blockers, and sedative-hypnotics. Hypotension with tachycardia occurs with tricyclic antidepressants, phenothiazines, and theophylline. Hyperthermia is most frequently a result of overdose of drugs with antimuscarinic actions, the salicylates, or sympathomimetics. Hypothermia is more likely to occur with toxic doses of ethanol and other central nervous system (CNS) depressants. Increased respiratory rate is often a feature of overdose with carbon monoxide, salicylates, and other drugs that cause metabolic acidosis or cellular asphyxia. Overdoses of agents that depress the heart are likely to affect the functions of all organ systems that are critically dependent on blood flow, including the brain, liver, and kidney.

Cause of Death in Intoxicated Patients

The most common causes of death from drug overdose in the United States reflect the drug groups most often selected for abuse or for suicide. Sedative-hypnotics and opioids cause respiratory depression, coma, aspiration of gastric contents, and other respiratory malfunctions. Drugs such as cocaine, PCP, tricyclic antidepressants, and theophylline cause seizures, which may lead to vomiting and aspiration of gastric contents and to postictal respiratory depression. Tricyclic antidepressants and cardiac glycosides cause dangerous and frequently lethal arrhythmias. Severe hypotension can occur with any of these drugs. A few intoxicants directly damage the liver and kidney. These include acetaminophen, mushroom poisons of the Amanita phalloides type, certain inhalants, and some heavy metals. (see Chapter 57).

Management of the Poisoned Patient

Management of the poisoned patient consists of maintenance of vital functions, identification of the toxic substance, decontamination procedures, enhancement of elimination, and, in a few instances, administration of a specific antidote.

Vital Functions

The most important aspect of treatment of a poisoned patient is maintenance of vital functions, as indicated by the mnemonic, ABCDs. The most commonly endangered or impaired vital function is respiration. Therefore, an open and protected airway (A) must be established first and effective ventilation (B for breathing) must be ensured. The circulation (C) should be evaluated and supported as needed. The cardiac rhythm should be determined, and if ventricular fibrillation is present, it must be corrected at once. The blood pressure should be measured but rarely needs immediate treatment except in cases of traumatic hemorrhage. Because of the danger of brain damage from hypoglycemia, intravenous 50% dextrose (D) should be given to comatose patients immediately after blood has been drawn for laboratory tests and before laboratory results have been obtained. Thiamine should be administered to prevent Wernicke’s syndrome in patients with suspected alcoholism or malnourishment. In patients with signs of respiratory or CNS depression, intravenous naloxone offsets possible toxic effects of opioid analgesic overdose.

Identification of Poisons

Many intoxicants cause a characteristic syndrome of clinical and laboratory changes. Table 58-1 summarizes toxic syndromes associated with major drug groups and the key interventions called for. The toxic features of selected individual agents are listed in Table 58-2. When the toxic agent cannot be directly examined and identified, the clinician must rely on indirect means to identify the type of intoxication and the progress of therapy. In addition to the history and physical examination, certain laboratory examinations may be useful. A few intoxicants can be directly identified in the blood or urine, especially when information in the history narrows the search. In the more common situation of a comatose patient unable to provide a history, general tests for replacement of anions or osmotic equivalents in the blood (anion gap, osmolar gap) may be useful. A few intoxicants can be identified or strongly suspected on the basis of electrocardiographic or radiologic findings.

TABLE 58-1 Toxic syndromes caused by major drug groups.

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