Name
METHANOL POISONING
DESCRIPTION
DETAIL
CAUSES Methanol ingestion -------------------------------------------------------------------------- DIFFERENTIAL DIAGNOSIS • Ingestion of other alcohols including ethyl alcohol, benzyl alcohol or isopropyl alcohol • Other toxic ingestions including ethylene glycol, paraldehyde, salicylates, and formaldehyde • Increased anion-gap metabolic acidosis caused by renal failure, diabetic ketoacidosis, and lactic acidosisLABORATORY • Serum methanol and ethanol concentrations, electrolytes, calcium, blood urea nitrogen & creatinine, osmolarity, hepatic aminotransferase enzymes, amylase, creatinine kinase, urinalysis, arterial blood gas • Calculate anion gap and osmolar gap • Calculated osmolarity is determined by (1.9[Na] + [BUN]/2.8 + [Glucose]/18). An osmolar gap exists if calculated osmolarity is greater than measured osmolarity by 10 mOsm/Kg H2O • Increase anion-gap metabolic acidosis noted on arterial blood gas and serum electrolytes • In acute intoxications serum methanol concentrations >20mg/dL are associated with CNS effects; > 100 mg/dL are associated with visual defects; > 200 mg/dL are associated with death in untreated patients • Methanol serum concentrations are not useful for treatment or prognosis decisions after the latency period since toxicity is determined by formic acid concentration in the blood • MCV may increase due to generalized cellular swelling • Elevated serum amylase may indicate the presence of pancreatitis SPECIAL TESTS Serum methanol concentration IMAGING CT or MRI scan of the brain if indicated by neurological exam. Brain imaging may reveal hypodensities in the putamen or caudate nucleus, cerebral edema, or cerebral hemorrhage DIAGNOSTIC PROCEDURES Visual evoked potentials and electroretinogram may give prognostic information about visual disturbances
TYPENOTES
RISK FACTORS: Alcoholism, Epidemics may occur in institutionalized settings where ethyl alcohol is unavailable (i.e. prisons)GENERAL MEASURES • Management priorities depend on the timing of presentation in relationship to ingestion or exposure • Assess the magnitude of ingestion and inhibit methanol metabolism if ingestion is likely. Initial management is directed towards preventing metabolic acidosis and ophthalmologic complications • Obtain laboratory studies • Obtain intravenous access and administer isotonic fluids to maintain adequate urine output • In general gastric decontamination with induced emesis, charcoal, or gastric lavage is not indicated unless a concomitant ingestion is known • Ethanol or fomepizole should be administered as soon as possible in order to prevent hepatic biotransformation of methanol to formic acid. Ethanol is less expensive but more cumbersome to compound and administer. Fomepizole is easier to administer but is quite expensive. • Sodium bicarbonate should be administered if serum pH < 7.2 to maintain pH > 7.3 • Folinic acid (Leucovorin) or folic acid may be administered • Consider urgent hemodialysis when signifi cant acidosis (pH < 7.2) unresponsive to therapy, deteriorating vital signs in spite of intensive support, renal failure, electrolyte imbalance, or serum methanol concentration > 50mg/dL DIET No special diets. Thiamine supplementation in chronic alcoholics DRUG(S) OF CHOICE . Ethanol may be administered orally, if the gastrointestinal tract is functioning, or intravenously. Monitor serum ethanol concentrations q 2 hrs to maintain at 100-150 mg/dL. Continue ethanol until serum methanol concentrations are <20 mg/dL and patient is asymptomatic with a normal serum pH. . Loading dose. 600-800 mg/kg [2mL/kg of 80 proof whiskey (31.6gm ethanol/100mL) or approximately four 1 ounce oral doses in adults] Ehanol Dosing in Methanol Poisoning ETOHõ Oralõõ IVõõõ mg/kg mL/kg mL/kg --------------------------------------- Loading 600 1.8 7.6 Maint ND 66 /hr 0.2 /hr 0.8 /hr Maint CD 160 /hr 0.5 /hr 2 /hr MntDi ND 170 /hr 0.5 /hr 2.1 /hr MntDi CD 260 /hr 0.8 /hr 3.3 /hr --------------------------------------- õ Absolute ETOH õõ Use 86 proof liquor õõõ 10% ETOH IV solution ND: non-drinker CD: chronic drinker MntDi: maintenance during dialysis ---------- . Fomepizole. IV loading dose of 15mg/kg followed by IV boluses of 10mg/kg q 12 hours for 4 doses. If patient still symptomatic continue 15mg/kg q 12 hours until the methanol level is < 20mg/dL and patient is asymptomatic . Folinic acid (leucovorin). 1mg/kg (up to 50 mg) q 4 hrs until clinical endpoints reached. Alternatively folic acid, 50 mg IV q 4 hrs Contraindications: Avoid ethanol if disulfiram used PATIENT MONITORING • Alcohol treatment program for chronic alcoholics • Ophthalmology follow-up for patients with visual disturbances PREVENTION/AVOIDANCE Avoid methanol containing fluids POSSIBLE COMPLICATIONS • Blindness and other visual disturbances • Myoglobinuric renal failure • Pancreatitis • Parkinson-like syndrome EXPECTED COURSE/PROGNOSIS • Outcome varies depending on the time to presentation and quantity ingested • Outcome is related to degree of acidosis, coma, or seizures at time of presentation • In one study 19/51 patients died in an 11 year period. • In a study from Ontario, Canada, 43 deaths in a 7 year period
RELATED DISEASE
Not Available Disease
DISEASE
INVESTIGATION
BLOOD UREA, SERUM CREATININE, SERUM AMYLASE, SERUM CALCIUM, SERUM SODIUM, SERUM POTASSIUM, CPK ( MALE ), URINE ROUTINE, CPK ( FEMALE ), COMPLETE BLOOD COUNT, LIVER FUNCTION TEST