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

Kidney outcomes after methanol and ethylene glycol poisoning: a systematic review and meta-analysis

INTRODUCTION

Ingestions with methanol, ethylene glycol, diethylene glycol, propylene glycol, and isopropanol are rare yet exceedingly dangerous conditions that may require emergent management with kidney replacement therapy. Little is known regarding short- and long-term kidney outcomes post-ingestion.

OBJECTIVES

To comprehensively synthesize existing evidence regarding short- and long-term kidney and other outcomes of adult patients following these poisonings.

METHODS

We developed a search strategy in MEDLINE via OVID and then translated it into other databases including EMBASE (via OVID), PubMed, CENTRAL (via OVID). The databases were searched from their dates of inception to 29 July 2021. A grey literature search was conducted in the International Traditional Medicine Clinical Trial Registry and ClinicalTrials.gov. All interventional and observational studies and case series with ≥ five participants that reported on the outcomes of toxic alcohol (methanol, ethylene glycol, diethylene glycol, propylene glycol and isopropanol) poisonings in adult patients ≥18 years old were included. Studies that reported mortality, kidney outcomes and/or complications attributed to toxic alcohol poisoning were eligible.

RESULTS

The search strategy identified 1,221 citations. Sixty-seven studies (13 retrospective observational studies, one prospective observational study, 53 case series) met inclusion criteria (total N = 2,327 participants). No randomized controlled trials were identified per our prespecified criteria. Generally, included studies had small sample sizes (median of 27 participants) and were of low quality. Methanol and/or ethylene glycol poisoning made up 94.1% of included studies, whereas one study reported on isopropanol and none reported on propylene glycol. Results of the 13 observational studies of methanol and/or ethylene glycol poisoning were pooled for meta-analyses. The pooled in-hospital mortality estimates amongst patients with methanol and ethylene glycol poisoning were 24 and 11%, respectively. A more recent year of publication, female sex and mean age were associated with lower in-hospital mortality amongst individuals with ethylene glycol poisoning. Although hemodialysis was the most frequently employed kidney replacement therapy, the indications for initiation of this therapy were not reported in the majority of studies. At hospital discharge, kidney recovery occurred in 64.7-96.3% of patients with ethylene glycol poisoning. In studies of methanol and/or ethylene glycol poisoning, 2-3.7% of individuals required ongoing dialysis. Only one study reported post-discharge mortality. Furthermore, long-term toxic alcohol-mediated sequelae, such as visual and neurologic outcomes, were scarcely reported.

DISCUSSION

Ingestions of methanol and ethylene glycol were associated with a significant short-term risk of mortality. Although a wealth of literature in the form of case reports and case series exists, high-quality evidence regarding kidney outcomes after these poisonings is lacking. We identified a paucity of standardized reporting in clinical presentations, therapeutics and outcomes amongst adults with toxic alcohol poisoning. Amongst the included studies, there was substantial heterogeneity encompassing study type, outcomes, duration of follow-up and treatment modalities. These sources of heterogeneity restricted our ability to perform comprehensive meta-analyses of all outcomes of interest. An additional limitation is the lack of studies pertaining to propylene glycol and the paucity of data on isopropanol.

CONCLUSIONS

The indications for hemodialysis, long-term kidney recovery and long-term mortality risk vary widely in these poisonings and are inconsistently reported in the literature. This highlights the need for further research with standardized reporting of baseline kidney function, indications for initiation of kidney replacement therapy and short-term and long-term kidney outcomes.

REGISTRATION

This systematic review protocol is registered at PROSPERO, CRD42018101955.

Methanol toxicity in a pediatric patient treated with fomepizole and hemodialysis

Methanol toxicity is an important cause of toxic alcohol exposure resulting in morbidity and mortality in both adult and pediatric populations. Methanol is metabolized into formaldehyde and formic acid: toxic metabolites that can cause altered mental status, visual disturbances, multisystem organ failure, and death. Recognition of methanol intoxication and rapid treatment are critical for the prevention of long-term sequelae. We present the case of a 16-year-old male with a past medical history of depression who intentionally ingested windshield wiper fluid containing methanol. Based on the patient's osmolal gap, he was estimated to have a serum methanol level of 374 mg/dL; a send-out laboratory measurement later revealed a serum methanol level of 436 mg/dL. Therapy included two hemodialysis treatments as well as fomepizole and supportive care. The patient recovered remarkably with no long-term sequelae. This case demonstrates the effectiveness of swift recognition and treatment of methanol ingestion. Optimization of methods of measuring serum methanol and evidence-based guidelines for therapy are needed to improve the care of patients with methanol intoxication.

Osmolal and anion gaps after acute self-poisoning with agricultural formulations of the organophosphorus insecticides profenofos and diazinon: A pilot study

Self-poisoning with organophosphorus (OP) insecticides is an important means of global self-harm. The insecticides are formulated with solvents that may also contribute to toxicity. We set up a study to detect changes in osmolal and anion gaps following ingestion of OP insecticides. We recruited consecutive patients admitted to a Teaching Hospital, Sri Lanka, with a history of OP self-poisoning. The osmolal and anion gaps were calculated on admission and at 4, 24 and 72 h post-ingestion together with ethanol concentration. Forty-nine patients were recruited (28 profenofos, 10 diazinon, one coumaphos, one chlorpyrifos, one phenthoate and eight unknown OP). Only modest increases in osmolal and anion gaps were noted. Small rises in osmolal gap above the upper limit of normal were noted in 16/49 (32.7%) of all cases, 9/28 (32.1%) profenofos cases and 4/10 (40.0%) diazinon cases. The anion gap was raised in 24/49 (49.0%) of all cases, 15/28 (53.6%) profenofos cases and 5/10 (50.0%) diazinon cases. We observed a trend for a fall in osmolal gap during the first 24 h, followed by an increase up to 72 h. There was no correlation between the anion gap and serum lactate concentration, indicating that a lactic acidosis was not responsible for the anion gap. Formate, which could have explained the increased gap, was not detected in any of the samples; ketoacids (beta-hydroxybutyrate and acetoacetate) were not measured. This pilot study found that profenofos and diazinon poisoning caused only modest increases in the osmolal and anion gaps in a minority of cases.

The outbreak of methanol intoxication during COVID-19 pandemic: prevalence of brain lesions and its predisposing factors

During the COVID-19 pandemic, methanol-containing beverages' consumption has risen because people mistakenly believed that alcohol might protect them against the virus. This study aimed to evaluate the prevalence and predisposing factors of brain lesions in patients with methanol toxicity and its outcome. A total of 516 patients with confirmed methanol poisoning were enrolled in this retrospective study, of which 40 patients underwent spiral brain computed tomography (CT) scan. The presence of unilateral or bilateral brain necrosis was significantly higher in the non-survival group (p = 0.001). Also, intracerebral hemorrhage (ICH) and brain edema were prevalent among patients that subsequently died (p = 0.004 and p = 0.002, respectively). Lower Glasgow Coma Scale (GCS) was related to a higher mortality rate (p = 0.001). The mortality rate in chronic alcohol consumption was lower than the patients who drank alcohol for the first time (p = 0.014). In conclusion, increasing the number of methanol poisoning and its associated mortality and morbidity should be considered a threat during the COVID-19 pandemic.

Correlation of osmolal gap with measured concentrations of acetone, ethylene glycol, isopropanol, methanol, and propylene glycol in patients at an academic medical center

The ingestion of toxic alcohols including methanol, ethylene glycol, and isopropanol remains a significant public health problem. These compounds can cause central nervous system depression and, for methanol and ethylene glycol, organ damage from toxic metabolites. The presence of these compounds in serum/plasma can often be determined and monitored by measuring the osmolal gap (OG). However, other compounds originating from endogenous or exogenous sources, such as propylene glycol and acetone, can also increase the OG. Conversion factors can be used to estimate specific concentrations of acetone and toxic alcohols from OG. In this retrospective study, data were analyzed for 260 samples originating from 158 unique patients that had determination of both OG and concentrations for toxic alcohols at an academic medical center central laboratory. Specific analysis included gas chromatography (acetone, isopropanol, methanol, ethylene glycol, propylene glycol) and/or enzymatic assay (ethylene glycol). Many samples also contained ethanol. The data was grouped by type of ingestion. The present study analyzed the relationship between the OG calculated from measured plasma/serum osmolality and the OG estimated by applying conversion factors to measured concentrations of the different compounds. The correlations tend to be linear and vary by compound, with methanol and ethylene glycol having the highest R2 values of 0.93 and 0.95, respectively, consistent with other published studies. Higher variability was seen for the data for isopropanol and acetone. For each of the data subsets, the estimated toxic alcohol concentration calculated using conversion factors from OG tends to overestimate the actual concentration of the compound. Overall, the present study demonstrates the generally linear relationship between OG determined by osmolality and the OG estimated using measured concentrations of acetone and toxic alcohols.

The role of the clinical laboratory in diagnosing acid-base disorders

Acid-base homeostasis is fundamental for life. The body is exceptionally sensitive to changes in pH, and as a result, potent mechanisms exist to regulate the body's acid-base balance to maintain it in a very narrow range. Accurate and timely interpretation of an acid-base disorder can be lifesaving but establishing a correct diagnosis may be challenging. The underlying cause of the acid-base disorder is generally responsible for a patient's signs and symptoms, but laboratory results and their integration into the clinical picture is crucial. Important acid-base parameters are often available within minutes in the acute hospital care setting, and with basic knowledge it should be easy to establish the diagnosis with a stepwise approach. Unfortunately, many caveats exist, beginning in the pre-analytical phase. In the post-analytical phase, studies on the arterial reference pH are scarce and therefore many different reference values are used in the literature without any solid evidence. The prediction models that are currently used to assess the acid-base status are approximations that are mostly based on older studies with several limitations. The two most commonly used methods are the physiological method and the base excess method, both easy to use. The secondary response equations in the base excess method are the most convenient. Evaluation of acid-base disorders should always include the assessment of electrolytes and the anion gap. A major limitation of the current acid-base laboratory tests available is the lack of rapid point-of-care laboratory tests to diagnose intoxications with toxic alcohols. These intoxications can be fatal if not recognized and treated within minutes to hours. The surrogate use of the osmolal gap is often an inadequate substitute in this respect. This article reviews the role of the clinical laboratory to evaluate acid-base disorders.

Serum osmolal gap in clinical practice: usefulness and limitations

BACKGROUND

Although serum osmolal gap can be a useful diagnostic tool, clinicians are not familiar with its use in clinical practice.

OBJECTIVES

The review presents in a series of questions-answers and under a clinical point of view the current data regarding the use of osmolal gap.

DISCUSSION

The definition and the best formula used for the calculation of osmolal gap, the main causes of increased osmolal gap with or without increased anion gap metabolic acidosis, as well as the role of concurrent lactic acidosis or ketoacidosis are presented under a clinical point of view.

CONCLUSIONS

The calculation of osmolal gap is crucial in the differential diagnosis of many patients presenting in emergency departments with possible drug or substance overdose as well as in comatose hospitalized patients.

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.

Acute intoxication with the adjuvant itself for Gramoxone INTEON

The adjuvant for Gramoxone INTEON is composed of 20% methanol, 20% sodium lingo sulphonate, 10% alkylaryl polyoxyethylene ether, and 50% water. Although the adjuvant is a potential source of intoxication due to the widespread use of Gramoxone INTEON, there has been no prior report characterizing the acute toxicity of this adjuvant. This study evaluated the acute toxicity of adjuvant ingestion. Seven patients presenting with acute adjuvant intoxication at Chonnam National University Hospital were enrolled in this retrospective study. The patients had intentionally or accidentally ingested 20-150 mL of adjuvant. Gastrointestinal symptoms such as nausea and vomiting were most common, and no ocular symptoms were reported. Cardiovascular symptoms were limited to electrocardiogram changes such as corrected QT interval (QTc) prolongation (71.4%) and sinus tachycardia (28.6%). All patients had an elevated serum osmolar gap and lactate levels. One patient had metabolic acidosis with a high anion gap that required administration of sodium bicarbonate. These clinical symptoms were resolved within 3 days with supportive treatment without any sequelae. There were no life-threatening symptoms and no deaths. However, the physician should keep in mind the possibility of methanol intoxication in patients poisoned with this adjuvant.

Toxic alcohol ingestions: clinical features, diagnosis, and management

Alcohol-related intoxications, including methanol, ethylene glycol, diethylene glycol, and propylene glycol, and alcoholic ketoacidosis can present with a high anion gap metabolic acidosis and increased serum osmolal gap, whereas isopropanol intoxication presents with hyperosmolality alone. The effects of these substances, except for isopropanol and possibly alcoholic ketoacidosis, are due to their metabolites, which can cause metabolic acidosis and cellular dysfunction. Accumulation of the alcohols in the blood can cause an increment in the osmolality, and accumulation of their metabolites can cause an increase in the anion gap and a decrease in serum bicarbonate concentration. The presence of both laboratory abnormalities concurrently is an important diagnostic clue, although either can be absent, depending on the time after exposure when blood is sampled. In addition to metabolic acidosis, acute renal failure and neurologic disease can occur in some of the intoxications. Dialysis to remove the unmetabolized alcohol and possibly the organic acid anion can be helpful in treatment of several of the alcohol-related intoxications. Administration of fomepizole or ethanol to inhibit alcohol dehydrogenase, a critical enzyme in metabolism of the alcohols, is beneficial in treatment of ethylene glycol and methanol intoxication and possibly diethylene glycol and propylene glycol intoxication. Given the potentially high morbidity and mortality of these intoxications, it is important for the clinician to have a high degree of suspicion for these disorders in cases of high anion gap metabolic acidosis, acute renal failure, or unexplained neurologic disease so that treatment can be initiated early.

CRITICAL CARE ISSUES FOR THE NEPHROLOGIST: Acid-base Disturbances in the Intensive Care Unit: Metabolic Acidosis

This article will discuss metabolic acidosis and, to a lesser extent, metabolic alkalosis in the ICU setting. A classification and clinical approach will be the focus.