Toxicologic, Environmental, and Metabolic Emergencies
Core concepts
Learn toxidromes rather than individual drugs: anticholinergic (hot, dry, flushed, mydriatic, agitated), cholinergic (SLUDGE plus bradycardia), sympathomimetic (hypertensive, tachycardic, diaphoretic), opioid (miosis, hypoventilation), sedative-hypnotic, serotonin (clonus, hyperreflexia, dilated pupils), and neuroleptic malignant syndrome (rigidity, hyporeflexia, delayed onset). Acetaminophen toxicity is predicted by the Rumack-Matthew nomogram at 4 hours; give N-acetylcysteine when timing is unknown or delayed. Salicylate poisoning causes mixed respiratory alkalosis and metabolic acidosis, treated with alkaline diuresis and dialysis for severe cases. Toxic alcohols produce an osmolar gap and high anion gap acidosis - give fomepizole and consider dialysis. Carbon monoxide: 100% oxygen, and pulse oximetry is falsely normal. Methemoglobinemia responds to methylene blue; cyanide from smoke inhalation responds to hydroxocobalamin. Metabolic emergencies: in DKA give fluids before insulin and check potassium, since total-body potassium is depleted even when serum is high; HHS needs more fluid and less insulin. Adrenal crisis needs hydrocortisone before confirmatory testing. Heat stroke is cooled immediately; hypothermia is rewarmed with resuscitation continued.
Traps
A normal osmolar gap does not exclude a toxic alcohol. An acetaminophen level drawn before 4 hours is uninterpretable. In DKA, insulin before volume resuscitation worsens shock, and withholding potassium below 3.3 is dangerous. A wide QRS in overdose means sodium channel blockade - give bicarbonate.
Rule of thumb
In any overdose with a wide QRS or a crashing patient, treat the toxidrome and give sodium bicarbonate for suspected sodium-channel toxicity rather than waiting for drug levels.