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Isopropanol Poisoning

Isopropanol intoxication usually results from ingestion of rubbing alcohol, hand sanitizer, and various industrial products, but intoxication can also be due to inhalation or absorption through dermal or rectal routes. Isopropanol is metabolized to acetone. Common clinical features include inebriation, depressed sensorium and abdominal pain. Severe cases may have respiratory depression, cardiovascular collapse, acute pancreatitis, hypotension, and lactic acidosis. Symptoms usually begin within two to four hours after exposure. 

Serum isopropanol concentrations above 500 mgdL (83 mmol/L) are clinically significant, and those greater than 1500 mg/dL (250 mmol/L) are associated with deep coma. Major laboratory findings include increased osmolal gap, acetonemia and ketonuria. Acetone can produce a spurious increase in serum creatinine concentration as a result of interference with laboratory measurement.

Measurement of serum osmolality and calculation of the osmolal gap are also useful. Accumulation of the alcohol increases the serum osmolality and the osmolal gap, which is the difference between the serum osmolality, measured by freezing-point depression, and calculated serum osmolarity. The osmolal gap varies during the course of intoxication. Accumulation of the parent alcohol initially elevates the osmolal gap, but as metabolism progresses, osmolal gap decreases.

The expected normal osmolal gap is 10 to 20 mOsm per kilogram of water. An osmolal gap greater than 20 mOsm/kg is consistent with ingestion of a foreign substance (see Osmolality for further details). A normal osmolal gap cannot be used to rule out toxic alcohol ingestion because some patients with toxic alcohol poisonings have osmolal gaps within the normal range.

Supportive measures are often sufficient, but hemodialysis may be necessary if the serum isopropanol concentration is 500 mg/dL or more or if hypotension or lactic acidosis is present. Alcohol dehydrogenase inhibitors slow the removal of isopropanol and should not be used.

References

Slaughter RJ, et al. Isopropanol poisoning. Clin Toxicol (Phila) 2014; 52: 470-8.

Kraut JA and Mullins ME. Toxic Alcohols. New Engl J Med 2018;378:270-80

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