Steven C. Curry

The mechanism underlying acetaminophen-induced hepatotoxicity in humans and mice involves mitochondrial damage and nuclear DNA fragmentation

Acetaminophen (APAP) overdose is the predominant cause of acute liver failure in the United States. Toxicity begins with a reactive metabolite that binds to proteins. In rodents, this leads to mitochondrial dysfunction and nuclear DNA fragmentation, resulting in necrotic cell death. While APAP metabolism is similar in humans, the later events resulting in toxicity have not been investigated in patients. In this study, levels of biomarkers of mitochondrial damage (glutamate dehydrogenase [GDH] and mitochondrial DNA [mtDNA]) and nuclear DNA fragments were measured in plasma from APAP-overdose patients. Overdose patients with no or minimal hepatic injury who had normal liver function tests (LTs) (referred to herein as the normal LT group) and healthy volunteers served as controls. Peak GDH activity and mtDNA concentration were increased in plasma from patients with abnormal LT. Peak nuclear DNA fragmentation in the abnormal LT cohort was also increased over that of controls. Parallel studies in mice revealed that these plasma biomarkers correlated well with tissue injury. Caspase-3 activity and cleaved caspase-3 were not detectable in plasma from overdose patients or mice, but were elevated after TNF-induced apoptosis, indicating that APAP overdose does not cause apoptosis. Thus, our results suggest that mitochondrial damage and nuclear DNA fragmentation are likely to be critical events in APAP hepatotoxicity in humans, resulting in necrotic cell death.

Affinity-Purified, Mixed Monospecific Crotalid Antivenom Ovine Fab for the Treatment of Crotalid Venom Poisoning

SUBJECT OBJECTIVE To test the efficacy and safety of a new antivenom, affinity-purified, mixed monospecific crotalid antivenom ovine Fab, in human subjects with minimal or moderate crotalid envenomation. METHODS We conducted a prospective multicenter clinical trial of 11 patients 10 years or older with progressive manifestations after mild to moderate crotalid snakebite. After giving their consent, subjects received four to eight vials of study drug and were then repeatedly examined over 48 hours and at 7 and 14 days after discharge. Each patients clinical condition was evaluated serially with the use of a validated severity score, as well as on the basis of the investigators assessment. RESULTS In all 11 subjects to the antivenom was judged by the investigator to have had a beneficial response. The severity score for each patient remained the same or decreased over the first 4 hours. However, two subjects demonstrated worsened condition 12 to 15 hours after antivenom administration. In no subject did an allergic reaction develop. CONCLUSION In this patient group, affinity-purified, mixed monospecific crotalid antivenom ovine Fab was associated with a halt of progressive crotalid venom poisoning. Initial safety data are promising but must be addressed further in subsequent studies.

Poisoning by sodium channel blocking agents

Poisoning by drugs that block voltage-gated sodium channels produces intraventricular conduction defects, myocardial depression, bradycardia, and ventricular arrhythmias. Human and animal reports suggest that hypertonic sodium bicarbonate may be effective therapy for numerous agents possessing sodium channel blocking properties, including cocaine, quinidine, procainamide, flecainide, mexiletine, bupivacaine, and others.

Circulating microRNA profiles in human patients with acetaminophen hepatotoxicity or ischemic hepatitis

Significance Hundreds of microRNAs become dramatically elevated in the plasma or serum of acetaminophen (APAP) overdose patients and then recover back toward normal during successful treatment with the APAP antidote, N-acetyl cysteine (NAC). Importantly, the elevation of these circulating miRNAs can precede the rise in the standard biomarker, alanine aminotransferase (ALT), and the recovery of these miRNAs during NAC treatment is more rapid than ALT. We identify a set of 11 miRNAs whose profiles and dynamics in circulation during NAC treatment can discriminate APAP hepatotoxicity from another common hepatotoxic condition, ischemic hepatitis. These findings suggest that miRNAs are sensitive diagnostic and prognostic biomarkers for liver injury with broad potential for use in monitoring drug-induced liver injury in clinical and research contexts. We have identified, by quantitative real-time PCR, hundreds of miRNAs that are dramatically elevated in the plasma or serum of acetaminophen (APAP) overdose patients. Most of these circulating microRNAs decrease toward normal levels during treatment with N-acetyl cysteine (NAC). We identified a set of 11 miRNAs whose profiles and dynamics in the circulation during NAC treatment can discriminate APAP hepatotoxicity from ischemic hepatitis. The elevation of certain miRNAs can precede the dramatic rise in the standard biomarker, alanine aminotransferase (ALT), and these miRNAs also respond more rapidly than ALT to successful treatment. Our results suggest that miRNAs can serve as sensitive diagnostic and prognostic clinical tools for severe liver injury and could be useful for monitoring drug-induced liver injury during drug discovery.

Envenomation by the Scorpion Centruroides Sculpturatus

Envenomation by the scorpion C. sculpturatus can be life threatening. The action of the venom is to produce prolonged and excessive firing of neuronal axons which results in a wide variety of signs and symptoms. Records of 670 patients suffering from scorpion stings in central Arizona in 1982 were reviewed to characterize the clinical course of these patients. While adults appear to be stung more often than children, children are more likely to develop a severe illness requiring intensive supportive care. The intravenous administration of specific C. sculpturatus antivenom results in resolution of serious signs and symptoms within minutes, with patients completely asymptomatic within 1 1/2 hours. The administration of antivenom is recommended as the treatment of choice for severe envenomations after the initiation of appropriate supportive care.

Effect of the Cyanide Antidote Hydroxocobalamin on Commonly Ordered Serum Chemistry Studies

STUDY HYPOTHESIS Concentrated aqueous solutions of hydroxocobalamin (OHCob) are given intravenously for the treatment of cyanide poisoning. Because OHCob solutions are intensely red and have peak light absorptions at 352 nm and 525 nm, we investigated whether the presence of OHCob in serum would interfere with various automated, colorimetric chemistry measurements. DESIGN Selected serum chemistry colorimetric measurements were compared in seven patients, using their own serum as control, with serum containing OHCob at the following concentrations: 100 mg/L, 500 mg/L, and 1,000 mg/L. These concentrations are in the range achieved with therapeutic doses of OHCob when given for cyanide poisoning. MEASUREMENTS AND MAIN RESULTS Statistically significant alterations in serum values for aspartate aminotransferase, total bilirubin, creatinine, magnesium, and iron were seen in the presence of OHCob. CONCLUSION The presence of OHCob in serum interferes with several chemistry methodologies, and such interference should be anticipated when this antidote is used.

Results of a protocol for the management of patients with fulminant liver failure

Objective:To assess the safety and efficacy of a protocol to support management of intracerebral pressure in patients with fulminant liver failure (FLF). Design and Setting:A prospective series was conducted between May 2004 and September 2006 at Banner Good Samaritan Medical Center, a 650-bed teaching hospital in Phoenix, Arizona. Patients:We recruited consecutive patients with FLF and stage 3 or 4 encephalopathy. Interventions:We placed an intracranial pressure monitor in each patient and employed a protocol to support decisions regarding hemostatic management and prevention and treatment of intracranial hypertension (IHTN). Treatment modalities included hypothermia, hypocarbia, intravenous pentobarbital, intravenous mannitol and vasopressor titration for maintenance of cerebral perfusion pressure. The main outcome measure was survival in transplant candidates. Measurements and Main Results:Twenty-two patients entered the study and 21 (95%) had at least one episode of IHTN. Eighty-two discrete episodes of IHTN occurred, and 78 of these (95%) resolved with treatment. Overall survival was 55%. Eleven of 18 (61%) of transplant candidates survived with good neurologic outcome. No patient died from isolated cerebral edema. Three patients had intracranial hemorrhages related to the intracranial pressure monitor. Conclusions:Protocol-driven management of intracranial pressure in FLF can result in good clinical outcomes in most transplant candidates, even if IHTN occurs. LEARNING OBJECTIVESOn completion of this article, the reader should be able to: Explain the most common cause of death in fulminant liver failure. Describe the protocol for management of patients with fulminant liver failure. Use this information in a clinical setting. Dr. Raschke has disclosed that he was a consultant/advisor for Cardinal Health and attended and spoke at several paid meetings and conferences in regards to intravenous heparin. The remaining authors have not disclosed any potential conflicts of interest. The authors have disclosed that the U.S. Food and Drug Administration has not approved pentobarbital for the treatment of intracranial hypertension discussed in this article. Please consult the products labeling information for approved indications and usage. All faculty and staff in a position to control the content of this CME activity have disclosed that they have no financial relationship with, or financial interests in, any commercial companies pertaining to this educational activity. Lippincott CME Institute, Inc., has identified and resolved all faculty conflicts of interest regarding this educational activity. Visit the Critical Care Medicine Web Site (www.ccmjournal.org) for information on obtaining continuing medical education credit.

Circulating acylcarnitines as biomarkers of mitochondrial dysfunction after acetaminophen overdose in mice and humans

Acetaminophen (APAP) is a widely used analgesic. However, APAP overdose is hepatotoxic and is the primary cause of acute liver failure in the developed world. The mechanism of APAP-induced liver injury begins with protein binding and involves mitochondrial dysfunction and oxidative stress. Recent efforts to discover blood biomarkers of mitochondrial damage have identified increased plasma glutamate dehydrogenase activity and mitochondrial DNA concentration in APAP overdose patients. However, a problem with these markers is that they are too large to be released from cells without cell death or loss of membrane integrity. Metabolomic studies are more likely to reveal biomarkers that are useful at early time points, before injury begins. Similar to earlier work, our metabolomic studies revealed that acylcarnitines are elevated in serum from mice after treatment with toxic doses of APAP. Importantly, a comparison with furosemide demonstrated that increased serum acylcarnitines are specific for mitochondrial dysfunction. However, when we measured these compounds in plasma from humans with liver injury after APAP overdose, we could not detect any significant differences from control groups. Further experiments with mice showed that N-acetylcysteine, the antidote for APAP overdose in humans, can reduce acylcarnitine levels in serum. Altogether, our data do not support the clinical measurement of acylcarnitines in blood after APAP overdose due to the standard N-acetylcysteine treatment in patients, but strongly suggest that acylcarnitines would be useful mechanistic biomarkers in other forms of liver injury involving mitochondrial dysfunction.

CROTALID SNAKE ENVENOMATION

Over 5000 Americans suffer from snake bites annually, and of these, nearly one quarter are from poisonous species. Although these cases are undeniably reported, death appears to occur in only a few cases each year, and often reflects delay in obtaining medical care. Two families of venomous snake indigenous to the United States account for most envenomations: Crotalidae (pit vipers or new world vipers) and Elapidae. This article focuses on the snakes of the Crotalidae family.

First-order elimination kinetics following baclofen overdose

We followed serial plasma baclofen concentrations in a woman who ingested more than 2 g of baclofen in a suicide attempt, the largest ingestion of baclofen reported to date. The plasma clearance of baclofen was characterized by first-order elimination kinetics with a half-life of 8.6 hours. The persistent central nervous system depression noted in our patient after the return of plasma baclofen levels to the therapeutic range is best explained by delayed clearance of baclofen from the CNS. She made a full recovery with supportive care. No evidence of saturable elimination kinetics was found.