Isopropyl alcohol ingestion is common among children and adults as both accidental and suicidal ingestions because it is an easily available product. It is best known as the main ingredient in rubbing alcohol, but is also present in window cleaners, toiletries, disinfectants, antifreeze, and paint remover. To complicate matters some products that contain isopropyl alcohol also contain methanol, ethanol, or ethylene glycol.
Pharmacology:
Isopropyl alcohol is a clear, colorless liquid with a somewhat bitter taste and a smell of acetone. Unless the ingested dose is large, absorption occurs in as little as 30 minutes. This agent is well absorbed through the lungs and rectal mucosa. The alcohol can also penetrate the skin, but with less success than via a pulmonary or GI exposure. Isopropyl alcohol is metabolized to acetone in the liver by alcohol dehydrogenase. Eighty percent of the absorbed dose is then excreted by the kidneys as acetone with 20% being excreted unchanged. The acetone is also excreted in the lungs, saliva, and gastric juices.
Animal studies have suggested that isopropyl alcohol is two-three times more potent than ethanol as a CNS depressant. The breakdown product, acetone, is also a CNS depressant.
Clinical Presentation:
The symptoms of ingestion occur within 30 minutes, with GI complaints of pain, vomiting, and hematemesis being predominant. Central nervous system effects include headache, muscular incoordination, ataxia, confusion, and coma. The initial excitatory phase that is well recognized with ethanol intoxication does not seem to be present with isopropanol ingestion. Pupil size may vary, but it is not uncommon to have miotic pupils. Should the eyes have direct exposure to isopropyl alcohol corneal de-epithelialization has been reported. The patient may have a distinct odor of acetone. With very large doses cardiovascular effects include myocardial depression and severe hypotension. Less common presentations include renal tubular necrosis, hemolytic anemia, acute myopathy, and hypothermia.
Diagnosis:
The patient presenting in coma who has a suspected exposure to some type of alcohol, the diagnosis can be challenging. The patient will be unresponsive to narcan and glucose, and usually entities such as DKA, hepatic coma (in an older patient), carbon monoxide, trauma, etc. can usually be quickly ruled out by a careful exam and a few simple tests. Once the diagnosis of a toxic alcohol (or a toxic amount of a usually nontoxic alcohol) is suspected the difficulty comes in making the diagnosis. The onset of the central nervous system effects of all the alcohols is rapid. The more severe consequences of ethylene glycol and methanol (the blindness, renal failure, and severe metabolic acidosis may be slightly delayed. All of the major alcohols have a distinct odor except ethylene glycol. In the case of isopropyl alcohol the odor is a sweet ketotic scent due to the release of acetone in the breath. Isopropyl alcohol tends to produce only a mild elevation of the anion gap and only a mild acidosis if any. It is alsounique in producing a very large amount of ketones (the acetone that is being excreted from the kidneys) in the urine.
Serum osmolality may be greater than calculated with all four alcohols, thus isopropanol is similar to ethanol in that it produces little to no anion gap metabolic acidosis (unless the patient has other problems such as hypotension, hypoxia, etc.), but does have an elevated osmolol gap. Isopropyl alcohol also tends to have significant hypoglycemia.
Treatment:
The treatment of isopropyl alcohol exposure is recognition and support of the complications. If exposure was through the skin then decontamination is appropriate while trying to maintain body temperature. If the exposure was respiratory the patient should be removed from the environment. Hemorrhagic trachoebronchitis is a complication of inhaled isopropanol. If the exposure was a large, recent dose of isopropanol, gastric lavage and charcoal may be appropriate. Isopropanol does undergo gastric re-excretion and continuous gastric emptying has been recommended, but this is usually not required. Should the patient be stable after the initial evaluation it is reasonable to observe the patient and use simple supportive measures until the patient recovers. Suspicion should always be present about other ingestions and the labs previously discussed should be ordered.
Isopropanol is an ideal substance for dialysis because of its low molecular weight, low volume of distribution, and low protein plasma binding. The question then, is who requires dialysis? Those patients with isopropyl levels above 400-500 mg/dl are usually the ones that have significant hypotension and coma. Thus, patients with coma and hypotension with or without a level of 400-500 mg/dl should probably receive hemodialysis.
Pediatric Considerations:
Young children may accidentally ingest isopropyl alcohol just as they can with any other available substance. However, children may develop a serious intoxication following topical application of isopropyl alcohol for the relief of fever. This exposure may actually be more of an inhalation injury than a dermal exposure, but the end result in the same. Isopropyl alcohol can come in concentrations of 70%. At this concentration as little as 2-2.5 ml/kg may lead to toxicity. The children may present with altered mental status or coma. The key to diagnosis is the same as with adults. The child should have acetonuria, coma, little to no acidosis and anion gap, with a wide osmolol gap. Treatment is the same as for adults.
Pharmacology: