Hemodialysis for methanol intoxication

Methanol Induced Optic Neuropathy: Molecular Mysteries, Public Health Perspective, Clinical Insights and Treatment Strategies

Methanol-induced optic neuropathy (MION) represents a critical public health issue, particularly prevalent in lower socioeconomic populations and regions with restricted alcohol access. MION, characterized by irreversible visual impairment, arises from the toxic metabolization of methanol into formaldehyde and formic acid, leading to mitochondrial oxidative phosphorylation inhibition, oxidative stress, and subsequent neurotoxicity. The pathogenesis involves axonal and glial cell degeneration within the optic nerve and potential retinal damage. Despite advancements in therapeutic interventions, a significant proportion of affected individuals endure persistent visual sequelae. The study comprehensively investigates the pathophysiology of MION, encompassing the absorption and metabolism of methanol, subsequent systemic effects, and ocular impacts. Histopathological changes, including alterations in retinal layers and proteins, Müller cell dysfunction, and visual symptoms, are meticulously examined to provide insights into the disease mechanism. Furthermore, preventive measures and public health perspectives are discussed to highlight the importance of awareness and intervention strategies. Therapeutic approaches, such as decontamination procedures, ethanol and fomepizole administration, hemodialysis, intravenous fluids, electrolyte balance management, nutritional therapy, corticosteroid therapy, and erythropoietin (EPO) treatment, are evaluated for their efficacy in managing MION. This comprehensive review underscores the need for increased awareness, improved diagnostic strategies, and more effective treatments to mitigate the impact of MION on global health.

Awareness raising and dealing with methanol poisoning based on effective strategies

Intoxication with methanol most commonly occurs as a consequence of ingesting, inhaling, or coming into contact with formulations that include methanol as a base. Clinical manifestations of methanol poisoning include suppression of the central nervous system, gastrointestinal symptoms, and decompensated metabolic acidosis, which is associated with impaired vision and either early or late blindness within 0.5-4 h after ingestion. After ingestion, methanol concentrations in the blood that are greater than 50 mg/dl should raise some concern. Ingested methanol is typically digested by alcohol dehydrogenase (ADH), and it is subsequently redistributed to the body's water to attain a volume distribution that is about equivalent to 0.77 L/kg. Moreover, it is removed from the body as its natural, unchanged parent molecules. Due to the fact that methanol poisoning is relatively uncommon but frequently involves a large number of victims at the same time, this type of incident occupies a special position in the field of clinical toxicology. The beginning of the COVID-19 pandemic has resulted in an increase in erroneous assumptions regarding the preventative capability of methanol in comparison to viral infection. More than 1000 Iranians fell ill, and more than 300 of them passed away in March of this year after they consumed methanol in the expectation that it would protect them from a new coronavirus. The Atlanta epidemic, which involved 323 individuals and resulted in the deaths of 41, is one example of mass poisoning. Another example is the Kristiansand outbreak, which involved 70 people and resulted in the deaths of three. In 2003, the AAPCC received reports of more than one thousand pediatric exposures. Since methanol poisoning is associated with high mortality rates, it is vital that the condition be addressed seriously and managed as quickly as feasible. The objective of this review was to raise awareness about the mechanism and metabolism of methanol toxicity, the introduction of therapeutic interventions such as gastrointestinal decontamination and methanol metabolism inhibition, the correction of metabolic disturbances, and the establishment of novel diagnostic/screening nanoparticle-based strategies for methanol poisoning such as the discovery of ADH inhibitors as well as the detection of the adulteration of alcoholic drinks by nanoparticles in order to prevent methanol poisoning. In conclusion, increasing warnings and knowledge about clinical manifestations, medical interventions, and novel strategies for methanol poisoning probably results in a decrease in the death load.

Methanol poisoning outbreak in Saudi Arabia: a case series

Background

Outbreaks of methanol poisoning have been described in the medical literature in different regions around the world. Even though in Saudi Arabia a few outbreaks of methanol poisoning have occurred, they remain undocumented. Herein, we describe several cases of methanol poisoning in Saudi Arabia with the goal of increasing awareness about the dangers of methanol poisoning among healthcare staff.

Case presentation

Nine middle-aged Saudi patients (five men aged 24, 26, 27, 36, and 49 years and four females aged 19, 20, 24, and 25 years) were admitted to our emergency department after alcohol consumption. All patients presented with severe metabolic acidosis and some visual impairment. Treatment was initiated based on the clinical suspicion of methanol intoxication because of laboratory test limitations and time constraints. Patients showed improvement and favorable hospital outcomes after aggressive empirical treatment.

Conclusions

Many social and cultural factors influence the lack of reporting of methanol poisoning cases in Saudi Arabia. We believe it is important to document these outbreaks to increase the knowledge among healthcare providers and promote public health awareness. A high index of suspicion and the development of local public health networks to monitor, survey, follow-up, and facilitate data exchange can help healthcare providers recognize and aggressively treat affected individuals. Early empiric and aggressive management can greatly decrease morbidity and mortality despite challenges and limited resources.

Methanol Poisoning Leading to Brain Death: A Case Report

Introduction

The COVID-19 pandemic has put increased stress on medical systems, infrastructure, and the public in expected and unexpected ways. This case report summarises an unexpected case of methanol poisoning from hand sanitiser ingestion due to changes in industry regulations, increased demand for cleaning products and severe psychosocial stressors brought on by the pandemic. Severe methanol toxicity results in profound metabolic disturbances, damage to the retina and optic nerves, and potentially death.

Case Presentation

The patient was a 26-year-old male with alcohol use disorder who presented with one day of nausea, vomiting, and abdominal pain after consuming hand sanitiser. Within a few hours, the patient had suffered multiple seizures, cardiac arrests and required admission to the ICU for emergent management of methanol poisoning. EEG and brain perfusion imaging were performed to confirm brain death, given concerns about the cranial nerve exam after methanol poisoning.

Conclusions

While rare, methanol toxicity remains a potentially fatal poisoning in the United States and worldwide. When healthcare and public resources are strained, healthcare professionals must consider particularly abnormal presentations. In patients suspected of brain death from methanol toxicity, cranial nerve examination may be unreliable. Therefore, additional testing is necessary to confirm brain death.

Reducing complexity in acid-base diagnosis - how far should we go?

PURPOSE

To place in context the potential value of isolated plasma strong ion difference (SID) calculations and strong ion gap (SIG) calculations versus suggested cut-down versions such as SIDa adj and the BICgap respectively.

METHODS

Stewart's physical chemical approach is seen as a mathematical model of isolated plasma not displacing traditional Copenhagen and Boston approaches. Scanning tools for unmeasured ions based on the Principle of Electrical Neutrality such as the SIG and suggested cut-down versions such as the albumin adjusted anion gap and the BICgap are evaluated for accuracy and clinical usefulness.

RESULTS

Plasma SID and abbreviations such as SIDa adj are not independent variables in vivo since they vary with PCO due to Gibbs Donnan ion traffic. They can also exhibit positive and negative bias, and SID values must be partnered with non-volatile weak acid concentrations when evaluating metabolic acid-base status. The BICgap calculation is a cut down version of the SIG fixed for pH 7.4. It includes phosphate but is otherwise similar in form to the albumin corrected anion gap, with similar sensitivity and specificity characteristics.

CONCLUSIONS

Clinicians are unlikely to find SID calculations or cut-down versions such as the SIDa adj clinically useful. The albumin corrected anion gap is in current use and easily determined by mental arithmetic from point of care anion gap printouts plus recent plasma albumin measurements. Any slight advantage of the BICgap would be offset by the complexity of its calculation.

Antidotes for poisoning by alcohols that form toxic metabolites

The alcohols, methanol, ethylene glycol and diethylene glycol, have many features in common, the most important of which is the fact that the compounds themselves are relatively non-toxic but are metabolized, initially by alcohol dehydrogenase, to various toxic intermediates. These compounds are readily available worldwide in commercial products as well as in homemade alcoholic beverages, both of which lead to most of the poisoning cases, from either unintentional or intentional ingestion. Although relatively infrequent in overall occurrence, poisonings by metabolically-toxic alcohols do unfortunately occur in outbreaks and can result in severe morbidity and mortality. These poisonings have traditionally been treated with ethanol since it competes for the active site of alcohol dehydrogenase and decreases the formation of toxic metabolites. Although ethanol can be effective in these poisonings, there are substantial practical problems with its use and so fomepizole, a potent competitive inhibitor of alcohol dehydrogenase, was developed for a hopefully better treatment for metabolically-toxic alcohol poisonings. Fomepizole has few side effects and is easy to use in practice and it may obviate the need for haemodialysis in some, but not all, patients. Hence, fomepizole has largely replaced ethanol as the toxic alcohol antidote in many countries. Nevertheless, ethanol remains an important alternative because access to fomepizole can be limited, the cost may appear excessive, or the physician may prefer ethanol due to experience.

Prediction and validation of hemodialysis duration in acute methanol poisoning

The duration of hemodialysis (HD) in methanol poisoning (MP) is dependent on the methanol concentration, the operational parameters used during HD, and the presence and severity of metabolic acidosis. However, methanol assays are not easily available, potentially leading to undue extension or premature termination of treatment. Here we provide a prediction model for the duration of high-efficiency HD in MP. In a retrospective cohort study, we identified 71 episodes of MP in 55 individuals who were treated with alcohol dehydrogenase inhibition and HD. Four patients had residual visual abnormality at discharge and only one patient died. In 46 unique episodes of MP with high-efficiency HD the mean methanol elimination half-life (T_1/2) during HD was 108 min in women, significantly different from the 129 min in men. In a training set of 28 patients with MP, using the 90th percentile of gender-specific elimination T_1/2 (147 min in men and 141 min in women) and a target methanol concentration of 4 mmol/l allowed all cases to reach a safe methanol of under 6 mmol/l. The prediction model was confirmed in a validation set of 18 patients with MP. High-efficiency HD time in hours can be estimated using 3.390 × (Ln (MCi/4)) for women and 3.534 × (Ln (MCi/4)) for men, where MCi is the initial methanol concentration in mmol/l, provided that metabolic acidosis is corrected.

Methanol and ethylene glycol poisoning: a case study and review of current literature

Poisoning is an uncommon but potentially fatal outcome of toxic alcohol ingestion. The toxic alcohols methanol, ethylene glycol and isopropyl alcohol are commonly found in household and commercial products. Because the toxic effects are caused by the metabolites of methanol and ethylene glycol rather than the agents themselves, there is often a substantial delay between ingestion and onset of clinical toxicity. Anion and osmolar gaps are often used for the diagnosis and exclusion of these sometimes subtle overdoses. The pitfalls of using these tests to rule out alcohol ingestion are reviewed. Ethanol infusion is the traditional therapy for such overdoses. In addition to the pathophysiology and clinical findings in poisoning, recent evidence for the use of fomepizole and adjuvant therapies is reviewed.

Recommendations for the role of extracorporeal treatments in the management of acute methanol poisoning: a systematic review and consensus statement

OBJECTIVE

Methanol poisoning can induce death and disability. Treatment includes the administration of antidotes (ethanol or fomepizole and folic/folinic acid) and consideration of extracorporeal treatment for correction of acidemia and/or enhanced elimination. The Extracorporeal Treatments in Poisoning workgroup aimed to develop evidence-based consensus recommendations for extracorporeal treatment in methanol poisoning.

DESIGN AND METHODS

Utilizing predetermined methods, we conducted a systematic review of the literature. Two hundred seventy-two relevant publications were identified but publication and selection biases were noted. Data on clinical outcomes and dialyzability were collated and a two-round modified Delphi process was used to reach a consensus.

RESULTS

Recommended indications for extracorporeal treatment: Severe methanol poisoning including any of the following being attributed to methanol: coma, seizures, new vision deficits, metabolic acidosis with blood pH ≤ 7.15, persistent metabolic acidosis despite adequate supportive measures and antidotes, serum anion gap higher than 24 mmol/L; or, serum methanol concentration 1) greater than 700 mg/L (21.8 mmol/L) in the context of fomepizole therapy, 2) greater than 600 mg/L or 18.7 mmol/L in the context of ethanol treatment, 3) greater than 500 mg/L or 15.6 mmol/L in the absence of an alcohol dehydrogenase blocker; in the absence of a methanol concentration, the osmolal/osmolar gap may be informative; or, in the context of impaired kidney function. Intermittent hemodialysis is the modality of choice and continuous modalities are acceptable alternatives. Extracorporeal treatment can be terminated when the methanol concentration is <200 mg/L or 6.2 mmol/L and a clinical improvement is observed. Extracorporeal Treatments in Poisoning inhibitors and folic/folinic acid should be continued during extracorporeal treatment. General considerations: Antidotes and extracorporeal treatment should be initiated urgently in the context of severe poisoning. The duration of extracorporeal treatment extracorporeal treatment depends on the type of extracorporeal treatment used and the methanol exposure. Indications for extracorporeal treatment are based on risk factors for poor outcomes. The relative importance of individual indications for the triaging of patients for extracorporeal treatment, in the context of an epidemic when need exceeds resources, is unknown. In the absence of severe poisoning but if the methanol concentration is elevated and there is adequate alcohol dehydrogenase blockade, extracorporeal treatment is not immediately required. Systemic anticoagulation should be avoided during extracorporeal treatment because it may increase the development or severity of intracerebral hemorrhage.

CONCLUSION

Extracorporeal treatment has a valuable role in the treatment of patients with methanol poisoning. A range of clinical indications for extracorporeal treatment is provided and duration of therapy can be guided through the careful monitoring of biomarkers of exposure and toxicity. In the absence of severe poisoning, the decision to use extracorporeal treatment is determined by balancing the cost and complications of extracorporeal treatment to that of fomepizole or ethanol. Given regional differences in cost and availability of fomepizole and extracorporeal treatment, these decisions must be made at a local level.

A systematic review of ethanol and fomepizole use in toxic alcohol ingestions

Objectives. The optimal antidote for the treatment of ethylene glycol or methanol intoxication is not known. The objective of this systematic review is to describe all available data on the use of ethanol and fomepizole for methanol and ethylene glycol intoxication. Data Source. A systematic search of MEDLINE and EMBASE was conducted. Study Selection. Published studies involving the use of ethanol or fomepizole, or both, in adults who presented within 72 hours of toxic alcohol ingestion were included. Our search yielded a total of 145 studies for our analysis. There were no randomized controlled trials, and no head-to-head trials. Data Extraction. Variables were evaluated for all publications by one independent author using a standardized data collection form. Data Synthesis. 897 patients with toxic alcohol ingestion were identified. 720 (80.3%) were treated with ethanol (505 Me, 215 EG), 146 (16.3%) with fomepizole (81 Me, 65 EG), and 33 (3.7%) with both antidotes (18 Me, 15 EG). Mortality in patients treated with ethanol was 21.8% for Me and 18.1% for EG. In those administered fomepizole, mortality was 17.1% for Me and 4.1% for EG. Adverse events were uncommon. Conclusion. The data supporting the use of one antidote is inconclusive. Further investigation is warranted.

Is salt, vitamin, or endocrinopathy causing this encephalopathy? A review of endocrine and metabolic causes of altered level of consciousness

Altered level of consciousness describes the reason for 3% of critical emergency department (ED) visits. Approximately 85% will be found to have a metabolic or systemic cause. Early laboratory studies such as a bedside glucose test, serum electrolytes, or a urine dipstick test often direct the ED provider toward endocrine or metabolic causes. This article examines common endocrine and metabolic causes of altered mentation in the ED via sections dedicated to endocrine-, electrolyte-, metabolic acidosis-, and metabolism-related causes.

Methanol induces a discrete transcriptional dysregulation that leads to cytokine overproduction in activated lymphocytes

Methanol is an important cause of acute alcohol intoxication; it is ubiquitously present at home and in the workplace. Although the existing literature provides a reasonable insight into the immunological impact of ethanol and to a much lesser extent of isopropanol, much less data are available on methanol. We hypothesized on structural grounds that methanol would share the immunosuppressive properties of the two other short-chain alcohols. We report here that methanol increases the proliferative capacity of human T lymphocytes and synergizes with the activating stimuli to augment cytokine production. The cytokine upregulation was observed in vitro at methanol concentrations as low as 0.08% (25mM) as measured by interleukin-2, interferon-γ, and tumor necrosis factor-α release in T cells. Methanol did not affect the antigen receptor-mediated early signaling but promoted a selective and differential activation of the nuclear factor of activated T cells family of transcription factors. These results were further substantiated in a mouse model of acute methanol intoxication in which there was an augmented release of proinflammatory cytokines in the serum in response to the staphylococcal enterotoxin B. Our results suggest that methanol has a discrete immunological footprint of broad significance given the exposure of the general population to this multipurpose solvent.

Formate concentrations in plasma from patients poisoned with methanol

Formate and methanol were quantified in blood samples from 11 untreated methanol-poisoned subjects. The range for whole blood methanol concentrations was 0-137 mmol/l and for plasma formate concentrations 0.4-17.1 mmol/l. Simultaneously determined acid-base status and serum electrolyte concentrations allowed assessment of the relative importance of formate accumulation for the acidosis. The plasma formate concentration was highly correlated to both the calculated anion gap (r = 0.833), the bicarbonate concentration (r = 0.852) and the negative base excess (r = 0.865). The accumulation of formate fully accounted for the increase in the anion gap and the fall in plasma bicarbonate, whereas the negative base excess values were about 22% higher than the plasma formate concentration. We conclude that formate accumulation is the main or only reason for acidosis in the early, uncomplicated stages of methanol poisoning. Lactate may appear at more advanced stages.

Studies on methanol poisoning

Eleven patients concomitantly poisoned with methanol are described. Their whole blood methanol concentration ranged from 137.2 mmol/l (4.39 g/l) to 7.4 mmol/l (0.24 g/l). The clinical course in most patients was mild, which was attributed to the concomitant and subsequent ethanol ingestion and rapid transport to dialysing units. One patient suffered permanent visual impairment of one eye while the others recovered completely. Symptoms of poisoning were most clearly correlated to the degree of metabolic acidosis. All patients were hemodialysed. In two patients the average dialysator clearance of methanol was 157 and 176 ml/min at blood flows of 200 and 215 ml/min, respectively. In the same patients the average dialysator clearance of ethanol was 149 and 164 ml/min. Assuming a volume of distribution of methanol of 0.7 l/kg, the dialysator represented about 89 and 95%, respectively, of the total body clearance of methanol during ethanol therapy. Ethanol in concentrations even lower than usually recommended may be useful as the only treatment of patients with blood methanol concentrations up to 15 mmol/l (0.5 g/l), provided there is no acidosis or visual impairment.

Keeping a high index of suspicion: lessons learned in the management of methanol ingestion

Methanol ingestion is an uncommon form of poisoning that can cause severe metabolic disturbances and potentially fatal and often irreversible organ/tissue damage. The diagnosis is sometimes elusive and requires a high index of suspicion. Because extent and irreversibility of the damage caused by formic acid is time sensitive, methanol poisoning should be recognised promptly so that it can be treated. Metabolic acidosis associated with an increased anion gap and osmolar gap is an important laboratory finding but is not always present. A case of severe methanol poisoning is presented that demonstrates the unique challenges in the diagnosis and management, and the lack of readiness of the health care system for such cases. We highlight some of the diagnostic difficulties associated with treating a patient with a reduced level of consciousness and severe metabolic acidosis. We also review the pitfalls of using laboratory tests to rule out alcohol ingestion and discuss the definitive management of methanol poisoning.

Expert opinion: fomepizole may ameliorate the need for hemodialysis in methanol poisoning

Fomepizole is now the antidote of choice in methanol poisoning. The use of fomepizole may also change the indications for hemodialysis in these patients. We have addressed this change in a review of articles on methanol poisonings. Review of the literature (through PubMed) combined with our own experiences from two recent methanol outbreaks in Estonia and Norway. The efficiency of dialysis during fomepizole treatment was reported in only a few reports. One recent study challenged the old indications, suggesting a new approach with delayed or even no hemodialysis. Methanol-poisoned patients on fomepizole treatment may be separated into two categories: 1) The critically ill patient, with severe metabolic acidosis (base deficit >15 mM) and/or visual disturbances should be given buffer, fomepizole and immediate hemodialysis: dialysis removes the toxic anion formate, and assists in correcting the metabolic acidosis, thereby also reducing formate toxicity. The removal of methanol per se is not important in this setting because fomepizole prevents further production of formic acid. 2) The stable patient, with less metabolic acidosis and no visual disturbances, should be given buffer and fomepizole. This treatment allows for the possibility to delay, or even drop, dialysis in this setting, because patients will not develop more clinical features from methanol poisoning when fomepizole and bicarbonate is given in adequate doses. Indications and triage for hemodialysis in methanol poisonings should be modified. Delayed hemodialysis or even no hemodialysis may be an option in selected cases.

Methanol poisoning: acute MR and CT findings in nine patients

INTRODUCTION

Methanol poisoning is an uncommon but potent central nervous system toxin. We describe here the CT and MR findings in nine patients following an outbreak of methanol poisoning.

METHODS

Five patients with a typical clinical presentation and elevated anion and osmolar gaps underwent conventional brain MRI with a 1.5-T Gyroscan Interna scanner. In addition nonenhanced CT was performed in another three patients with more severe toxicity.

RESULTS

Bilateral hemorrhagic or nonhemorrhagic necrosis of the putamina, diffuse white matter necrosis, and subarachnoid hemorrhage were among the radiological findings. Various patterns of enhancement of basal ganglial lesions were found including no enhancement, strong enhancement and rim enhancement.

CONCLUSION

A good knowledge of the radiological findings in methanol poisoning seems to be necessary for radiologists. The present study is unique in that it enables us to include in a single report most of the radiological findings that have been reported previously.

Differential Diagnosis of Metabolic Acidosis

Metabolic acidosis is defined as an acidemia created by one of three mechanisms: increased production of acids, decreased excretion of acids, or loss of alkali. This article addresses the identification and correct diagnosis of metabolic acidosis by reviewing important historical factors, pathophysiological principles, clinical presentation,and laboratory findings accompanying common high and normal anion gap metabolic acidoses in emergency department patients.

Deadly pediatric poisons: nine common agents that kill at low doses

More than 97% of pediatric exposures reported to the AAPCC in 2001 had either no effect or mild clinical effects. Despite the large number of exposures, only 26 of the 1074 reported fatalities occurred in children younger than age 6. These findings reflect the fact that, in contrast to adolescent or adult ingestions, pediatric ingestions are unintentional events secondary to development of exploration behaviors and the tendency to place objects in the mouth. Ingested substances typically are nontoxic or ingested in such small quantities that toxicity would not be expected. As a result, it commonly is believed that ingestion of one or two tablets by a toddler is a benign act and not expected to produce any consequential toxicity. Select agents have the potential to produce profound toxicity and death, however, despite the ingestion of only one or two tablets or sips. Although proven antidotes are a valuable resource, their value is diminished if risk after ingestion is not adequately appreciated and assessed. Future research into low-dose, high-risk exposures should be directed toward further clarification of risk, improvements in overall management strategies,and, perhaps most importantly, prevention of toxic exposure through parental education and appropriate safety legislation.

Methanol intoxication: differential diagnosis from anion gap-increased acidosis

We report a case of methanol intoxication, which was not distinguished from ethylene glycol intoxication during treatment. A 65-year-old man was transferred to our emergency department because of drowsiness and remarkable metabolic acidosis. He was intubated because his consciousness disturbance worsened. The diagnosis was suspected as methanol or ethylene glycol intoxication in addition to ethanol intoxication. Administration of ethanol and hemodialysis were chosen for his essential treatments. When he was extubated, he complained about visual loss. His brain computed tomography scans revealed putaminal lesions, which are rarely reported in methanol intoxication. Diagnosis of methanol intoxication was confirmed by the serum high methanol levels.

Rethinking the Toxic Methanol Level

INTRODUCTION

Treatment thresholds for methanol poisoning are based on case reports and published opinion. Most guidelines recommend treatment for a methanol level > or = 20 mg/dL in a nonacidotic patient. No supportive data have been offered nor has the time of the exposure been addressed. For instance, no distinction has been drawn between a methanol level drawn 1 hr vs. 24 hr from ingestion. We analyzed all published cases of methanol poisoning to determine the applicability of the 20 mg/dL threshold in a nonacidotic patient, specifically those arriving early for care (within 6 hr) with a peak or near-peak blood methanol concentration.

METHODS

Using predefined search criteria, a systematic review of the world literature was performed using MEDLINE and EMBASE. In addition, each article's references were hand searched for pre-1966 articles, as were fatality abstracts from all U.S. poison centers. Human cases were included if they reported a known time of a single methanol exposure, acid-base data, blood methanol, and blood ethanol (if not acidotic).

RESULTS

Dating to 1879, 372 articles in 18 languages were abstracted using a standard format; 329 articles (2433 patients) involved methanol poisoning, and 70 articles (173 patients) met inclusion criteria. Only 22 of these patients presented for care within 6hr of ingestion with an early methanol level. All but 1 patient was treated with an inhibitor of alcohol dehydrogenase (ADH). A clear acidosis developed only with a methanol level > or = 126 mg/dL. The patient that did not receive an ADH inhibitor was an infant with an elevated early methanol level (46 mg/dL) that was given folate alone and never became acidotic. Intra and inter-rater reliability were 0.95.

CONCLUSIONS

Nearly all reports of methanol poisoning involve acidotic patients far removed from ingestion. The small amount of data regarding patients arriving early show that 126 mg/dL is the lowest early blood methanol level ever clearly associated with acidosis. Contrary to conventional teaching, there are case reports of acidosis after only a few hours of ingestion. The data are insufficient to apply 20 mg/dL as a treatment threshold in a nonacidotic patient arriving early for care. Prospective studies are necessary to determine if such patients may be managed without antidotal therapy or dialysis.

Methanol ingestion: prevention of toxic sequelae after massive ingestion

Methanol ingestion, a rare but potentially fatal poisoning, is often difficult to diagnose in the emergency department (ED) and historically has been difficult to treat. In this article, we report a methanol ingestion with a blood concentration of 692 mg/dL, which was treated with 4-methylpyrazole (Fomepizole) and dialysis, without sequelae. To our knowledge, such a massive ingestion has never been treated with this modality without development of long-term disability. Another unusual feature of this case is the significantly elevated serum osmolal gap at presentation without elevation in anion gap, demonstrating the effects of co-ingestion of ethanol. Additionally, there was a marked disparity between the patient's breath alcohol analyzer level and the blood ethanol concentration, illustrating the inability of the breath alcohol analyzer to differentiate between volatile alcohols. Treatment of the methanol-poisoned patient with Fomepizole is discussed.

Unexplained drowsiness and progressive visual loss: Methanol poisoning diagnosed at autopsy

A patient was admitted to the emergency department with a reduced level of consciousness and deteriorating vision. Her pupils became fixed and dilated and she developed a third nerve palsy with extensor posturing of her limbs. Biochemistry profile showed an increased serum osmolar gap with a raised anion gap metabolic acidosis. Supportive treatment was instituted, but she made no recovery and brainstem death was later confirmed. Post mortem examination and toxicology screen confirmed the cause of death as methanol poisoning leading to cerebral oedema and transtentorial herniation. We highlight some of the diagnostic difficulties associated with treating a patient with a reduced level of consciousness. The clinical and biochemical findings that are critical in establishing a diagnosis of methanol intoxication are discussed. The definitive management of methanol poisoning is reviewed.

Drug and chemical metabolites in clinical toxicology investigations: the importance of ethylene glycol, methanol and cannabinoid metabolite analyses

Metabolic pathways in humans have been elucidated for most therapeutic drugs, drugs of abuse, and various chemical/solvents. In most drug overdose cases and chemical exposures, laboratory analysis is directed toward identification and quantitation of the unchanged drug or chemical in a biologic fluid such as serum or whole blood. Specifically, most clinical laboratories routinely screen and quantitate unchanged methanol and/or ethylene glycol in suspected poisonings without toxic metabolite analysis. Martin-Amat established in 1978 that methanol associated toxicity to the optic nerve in human poisonings was due to the toxic metabolite formic acid found in methanol poisonings and not due to the direct action by unchanged methanol. Jacobsen reported in 1981 that ethylene glycol central nervous system and renal toxicity were primarily due to one acidic metabolite (glycolic acid) and not due to unchanged ethylene glycol. The first objective of this review is to describe clinical experience with formic acid and glycolic acid analysis in methanol and ethylene glycol human poisonings. Drug metabolite analysis also provides useful information in the assessment and monitoring of drug use in psychiatry and substance abusing populations. Drug analysis in substance abuse monitoring is focused on urine analysis of one or more major metabolites, and less frequently on the unchanged drug(s). Serial monitoring of the major urinary cannabinoid metabolite (delta(9)-THC-COOH) to creatinine ratios in paired urine specimens (collected at least 24 h apart) could differentiate new marijuana or hashish use from residual cannabinoid metabolite excretion in urine after drug use according to Huestis. The second objective is to demonstrate that creatinine corrected urine specimens positive for cannabinoids may help differentiate new marijuana use from the excretion of residual delta(9) -THC-COOH in chronic users of marijuana or hashish. Analysis of toxic chemical metabolites are helpful in the assessment and treatment of chemical poisoning whereas serial monitoring of urinary cannabinoid metabolites are predictive of illicit drug use in the substance abusing population.

Acute methanol ingestion

Methanol poisoning is an insidious event that can culminate in severe metabolic disturbances, permanent neurologic dysfunction, blindness, and death. Although numerous adult cases have been extensively reviewed, there is a paucity of reports about pediatric ingestions. We present a case of acute methanol intoxication in a 6-year-old male patient who presented with headache, nausea, altered mental status, and drowsiness. His blood methanol level was 350 mg/dL (109.4 mmol/L), despite the absence of any history or identifiable source of methanol. Treatment with ethanol, alkalinization, and hemodialysis resulted in full recovery without residua. Unusual facets of this case are the child's relatively older age, the extremely high methanol blood level, and, most remarkably, the complete lack of visual disturbances on routine ophthalmologic evaluation.

American Academy of Clinical Toxicology practice guidelines on the treatment of methanol poisoning

EPIDEMIOLOGY

Almost all cases of acute methanol toxicity result from ingestion, though rarely cases of poisoning have followed inhalation or dermal absorption. The absorption of methanol following oral administration is rapid and peak methanol concentrations occur within 30-60minutes.

MECHANISMS OF TOXICITY

Methanol has a relatively low toxicity and metabolism is responsible for the transformation of methanol to its toxic metabolites. Methanol is oxidized by alcohol dehydrogenase to formaldehyde. The oxidation of formaldehyde to formic acid is facilitated by formaldehyde dehydrogenase. Formic acid is converted by 10-formyl tetrahydrofolate synthetase to carbon dioxide and water. In cases of methanol poisoning, formic acid accumulates and there is a direct correlation between the formic acid concentration and increased morbidity and mortality. The acidosis observed in methanol poisoning appears to be caused directly or indirectly by formic acid production. Formic acid has also been shown to inhibit cytochrome oxidase and is the prime cause of ocular toxicity, though acidosis can increase toxicity further by enabling greater diffusion of formic acid into cells.

FEATURES

Methanol poisoning typically induces nausea, vomiting, abdominal pain, and mild central nervous system depression. There is then a latent period lasting approximately 12-24 hours, depending, in part, on the methanol dose ingested, following which an uncompensated metabolic acidosis develops and visualfunction becomes impaired, ranging from blurred vision and altered visual fields to complete blindness.

MANAGEMENT

For the patient presenting with ophthalmologic abnormalities or significant acidosis, the acidosis should be corrected with intravenous sodium bicarbonate, the further generation of toxic metabolite should be blocked by the administration of fomepizole or ethanol and formic acid metabolism should be enhanced by the administration of intravenous folinic acid. Hemodialysis may also be required to correct severe metabolic abnormalities and to enhance methanol and formate elimination. For the methanol poisoned patient without evidence of clinical toxicity, the first priority is to inhibit methanol metabolism with intravenous ethanol orfomepizole. Although there are no clinical outcome data confirming the superiority of either of these antidotes over the other, there are significant disadvantages associated with ethanol. These include complex dosing, difficulties with maintaining therapeutic concentrations, the need for more comprehensive clinical and laboratory monitoring, and more adverse effects. Thus fomepizole is very attractive, however, it has a relatively high acquisition cost.

CONCLUSION

The management of methanol poisoning includes standard supportive care, the correction of metabolic acidosis, the administration of folinic acid, the provision of an antidote to inhibit the metabolism of methanol to formate, and selective hemodialysis to correct severe metabolic abnormalities and to enhance methanol and formate elimination. Although both ethanol and fomepizole are effective, fomepizole is the preferred antidote for methanol poisoning.

Short- and long-term success of organs transplanted from acute methanol poisoned donors

BACKGROUND

The shortage of organs for transplantation has made it necessary to extend the criteria for the selection of donors, among others including those patients who die because of toxic substances such as methanol. Methanol is a toxic which is distributed through all the systems and viscera of the organism and tends to cause a severe metabolic acidosis. It can specifically cause serious or irreversible lesions of the central nervous system (CNS) and retina, and ultimately brain death. We present our experience with 16 organ donors who died as a result of acute methanol intoxication in 10 Spanish hospitals over the last 14 yr.

PATIENTS AND METHODS

Between October 1985 and July 1999, 16 organ donors with brain death caused by acute methanol intoxication, 13 females and three males with a mean age of 38.4 +/- 7.6 yr (interval: 26-55 yr), allowed 37 elective transplants to be performed: 29 kidneys, four hearts and four livers for 37 recipients, and one urgent liver transplantation to a recipient with fulminant hepatitis.

RESULTS

The immediate postoperative period was favourable for the 38 graft recipients. None of the graft recipients presented gap anion metabolic acidosis in the immediate postoperative period, nor symptomatology or lesions of the CNS characteristic of methanol intoxication. Two patients died during the first month post-transplantation, a liver recipient and a heart recipient, at 16 and 24 days, respectively, because of acute rejection of the graft. At 1 month after transplantation 35 of the 36 recipients had been discharged from hospital with normal-functioning grafts. The last of the recipients, a kidney recipient, was discharged at 6 wk with normal-functioning graft. Actuarial survival of the graft and patient of kidney recipients at 1, 3 and 5 yr was 92.6, 77.8, and 75%, and 100, 88.9 and 83.3%, respectively; with average serum creatinines of 139.9 +/- 42.9, 150.4 +/- 42.8, and 164.4 +/- 82.5 micromol/L, respectively. At 1 yr after transplantation the three heart recipients and two of the three liver recipients had normal-functioning graft.

CONCLUSIONS

Methanol intoxication is not transferred from the donor to the recipient. The survival of the graft and kidney, heart and liver recipients using organs from donors who die because of methanol does not differ in the short- and long-term from the transplants performed with organs from donors who die from other causes.

Extracorporeal therapies for acute intoxications

Intoxications frequently perturb acid-base and electrolyte status, intravascular volume, and renal function. In selected cases, extracorporeal techniques effectively restore homeostasis and augment intoxicant removal. The use of 4-methylpyrazole, an inhibitor of alcohol dehydrogenase, is a new and effective treatment for patients exposed to toxic alcohols. In this section, practical approaches to commonly encountered intoxicants and the use of extracorporeal techniques are critically reviewed.

Pediatric toxicologic concerns

Pediatric poisonings account for significant morbidity in the United States each year. Clinicians must keep current with advances in toxicology to be familiar with the latest recommended treatment regimens and antidotes. They also must be familiar in identifying toxidromes and important physical examination findings. Having these skills can enable the clinician to determine who is at risk for significant morbidity or mortality and to provide the appropriate medical care.

Treatment of methanol and isopropanol poisoning with intravenous fomepizole

CASE REPORT

We report a case of mixed methanol and isopropanol poisoning in a patient who refused dialysis but agreed to treatment with intravenous fomepizole. The patient was asymptomatic on arrival, with initial blood methanol and isopropanol concentrations of 146 mg/dL and 39 mg/dL, respectively. Blood ethanol was undetectable. The patient was treated with fomepizole twice daily intravenously until blood methanol was undetectable. No side effects of therapy, other than transient eosinophilia, were observed. The evolution was uneventful and no metabolites of either alcohol were detected at any time during the hospitalization. The decay of plasma methanol and isopropanol under fomepizole treatment were well described by first-order kinetics. The plasma elimination half-lives of methanol and isopropanol were 47.6 hours and 27.7 hours, respectively. Fomepizole appears to have been effective in blocking the toxic metabolism of both methanol and isopropanol and was associated with a favorable outcome.

Artifactual elevation of measured plasma L-lactate concentration in the presence of glycolate

OBJECTIVES

To determine whether glycolate, a toxic metabolite of ethylene glycol that is chemically similar to lactate, can cause artifactual elevation of measured L-lactate concentrations.

DESIGN

Prospective in vitro study.

SETTING

Intensive care unit and chemical pathology laboratory in a university-affiliated hospital.

SUBJECTS

Heparinized normal human blood and four commercially available L-lactate analyzers.

INTERVENTIONS

Four analyzers were tested, three of which used L-lactate oxidase and one of which used L-lactate dehydrogenase. Glycolic acid (10 g/L) in saline was added to blood in a series of aliquots. Corresponding plasma L-lactate concentrations and blood pH, PCO2, and hemoglobin concentrations were measured and base excess was calculated initially and after the addition of each aliquot. One of the two L-lactate oxidase-type analyzers, which was found to show interference, was then used to measure plasma L-lactate and glucose concentrations in blood with glycolic, oxalic, or formic acid added until the base excess was reduced by >15 mmol/L.

MEASUREMENTS AND MAIN RESULTS

Artifactual plasma L-lactate elevations were observed in two analyzers, both of the L-lactate oxidase type. Small concentrations of glycolic acid (causing reductions of base excess of 2-5 mmol/L) were accompanied by artifactual plasma L-lactate elevations of 4-8 mmol/L. Artifactual plasma L-lactate elevations increased with further glycolic acid-induced reductions in base excess. Oxalate and formate did not interfere with plasma L-lactate measurements, and measured plasma glucose concentrations were unaffected by all three acids.

CONCLUSIONS

Glycolate causes large artifactual elevations in plasma L-lactate measurements by two analyzers in common use, with potential for misdiagnosis of lactic acidosis in ethylene glycol poisoning. A possible cause of the interference is incomplete specificity of the analytical reagent L-lactate oxidase, allowing cross-reaction with glycolate.

A comparison of the bioavailabilities of oral and intravenous ethanol in healthy male volunteers

OBJECTIVES

Ethanol (EtOH), the antidote for methanol and ethylene glycol, is administered by the oral (PO) and intravenous (IV) routes. Serum concentrations (SCs) of 100 mg/dL or more are targeted for clinical effect. This study was completed to validate the assumption that there are minimal differences in SC achieved between these two routes.

METHODS

Twenty healthy male volunteers were randomized to receive either PO or IV EtOH. Subjects abstained from EtOH for 48 hours before each phase. After a seven-day washout period, the subjects crossed over to the other group. Inclusion criteria were no history of medical problems, age between 21 and 40 years, and actual body weight within 10% of ideal weight. Baseline EtOH SCs were obtained before participation in each phase. Two hours after a standard breakfast, the subjects received 700 mg/kg of PO or IV EtOH. PO EtOH was administered as a 20% solution in juice over 10 minutes. IV EtOH, controlled by an infusion pump, was administered as a 10% solution over 30 minutes. Blood was drawn for EtOH SCs at 45, 75, 105, 135, 165, 225, 285, and 345 minutes after start of the dose.

RESULTS

All initial EtOH SCs were 0. EtOH SCs were higher after IV administration. Mean peak SC was 103.6 mg/dL after IV administration and 71.3 mg/dL after PO administration (p<0.0001). Mean time to peak was 46.5 minutes after IV administration and 103.5 minutes after PO administration (p<0.0001). Total area under the curve was 17,440 min-mg/dL after IV administration and 13,875 min-mg/dL after PO administration (p<0.003). The order of treatments did not affect results (p>0.1).

CONCLUSION

Significant differences exist between the SCs of EtOH as well as the times to peak SC after PO and IV administrations.

Acute blindness and putaminal necrosis in methanol intoxication

PURPOSE

To review the neuro-ophthalmological and radiological findings of acute methyl alcohol intoxication.

METHOD

8 acute methyl alcohol intoxication cases were evaluated.

RESULTS

All patients were male and their ages varied between 21 and 55. At the initial examination, 6 to 12 days after methanol intake, visual acuity ranged from no light perception to counting fingers at 2 meters with no color perception. Bilateral dense central scotomas were detected in patients whose vision was slightly preserved. Pupillary light reactions were either absent or sluggish. In 4 cases, edema of the optic disk and the peripapillary nerve fiber layer was observed. Three months later, optic atrophy had developed. Five patients underwent magnetic resonance imaging. Bilateral putaminal hyperintense lesions on T2 weighted images were observed in 3 cases. Two patients died and autopsy permission could not be obtained. Follow-up examination 12 months later revealed optic atrophy in the other six cases, with no improvement in vision.

CONCLUSION

Methanol intoxication is detrimental to health, possibly resulting in blindness and occasionally death. In association with ocular signs and the other systemic and laboratory features, the ophthalmologist should be alert to the diagnosis of methanol intoxication in which visual loss may be the only symptom.

Laboratory testing in ethanol, methanol, ethylene glycol, and isopropanol toxicities

Toxicity from ethanol, methanol, ethylene glycol, and isopropyl alcohol varies widely, and appropriate use of the available laboratory tests can aid in timely and specific treatment. Available testing includes direct measurements of serum levels of these alcohols; however, these levels often are not available rapidly enough for clinical decision making. This article discusses the indications and methods for both direct and indirect testing for ethanol, methanol, ethylene glycol, and isopropanol toxicity. Also discussed are the costs, availability, and turn-around times for these tests.

Poisoning and drug overdose

Poisoning is a common cause for intensive care unit admission for both children and adults, and most poisoning victims are effectively treated using standard decontamination measures and supportive care. For a small number of poisons, acceleration of toxin removal with hemodialysis or hemofiltration is indicated. Similarly, specific antidotes are indicated in a few selected circumstances. Rarely, patients may benefit from more aggressive supportive techniques such as cardiopulmonary bypass.

In vitro assessment of the effect of methanol and the metabolite, formic acid, on embryonic development of the rat

Inhalation studies in rats have indicated that methanol is embryotoxic at levels that are only mildly maternally toxic. In the present study, the embryotoxicity of methanol and its metabolite, formic acid, was evaluated using rat embryo culture. The results showed that both methanol and formic acid have a concentration-dependent embryotoxic effect on the developing rat embryo in vitro. The no-effect concentration of methanol was 211.7 mumol/ml culture medium, while embryotoxicity was observed at 286.5 mumol/ml. The no-effect concentration of formic acid was 3.74 mumol/ml, while a concentration of 18.66 mumol/ml was associated with severe embryotoxicity. When embryos were grown in sera containing 18.66 mumol sodium formate/ml or in sera adjusted with hydrochloric acid to pH values similar to those achieved with formic acid, the results indicated that both low pH and formate contributed to the observed embryotoxicity of formic acid. When the level of methanol found to be embryotoxic in the present study is compared to blood levels in the human following controlled industrial exposure there appears to be a large margin of safety. However, plasma methanol levels are only one aspect of methanol toxicity in the human. Of greater significance is the formate level and the associated acidosis. However, it appears that embryotoxicity due to low pH or high formate levels would only occur after very severe methanol intoxication. Based on these in vitro studies, current industrial safety limits would appear to provide protection for the developing embryo.

Methanol half-life during ethanol administration: implications for management of methanol poisoning

STUDY OBJECTIVE

To determine the half-life of methanol in methanol-poisoned patients who are treated with ethanol but not with hemodialysis.

DESIGN

Case series.

SETTING

University Hospital, University of Manitoba.

PARTICIPANTS

Three methanol-poisoned patients treated with ethanol but not with hemodialysis and three similar patients identified by a literature review.

RESULTS

Plots of terminal concentration versus time data were inconsistent with zero-order kinetics and were adequately explained by an apparent first-order process. The median half-life of methanol in these patients was 43.1 hours, with a range of 30.3 to 52.0 hours.

CONCLUSION

Because of the significantly increased risk of toxicity and complications during ethanol monotherapy, we suggest that hemodialysis be considered for methanol-poisoned patients who are treated with ethanol infusion.

Methanol intoxication. How to help patients who have been exposed to toxic solvents

Methanol intoxication can be a challenge, in part because it is relatively uncommon but also because of the pharmacokinetics involved. A patient may not experience symptoms and thus may not present for treatment for several hours, or even a day or two, after exposure to the toxic substance. Yet, the interval between ingestion and treatment is one of the most important factors in determining patient outcome. Typical symptoms of methanol intoxication include lethargy, vertigo, vomiting, blurred vision, and decreased visual acuity. Treatment focuses on prevention of methanol conversion to its toxic metabolites, correction of metabolic acidosis, and elimination of the toxic substances from the system. Ethanol and bicarbonate administration and hemodialysis have been effective.

Transport management of the patient with acute poisoning

Poisoning in children is a common clinical problem encountered by pediatricians, general practitioners, and emergency room physicians. Poisoning in children less than 5 years of age is usually accidental, whereas, in young adults, any disparity between expected history and clinical findings should suggest poisoning. It is imperative that the treating physician expeditiously recognize, begin treating, and plan to transfer, when indicated, by specialized pediatric transport team the critically ill poisoned child to a tertiary care facility.

Ethylene Glycol Intoxication

Commonly available as automotive antifreeze, ethylene glycol can cause toxicity and death if ingested. It is metabolized to several aldehyde and acid intermediates that can cause severe metabolic acidosis, central nervous system derangements, cardiorespiratory failure, and acute renal failure. A presumptive diagnosis can often be made by assessment of the anion gap and the osmol gap and the finding of metabolic acidosis. Corroborating findings include oxalate crystalluria and urine that fluoresces on exposure to ultraviolet light. Recognition is important because there are specific treatment methods available. Therapy consists of administering sodium bicarbonate to counter the acidosis, ethanol to slow the generation of toxic metabolites, and vitamin cofactors, which may speed detoxification of these intermediates. Hemodialysis is employed to remove both ethylene glycol and its metabolites, to correct the acidbase disturbances, and as treatment for acute renal failure.