Tintinalli's Emergency Medicine - Just the Facts, 3ed.

102. GENERAL MANAGEMENT OF POISONED PATIENTS

L. Keith French

EPIDEMIOLOGY

images In 2008, nearly 2.5 million toxic exposures were reported to poison centers in the United States, resulting in 1315 deaths.

images Over half of all reported poisonings occur in children <12 years of age.

images Most accidental poisonings are preventable through increased educational efforts and public awareness.

PATHOPHYSIOLOGY

images All substances have dose-dependent toxic potential.

images Poisons cause harm through various mechanisms including alteration or inhibition of cellular function(s); disruption of cellular uptake or transportation of substances within the body; or interference with utilization of essential substrates from the environment.

images Although ingestion is the most common route of poisoning, toxins can enter the body via inhalation, injection, transdermal or ocular absorption, or insufflation.

CLINICAL FEATURES

images A detailed history is paramount for proper management of the poisoned patient; however, a complete assessment may be difficult to obtain due to alteration in cognition or secondary motives.

images Every attempt should be made to ascertain the type(s), amount, timing, and route of exposure(s) as well as the number of persons involved. Corroboration may be needed from bystanders, family, hospital records, EMS personnel, or paraphernalia in the patient’s possession.

images A thorough physical examination is essential and special emphasis should focus on assessment of mental status, pupil size and reactivity, skin temperature and the presence or absence of sweat, muscular tone, gastrointestinal motility, and mucous membrane moisture.

DIAGNOSIS AND DIFFERENTIAL

images Recognition of a toxidrome can help narrow the differential diagnosis in the situation of an unknown or suspected poisoning (Table 102-1).

images In the emergency setting, toxicologic screening tests of blood and/or urine do not contribute significantly to the evaluation, management, or outcome for most patients.

images There are, however, instances where knowledge of serum concentrations of certain drugs can help guide or change management (Table 102-2).

images Caution should be used when interpreting urine drug screens as false-positive or negative results can be misleading.

images Acetaminophen and aspirin are common and treatable coingestants and should be screened for in any suspected intentional ingestion, unknown poisoning, or patient who presents with altered mental status of unknown etiology.

images Other helpful studies to consider include serum glucose, electrocardiography, arterial blood gas, serum electrolytes, complete blood count, liver function tests, pregnancy screening, and blood ethanol concentration.

TABLE 102-1 Common Toxidromes

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TABLE 102-2 Substances for Which Serum Level May Affect Therapy

Acetaminophen

Salicylate

Lithium

Digoxin

Valproate

Phenytoin

Carbamazepine

Theophylline

Carbon monoxide

Methemoglobin

Methanol

Ethylene glycol

Iron

Paraquat


EMERGENCY DEPARTMENT CARE AND DISPOSITION

images Except in rare circumstances, resuscitation of the poisoned patient begins with assessment and stabilization of the airway, breathing, and circulation rather than administration of a specific antidote (Table 102-3).

images For patients externally contaminated, removal of clothing and copious irrigation of the skin is a priority and should occur as soon as possible, before entry into the hospital. Rescue and hospital personnel should always wear personal protective gear, which may include gowns, eye protection, and masks.

images Patients presenting with sedation, obtundation, or coma, should receive empiric treatment with naloxone (0.2-2.0 milligram IV), glucose (50 mL 50% dextrose IV), and thiamine (100 milligrams IV), which are reasonable and generally accepted as safe. Empiric use of flumazenil, a benzodiazepine antagonist, is generally not recommended for adults, although may be helpful in children.

images Hypotension is first managed with fluid resuscitation; vasopressors should be considered only when blood pressure is refractory to fluid administration. Ventricular dysrhythmias are treated according to standard Advanced Cardiac Life Support (ACLS) measures unless treatment of a specific toxin dictates alternative therapy.

images Benzodiazepines are first-line therapy for seizures following exposure to most toxins.

images Ocular exposures are treated with copious irrigation using isotonic crystalloid. Administration of an ocular anesthetic can facilitate decontamination.

images The three general methods of GI decontamination involve removing toxin(s) from the gut, binding toxin(s) in the stomach, and enhancing transit through the intestines.

images Syrup of ipecac is no longer routinely recommended and should only be used in rare circumstances under the direction of a poison center.

images Orogastric lavage is reserved for potentially lethal poisonings (determined by the toxin and dose). Efficacy is increased when performed in a timely manner, generally within an hour of ingestion. Contraindications include an unprotected airway, caustic or hydrocarbon ingestion, or ingestion of pills that are known to be too large to fit through the side ports of the orogastric tube (OG tube).

images Activated charcoal (1 gram/kg or in a 10:1 AC to drug ratio, whichever is larger) is the agent most commonly used to decontaminate the GI tract and works by adsorbing substances in the gut lumen. Activated charcoal will bind to most organic and some inorganic substances.

images Benefit of activated charcoal is generally greater when administered soon after drug ingestion (up to an hour), although benefit outside this time frame cannot necessarily be excluded.

images Awake and cooperative patients can drink activated charcoal; alternatively, it can be instilled through an NG tube. If orogastric lavage is utilized, a dose of activated charcoal should be given before the OG tube is removed.

images Activated charcoal should not be used if the ingested substance is known not to bind to charcoal, for caustic or volatile substances, if the airway is not protected, or if the patient is actively vomiting.

images Multidose activated charcoal may improve the clearance of theophylline, carbamazepine, phenobarbital, quinine, and dapsone.

images Osmotic cathartics (1 gram/kg or 70% sorbitol or 4 milligrams/kg of 10% magnesium citrate) may be given with the first dose of activated charcoal, although evidence is lacking to support improved outcomes when compared to use of AC alone. Contraindications to cathartic use include age <5 years, caustic ingestions, bowel obstructions, renal failure, and poisonings by substances known to cause significant diarrhea.

images Whole bowel irrigation may enhance elimination of sustained-released products, heavy metals, drugs carried by body stuffers/packers, or agents known to form bezoars. Instill polyethylene glycol via an NG tube (1.5-2.0 L/h in adults, 1.0-1.5 L/h in children 6-12 years of age, and 0.5 L/h in children <6 years of age) until rectal effluent is clear.

images Along with, or subsequent to decontamination, specific techniques to enhance elimination, such as urinary alkalinization and hemodialysis, may be indicated.

images The duration of observation for asymptomatic patients following poisonings or potentially toxic exposures is variable and toxin specific. Consultation with a regional poison center or medical toxicologist may be warranted for expert opinion or assistance with management.

images All patients with intentional poisonings should be referred for psychiatric evaluation once medically stable. Pediatric poisonings may require social work evaluation.

TABLE 102-3 Common Antidotes: Initial Dosages and Indications

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For further reading in Tintinalli’s Emergency Medicine: A Comprehensive Guide, 7th ed., see Chapter 170, “General Management of the Poisoned Patient,” by Jason B. Hack and Robert S. Hoffman.