Studies on methanol poisoning

What's in this drink? Classification and adulterant detection in Irish Whiskey samples using near infrared spectroscopy combined with chemometrics

BACKGROUND

Near-infrared (NIR) spectroscopy coupled with principal component analysis (PCA) and partial least squares (PLS) regression was used to analyse a series of different Irish Whiskey samples in order to define their spectral profile and to assess the capability of the NIR method to identify samples based on their origin and storage (e.g. distiller, method of maturation). The ability of NIR spectroscopy to quantify the level of potential chemical adulterants was also investigated. Samples were spiked with 0.1%, 0.5%, 1.0%, 1.5% and 2.0% v/v of each adulterant (e.g. methanol, ethyl acetate, etc.) prior to NIR analysis.

RESULTS

The results of this study demonstrated the capability of NIR spectroscopy combined with PLS regression to classify the whiskey samples and to determine the level of adulteration. Moreover, the potential of NIR coupled with chemometric analysis as a rapid, portable, and non-destructive screening tool for quality control, traceability, and food/beverage adulteration for customs and other regulatory agencies, to mitigate beverage fraud was illustrated.

CONCLUSION

Given the non-specificity of the NIR technique, these positive preliminary results indicated that this method of analysis has the potential to be applied to identify the level of adulteration in distilled spirits. The rapid nature of the technique and lack of consumables or sample preparation required allows for a far more time and cost-effective analysis per sample. © 2021 Society of Chemical Industry.

Methanol poisoning as a new world challenge: A review

Background

Methanol poisoning (MP) occurs often via ingestion, inhalation, or dermal exposure to formulations containing methanol in base. Clinical manifestations of MP include gastrointestinal symptoms, central nervous system (CNS) suppression, and decompensated metabolic acidosis occurred with blurred vision and early or late blindness.

Objective

This study reviewed the clinical manifestations, laboratory and radiology findings, and treatment approaches in MP.

Discussion

Methanol is usually rapidly absorbed after ingestion and metabolized by alcohol dehydrogenase (ADH), then distributed to the body water to reach a volume distribution approximately equal to 0.77 L/kg. It is also eliminated from the body as unchanged parent compounds. Clinical manifestations of MP alone initiate within 0.5–4 h after ingestion and include gastrointestinal symptoms and CNS suppression. After a latent period of 6–24 h, depending on the absorbed dose, decompensated metabolic acidosis occurs with blurred vision and early or late blindness. Blurred vision with normal consciousness is a strong suspicious sign of an MP. The mortality and severity of intoxication are well associated with the severity of CNS depression, hyperglycemia, and metabolic acidosis, but not with serum methanol concentration. After initial resuscitation, the most important therapeutic action for patients with known or suspected MP is correction of acidosis, inhibition of ADH, and hemodialysis.

Conclusion

Since MP is associated with high morbidity and mortality, it should be considered seriously and instantly managed. Delay in treatment may cause complications, permanent damage, and even death.

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We attempt to review clinical manifestations, laboratory and radiology findings, and treatment approaches in Methanol poisoning (MP).

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The most important therapeutic action for patients with known MP is correction of acidosis, inhibition of alcohol dehydrogenase, and hemodialysis.

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The review emphasizes that MP has a high morbidity and mortality rate and it must be taken seriously and treated immediatly.

Late Functional and Morphological Findings after Methylalcohol Poisoning

AIM

The aim of the study was to determine the morphological and functional findings in a patient after methanol poisoning. Examination methods: The patient (male, 38 years old) was suffered methanol poisoning in eight years ago (2012). The following tests and examinations were performed: neurological visual field XR test (Medmont M700), retinal nerve fibre layer (RNFL), ganglion cell complex (GCC) and peripapillary vessel density (all using Avanti RTvue, Optovue), pattern electroretinography (PERG) and pattern visual evoked potential (PVEP) examination according to ISCEV methodology (Roland Consult Instrument) and brain MRI examination (Philips Achieva Dstream 3 T).

RESULTS

The biggest changes were found in RNFL and VD. PERG also showed damage to retinal ganglion cell axons. In left eye we determined decrease in oscillations (in comparison with contralateral eye) at N35-P50 and P50-N95. VEPs in both eyes were significantly reduced, almost inconspicuous in the left eye. Extension of latency time of P100 was not identified. Functional MRI showed a bilateral decrease in voxel activity with a greater decrease in the left eye. There were postmalatical changes in the dorsal parts of the putamen on MRI. The width of the optic nerve and chiasm was physiological.

CONCLUSION

Asymmetric damaging of RNFL and cortical centres of the brain were determined. We registered large pathological changes in VD, which are probably responsible for the deepening of optic nerve excavation and further loss of nerve fibers of retinal ganglion cells, which have not yet been described in the literature. Following these results is possible to define direct damage of nerve structures and blood vessels by toxins of methanol metabolism in the acute stage and upcoming reparation processes in following periods.

Methanol content in homemade alcohol from a province in North Vietnam

INTRODUCTION AND AIMS

Methanol poisonings pose a major risk especially where illegal alcohol is consumed. The source of the methanol in the drinks are debated. We aimed to evaluate whether home distillation of alcohol made from rice was capable of producing toxic amounts of methanol.

DESIGN AND METHODS

Twenty households with homemade alcohol production in Phu Tho province in Vietnam were included in this pilot study. We followed the whole production process and an alcohol sample from each household was analysed for methanol content.

RESULTS

17 (85%) of the samples contained detectable levels of methanol. The median concentration was 9 mg/L (range 2-37 mg/L). To develop clinical symptoms of methanol poisoning from the sample with the highest concentration would require drinking more than 424 L.

DISCUSSION AND CONCLUSIONS

Homemade alcohol from rice did not contain sufficient amount of methanol to cause toxicity in our study. This supports the theory of methanol being added to ethanol post production for economical purposes as the main source of mass poisonings.

Mild manifestation of methanol poisoning half a day after massive ingestion of a fuel alcohol product containing 70% ethanol and 30% methanol: a case report

Case

Is fomepizole necessary after massive ingestion of a mixture of methanol and ethanol? We report the case of a 37‐year‐old man who was transported to our Poison Center 12 h after ingesting 500 mL of fuel alcohol containing 70% methanol and 30% ethanol in a suicide attempt. On admission, he presented only with somnolence and mild metabolic acidosis. We hypothesized that most of the ethanol had been metabolized.

Outcome

As the estimated serum concentration of methanol was lethal (242.6 mg/dL), fomepizole was given i.v. and hemodialysis was carried out twice, resulting in complete recovery. Later, the serum concentrations of both methanol and ethanol on admission were found to be 224.1 and 0.51 mg/dL, respectively.

Conclusion

Therapeutic intervention was delayed by half a day after ingestion of a product containing methanol and ethanol in the present case. If the patient had arrived earlier, he may have only been treated with hemodialysis, but not fomepizole.

A Case of Methanol Poisoning

A 29-year-old male took about 300 ml industrial alcohol in a suicidal attempt. The industrial alcohol was later confirmed to be methanol. He presented to the emergency department 10 hours post-ingestion with an anion gap metabolic acidosis and an osmol gap of 76.7 mOsm/kg. Ethanol infusion was started in the emergency department at 11 hours post-ingestion before the availability of serum methanol level. The clinical diagnosis of toxic alcohol ingestion was based on the history, arterial blood gases results and the presence of a significant osmol gap. The patient was then admitted to the intensive care unit for ethanol therapy and haemodialysis. Prompt initiation of ethanol therapy and the subsequent intensive care prevented the development of life-threatening complications of methanol poisoning in this case.

Estimations of the lethal and exposure doses for representative methanol symptoms in humans

Background

The aim of this review was to estimate the lethal and exposure doses of a representative symptom (blindness) of methanol exposure in humans by reviewing data from previous articles.

Methods

Available articles published from 1970 to 2016 that investigated the dose-response relationship for methanol exposure (i.e., the exposure concentration and the biological markers/clinical symptoms) were evaluated; the MEDLINE and RISS (Korean search engine) databases were searched. The available data from these articles were carefully selected to estimate the range and median of a lethal human dose. The regression equation and correlation coefficient (between the exposure level and urinary methanol concentration as a biological exposure marker) were assumed from the previous data.

Results

The lethal human dose of pure methanol was estimated at 15.8–474 g/person as a range and as 56.2 g/person as the median. The dose-response relationship between methanol vapor in ambient air and urinary methanol concentrations was thought to be correlated. An oral intake of 3.16–11.85 g/person of pure methanol could cause blindness. The lethal dose from respiratory intake was reported to be 4000–13,000 mg/l. The initial concentration of optic neuritis and blindness were shown to be 228.5 and 1103 mg/l, respectively, for a 12-h exposure.

Conclusion

The concentration of biological exposure indices and clinical symptoms for methanol exposure might have a dose-response relationship according to previous articles. Even a low dose of pure methanol through oral or respiratory exposure might be lethal or result in blindness as a clinical symptom.

Positive serum ethanol concentration on admission to hospital as the factor predictive of treatment outcome in acute methanol poisoning

ABSTRACT

Mass methanol poisonings present a serious problem for health systems worldwide, with poor outcome associated with delayed treatment. Positive pre-hospital serum ethanol concentration may have predictive value as the prognostic factor of the treatment outcome. We studied the effect of positive serum ethanol level on admission to hospital on survival in patients treated during the Czech methanol outbreak during 2012-2014. Cross-sectional cohort study was performed in 100 hospitalized patients with confirmed methanol poisoning. Pre-hospital ethanol was administered in 42 patients (by paramedic/medical staff to 30 patients and self-administered by 12 patients before admission); 58 patients did not receive pre-hospital ethanol. Forty-two patients had detectable serum ethanol concentration on admission to hospital [median 18.3 (IQR 6.6-32.2) mmol dm-3]. Pre-hospital ethanol administration by paramedic/medical staff had a significant effect on survival without visual and CNS sequelae when adjusted for arterial blood pH on admission (OR 8.73; 95 % CI 3.57-21.34; p < 0.001). No patients receiving pre-hospital ethanol died compared with 21 not receiving (p < 0.001). Positive serum ethanol concentration on admission to hospital was a predictor for survival without health sequelae when adjusted for arterial blood pH (OR 8.10; 95 % CI 2.85-23.02; p < 0.001). The probability of visual and CNS sequelae in survivors reduced with increasing serum ethanol concentration on admission.

GRAPHICAL ABSTRACT

Prognostic factors in methanol poisoning

The aim of this study was to assess the clinical and laboratory factors in methanol poisoned patients to determine the prognosis of their toxicity. This survey was done as a prospective cross-sectional study in methanol-poisoned patients in Loghman-Hakim hospital poison center during 9 months from October 1999—June 2000. During this time 25 methanol-poisoned patients were admitted. The mortality rate was 12 (48%). Amongst survivors, three (23%) of the patients developed blindness due to their poisoning and the other 10 (77%) fully recovered without any complication. The mortality rate in comatose patients was nine (90%) while in non-comatose patients it was three (20%) ( P < 0.001). There was a significant difference in mean pH in the first arterial blood gas of patients who subsequently died (6.82 ± 0.03) and survivors (7.15 ± 0.06) ( P < 0.001, M-W). The mean time interval between poisoning and ED presentation in deceased patients were (46 ± 15.7) hours, in survived with sequelae were (16.7 ± 6.7) and in survived without sequelae were (10.3 ± 7.2) hours ( P < 0.002, K-W). We found no significant difference between the survivors versus the patients who died regarding methanol. Simultaneous presence of ethanol and opium affected the outcome of the treatment for methanol intoxication favourably and unfavourably, respectively. In our study, poor prognosis was associated with pH < 7, coma on admission and >24 hours delay from intake to admission. Human & Experimental Toxicology (2007) 26: 583—586.

Use of Out-of-Hospital Ethanol Administration to Improve Outcome in Mass Methanol Outbreaks

STUDY OBJECTIVE

Methanol poisoning outbreaks are a global public health issue, with delayed treatment causing poor outcomes. Out-of-hospital ethanol administration may improve outcome, but the difficulty of conducting research in outbreaks has meant that its effects have never been assessed. We study the effect of out-of-hospital ethanol in patients treated during a methanol outbreak in the Czech Republic between 2012 and 2014.

METHODS

This was an observational case-series study of 100 hospitalized patients with confirmed methanol poisoning. Out-of-hospital ethanol as a "first aid antidote" was administered by paramedic or medical staff before the confirmation of diagnosis to 30 patients; 70 patients did not receive out-of-hospital ethanol from the staff (12 patients self-administered ethanol shortly before presentation).

RESULTS

The state of consciousness at first contact with paramedic or medical staff, delay to admission, and serum methanol concentration were similar among groups. The median serum ethanol level on admission in the patients with out-of-hospital administration by paramedic or medical staff was 84.3 mg/dL (interquartile range 32.7 to 129.5 mg/dL). No patients with positive serum ethanol level on admission died compared with 21 with negative serum ethanol level (0% versus 36.2%). Patients receiving out-of-hospital ethanol survived without visual and central nervous system sequelae more often than those not receiving it (90.5% versus 19.0%). A positive association was present between out-of-hospital ethanol administration by paramedic or medical staff, serum ethanol concentration on admission, and both total survival and survival without sequelae of poisoning.

CONCLUSION

We found a positive association between out-of-hospital ethanol administration and improved clinical outcome. During mass methanol outbreaks, conscious adults with suspected poisoning should be considered for administration of out-of-hospital ethanol to reduce morbidity and mortality.

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.

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.

Fomepizole in the treatment of acute methanol poisonings: experience from the Czech mass methanol outbreak 2012-2013

OBJECTIVE

During an outbreak of mass methanol poisonings in the Czech Republic in 2012-2013, fomepizole was applied as an alternative antidote to ethanol. We present the laboratory data, clinical features, adverse reactions, and treatment outcomes in all patients treated with fomepizole.

METHODS

Combined retrospective and prospective case series study in 25 patients, median age 50 (16-73) years, 18 males and 7 females.

RESULTS

There were 24% fatalities, 36% survivors without health impairment, and 40% survivors with sequelae. All the patients who died were comatose on admission; the mortality was 50% among patients in a coma. The median intensive care unit length of stay was six (2-22) days. The median total dose of fomepizole was 2 (1-9) g. Complications were observed in 7/25 cases: aspiration pneumonia (4), sepsis (2), bleeding (2), malignant arrhythmia (1), delirium tremens (1), and rebound of acidosis (1). The patients who survived without impairment were less acidotic than those who died or survived with sequelae (P<0.01). No difference in serum methanol and formate was found between the three groups.

CONCLUSION

There is no evidence whether fomepizole is a more efficient antidote than ethanol with regards to the hospital mortality. The possibility of delirium tremens in the patients with a history of chronic alcohol abuse has to be taken in consideration. The benefits of fomepizole were indirect: no need to monitor serum ethanol's level during the hemodialysis in severely poisoned patients and less working overload on ICU doctors treating several poisoned patients simultaneously.

Intermittent hemodialysis is superior to continuous veno-venous hemodialysis/hemodiafiltration to eliminate methanol and formate during treatment for methanol poisoning

During an outbreak of methanol poisonings in the Czech Republic in 2012, we were able to study methanol and formate elimination half-lives during intermittent hemodialysis (IHD) and continuous veno-venous hemodialysis/hemodiafiltration (CVVHD/HDF) and the relative impact of dialysate and blood flow rates on elimination. Data were obtained from 11 IHD and 13 CVVHD/HDF patients. Serum methanol and formate concentrations were measured by gas chromatography and an enzymatic method. The groups were relatively comparable, but the CVVHD/HDF group was significantly more acidotic (mean pH 6.9 vs. 7.1 IHD). The mean elimination half-life of methanol was 3.7 and formate 1.6 h with IHD, versus 8.1 and 3.6 h, respectively, with CVVHD/HDF (both significant). The 54% greater reduction in methanol and 56% reduction in formate elimination half-life during IHD resulted from the higher blood and dialysate flow rates. Increased blood and dialysate flow on the CVVHD/HDF also increased elimination significantly. Thus, IHD is superior to CVVHD/HDF for more rapid methanol and formate elimination, and if CVVHD/HDF is the only treatment available then elimination is greater with greater blood and dialysate flow rates.

Risk factors related to poor outcome after methanol poisoning and the relation between outcome and antidotes--a multicenter study

INTRODUCTION. Thorough prognostic and metabolic studies of methanol poisonings are scarce. Our aims were to evaluate the factors associated with sequelae and death from methanol poisoning, to develop a simple risk-assessment chart to evaluate factors associated with sequelae and death from methanol poisoning, and to compare the antidotes ethanol and fomepizole. PATIENTS AND METHODS. We present a retrospective observational case series of methanol-poisoned patients from Norway (1979 and 2002-2005), Estonia (2001) and Tunisia (2003/2004), and patients from two different centers in Iran (Teheran 2004-2009 and Mashhad 2009-2010) who were identified by a positive serum methanol and had a blood acid-base status drawn on admission. The patients were divided into different groups according to their outcome: Survived, survived with sequelae, and died. RESULTS. A total of 320 patients were identified and 117 were excluded. Of the remaining 203 patients, 48 died, and 34 were discharged with neurological sequelae. A pH < 7.00 was found to be the strongest risk factor for poor outcome, along with coma (Glasgow Coma Scale (GCS) < 8) and a pCO(2) ≥ 3.1 kPa in spite of a pH < 7.00. More patients died despite hyperventilation (low pCO(2)) in the ethanol group. CONCLUSIONS. Low pH (pH < 7.00), coma (GCS < 8), and inadequate hyperventilation (pCO(2) ≥ 3.1 kPa in spite of a pH < 7.00) on admission were the strongest predictors of poor outcome after methanol poisoning. A simple flow-chart may help identify the patients associated with a poor outcome.

Severe necrosis of oesophageal and gastric mucosa in fatal methanol poisoning

Methanol is a potent neurotoxic substance that causes severe metabolic acidosis and serious neurological disorders. Most of the cases are accidental exposures to drinking beverages contaminated with methanol. There are few articles reporting pure methanol intoxication; however, it is well known that small quantities of pure methanol causes blindness and death, the minimum lethal dose being 50-100 ml.A case report is presented of a 67-year-old woman, who committed suicide by ingestion of 500 ml of absolute methanol. Despite symptomatic and supportive intensive care, the woman died 23 h after hospital admission due to metabolic acidosis and multiple organ dysfunction syndrome. A complete medico-legal autopsy was performed. Grossly, there was complete detachment of the oesophagus mucosa and brownish discolouration of the gastric mucosa. Histological findings showed diffuse haemorrhagic necrosis of the stomach mucosa and intense acute inflammatory infiltration of the lamina propria. To our knowledge, this is the first autopsy report of such severe digestive injuries. A discussion and review of the recent literature on the subject are given.

Hyperglycemia is a strong prognostic factor of lethality in methanol poisoning

Methanol poisoning is seen in the form of isolated episodes, or intentional ingestion and epidemics. Despite its efficient treatment, methanol poisoning has high morbidity and mortality rates. So far, several studies have been performed to identify the prognostic factors in methanol poisoning. Recently, during the treatment of patients with methanol poisoning, we observed that patients' blood glucose levels were high on presentation to the hospital, particularly in those who expired. Through a literature search, we found that no studies have been performed on blood glucose levels or hyperglycemia in methanol poisoning. Therefore, the present retrospective study was done as a preliminary investigation to understand whether there was a meaningful relationship between methanol poisoning and blood glucose level on presentation, and also if hyperglycemia could be considered as a prognostic factor for mortality. In this retrospective study, a review of the hospital charts was performed for all patients who were treated for methanol poisoning from March 2003 to March 2010 in two hospitals in Tehran, Iran. Those with definitive diagnosis of methanol poisoning, no history of diabetes mellitus, and normal or low body mass index (<25) were included. Patients' demographic information, clinical manifestations, time elapsed between ingestion and presentation, blood glucose level on presentation (before treatment), results of arterial blood gas analysis, and the clinical outcome were recorded. Statistical analysis was done using SPSS software (version 17, Chicago, Illinois, USA) and application of Mann-Whitney U test, Pearson's chi-square test, Pearson correlation coefficient (r), receiver operating characteristic (ROC) curve, and logistic regression. P values less than 0.05 were considered as the statistically significant levels. Ninety-five patients with methanol poisoning met the inclusion criteria and were included in the study. Of these, 91 (96%) were male and 4 (4%) were female. Mean age was 31.61 ± 14.3 years (range, 13 to 75). Among the 95 patients, 68 survived (72%) and 27 expired (28%). Median blood glucose level was 144 mg/dL (range, 75 to 500). There was no significant statistical correlation between blood glucose level and time of treatment, age, pCO(2), or serum bicarbonate concentration, but blood glucose level had a statistically significant correlation with pH (r = -0.242, P = 0.02) and base deficit (r = 0.230, P = 0.03). The mean blood glucose level was 140 ± 55 and 219 ± 99 mg/dL in the survivor and non-survivor patients, respectively (P < 001). Considering the cutoff level of 140 mg/dL for blood glucose and using logistic regression analysis, and adjusting according to the admission data with significant statistical difference in the two study groups, the odds ratio for hyperglycemia as a risk factor for death was 6.5 (95% confidence interval = 1.59-26.4). Our study showed that blood glucose levels were high in methanol poisoning and even higher in those who died in comparison with the survivors. Therefore, hyperglycemia might be a new prognostic factor in methanol poisoning, but further studies are needed to determine whether controlling hyperglycemia has therapeutic consequences.

Use of the osmolal gap to guide the start and duration of dialysis in methanol poisoning

OBJECTIVE

Rapid diagnosis and treatment of methanol poisoning is mandatory. Dependence on serum methanol analysis in this situation may delay diagnosis and treatment. The anion and osmolal gaps have been recommended for use as diagnostic tools, but the use of these gaps to evaluate the length of hemodialysis treatment has only been emphasized in a few reports. We evaluated the usefulness of the osmolal gap in estimating the need for dialysis and the duration of this treatment in 17 methanol-poisoned subjects.

MATERIAL AND METHODS

Patients were part of a recent outbreak of methanol poisoning, in which the diagnosis upon admission was mainly based on use of the anion and osmolal gaps. The duration of dialysis generally followed the standard recommendation of 8h. During dialysis, blood samples were frequently collected and analyzed to determine acid-base status and serum methanol and to calculate the osmolal gap. In nine patients, the duration of dialysis was compared with the duration necessary to normalize serum methanol and the osmolal gap.

RESULTS

There was a good correlation between serum methanol and the osmolal gap during hemodialysis (y=1.09x+3.82; R(2)=0.92). The osmolal gap therefore gives a good estimate of the serum methanol level during hemodialysis, and could have saved a total of 23 h of dialysis treatment (34%) in nine patients had it been applied.

CONCLUSIONS

In the absence of serum methanol analyses, the osmolal gap is useful to assess the indication for and duration of hemodialysis in methanol-poisoned patients. In mass poisoning situations, use of the osmolal gap makes it possible to reduce the duration of dialysis in a safe manner.

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.

Anion and osmolal gaps in the diagnosis of methanol and ethylene glycol poisoning

The diagnostic value of determination of the anion and osmolal gaps was studied in 6 patients poisoned with methanol and in 5 poisoned with ethylene glycol. Increased osmolal gap was present on admission in all patients, whereas increased anion gap was present in all except one. In the methanol-poisoned patients the mean blood values were: pH 7.27, anion gap 24 mmol/l, osmolal gap 81 mosmol/kg H2O, methanol 67 mmol/l, ethanol 11 mmol/l and in the ethylene glycol-poisoned patients: pH 6.93, anion gap 38 mmol/l, osmolal gap 35 mosmol/kg H2O and ethylene glycol 24 mmol/l. In the absence of alcoholic acidosis or diabetic coma the finding of a simultaneous increase in both the anion and osmolal gaps indicates methanol or ethylene glycol poisoning. Thus determinations of the anion and osmolal gaps are mandatory whenever facing metabolic acidosis of unknown etiology.

Toxicokinetics of formate during hemodialysis

During hemodialysis in a methanol poisoned patient, formate elimination followed first order kinetics with a plasma half-life of formate of 165 min. The mean dialysator (1.6 m2) clearance of formate was 148 ml/min (n = 8, SD +/- 11, range 128-161) at a blood flow of 215 ml/min. By applying first order kinetics, a volume of distribution of 0.5 l/kg was found, assuming that the dialysator clearance equals the total body clearance of formate. Formate, the main toxic agent in methanol poisoning, is thus probably more effectively removed by hemodialysis than methanol. This fact, and the very slow endogenous methanol elimination during appropriate ethanol treatment, should be considered when deciding on the treatment of a methanol poisoned patient presenting with metabolic acidosis.

Studies on ethylene glycol poisoning

Toxicokinetic studies during hemodialysis are presented in two patients with blood ethylene glycol concentrations of 40 and 41 mmol/l, respectively. Treatment involved bicarbonate, ethanol and hemodialysis with a 1.6 m2 dialysator. Both patients developed acute renal failure and one was discharged with permanent cerebral impairment. The other made an uneventful recovery. The average dialysator clearance of ethylene glycol at a blood flow of 200 ml/min was 145 and 148 ml/min, respectively. Assuming a volume of distribution of ethylene glycol of 0.7 l/kg, the dialysator represented about 92 and 95%, respectively, of the total body clearance of ethylene glycol during ethanol treatment. During hemodialysis a blood ethanol concentration of about 15 mmol/l (0.7 g/l) caused a near complete inhibition of ethylene glycol metabolism at ethylene glycol concentrations up to about 25 mmol/l (1.6 g/l). We recommend prompt hemodialysis in ethylene glycol poisoning to supplement alkali and ethanol treatment.

Methanol poisoning and long term sequelae - a six years follow-up after a large methanol outbreak

Background

Mass poisonings with methanol are rare but occur regularly both in developed and in developing countries. Data from the poisoning episodes are often published, but follow-up-data is scarce. We therefore conducted a six year follow-up study after the large methanol outbreak in Estonia in September 2001.

Methods

Surviving victims from the outbreak were contacted and invited to an interview and a clinical evaluation by an ophthalmologist and a physician. The patients that failed to respond were searched for in the Estonian Register of Population and through their General Practitioner.

Results

During the outbreak in 2001, 86/111 hospitalized patients survived: 66 without sequelae (Group I) and 20 with sequelae (Group II). Six years later, 26/86 were dead, 33/86 could not be tracked down, and so only 27/86 of these were followed up and examined: 22/66 of the patients in Group I, and 5/20 in Group II were found and examined. From Group I, 8/22 were identified with new neurological impairment and 8/22 with new visual disturbances after discharge. From Group II, visual disturbances (n = 4) and neurological impairment (n = 3) were still present in all patients. Among the 26 dead, 19 were from Group I, and seven were from Group II. Alcohol intoxication was the most frequent cause of death (7/26).

Conclusion

All sequelae were still present six years after the initial poisoning suggesting that these were irreversible damages. On follow-up, apparently new neurological and visual complications were identified in 36% and 36%, respectively. 35% of the patients initially discharged with sequelae and 29% discharged without were dead six years later; 27% of them from alcohol intoxication.

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.

Extremely slow formate elimination in severe methanol poisoning: A fatal case report

Methanol poisoning is a potentially fatal medical emergency because of its metabolism to formic acid. The half-life of formate has been reported in the range of 2.5-12.5 hours, but the degree of inter-individual variation is not known. We studied methanol and formate kinetics in a case of late diagnosed methanol poisoning with persisting metabolic acidosis and circulatory failure.

CASE REPORT

A 63-year-old man was referred to our hospital with a tentative diagnosis of stroke. He was awake on admission, but he soon deteriorated in the emergency department and a metabolic acidosis was revealed. Methanol poisoning was then suspected approximately five hours after admission but in spite of intensive treatment he died after six days.

RESULTS

The S-methanol half-lives during treatment with fomepizole before and during hemodialysis were 49.5 and 4.1 hours, respectively, while the similar half-lives of S-formate were 77.0 and 2.9 hours. S-fomepizole was measured and found to be within the therapeutic range during treatment.

DISCUSSION

The patient was treated with the established dosing regimen for fomepizole and the measured S-fomepizole levels throughout the treatment were adequate; the S-methanol elimination also suggests that methanol metabolism was blocked. Hence, other explanations for this exceptionally long formate half-life include slow formate metabolism, due to small hepatic folate stores or to genetic deficiencies in formate-metabolizing enzymes, or slow formate excretion, due to renal tubular acidosis, to a non-oliguric renal failure, or to genetic deficiencies in the renal formate transporters.

CONCLUSION

This case report indicates that the half-life of S-formate may have greater inter-individual variation than earlier expected, being by far the longest half-life reported in the medical literature. These results support the use of hemodialysis in the treatment of such patients.

Alcoholic ketoacidosis in an 11-year-old boy

A history of ethanol consumption combined with vomiting, anion gap metabolic acidosis, and altered mental status is consistent with a broad differential diagnosis, which requires a systematic approach. Alcoholic ketoacidosis is rare after binge drinking in the naïve individual and typically occurs in patients with heavy, chronic use. We present the case of an 11-year-old boy with acute ethanol intoxication and a clinical course that is most consistent with alcoholic ketoacidosis. Alcoholic ketoacidosis should be considered in the differential diagnosis of children with unexplained ketoacidosis when there is history or evidence of ethanol consumption combined with the appropriate clinical presentation.

Methanol mass poisoning in Estonia: outbreak in 154 patients

BACKGROUND

Knowledge of methanol toxicity is based on human data from case series and larger outbreaks. In many of these cases, however, diagnosis was not verified by methanol determinations. We present epidemiological and clinical data from one of the largest methanol outbreaks in which all patients had detectable serum methanol levels.

METHODS

Retrospective case series study of hospital and forensic charts from the five hospitals where patients were treated.

RESULTS

Of the 147 patients admitted with suspected methanol poisoning, the diagnosis was confirmed in 111, of whom 25 (23 %) died. In addition, 43 patients died outside the hospital, giving a total of 154 patients and a death toll of 68 (44 %). Outcome was related to the degree of metabolic acidosis, serum methanol concentration, coma upon admission, and the patient's ability to hyperventilate. Patients were treated with bicarbonate (85 %), ethanol (87 %), hemodialysis (71 %), and mechanical ventilation (61%) according to clinical features and blood gases, since serum methanol concentrations were analyzed retrospectively. Twenty patients (18 %) survived with permanent sequelae, 18 suffered from impaired vision, and 3 developed permanent brain damage.

DISCUSSION

Given limited resources, triage and use age of tertiary care centers allowed a small community hospital to treat a high number of methanol-poisoned patients. Critical resources were ventilators and dialyzing machines, whereas stores of antidote (ethanol) and bicarbonate were sufficient. Many patients were mechanically ventilated by hand and treated with bicarbonate and ethanol during transport to tertiary care centers for hemodialysis.

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.

Concentration changes of methanol in blood samples during an experimentally induced alcohol hangover state

A hangover is characterized by the unpleasant physical and mental symptoms that occur between 8 and 16 hours after drinking alcohol. After inducing experimental hangover in normal individuals, we measured the methanol concentration prior to and after alcohol consumption and we assessed the association between the hangover condition and the blood methanol level. A total of 18 normal adult males participated in this study. They did not have any previous histories of psychiatric or medical disorders. The blood ethanol concentration prior to the alcohol intake (2.26+/-2.08) was not significantly different from that 13 hours after the alcohol consumption (3.12+/-2.38). However, the difference of methanol concentration between the day of experiment (prior to the alcohol intake) and the next day (13 hours after the alcohol intake) was significant (2.62+/-1.33/l vs. 3.88+/-2.10/l, respectively). A significant positive correlation was observed between the changes of blood methanol concentration and hangover subjective scale score increment when covarying for the changes of blood ethanol level (r=0.498, p<0.05). This result suggests the possible correlation of methanol as well as its toxic metabolite to hangover.

Methanol outbreak in Norway 2002-2004: epidemiology, clinical features and prognostic signs

OBJECTIVES

Knowledge on methanol poisoning does mainly come from clinical studies. We therefore report epidemiological, clinical and prognostic features from the large methanol outbreak in Norway in 2002-2004 where the new antidote fomepizole was the primary antidote in use.

DESIGN AND SUBJECTS

Combined prospective and retrospective case series study of 51 hospitalized patients who were confirmed poisoned with methanol, of whom nine died. In addition, eight patients died outside hospital. Most patients were admitted in a late stage and because of symptoms. Treatment consisted of alkali, fomepizole (71%) and haemodialysis (73%).

RESULTS

The median serum methanol was 25.0 mmol L-1 (80 mg dL-1) (range 3.1-147.0 mmol L-1), median pH was 7.20 (6.50-7.50), and median base deficit 22 mmol L-1 (range 0-31). The most frequent clinical features reported were visual disturbances (55%), dyspnoea (41%), and gastrointestinal symptoms (43%). Twenty-four per cent were comatose on admission, of whom 67% died. There was a trend towards decreasing pCO2 with decreasing pH amongst the patients surviving. The opposite trend was demonstrated in the dying; the difference was highly significant by linear regression analyses (P<0.001).

CONCLUSIONS

Methanol poisoning still has a high morbidity and mortality, mainly because of late diagnosis and treatment. Respiratory arrest, coma and severe metabolic acidosis (pH<6.90, base deficit>28 mmol L-1) upon admission were strong predictors of poor outcome. Early admission and ability of respiratory compensation of metabolic acidosis was associated with survival.

Anion and osmolal gaps in the diagnosis of methanol poisoning: clinical study in 28 patients

OBJECTIVE

To evaluate anion and osmolal gaps as diagnostic tools in methanol poisoning.

DESIGN AND SETTING

Clinical observational study.

PATIENTS AND METHODS

In a recent methanol outbreak, the initial triage and treatment decisions in 28 patients were based mainly upon the values of the osmolal and anion gaps on admission. Methanol and formate levels were later compared to these gaps by linear regression analysis.

RESULTS

The correlation between the osmolal gaps and serum methanol concentrations on admission was linear (y = 1.03x+12.71, R2 = 0.94). The anion gaps correlated well with the serum formate concentrations (y = 1.12x+13.82, R2 = 0.86). Both gaps were elevated in 24 of the 28 subjects upon admission. Three patients had an osmolal gap within the reference area (because of low serum methanol), but elevated anion gap because of formate accumulation. One patient with probable concomitant ethanol ingestion had a high osmolal gap and a normal anion gap.

CONCLUSION

Osmolal and anion gaps are useful in the diagnosis and triage of methanol-exposed subjects. Confounders are low serum methanol and concomitant ethanol ingestion.

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.

Reversal of severe methanol-induced visual impairment: no evidence of retinal toxicity due to fomepizole

CASE REPORT

We report a case of methanol poisoning exhibiting complete recovery from severe visual impairment following treatment with ethanol, fomepizole, and hemodialysis. An adult male presented with central blindness after ingesting methanol. Initial visual acuity was <20/800 (finger counting at 1-2 feet) with retinal edema on fundoscopy, arterial pH 7.19, methanol 97 mg/dL (30 mmol/L), formate 14.3 mmol/L, and ethanol undetectable. The patient was treated with ethanol, then fomepizole intravenously (15, 10, then 5 mg/kg), and hemodialysis. Methanol metabolism was effectively blocked by fomepizole even after ethanol had been eliminated, and the patient recovered 20/20 vision by day 14 with normal fundoscopy. This case report confirms highly efficient inhibition of alcohol dehydrogenase by fomepizole, as well as demonstrate the safety of fomepizole in a patient already exhibiting end-organ retinal toxicity. The potential for fomepizole to inhibit retinol dehydrogenase, an isoenzyme of alcohol dehydrogenase essential to vision, did not appear to be clinically significant in this symptomatic methanol-poisoned patient.

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.

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.

Delayed toxidromes

Some toxins do not result in clinical manifestations until several hours after exposure. This article reviews those agents that may cause delayed-onset toxicity. They are organized into four classes: specific pharmaceuticals, biologicals, pharmaceutical dosage forms, and chemicals. There are five basic mechanisms for delayed toxicity: delayed absorption, distribution factors, metabolic factors, cellular and organ capacity effects, and unknown. Scientific evidence for delayed-onset of effects varies considerably among the individual toxins.

Prognostic factors in patients with methanol poisoning

OBJECTIVE

To identify prognostic factors in methanol poisoning and determine the effect of medical interventions on clinical outcome.

METHODS

Retrospective review of all patients treated for methanol poisoning from 1982 through 1992 at The Toronto Hospital. Presenting history, physical examination, results of laboratory tests, medical interventions, and final outcomes after hemodialysis were abstracted.

RESULTS

Of 50 patients treated for methanol poisoning, 18 (36%) died, 32 (64%) survived. Seven of the 32 survivors sustained visual sequelae (22%), the remaining 25 (78%) recovered completely. Patients presenting with coma or seizure had 84% (16/19) mortality compared to 6% (2/31) in those without (p < 0.001). Initial arterial pH < 7 was also associated with significantly higher mortality (17/19, 89% vs 1/31, 3%, p < 0.001). There were no differences in time from presentation to dialysis between survivors and fatalities (8.4 +/- 3.6 vs 7.6 +/- 3.5 hours, p = 0.47). The deceased patients had higher mean methanol concentration than the survivors (83 +/- 53 vs 41 +/- 25 mmol/L, p = 0.004). Subgroup analysis of 19 patients presenting with visual symptoms who survived showed prolonged acidosis (5.4 +/- 2.3 vs 3.0 +/- 2.1 hours, p = 0.06) in those with persistent visual sequelae.

CONCLUSIONS

Coma or seizure on presentation and severe metabolic acidosis, in particular initial arterial pH < 7, are poor prognostic indicators in methanol poisoning. Survivors presented with lower methanol concentrations. Patients with residual visual sequelae had more prolonged acidosis than those with complete recovery. Future studies will be needed to confirm the effect of correction of acidosis on final clinical outcome.

Kinetic interactions between 4-methylpyrazole and ethanol in healthy humans

4-Methylpyrazole (4-MP), a potent inhibitor of alcohol dehydrogenase activity, is a candidate to replace ethanol as the antidote for methanol and ethylene glycol intoxications, because it has a longer duration of action and apparently fewer adverse effects. To study a probable mutual inhibitory effect between ethanol and 4-MP on their elimination, two studies were performed in healthy human volunteers using double-blind crossover designs. In study A1 4-MP in the presumed therapeutic dose range of 10 to 20 mg/kg caused a 40% reduction in the rate of elimination of ethanol in 12 subjects given 0.5 to 0.7 g/kg of ethanol. These data suggest that such doses of 4-MP inhibit alcohol dehydrogenase activity in humans in vivo and would be effective at blocking methanol or ethylene glycol metabolism. In study B, ethanol (0.6 g/kg followed by 0.2 g/kg twice) significantly decreased the rate of elimination of 4-MP (5 mg/kg, given intravenously to four subjects). These moderate doses of ethanol also inhibited the rate of urinary excretion of 4-carboxypyrazole, the primary metabolite of 4-MP in humans. Data suggest that ethanol inhibits 4-MP metabolism, thereby increasing the duration of therapeutic blood levels of 4-MP in the body. This mutual interaction may have clinical implications, because most self-poisoned patients have also ingested ethanol. Theoretically, methanol and ethylene glycol might also show such interactions with 4-MP.

Severe metabolic acidosis in the alcoholic: differential diagnosis and management

1. A chronic alcoholic with severe metabolic acidosis presents a difficult diagnostic problem. The most common cause is alcoholic ketoacidosis, a syndrome with a typical history but often misleading laboratory findings. This paper will focus on this important and probably underdiagnosed syndrome. 2. The disorder occurs in alcoholics who have had a heavy drinking-bout culminating in severe vomiting, with resulting dehydration, starvation, and then a beta-hydroxybutyrate dominated ketoacidosis. 3. Awareness of this syndrome, thorough history-taking, physical examination and routine laboratory analyses will usually lead to a correct diagnosis. 4. The treatment is simply replacement of fluid, glucose, electrolytes and thiamine. Insulin or alkali should be avoided. 5. The most important differential diagnoses are diabetic ketoacidosis, lactic acidosis and salicylate, methanol or ethylene glycol poisoning, conditions which require quite different treatment. 6. The diagnostic management of unclear cases should always include toxicological tests, urine microscopy for calcium oxalate crystals and calculation of the serum anion and osmolal gaps. 7. It is suggested here, however, that the value of the osmolal gap should be considered against a higher reference limit than has previously been recommended. An osmolal gap above 25 mosm/kg, in a patient with an increased anion gap acidosis, is a strong indicator of methanol or ethylene glycol intoxication.