For example, determination of the acetaminophen level is useful in assessing the need for antidotal therapy with acetylcysteine. Serum levels of salicylate (aspirin), ethylene glycol, methanol, theophylline, carbamazepine, lithium, valproic acid, and other drugs and poisons may indicate the need for hemodialysis (Table 58–2).
Decontamination procedures should be undertaken simultaneously with initial stabilization, diagnostic assessment, and laboratory evaluation. Decontamination involves removing toxins from the skin or gastrointestinal tract.
A. Skin
Contaminated clothing should be completely removed and double-bagged to prevent illness in health care providers and for possible laboratory analysis. Wash contaminated skin with soap and water.
B. Gastrointestinal Tract
Controversy remains regarding the efficacy of gastrointestinal decontamination, especially when treatment is initiated more than 1 hour after ingestion. For most ingestions, clinical toxicologists recommend simple administration of activated charcoal to bind ingested poisons in the gut before they can be absorbed (as in the case study). In unusual circumstances, gastric lavage or whole bowel irrigation may also be used.
TABLE 58–2 Hemodialysis in drug overdose and poisoning.1
Hemodialysis may be indicated depending on the severity of poisoning or the blood concentration:
Hemodialysis is ineffective or is not useful: 1This listing is not comprehensive.
1.
Emesis—Emesis induced by ipecac syrup was previously used to treat some childhood ingestions at home under telephone supervision of a physician or poison control center personnel. However, the risks involved with inappropriate use outweighed the unproven benefits, and this treatment is no longer used in the home or hospital. Other methods of inducing emesis such as fingertip stimulation of the pharynx, salt water, and apomorphine are ineffective or dangerous and should not be used.
2.
Gastric lavage—If the patient is awake or if the airway is protected by an endotracheal tube, gastric lavage may be performed using an orogastric or nasogastric tube—as large a tube as possible. Lavage solutions (usually 0.9% saline) should be at body temperature to prevent hypothermia.
3.
Activated charcoal—Owing to its large surface area, activated charcoal can adsorb many drugs and poisons. It is most effective if given in a ratio of at least 10:1 of charcoal to estimated dose of toxin by weight. Charcoal does not bind iron, lithium, or potassium, and it binds alcohols and cyanide only poorly. It does not appear to be useful in poisoning due to corrosive mineral acids and alkali. Repeated doses of oral activated charcoal may enhance systemic elimination of some drugs (including carbamazepine, dapsone, and phenobarbital) by a mechanism referred to as “gut dialysis,” although the clinical benefit is unproved.
4.
Cathartics—Administration of a cathartic (laxative) agent may hasten removal of toxins from the gastrointestinal tract and reduce absorption, although no controlled studies have been done. Whole bowel irrigation with a balanced polyethylene glycol-electrolyte solution (GoLYTELY, CoLyte) can enhance gut decontamination after ingestion of iron tablets, enteric-coated medicines, illicit drug-filled packets, and foreign bodies. The solution is administered orally at 1–2 L/h (500 mL/h in children) for several hours until the rectal effluent is clear.
There is a popular misconception that there is an antidote for every poison. Actually, selective antidotes are available for only a few classes of toxins. The major antidotes and their characteristics are listed in Table 58–3.
Methods of Enhancing Elimination of Toxins