Chapter 102. Toxicology in Adults

General Measures

• Supportive measures supercede other considerations in the management of the poisoned patient. After addressing the ABCDs of life support, the focus can switch to confirmation of intoxication and targeted therapy.
• Administer a “cocktail” of oxygen, dextrose, thiamine, and naloxone to patients with depressed mental status.
• An increase in anion gap, osmolal gap, or arterial saturation gap should raise the suspicion of intoxication.
• An osmolal gap of large magnitude (>25 mOsm) suggests methanol or ethylene glycol poisoning; however, serious intoxication with either agent can occur without increasing the osmolal gap. Serum levels of these alcohols should be measured when clinical features are suggestive.
• Carbon monoxide and methemoglobin elevate the arterial oxygen saturation gap. These toxins interfere with oxygen binding to hemoglobin and decrease oxygen content without lowering the PaO2. Oxygen saturation measured by pulse oximetry is falsely high in this setting.
• Toxicology screening can provide direct evidence of intoxication, but it rarely impacts initial management.
• Poison control center consultation is advised to determine appropriate laboratory testing and patient disposition and treatment. The emergency phone number is 1-800-222-1222.
• Gastric lavage only improves outcome in obtunded patients if performed within 1 hour of ingestion (this time may be extended in poisonings that delay gastric emptying). Risks of lavage preclude its use in nontoxic ingestions, subtoxic amounts of a toxic ingestion, ingestion of caustic liquids, and when the toxin is no longer expected to be in the stomach. The airway must be protected prior to lavage.
• Activated charcoal should be administered for most oral ingestions after the airway has been protected.
• Whole-bowel irrigation with a polyethylene glycol electrolyte solution is indicated for iron overdose, ingestion of sustained-release tablets, and “body packing" with illicit drugs.
• Urinary alkalinization enhances excretion of nonpolar weak acids. Urinary acidification augments excretion of nonpolar weak bases, but is generally not recommended.

Acetaminophen

• All overdose cases should be screened for acetaminophen poisoning.
• The antidote, n-acetylcysteine (NAC), should be started within 8 hours of ingestion to decrease the risk of hepatotoxicity. The Rumack-Matthew nomogram allows for stratification of selected patients into categories of probable, possible, and no hepatic toxicity.

Alcohols

• Metabolic acidosis with an elevated anion gap and/or the presence of an osmolal gap are classic in methanol and ethylene glycol poisoning.
• Features of methanol poisoning include inebriation, optic papillitis, and pancreatitis. Treatment with fomepizole or ethanol inhibits metabolism by alcohol dehydrogenase to the toxic metabolite formic acid. Dialysis is indicated in severe cases.
• Features of ethylene glycol poisoning include inebriation, acute renal failure, crystalluria, and myocardial dysfunction.
• Treatment with fomepizole or ethanol inhibits metabolism by alcohol dehydrogenase to toxic metabolites (oxalic and glycolic acids). Dialytic removal of ethylene glycol and its metabolites is indicated in severe poisonings.
• Isopropanol causes hemorrhagic gastritis, ketonemia, and ketonuria, but not acidosis. Fomepizole and ethanol are not indicated because metabolites are nontoxic. Dialysis is effective in severe cases.

Barbiturates