperglycaemia) are present. The role of haemodialysis is debated, in part because the evidence base is weak and the endogenous clearance of acetaminophen is high. There is also concern because the antidote acetylcysteine is also dialyzable. We prospectively measured serum acetylcysteine concentrations during haemodialysis in three such cases.

CASE DETAILS

Three adults each presented comatose and acidemic 10 to ~18 h after ingesting > 1000mg/kg of acetaminophen. Two were hypothermic and hyperglycaemic. Serum lactate concentrations ranged from 7 mM to 12.5 mM. All three were intubated, and initial acetaminophen concentrations were as high as 5980 μM (900 μg/mL). An intravenous loading dose of 150 mg/kg acetylcysteine was initiated between 10.8 and ~18 h post ingestion, and additional doses were empirically administered during haemodialysis to compensate for possible antidote removal. A single run of 3-4 h of haemodialysis removed 10-20 g of acetaminophen (48-80% of remaining body burden), reduced serum acetaminophen concentrations by 56-84% (total clearance 3.4-7.8 mL/kg/min), accelerated native acetaminophen clearance (mean elimination half-life 580 min pre-dialysis, 120 min during and 340 min post-dialysis) and corrected acidemia. Extraction ratios of acetylcysteine across the dialysis circuit ranged from 73% to 87% (dialysance 3.0 to 5.3 mL/kg/min). All three patients recovered fully, and none developed coagulopathy or other signs of liver failure.

DISCUSSION

When massive acetaminophen ingestion is accompanied by coma and lactic acidosis, emergency haemodialysis can result in rapid biochemical improvement. As expected, haemodialysis more than doubles the clearance of both acetaminophen and acetylcysteine. Because acetylcysteine dosing is largely empirical, we recommend doubling the dose during haemodialysis, with an additional half-load when dialysis exceeds 6 h.

[Charcoal, cocaine and rattlesnakes: evidence-based treatment of poisoning]

BACKGROUND

Since ancient times poisoning has been treated medicinally. Clinical toxicology, in the narrow sense of the term, developed from the foundation of specialized medical treatment units for poisoning and the formation of the first poison information centers in the second half of the twentieth century. Historically, the first poison information centers were often localized at pediatric clinics or departments of internal medicine. It became increasingly more obvious that this pooling of competences made sense.

AIM

This article gives a general introduction in clinical toxicology and presents the functions and key activities of emergency poison centers.

MATERIAL AND METHODS

The organisation and work of a poisons centre is demonstrated on the basis of the Poisons Information Center (GIZ) North annual report for 2011. In a short summary the basic principles of clinical toxicology are elucidated: the primary removal of poisons by gastric lavage and administration of activated charcoal, secondary removal of poisons by enhanced elimination using hemodialysis, hemoperfusion, multi-dose activated charcoal and molecular adsorbent recirculating systems (MARS) and the indications for administration of specific antidotes or antivenins (antisera against poisoning by poisonous animals).

RESULTS

Gastric lavage is indicated within 1 h after ingestion of a potentially life-threatening dose of a poison. In cases of poisoning with substances which penetrate the central nervous system (CNS) gastric lavage should be performed only after endotracheal intubation due to the risk of aspiration. The basic management of poisoned patients by emergency medicine personnel out of hospital and on the way to hospital is presented. The Bremen list, a compilation of the five antidotes, atropine, 4-dimethylaminophenol (4-DMAP), tolonium chloride, naloxone and activated charcoal for out of hospital treatment by emergency doctors is presented.

CONCLUSION

In all, even questionable cases of poisoning consultation at emergency poison centers is recommended. An extensive list of all German speaking poison information centers is available on the homepage of GIZ-Nord (http://www.giz-nord.de).

Oral and Intravenous Acetylcysteine for Treatment of Acetaminophen Toxicity: A Systematic Review and Meta-analysis

INTRODUCTION

There are few reports summarizing the effectiveness of oral and intravenous (IV) acetylcysteine. We determined the proportion of acetaminophen poisoned patients who develop hepatotoxicity (serum transaminase > 1000 IU/L) when treated with oral and IV acetylcysteine.

METHODS

Studies were double abstracted by trained researchers. We determined the proportions of patients who developed hepatotoxicity for each route using a random effects model. Studies were further stratified by early and late treatment.

RESULTS

We screened 4,416 abstracts; 16 articles, including 5,164 patients, were included in the meta-analysis. The overall rate of hepatotoxicity for the oral and IV routes were 12.6% and 13.2%, respectively. Treatment delays are associated with a higher rate of hepatotoxicity.

CONCLUSION

Studies report similar rates of hepatotoxicity for oral and IV acetylcysteine, but direct comparisons are lacking. While it is difficult to disentangle the effects of dose and duration from route, our findings suggest that the rates of hepatotoxicity are similar for oral and IV administration.

Scottish and Newcastle antiemetic pre-treatment for paracetamol poisoning study (SNAP)

Background

Paracetamol (acetaminophen) poisoning remains the commonest cause of acute liver injury in Europe and North America. The intravenous (IV) N-acetylcysteine (NAC) regimen introduced in the 1970s has continued effectively unchanged. This involves 3 different infusion regimens (dose and time) lasting over 20 hours. The same weight-related dose of NAC is used irrespective of paracetamol dose. Complications include frequent nausea and vomiting, anaphylactoid reactions and dosing errors. We designed a randomised controlled study investigating the efficacy of antiemetic pre-treatment (ondansetron) using standard NAC and a modified, shorter, regimen.

Methods/Design

We designed a double-blind trial using a 2 × 2 factorial design involving four parallel groups. Pre-treatment with ondansetron 4 mg IV was compared against placebo on nausea and vomiting following the standard (20.25 h) regimen, or a novel 12 h NAC regimen in paracetamol poisoning. Each delivered 300 mg/kg bodyweight NAC. Randomisation was stratified on: paracetamol dose, perceived risk factors, and time to presentation. The primary outcome was the incidence of nausea and vomiting following NAC. In addition the frequency of anaphylactoid reactions and end of treatment liver function documented. Where clinically necessary further doses of NAC were administered as per standard UK protocols at the end of the first antidote course.

Discussion

This study is primarily designed to test the efficacy of prophylactic anti-emetic therapy with ondansetron, but is the first attempt to formally examine new methods of administering IV NAC in paracetamol overdose. We anticipate, from volunteer studies, that nausea and vomiting will be less frequent with the new NAC regimen. In addition as anaphylactoid response appears related to plasma concentrations of both NAC and paracetamol anaphylactoid reactions should be less likely. This study is not powered to assess the relative efficacy of the two NAC regimens, however it will give useful information to power future studies. As the first formal randomised clinical trial in this patient group in over 30 years this study will also provide information to support further studies in patients in paracetamol overdose, particularly, when linked with modern novel biomarkers of liver damage, patients at different toxicity risk.

Trial registration

EudraCT number 2009-017800-10, ClinicalTrials.gov IdentifierNCT01050270

Of pills, plants, and paraquat: the relevance of poison centers in emergency medicine

The organization and work of a poisons center are demonstrated on the basis of GIZ-Nord Poisons Center Annual Report for 2011. In a short summary the basic principles of clinical toxicology are elucidated: the indications for gastric lavage and the application of activated charcoal. Moreover the means of enhanced elimination are presented: hemodialysis, hemoperfusion, multi-dose activated charcoal and molecular absorbent recirculating system (MARS). Gastric lavage is indicated within one hour after ingestion of a life-threatening dose of a poison. In intoxications with CNS penetrating substances gastric lavage should be performed only after endotracheal intubation due to the risk of aspiration. The basic management of the intoxicated patient by emergency medicine personnel out of hospital and on the way into the hospital is presented. The "Bremen List", a compilation of five antidotes (atropine, 4-DMAP, tolonium chloride, naloxone, activated charcoal) for the out of hospital treatment by emergency doctors is introduced.

State of the art: emergency department observation units

Hospitals and emergency departments face the challenges of escalating healthcare costs, mismatched resource utilization, concern over avoidable admissions, and hospital and emergency department overcrowding. One approach that has been used by hospitals to address these issues is the use of emergency department observation units. Research in this setting has increased in recent years, leading to a better understanding of the role of these units and their unique benefits. These benefits have been proven for health systems as a whole and for several acute conditions including chest pain, asthma, syncope, transient ischemic attack, atrial fibrillation, heart failure, abdominal pain, and more. Benefits include a decrease in diagnostic uncertainty, lower cost and resource utilization, improved patient satisfaction, and clinical outcomes that are comparable to admitted patients. As more hospitals begin to use observation units, there is a need for further education and research in how to optimize the use of emergency department observation units. The purpose of this article is to provide a general overview of observation units, including advancements and research in this field.

A retrospective evaluation of shortened-duration oral N-acetylcysteine for the treatment of acetaminophen poisoning

INTRODUCTION

The use of less than the traditional 72-hour course of oral N-acetylcysteine has been an alternative treatment option following potentially toxic acute and chronic acetaminophen ingestions felt to be at low risk of developing hepatotoxicity. While clinical experience with shortened treatment duration is extensive, there are few studies evaluating the effectiveness and extent to which these regimens may be used.

METHODS

A large statewide poison center database was reviewed for all acetaminophen exposures involving potentially toxic acute and chronic ingestions, in addition to those taking place at unknown times. Patients were identified who met laboratory criteria for early N-acetylcysteine (NAC) discontinuation (APAP>10 micro/mL, INR<or=1.3, and AST/ALT<or=60 IU) after a minimum of a 140-mg/kg oral NAC loading dose and 5 additional 70-mg/kg doses over 20 hours. A further search of the poison center database was conducted for individuals who received shortened-course (20-48 hours) oral NAC treatment who developed subsequent hepatotoxicity or death.

RESULTS

Of 3303 individuals with potentially toxic acetaminophen ingestions, 1932 met criteria for early NAC discontinuation. Mean treatment duration was 36.4+/-7.7 hours (acute=37.3+/-7.6 hours; chronic=34.8+/-7.4 hours; unknown=35.2+/-7.6 hours). The poison center database search identified no short-course eligible subjects who developed subsequent hepatotoxicity or death following<or=48 hours of oral NAC.

CONCLUSION

Treatment with shortened-course oral NAC in patients meeting criteria for early discontinuation may be an effective treatment option in a sizeable proportion of individuals with potentially toxic acetaminophen ingestions.

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.

Screening of herbal medicines for recovery of acetaminophen-induced nephrotoxicity

This study was conducted to quantitatively evaluate the recovery effects of herbal medicines on acetaminophen-induced nephrotoxicity. In the present study, the recovery effects of 251 herb medicines on HEK 293 cells that had been damaged by acetaminophen were evaluated using an MTS assay. HEK 293 cells were cultured in 96-well plates and then pretreated with or without 20μM acetaminophen (IC(50) value: 17.5±1.9) for 1h. Next, different herbal medicines were added to the wells, after which the cells were reincubated at 37°C for 24h. After the first round of screening, the candidate herbal medicines were selected based on a recovery rate of greater than 20% and their efficacy were then determined by dose response kinetic analysis. Among these extracts, 8 herbal medicines (Ledebouriella divaricata, Sparganium simplex, Panax ginseng, Aster tataricus, Citrus aurantium, Sanguisorba officianlis, Arisaema consanguineum, and Polygonum aviculare) had a strong recovery effect on acetaminophen-induced damage in HEK 293 cells. Dose response non-linear regression analysis demonstrated that P. aviculare showed the best recovery rate (98%), and that its EC(50) (0.1ng/mL) was the smallest among the screened candidate herbal medicines. Additional studies of these herbal medicines should be conducted to determine if they possess novel therapeutic agents for the prevention or treatment of renal disorders.

Development and Implementation of An Emergency Department Observation Unit Protocol for Deliberate Drug Ingestion in Adults – Preliminary Results

BACKGROUND

Patients presenting after reported overdose are typically precluded from admission to emergency department observation units (EDOU). The purpose of this study was to describe the initial experience with an EDOU overdose protocol.

METHODS

Retrospective chart review of all individuals presenting to a tertiary care hospital with a chief complaint of overdose or intoxication for the period 7/1/2004 through 12/24/2004. Inclusion criteria for EDOU placement included asymptomatic patients aged >or= 15 years presenting after known or suspected potentially toxic exposure. Exclusion criteria included isolated ethanol intoxication, presence of persistent self-injurious or violent behaviors, chronic intoxication, ingestion of sustained release preparation, and presence of previously defined high-risk criteria.

RESULTS

Retrospective chart review demonstrated that 163 patients presented to the ED after ingestion during this time period, of which 15 were excluded secondary to age. Six patients were admitted to the EDOU. No patient eloped or attempted further self-harm while in the EDOU. No clinical decompensation occurred. Another 27 patients were retrospectively identified as EDOU candidates, eight of whom were admitted to the MICU.

CONCLUSION

Although initial numbers are too small for meaningful analysis, the results suggest that prolonged observation of this problematic patient subset within an EDOU is feasible.

Estimated risk of hepatotoxicity after an acute acetaminophen overdose in alcoholics

A published logistic regression model based on the Canadian Acetaminophen Overdose Study registry was used to calculate the risk of hepatotoxicity after an acute acetaminophen overdose and to estimate a treatment threshold line for alcoholic patients who did not co-ingest alcohol (i.e., abstinent alcoholics) on the Rumack-Matthew nomogram. The risk of hepatotoxicity in nonalcoholic and abstinent alcoholic patients was calculated at the acetaminophen concentration of 150 microg/ml at 4h (37.5 microg/ml at 12h) treatment threshold line. This corresponds to the "possible risk" line on the Rumack-Matthew nomogram and represents a 1.6% risk of hepatotoxicity for nonalcoholic patients at or below this line. At or below this same 150 microg/ml at 4-h line, abstinent alcoholic patients have a hepatotoxicity risk of 10.7%. The risk of hepatotoxicity in abstinent alcoholics' equivalent to that of nonalcoholics (i.e., 1.6%) occurs at a lower acetaminophen concentrations treatment threshold line, that is, 104 microg/ml at 4h (26 microg/ml at 12h). Because of difficulties plotting this new line on the familiar Rumack-Matthew semilogarithmic scale, a line connecting 100 microg/ml at 4h (25 microg/ml at 12h) is proposed. This line equates to a 1.1% risk of hepatotoxicity in abstinent alcoholic patients. The analysis supports the observation that based on the published model abstinent alcoholics might have a greater risk of hepatotoxicity after an acute acetaminophen overdose. This proposed new risk line can be used in hypothesis generation for future clinical studies in this alcohol related problem.

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.

[Clinical value of estimated half-life in paracetamol poisoning as a complement to Rumack's nomogram]

BACKGROUND AND OBJECTIVE

Rumack's nomogram is usually used to indicate the treatment with N-acetilcysteine in the paracetamol poisoning, but it has several limitations. Paracetamol half-life elimination (t1/2) is approximately of 2 h with therapeutic doses and it increases to more than 4 h in patients with hepatotoxicity. The aim of this study was to determine the usefulness of estimated paracetamol t1/2 as greater than or inferior to 4 h by using a simple ratio in relation to the development of hepatotoxicity.

PATIENTS AND METHOD

21 patients with paracetamol overdose were admitted to Son Dureta Hospital (Palma de Mallorca) and Clínic Hospital (Barcelona) over 13 months. The estimated t1/2 is calculated using the quotient between 2 plasma paracetamol concentrations separated by 2 or more hours.

RESULTS

We found a significant difference (p < 0.005) between the group with hepatotoxicity (n = 3; t1/2 = 8,5 h; range: 3,6 - 8,7 h); and without hepatotoxicity (n = 18; t1/2 = 2,4 h; (range: 1,6 - 4,3 h). We observed an agreement between positive ratio and a t1/2 > 4 h, and negative ratio with t1/2 < 4 h, bearing in mind that the quotient is obtained through mathematical equations.

CONCLUSIONS

Rumack's nomogram should be complemented with t1/2 estimation in all cases of paracetamol poisoning, especially with those patients for whom we are not able to determine the time of ingestion at presentation or if there has been a multiple-timepoint ingestion.

Validation of ICD-9-CM/ICD-10 coding algorithms for the identification of patients with acetaminophen overdose and hepatotoxicity using administrative data

Background

Acetaminophen overdose is the most common cause of acute liver failure (ALF). Our objective was to develop coding algorithms using administrative data for identifying patients with acetaminophen overdose and hepatic complications.

Methods

Patients hospitalized for acetaminophen overdose were identified using population-based administrative data (1995–2004). Coding algorithms for acetaminophen overdose, hepatotoxicity (alanine aminotransferase >1,000 U/L) and ALF (encephalopathy and international normalized ratio >1.5) were derived using chart abstraction data as the reference and logistic regression analyses.

Results

Of 1,776 potential acetaminophen overdose cases, the charts of 181 patients were reviewed; 139 (77%) had confirmed acetaminophen overdose. An algorithm including codes 965.4 (ICD-9-CM) and T39.1 (ICD-10) was highly accurate (sensitivity 90% [95% confidence interval 84–94%], specificity 83% [69–93%], positive predictive value 95% [89–98%], negative predictive value 71% [57–83%], c-statistic 0.87 [0.80–0.93]). Algorithms for hepatotoxicity (including codes for hepatic necrosis, toxic hepatitis and encephalopathy) and ALF (hepatic necrosis and encephalopathy) were also highly predictive (c-statistics = 0.88). The accuracy of the algorithms was not affected by age, gender, or ICD coding system, but the acetaminophen overdose algorithm varied between hospitals (c-statistics 0.84–0.98; P = 0.003).

Conclusion

Administrative databases can be used to identify patients with acetaminophen overdose and hepatic complications. If externally validated, these algorithms will facilitate investigations of the epidemiology and outcomes of acetaminophen overdose.

A Prospective Evaluation of Shortened Course Oral N-Acetylcysteine for the Treatment of Acute Acetaminophen Poisoning

STUDY OBJECTIVE

Treatment with a shortened duration of oral N-acetylcysteine (20 to 48 hours) after acute acetaminophen poisoning is effective in the prevention of subsequent hepatic failure and death when administered to individuals meeting appropriate laboratory criteria.

METHODS

Individuals with a potentially toxic acetaminophen ingestion according to serum acetaminophen levels were identified prospectively using a large statewide poison control system database throughout a 12-month period. N-acetylcysteine was administered for a minimum of 6 doses (20 hours), after which laboratory studies were obtained. Discontinuation of N-acetylcysteine was recommended by the poison center when 2 criteria were met: serum acetaminophen was undetectable (<10 microg/mL) and liver test results were normal (serum aminotransferase, international normalized ratio). A follow-up questionnaire was administered to individuals treated with N-acetylcysteine for 48 hours or less to ascertain the presence of symptoms consistent with progressive hepatotoxicity.

RESULTS

Of 205 acutely poisoned individuals treated with N-acetylcysteine for 48 hours or less, 195 were successfully contacted after discharge, and 187 of 195 (95.9%) reported no symptoms consistent with hepatic failure. Eight individuals (4.1%) reported abdominal pain or vomiting; however, none received further N-acetylcysteine treatment or additional hospitalization.

CONCLUSION

A shortened duration of treatment with N-acetylcysteine (20 to 48 hours) may be an effective treatment option in individuals considered to be at no further risk of developing liver toxicity according to the fulfillment of appropriate laboratory criteria before N-acetylcysteine discontinuation.

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.