The chemokine CXCL14 is a novel early prognostic biomarker for poor outcome in acetaminophen-induced acute liver failure.

BACKGROUND AND AIMS: Patients with acetaminophen-induced acute liver failure are more likely to die while on the liver transplant waiting list than those with other causes of acute liver failure. Therefore, there is an urgent need for prognostic biomarkers that can predict the need for liver transplantation early after an acetaminophen overdose. APPROACH AND RESULTS: We evaluated the prognostic potential of plasma chemokine C-X-C motif ligand 14 (CXCL14) concentrations in patients with acetaminophen (APAP) overdose (n=50) and found that CXCL14 is significantly higher in nonsurviving patients compared to survivors with acute liver failure ( p < 0.001). Logistic regression and AUROC analyses revealed that CXCL14 outperformed the MELD score, better discriminating between nonsurvivors and survivors. We validated these data in a separate cohort of samples obtained from the Acute Liver Failure Study Group (n = 80), where MELD and CXCL14 had similar AUC (0.778), but CXCL14 demonstrated higher specificity (81.2 vs. 52.6) and positive predictive value (82.4 vs. 65.4) for death or need for liver transplantation. Next, combining the patient cohorts and using a machine learning training/testing scheme to mimic the clinical scenario, we found that CXCL14 outperformed MELD based on AUC (0.821 vs. 0.787); however, combining MELD and CXCL14 yielded the best AUC (0.860). CONCLUSIONS: We find in 2 independent cohorts of acetaminophen overdose patients that circulating CXCL14 concentration is a novel early prognostic biomarker for poor outcomes, which may aid in guiding decisions regarding patient management. Moreover, our findings reveal that CXCL14 performs best when measured soon after patient presentation to the clinic, highlighting its importance for early warning of poor prognosis.

Clinical decision support to reduce unnecessary diagnostic testing for heparin-induced thrombocytopenia.

Appropriate evaluation of heparin-induced thrombocytopenia (HIT) is imperative because of the potentially life-threatening complications. However, overtesting and overdiagnosis of HIT are common. Our goal was to evaluate the impact of clinical decision support (CDS) based on the HIT computerized-risk (HIT-CR) score, designed to reduce unnecessary diagnostic testing. This retrospective observational study evaluated CDS that presented a platelet count versus time graph and 4Ts score calculator to clinicians who initiated a HIT immunoassay order in patients with predicted low risk (HIT-CR score 0-2). The primary outcome was the proportion of immunoassay orders initiated but cancelled after firing of the CDS advisory. Chart reviews were conducted to assess anticoagulation usage, 4Ts scores and the proportion of patients who had HIT. In a 20-week period, 319 CDS advisories were presented to users who initiated potentially unnecessary HIT diagnostic testing. The diagnostic test order was discontinued in 80 (25%) patients. Heparin products were continued in 139 (44%) patients, and alternative anticoagulation was not given to 264 (83%). The negative predictive value of the advisory was 98.8% (95% CI: 97.2-99.5). HIT-CR score-based CDS can reduce unnecessary diagnostic testing for HIT in patients with a low pretest probability of HIT.

Interruption of bile acid uptake by hepatocytes after acetaminophen overdose ameliorates hepatotoxicity.

BACKGROUND & AIMS: Acetaminophen (APAP) overdose remains a frequent cause of acute liver failure, which is generally accompanied by increased levels of serum bile acids (BAs). However, the pathophysiological role of BAs remains elusive. Herein, we investigated the role of BAs in APAP-induced hepatotoxicity. METHODS: We performed intravital imaging to investigate BA transport in mice, quantified endogenous BA concentrations in the serum of mice and patients with APAP overdose, analyzed liver tissue and bile by mass spectrometry and MALDI-mass spectrometry imaging, assessed the integrity of the blood-bile barrier and the role of oxidative stress by immunostaining of tight junction proteins and intravital imaging of fluorescent markers, identified the intracellular cytotoxic concentrations of BAs, and performed interventions to block BA uptake from blood into hepatocytes. RESULTS: Prior to the onset of cell death, APAP overdose causes massive oxidative stress in the pericentral lobular zone, which coincided with a breach of the blood-bile barrier. Consequently, BAs leak from the bile canaliculi into the sinusoidal blood, which is then followed by their uptake into hepatocytes via the basolateral membrane, their secretion into canaliculi and repeated cycling. This, what we termed 'futile cycling' of BAs, led to increased intracellular BA concentrations that were high enough to cause hepatocyte death. Importantly, however, the interruption of BA re-uptake by pharmacological NTCP blockage using Myrcludex B and Oatp knockout strongly reduced APAP-induced hepatotoxicity. CONCLUSIONS: APAP overdose induces a breach of the blood-bile barrier which leads to futile BA cycling that causes hepatocyte death. Prevention of BA cycling may represent a therapeutic option after APAP intoxication. LAY SUMMARY: Only one drug, N-acetylcysteine, is approved for the treatment of acetaminophen overdose and it is only effective when given within ∼8 hours after ingestion. We identified a mechanism by which acetaminophen overdose causes an increase in bile acid concentrations (to above toxic thresholds) in hepatocytes. Blocking this mechanism prevented acetaminophen-induced hepatotoxicity in mice and evidence from patients suggests that this therapy may be effective for longer periods after ingestion compared to N-acetylcysteine.

Comparing N-acetylcysteine and 4-methylpyrazole as antidotes for acetaminophen overdose.

Acetaminophen (APAP) overdose can cause hepatotoxicity and even liver failure. N-acetylcysteine (NAC) is still the only FDA-approved antidote against APAP overdose 40 years after its introduction. The standard oral or intravenous dosing regimen of NAC is highly effective for patients with moderate overdoses who present within 8 h of APAP ingestion. However, for late-presenting patients or after ingestion of very large overdoses, the efficacy of NAC is diminished. Thus, additional antidotes with an extended therapeutic window may be needed for these patients. Fomepizole (4-methylpyrazole), a clinically approved antidote against methanol and ethylene glycol poisoning, recently emerged as a promising candidate. In animal studies, fomepizole effectively prevented APAP-induced liver injury by inhibiting Cyp2E1 when treated early, and by inhibiting c-jun N-terminal kinase (JNK) and oxidant stress when treated after the metabolism phase. In addition, fomepizole treatment, unlike NAC, prevented APAP-induced kidney damage and promoted hepatic regeneration in mice. These mechanisms of protection (inhibition of Cyp2E1 and JNK) and an extended efficacy compared to NAC could be verified in primary human hepatocytes. Furthermore, the formation of oxidative metabolites was eliminated in healthy volunteers using the established treatment protocol for fomepizole in toxic alcohol and ethylene glycol poisoning. These mechanistic findings, together with the excellent safety profile after methanol and ethylene glycol poisoning and after an APAP overdose, suggest that fomepizole may be a promising antidote against APAP overdose that could be useful as adjunct treatment to NAC. Clinical trials to support this hypothesis are warranted.

Computerised risk scores to guide recognition and diagnosis in patients with possible heparin-induced thrombocytopenia.

The heparin-induced thrombocytopenia computerised risk (HIT-CR) score is designed to aid in the diagnosis of HIT. We sought to evaluate its potential clinical utility. In this retrospective cohort study, we collected HIT-CR scores on all inpatients receiving heparin over a 4-month period and performed chart reviews on the subset who independently underwent clinical diagnostic testing for HIT to identify patients with HIT. In all, 34 342 patients received heparin, 1744 had high-risk HIT-CR scores of ≥3 and 220 had the maximal risk score of 4. Only 6% of high-risk and 10% of maximal-risk patients underwent testing for HIT. Conversely, among all 317 patients who underwent independent testing for HIT, 67% had low-risk HIT-CR scores (<3). Among patients independently tested, the positive predictive value (PPV) was 6·6% [95% confidence interval (CI) 4·9-8·8%] and the negative predictive value (NPV) was 99·5% (95% CI 97·1-99·9%) at a HIT-CR score cut-off of 3, and the PPV was 22·7% (95% CI 12·7-37·4%) and NPV was 99·0% (95% CI 97·6-99·6%) at a cut-off of 4. This study suggests clinicians fail to test most high-risk patients and unnecessarily test many low-risk patients for HIT. A reasonable approach to clinical application of HIT-CR scores would be recommending no testing for patients with a score of <3 and recommend testing for patients with a score of 4.

Delayed administration of N-acetylcysteine blunts recovery after an acetaminophen overdose unlike 4-methylpyrazole.

N-acetylcysteine (NAC) is the only clinically approved antidote against acetaminophen (APAP) hepatotoxicity. Despite its efficacy in patients treated early after APAP overdose, NAC has been implicated in impairing liver recovery in mice. More recently, 4-methylpyrazole (4MP, Fomepizole) emerged as a potential antidote in the mouse APAP hepatotoxicity model. The objective of this manuscript was to verify the detrimental effect of NAC and its potential mechanism and assess whether 4MP has the same liability. C57BL/6J mice were treated with 300 mg/kg APAP; 9 h after APAP and every 12 h after that, the animals received either 100 mg/kg NAC or 184.5 mg/kg 4MP. At 24 or 48 h after APAP, parameters of liver injury, mitochondrial biogenesis and cell proliferation were evaluated. Delayed NAC treatment had no effect on APAP-induced liver injury at 24 h but reduced the decline of plasma ALT activities and prevented the shrinkage of the areas of necrosis at 48 h. This effect correlated with down-regulation of key activators of mitochondrial biogenesis (AMPK, PGC-1α, Nrf1/2, TFAM) and reduced expression of Tom 20 (mitochondrial mass) and PCNA (cell proliferation). In contrast, 4MP attenuated liver injury at 24 h and promoted recovery at 48 h, which correlated with enhanced mitochondrial biogenesis and hepatocyte proliferation. In human hepatocytes, 4MP demonstrated higher efficacy in preventing cell death compared to NAC when treated at 18 h after APAP. Thus, due to the wider treatment window and lack of detrimental effects on recovery, it appears that at least in preclinical models, 4MP is superior to NAC as an antidote against APAP overdose.

Identification of populations likely to benefit from pharmacogenomic testing.

OBJECTIVES: Pharmacogenomic testing (PGX) implementation is rapidly expanding, including pre-emptive testing funded by health systems. PGX continues to develop an evidence base that it saves money and improves clinical outcomes. Identifying the potential impact of pre-emptive testing in specific populations may aid in the development of a business case. METHODS: We utilized a software tool that can evaluate patient drug lists and identified groups of patients most likely to benefit from implementation of a PGX testing program in a major medical system population. RESULTS: Medication lists were obtained for sixteen patient groups with a total of 82 613 patients. The percent of patients in each group with testing 'Recommended', 'Strongly recommended', or 'Required' ranged from 12.7% in the outpatient pediatric psychiatry group to 75.7% in the any adult inpatient age >50 years group. Some of the highest yield drugs identified were citalopram, simvastatin, escitalopram, metoprolol, clopidogrel, tramadol, and ondansetron. CONCLUSION: We demonstrate a significant number of patients in each group may have benefit, but targeting certain ones for pre-emptive testing may result in the initial highest yield for a health system.

4-methylpyrazole protects against acetaminophen-induced acute kidney injury.

Acetaminophen (APAP) hepatotoxicity is the most common cause of acute liver failure in the United States, and while a significant percentage of APAP overdose patients develop kidney injury, molecular mechanisms involved in APAP-induced nephrotoxicity are relatively unknown. We have shown that 4-methylpyrazole (4MP, Fomepizole) protects against APAP-induced liver injury by inhibiting reactive metabolite formation through Cyp2E1, and analysis of data from APAP overdose patients indicated that kidney dysfunction strongly correlated with severe liver injury. Since Cyp2E1 is also expressed in the kidney, this study explored protection by 4MP against APAP-induced nephrotoxicity. Male C57BL/6 J mice were treated with either 300 or 600 mg/kg APAP with or without 4MP for 2, 6 or 24 h, followed by measurement of APAP metabolism and tissue injury. Interestingly, levels of APAP and its non-oxidative metabolites were significantly higher in kidneys when compared to the liver. APAP-protein adducts were present in both tissues within 2 h, but were absent in kidney mitochondria, unlike in the liver. While GSH depletion was seen in both tissues, activation of c-jun N-terminal kinase and its translocation to the mitochondria, which is a critical feature of APAP-induced liver injury, was not detected in the kidney. Treatment with 4MP attenuated APAP oxidative metabolite generation, GSH depletion as well as kidney injury indicating its potential use in protection against APAP-induced nephrotoxicity. In conclusion, since reactive metabolite formation seems to be common in both liver and kidney, 4MP mediated inhibition of Cyp2E1 protects against APAP-induced nephrotoxicity. However, downstream mechanisms of APAP-induced nephrotoxicity seem distinct from the liver.

Plasma biomarkers to study mechanisms of liver injury in patients with hypoxic hepatitis.

BACKGROUND & AIMS: Hypoxic hepatitis is a clinical condition precipitated by prolonged periods of oxygen deprivation to the liver. It can have several underlying causes. Despite its prevalence in critically ill patients, which can reach upwards of 10%, very little is known about the mechanisms of injury. Thus, we set out to measure previously identified circulating biomarkers in an attempt to describe mechanisms of injury following hypoxic hepatitis. METHODS: Plasma from patients diagnosed with hypoxic hepatitis was collected for this study. Biomarkers of hepatocellular injury, mitochondrial damage and cell death were measured. These results were compared against results obtained from well-characterized acetaminophen overdose patients. RESULTS: At peak injury, ALT measured 4082±606 U/L and gradually decreased over 5 days, corresponding to the clinically observed pattern of hypoxic hepatitis. Levels of GDH showed a similar pattern, but neither ALT nor GDH were significantly higher in these patients than in acetaminophen patients. Plasma levels of DNA fragments mimicked hepatocellular injury as measured by ALT and miRNA-122. Interestingly, we found a significant increase in caspase-cleaved cytokeratin-18; however, the full-length form greatly exceeded the cleaved form at the time of maximum injury (45837±12085 vs 2528±1074 U/L). We also found an increase in acHMGB1 at later time points indicating a possible role of inflammation, but cytokine levels at these times were actually decreased relative to early time points. CONCLUSIONS: The mechanism of injury following hypoxic hepatitis involves mitochondrial damage and DNA fragmentation. Importantly, necrosis, rather than apoptosis, is the main mode of cell death.

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

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.

A new F(ab')2 antivenom for the treatment of crotaline envenomation in children.

STUDY OBJECTIVE: To evaluate the efficacy and safety of a new F(ab')2 antivenom preparation in the treatment of Crotalinae envenomation in children. METHODS: We present a case series of children younger than 16 years who suffered Crotalinae envenomation and were treated with a new F(ab')2 antivenom. Envenomated children treated with the new antivenom were assessed for efficacy of the product, defined as improvement of any hemotoxicity (hypofibrinogenemia, defined as fibrinogen <150 mg/dL, or thrombocytopenia, defined as platelets <150 000/mm3), and the cessation of the advancement of swelling. Safety was also evaluated by monitoring for adverse events. A secondary parameter assessed in these children was recurrent hemotoxicity after initial control of signs and symptoms with follow-up visits and laboratory testing on posttreatment days 5, 8, and 15. RESULTS: Twenty-one children received the F(ab')2 antivenom. Efficacy was achieved in all children receiving the product with initial control of swelling and improvement in those with hemotoxicity. No patients suffered anaphylaxis or any other serious adverse events from the F(ab')2 treatment. There were no cases of recurrent hemotoxicity recorded in the study between time of initial control and postinfusion day 15. CONCLUSIONS: In this series of children, the F(ab')2 antivenom appeared to be both safe and effective in the treatment of hemotoxicity and local tissue toxicity (swelling) from Crotalinae envenomation.

Argininosuccinate synthetase as a plasma biomarker of liver injury after acetaminophen overdose in rodents and humans.

CONTEXT: New biomarkers are needed in acetaminophen (APAP) hepatotoxicity. Plasma argininosuccinate synthetase (ASS) is a promising candidate. OBJECTIVE: Characterize ASS in APAP hepatotoxicity. METHODS: ASS was measured in plasma from rodents and humans with APAP hepatotoxicity. RESULTS: In mice, ASS increased before injury, peaked before alanine aminotransferase (ALT) and decreased rapidly. Fischer rats had a greater increase in ASS relative to ALT. Patients with abnormal liver test results had very high ASS compared to controls. ASS appeared to increase early in some patients, and declined rapidly in all. CONCLUSIONS: ASS may be a useful biomarker of acute cell death in APAP hepatotoxicity.

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.

Clinically relevant therapeutic approaches against acetaminophen hepatotoxicity and acute liver failure.

Liver injury and acute liver failure caused by an acetaminophen (APAP) overdose is a significant clinical problem in western countries. With the introduction of the mouse model of APAP hepatotoxicity in the 1970 s, fundamental mechanisms of cell death were discovered. This included the recognition that part of the APAP dose is metabolized by cytochrome P450 generating a reactive metabolite that is detoxified by glutathione. After the partial depletion of glutathione, the reactive metabolite will covalently bind to sulfhydryl groups of proteins, which is the initiating event of the toxicity. This insight led to the introduction of N-acetyl-L-cysteine, a glutathione precursor, as antidote against APAP overdose in the clinic. Despite substantial progress in our understanding of the pathomechanisms over the last decades viable new antidotes only emerged recently. This review will discuss the background, mechanisms of action, and the clinical prospects of the existing FDA-approved antidote N-acetylcysteine, of several new drug candidates under clinical development [4-methylpyrazole (fomepizole), calmangafodipir] and examples of additional therapeutic targets (Nrf2 activators) and regeneration promoting agents (thrombopoietin mimetics, adenosine A2B receptor agonists, Wharton's Jelly mesenchymal stem cells). Although there are clear limitations of certain therapeutic approaches, there is reason to be optimistic. The substantial progress in the understanding of the pathophysiology of APAP hepatotoxicity led to the consideration of several drugs for development as clinical antidotes against APAP overdose in recent years. Based on the currently available information, it is likely that this will result in additional drugs that could be used as adjunct treatment for N-acetylcysteine.

Critical care management of verapamil and diltiazem overdose with a focus on vasopressors: a 25-year experience at a single center.

STUDY OBJECTIVE: Verapamil or diltiazem overdose can cause severe morbidity and death, and there exist limited human data describing management and outcome of a large number of such patients. This article describes the management and outcome of patients with nondihydropyridine calcium-channel blocker overdose, with an emphasis on vasopressor dosing, at a single center. METHODS: This study is a retrospective chart review of patients older than 14 years and admitted to the inpatient toxicology service of a single tertiary care medical center for treatment of verapamil or diltiazem overdose from 1987 through 2012, and who had the presence of either drug confirmed by urine drug screening. Patients were identified by review of patient encounter logs. Data abstracted from medical records included demographics, laboratory results, drugs used to support blood pressure, complications, and outcomes. A second group included patients with a reported calcium channel blocker ingestion but for whom results of the urine drug testing were no longer available. In an effort to assess selection bias, this group was included to determine whether patients who were excluded from the primary group only because of unavailability of urine drug screen results had different outcomes. RESULTS: During the study period, 48 patients met inclusion criteria. The median age was 45 years, with a range of 15 to 76 years, and 52% were male patients. Verapamil accounted for 24 of 48 (50%) ingestions. Vasopressors were administered to 33 of 48 (69%) patients. Maximal vasopressor infusion doses were epinephrine 150 µg/minute, dopamine 100 µg/kg per minute, dobutamine 245 µg/kg per minute, isoproterenol 60 µg/minute, phenylephrine 250 µg/minute, and norepinephrine 100 µg/minute. The use of multiple vasopressors was common. Hyperinsulinemic euglycemia was used in 3 patients who also received multiple vasopressors. Eight probable or possible ischemic complications were noted in 5 of 48 (10%) patients. Gastrointestinal bleeding occurred in 3 of 48 (6%) patients; a brain magnetic resonance imaging in 1 patient suggested mild ischemia, without clinical evidence of infarction; 1 patient had ischemic bowel; and 3 patients developed renal failure from acute tubular necrosis, which resolved in each case. Six of the 8 ischemic complications were evident before use of vasopressor therapy. Three patients sustained inhospital cardiac arrest before admission and were successfully resuscitated. Each of these arrests occurred before instituting vasopressor infusions. One patient experienced a late cardiac arrest from primary respiratory arrest from administration of sedatives, and multiple organ system failure followed resuscitation, with death occurring during manipulation of a pulmonary artery catheter. The remaining 47 patients recovered. There were 12 patients in the group of additional poisoned patients for whom results of urine drug screening were unavailable. Four patients were treated with vasopressors, 2 experienced acute tubular necrosis that was present before vasopressor use, and all recovered. CONCLUSION: In our series of patients admitted with verapamil or diltiazem overdose, hypotension was common and managed with the use of multiple vasopressors and without hyperinsulinemic euglycemia in all but 3 cases. Despite high doses of vasopressors, ischemic complications were the exception and were usually present before use of vasopressors. Death occurred in a single patient whose death was not attributed directly to calcium-channel blocker toxicity. Vasopressor use after verapamil or diltiazem overdose was associated with good clinical outcomes without permanent sequelae.

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.

The Computational Acid-Base Chemistry of Hepatic Ketoacidosis.

Opposing evidence exists for the source of the hydrogen ions (H+) during ketoacidosis. Organic and computational chemistry using dissociation constants and alpha equations for all pertinent ionizable metabolites were used to (1) document the atomic changes in the chemical reactions of ketogenesis and ketolysis and (2) identify the sources and quantify added fractional (~) H+ exchange (~H+e). All computations were performed for pH conditions spanning from 6.0 to 7.6. Summation of the ~H+e for given pH conditions for all substrates and products of each reaction of ketogenesis and ketolysis resulted in net reaction and pathway ~H+e coefficients, where negative revealed ~H+ release and positive revealed ~H+ uptake. Results revealed that for the liver (pH = 7.0), the net ~H+e for the reactions of ketogenesis ending in each of acetoacetate (AcAc), ß-hydroxybutyrate (ß-HB), and acetone were -0.9990, 0.0026, and 0.0000, respectively. During ketogenesis, ~H+ release was only evident for HMG CoA production, which is caused by hydrolysis and not ~H+ dissociation. Nevertheless, there is a net ~H+ release during ketogenesis, though this diminishes with greater proportionality of acetone production. For reactions of ketolysis in muscle (pH = 7.1) and brain (pH = 7.2), net ~H+ coefficients for ß-HB and AcAc oxidation were -0.9649 and 0.0363 (muscle), and -0.9719 and 0.0291 (brain), respectively. The larger ~H+ release values for ß-HB oxidation result from covalent ~H+ release during the oxidation-reduction. For combined ketogenesis and ketolysis, which would be the metabolic condition in vivo, the net ~H+ coefficient depends once again on the proportionality of the final ketone body product. For ketone body production in the liver, transference to blood, and oxidation in the brain and muscle for a ratio of 0.6:0.2:0.2 for ß-HB:AcAc:acetone, the net ~H+e coefficients for liver ketogenesis, blood transfer, brain ketolysis, and net total (ketosis) equate to -0.1983, -0.0003, -0.2872, and -0.4858, respectively. The traditional theory of ketone bodies being metabolic acids causing systemic acidosis is incorrect. Summation of ketogenesis and ketolysis yield H+ coefficients that differ depending on the proportionality of ketone body production, though, in general, there is a small net H+ release during ketosis. Products formed during ketogenesis (HMG-CoA, acetoacetate, ß-hydroxybutyrate) are created as negatively charged bases, not acids, and the final ketone body, acetone, does not have pH-dependent ionizable groups. Proton release or uptake during ketogenesis and ketolysis are predominantly caused by covalent modification, not acid dissociation/association. Ketosis (ketogenesis and ketolysis) results in a net fractional H+ release. The extent of this release is dependent on the final proportionality between acetoacetate, ß-hydroxybutyrate, and acetone.

Ethylene glycol elimination kinetics and outcomes in patients managed without hemodialysis.

STUDY OBJECTIVE: Ethylene glycol remains an important toxic cause of metabolic acidosis and acute renal failure. Traditionally, inhibition of alcohol dehydrogenase along with hemodialysis has been used for treatment. Because of reported long elimination half-life of ethylene glycol during alcohol dehydrogenase inhibition, hemodialysis has been used in patients who are otherwise doing well to clear ethylene glycol. We study ethylene glycol elimination kinetics in patients treated with fomepizole, but without hemodialysis. METHODS: This was a retrospective, multicenter cohort study of patients older than 15 years who were treated at one of 3 medical centers during an 8-year period. Inclusion criteria were peak serum ethylene glycol concentration greater than 20 mg/dL, lack of renal failure on admission, treatment with fomepizole but without hemodialysis, and availability of serial serum ethylene glycol concentrations, allowing calculation of elimination half-life. The primary outcome variable was ethylene glycol elimination half-life; mortality and onset of renal failure were secondary outcome variables. RESULTS: During the study period, 85 patients were treated for ethylene glycol toxicity, of whom 40 met inclusion criteria. The mean serum ethylene glycol elimination half-life was 14.2 hours (SD=3.7 hours; 95% confidence interval 13.1 to 15.3 hours). One patient presented with metabolic acidosis on admission and developed mild transient renal insufficiency but did not require hemodialysis. No patient died. CONCLUSION: The mean elimination half-life of ethylene glycol in this population was shorter than previously reported without hemodialysis, and this select group of patients did well without enhanced elimination by hemodialysis.

Early Experience with Crotalidae Immune F(ab')2 Antivenom to Treat Arizona Rattlesnake Envenomations.

INTRODUCTION: Crotalidae immune F(ab')2 (Fab2AV) became available in the USA in 2019 for treatment of rattlesnake envenomation. In the clinical trial comparing Fab2AV to crotalidae immune polyvalent fab (FabAV), Fab2AV was associated with less late hemotoxicity. The purpose of this study was to describe outcomes following use of Fab2AV in patients with rattlesnake envenomation in Arizona. METHODS: This is an observational study of patients admitted to a medical toxicology service at two hospitals in Arizona between January 1, 2019 and December 31, 2020. Patients with rattlesnake envenomation who received Fab2AV were included. Patients who received FabAV, alone or in combination with Fab2AV, were excluded. The main outcomes of interest were antivenom dose, adverse reactions, late hemotoxicity, and hospital readmission or retreatment. RESULTS: Forty-six patients were included. The mean age was 40 years, with 15% under 12 years of age. All exhibited swelling, 20% thrombocytopenia, and 35% coagulopathy. Median time to treatment was 3 h and median total Fab2AV dose was 20 vials. Three patients had an acute reaction to Fab2AV which was non-life-threatening and resolved with antihistamines and/or steroids. In the follow-up period, one case of delayed thrombocytopenia (platelets = 108 K/mm3) and one case of recurrent thrombocytopenia (platelets = 111 K/mm3) were identified. There was no late coagulopathy. Five patients reported symptoms consistent with mild serum sickness. CONCLUSIONS: In this series of patients with rattlesnake envenomation in Arizona who were treated with Fab2AV, there were no cases of clinically significant late hemotoxicity, and no patients required late retreatment with antivenom. Acute and delayed reactions did occur in some patients but were mild and easily treated.