LAUSR

Background: Methanol toxicity is a potentially life-threatening condition that usually occurs by ingestion. Objective: To alert clinicians to the possibility of methanol toxicity from inhalation or dermal absorption (1). Case Report: A 42-year-old man came to our emergency department with flank pain and headache. He described 1 day of nausea, multiple episodes of emesis, and blurred vision leading to bilateral vision loss. His wife reported that he had begun a new job as a materials handler at a propane company 6 weeks earlier. Two weeks after starting the new job, he had begun having lapses in memory and atypical behaviors, such as leaving his car running or the lawn sprinklers on overnight. The only other medical history was alcohol abuse in remission. The patient's vital signs were initially stable, but he soon developed cyanosis, respiratory distress, and seizure-like activity. He was intubated, and a computed tomography scan of his brain was nondiagnostic. His initial laboratory studies showed severe metabolic acidosis, with a pH less than 6.8 (normal range, 7.35 to 7.45), PCO 2 of 3.95 kPa (normal range, 4.66 to 5.99 kPa), bicarbonate level of 4.2 mmol/L (normal range, 22 to 26 mmol/L), anion gap of 32 mmol/L (normal range, 8 to 16 mmol/L), and lactic acid level of 9.66 mmol/L (normal range, 0.50 to 2.20 mmol/L). In addition, he had a serum potassium level of 6.1 mmol/L (normal range, 3.6 to 5.1 mmol/L), creatinine level of 229.84 mol/L (2.60 mg/dL) (normal range, 53.92 to 109.62 mol/L [0.61 to 1.24 mg/dL]), and blood urea nitrogen level of 7.85 mmol/L (22 mg/dL) (normal range, 2.86 to 9.28 mmol/L [8 to 26 mg/dL]). He had a total leukocyte count of 18.0109 cells/L (normal range, 4.5109 to 11.0109 cells/L), hemoglobin level of 205 g/L (normal range, 120 to 172 g/L), hematocrit of 63.0 (normal range, 36.0 to 53.0), and platelet count of 408109 cells/L (normal range, 140109 to 440109 cells/L). He started receiving a sodium bicarbonate infusion and was admitted to the neurologic intensive care unit, where additional laboratory studies found a serum osmolality of 335 mmol/kg (normal range, 270 to 300 mmol/kg) with an osmolar gap of 39 mmol/kg (normal range, <10 mmol/kg). Tests for volatile alcohols found a methanol level of 5.15 mmol/L (normal range, <0.31 mmol/L) and an acetone level of 0.55 mmol/L (normal range, <0.17 mmol/L) but no ethanol, isopropanol, or ethylene glycol. We started treatment with fomepizole (15 mg/kg of body weight intravenously in 5% dextrose with water) followed by hemodialysis and folic acid (50 mg intravenously every 6 hours). The next morning, the patient's anion gap had resolved and his pH and bicarbonate levels were normal. We withdrew his bicarbonate infusion, extubated him, stopped his hemodialysis, and took a more detailed history. His job was to inspect, fill, and load propane cylinders in a building with windows, doors, and vents. He did not wear a mask or gloves, and he would commonly open the cylinder valves indoors to empty any residual propane. We also learned that methanol is routinely added to propane to prevent valve freezing (2). As a result, we concluded that the patient had occupational exposure to a mixture of propane and methanol, and we diagnosed methanol toxicity secondary to inhalation and dermal absorption. We discharged him 4 days after admission in stable condition, and we have continued to follow him as an outpatient. Now, 6 months after discharge, he has mildly blurred vision that does not interfere with daily activities and residual neuropathy that is improving slowly with gabapentin and physical therapy. He has not been able to return to work. Discussion: Clinicians should keep in mind that methanol toxicity usually occurs when an alcohol-dependent person drinks low-cost household products, such as solvents, antifreeze, or fuel. Methanol toxicity has only rarely been reported as a consequence of occupational exposure (3). Clinicians should also remember that methanol toxicity can present with nonalarming symptoms, such as drowsiness and headaches, before development of significant sequelae that include vision changes, blindness, coma, convulsions, and respiratory arrest. Methanol itself is not especially toxic, but it is metabolized to formaldehyde and formic acid, which can cause severe metabolic and neurologic derangements. Supportive treatment is important for all exposures, and treatment for most exposures also includes altering the body's metabolism. One way is to administer ethanol, which competes with methanol for access to the alcohol dehydrogenase enzyme that metabolizes both methanol and ethanol (4). Another way is to administer fomepizole, which inhibits this enzyme. Hemodialysis can also accelerate clearance of toxic metabolites when the kidneys are affected. Moreover, folate has the theoretical benefit of aiding in the conversion of formic acid to carbon dioxide and water (5).