According to United States poison control center data, more than 2 million human poison exposure cases occurred in 1995.¹ Children less than six years of age accounted for 53 percent of these cases, but only 2.8 percent of the fatalities. Therefore, children less than six years of age represent the patient population most frequently affected by poison exposures. Because their ingestions are most commonly accidental, they rarely ingest enough poison to cause death. In contrast, patients older than 19 years of age are less frequently exposed to poisons but because their exposure is more commonly intentional, they represent over 90 percent of drug-related fatalities. Each year approximately 7,000 drug exposures are reported in pregnant patients.

More than 1.5 million cases of poisoning in 1995 were the result of ingestions, and they accounted for 73.6 percent of all poison exposures.¹ These data represent an estimated 83 percent of exposures that resulted in contact with poison control centers. Since many patients with toxic ingestions are managed without contact with poison control centers or emergency departments, the total number of cases is much larger than the numbers reported by the poison control centers. Because primary care physicians are frequently the health care professionals first contacted by patients who have ingested poisons, knowledge of the proper initial evaluation and treatment of these patients is essential.

Patients who have ingested toxic substances contact health care providers in various ways, including telephone calls and unannounced arrivals at the physician's office or an emergency department, with or without symptoms. Although the presentations may vary, management of poisoned patients should include, whenever possible, an accurate history; stabilization of the patient's condition; physical examination to evaluate the extent of poisoning and the presence of concurrent conditions; decontamination; poison-specific treatment, including administration of antidotes when appropriate, and disposition.

History

The history should address the “Five Ws”: who—the patient's age, weight, relationship to others present and gender; what—the name and dosage of medication(s) or substances of abuse, coingestants and amount ingested; when—the time and date of ingestion; where—both the route of poisoning (e.g., ingestion or injection) and the geographic location where the poisoning occurred, and why—whether intentional or unintentional, and associated details. In addition, a detailed past medical history should be obtained, including previous poisonings, medical conditions and concurrent medications that might affect the patient's response to and metabolism or elimination of ingestants, psychiatric history and history of substance abuse. Particular attention should be devoted to eliciting a history of alcoholism, and renal or hepatic disease.

Clinicians should attempt to obtain this information in all cases, even for apparently minor ingestions reported over the telephone. Information obtained from the patient may be inaccurate or incomplete, and additional history obtained from friends, family members or other health professionals (e.g., clinicians, pharmacists) can be invaluable help in management decisions.² Table 1 lists several inert substances that, if taken in moderate amounts, are usually harmless.

Assessment and Stabilization

Emergency Assessment

A brief physical assessment should be performed immediately in all patients to determine the effects of toxin(s) and other conditions that might be present. Particular attention should be directed to adequacy of the airway and ventilation, level of mental status and cardiac function. Unstable patients should be placed on a cardiac monitor, with measurement of vital signs every five to 15 minutes until the patient is stabilized to the point that monitoring is no longer necessary.

The initial assessment is especially important in patients with decreased responsiveness and unstable vital signs because, for example, head trauma or penetrating body trauma can masquerade as an overdose. Evidence of head injury, penetrating wounds or chemical burns of the mouth and face mandate specific evaluation and management strategies and should not be missed. Focal neurologic signs are suggestive of central nervous system (CNS) vascular events, including cerebrovascular accidents and subdural hematoma. A more detailed physical assessment should be performed after the patient's cardiopulmonary status has been stabilized.

Initial Stabilization Procedures

Stabilization of the patient is the first priority in managing toxic ingestions and is performed simultaneously with the initial physical assessment. Treatment should address the “ABCs” (airway, breathing, circulation) without delay. Also, the potential for rapid changes in the patient's condition should be considered in making decisions about airway and ventilatory support. Treatment with naloxone (Narcan), dextrose and thiamine should be considered in patients with altered mental status.^2–4 Naloxone is a competitive antagonist at opiate receptors and can reverse narcotic-induced symptoms when given intravenously, intramuscularly, endotracheally, subcutaneously or intralingually. Successful submental administration of naloxone has also been reported.⁵

Naloxone can safely be given to patients with respiratory and/or CNS depression who have a low likelihood of opioid addiction. Because of concern about withdrawal symptoms and/or unmasking symptoms from coingestants, caution is indicated in cases of suspected opioid addiction and multi-drug poisonings.³ Naloxone is administered to adults for treatment of respiratory depression in a dosage of 2.0 mg initially, repeated every two minutes as needed up to a total of 10 mg; in narcotic-dependent patients or those with non–life-threatening symptoms, the dosage is 0.1 mg initially, doubled every two minutes up to a total of 10 mg; in children older than five years of age or weighing more than 20 kg, the dosage is 2.0 mg initially for patients with respiratory depression and 0.1 to 0.8 mg if respiratory depression is not present; in neonates and young children, the initial dosage is 0.1 mg per kg.⁶

Symptoms of hypoglycemia (e.g., altered mental status, cool, clammy skin, coma) are rapidly reversed with administration of hypertonic dextrose. Patients with altered mental status, absent focal neurologic signs and low or borderline hypoglycemia (blood sugar less than 80 mg per dL on rapid reagent testing) should receive intravenous dextrose (adults: 50 mL of 50 percent dextrose; children: 4 mL per kg of 25 percent dextrose; neonates: 5 mL per kg of 10 percent dextrose).^4,7 Dextrose may be administered empirically if rapid reagent testing is not available. The safety of hypertonic dextrose in settings of cerebral ischemia has been questioned and, whenever feasible, bedside documentation of hypoglycemia should be obtained before administering dextrose.

In cases where intravenous access is difficult, glucagon, 1.0 mg intramuscularly, may be given as a temporizing measure. Intravenous thiamine (vitamin B₁) should be given to patients treated with hypertonic dextrose (adults: 100 mg; children: 10 to 25 mg), theoretically before the dextrose is administered, to prevent Wernicke's encephalopathy.

Determination of Ingested Substance

Physical findings may suggest the type of toxin(s) ingested but, more often, a detailed history, examination of medication containers or toxicologic analysis reveals the answer. Physical findings, however, often enable the clinician to determine if the toxin is a physiologic stimulant or a depressant, and which common poisons should be considered in the initial management of the patient.

Physical signs following ingestion of stimulants often include mydriasis (dilated pupils), tremor, tachycardia, irritability, diaphoresis, mania, convulsions and tachyarrhythmias. Commonly ingested stimulants include cocaine, amphetamines, caffeine, theophylline, tricyclic antidepressants (early symptoms after overdose), antihistamines and hallucinogens.

Physical findings produced by physiologic depressants include lethargy, decreased responsiveness to verbal and physical stimulation, miosis (constricted pupils), hypothermia and coma. Common sedative-hypnotics include alcohol, benzodiazepines, barbiturates, muscle relaxants and chloral hydrate.

Cardiovascular agents include antihypertensive agents (angiotensin-converting enzyme inhibitors, beta blockers, calcium channel blockers and centrally acting agents), digitalis and antiarrhythmic agents. Table 2 lists clinical syndromes (“toxidromes”) associated with toxins that are frequently ingested and/or that cause significant mortality.¹

Additional physical findings may be evaluated with the help of an appropriate text, by consulting experienced colleagues or by contacting a regional poison control center. Telephone numbers of poison centers certified by the American Association of Poison Control Centers are included in Table 3.

Laboratory Evaluation

Laboratory evaluation is indicated in most symptomatic patients, when ingested substances are unknown, if the poison has the potential to produce moderate to severe toxicity and if the ingestion was intentional. Routine studies should include a complete blood cell count, determination of serum electrolyte and glucose levels, a chemical screen with hepatic and renal function studies (e.g., calcium, aspartate aminotransferase, alanine aminotransferase, bilirubin, alkaline phosphatase, lactate dehydrogenase, prothrombin time, blood urea nitrogen, creatinine) and urinalysis. Measurement of serum osmolarity may be helpful if poisoning with methanol, ethylene glycol or isopropanol is suspected.

Drug screening has limited value because care in most cases of toxic ingestion is supportive and not affected by identification of the ingestant.^2,8,9 However, drug screening is common practice in many medical settings where poisonings are managed and can provide useful information. Qualitative toxicology screening is most useful when the ingested toxin is unknown, in cases of multiple ingestion and when symptoms and physical findings are not compatible with the history. Quantitative toxicology screening is useful when knowledge of drug serum levels may affect patient management; examples include ingestions of acetaminophen, salicylates, ethanol, ethylene glycol, isopropyl alcohol, digoxin, iron, lithium, theophylline, anticonvulsants and methanol.^2,10

Ancillary Tests

An electrocardiogram should be performed in patients with arrhythmias and/or suspected ingestion of cardiotoxic drugs. Chest radiographs should be obtained in patients with suspected aspiration, coma or ingestion of medications (salicylates, narcotics, paraquat, sedative-hypnotics) that can produce noncardiogenic pulmonary edema.¹¹ Abdominal radiographs may detect abnormal densities in patients who have ingested drug packets, salicylates, calcium salts, heavy metals (e.g., iron tablets) or radiopaque foreign bodies. Ingested hydrocarbons may be visualized as a “layer” between gastric fluid and the gastric air bubble.

Ancillary tests such as electrocardiograms, chest radiographs and plain abdominal films need not be routinely ordered but, when appropriate, can provide the clinician with additional useful information.

Decontamination

Following evaluation and stabilization of the poisoned patient, attention is directed toward decontamination, i.e., decreasing absorption of the ingested poison from the gastrointestinal tract. This can be accomplished by emptying the stomach via gastric lavage, administration of activated charcoal within the gut lumen and use of methods for increasing transit of the toxic substances through the gastrointestinal tract.

Gastric emptying should not routinely be used in all oral poisoning cases because it is ineffective when used at a late stage, may delay more effective interventions and can cause needless complications, such as aspiration.^2,8,12,13 However, it is often beneficial when used early in the treatment of potentially severe poisonings. Gastric emptying is most effective when used within one hour of the ingestion and cannot be justified beyond four hours following the ingestion except in patients with concretions, massive ingestions or ingestions of substances that markedly decrease gastric motility. The stomach may be emptied by gastric lavage or by inducing emesis with syrup of ipecac.

Gastric Lavage

In most situations, gastric lavage is preferable to administration of ipecac, particularly in emergency departments where prolonged ipecac-induced vomiting may delay treatment with activated charcoal. Indications for lavage include ingestions of highly toxic substances (large ingestions or substances associated with high morbidity and/or mortality); substances not well adsorbed by activated charcoal (i.e., lithium, iron, lead, methanol) and in patients with the potential for a jeopardized airway (e.g., altered alertness).¹²

Contraindications to gastric lavage include ingestion of corrosives and most hydrocarbons (gastric emptying is indicated after ingestions of hydrocarbon products containing benzene, toluene, camphor, halogenated hydrocarbons, pesticides or heavy metals, or if the ingestion was greater than 4 to 5 mL per kg); patients with depressed gag reflexes who are not intubated and clinically insignificant ingestions. Complications include aspiration, and perforation of the esophagus or bronchus. A 28- to 36-in French tube is suitable for use in children; a 36- to 40-in French tube is suitable for use in adults.^8,12

Gastric lavage is accomplished in children using normal saline or tap water in 15 mL per kg aliquots until clear.³ Lavage in adults uses 300 mL aliquots until clear, up to 10 to 20 L, if necessary. Administration of activated charcoal through the lavage tube before and after lavage may be beneficial in patients with potentially fatal ingestions.

Ipecac

Ipecac continues to be useful in the telephone management of alert patients unable to travel to a health care facility within one hour of the ingestion. It has been shown that ipecac used at home by experienced hospital staff treating pediatric poisonings following ingestions identified as not being “high-risk” decreases pediatric emergency department visits without jeopardizing safety.¹⁴

Syrup of ipecac is administered in the following dosages: in infants six months to one year of age, 10 mL; in children one to 12 years of age, 15 mL; in adolescents over 12 years of age, 30 mL. Water is given immediately after the ipecac to enhance the efficacy of gastric emptying with emesis; adults should receive 8 to 16 oz; children should receive 4 to 8 oz; children less than one year of age should receive 5 to 15 mL per kg body weight.

Ipecac should not be given to children who are less than six months of age, patients who are already vomiting, patients with altered mental status or impaired gag reflexes, and patients who have ingested medications that cause seizures or decreased responsiveness. Use of ipecac should be avoided following ingestion of corrosives (acids or alkalis), sharp objects, most hydrocarbons (similar to gastric lavage) or when treatment with activated charcoal is anticipated within 60 to 90 minutes.

Activated Charcoal

Activated charcoal forms the mainstay of gastric decontamination and is effective for most oral poisonings when given alone or following gastric emptying. Exceptions include ingestions of caustic acids and alkalis, alcohols, lithium and heavy metals (e.g., iron, arsenic). Activated charcoal is inert and remains within the gastrointestinal tract, offering a large surface area for adsorption of ingested toxins. In addition, activated charcoal may decrease the absorption of drugs that undergo enterogastric or enterohepatic circulation.

The usual dosage is 1 to 2 g per kg for children and adults, usually given as a single dose combined with a cathartic. The charcoal is mixed with water in a ratio of 1:4 to 1:8 (1 part charcoal to 4 or 8 parts water) to form a slurry; small quantities of fruit juice or chocolate powder can improve the taste. Multiple dosing (1 g per kg every two to six hours) has been shown to be effective for poisonings with phenobarbital, phenytoin (Dilantin), carbamazepine (Tegretol), salicylates, digitalis, theophylline and dapsone.^12,15–17 When multiple dosing is used, a cathartic can be given with the first dose but should not be administered with subsequent doses because of the potential for serious fluid and electrolyte abnormalites. Contraindications to activated charcoal use include mechanical bowel obstruction and ileus.

Whole Bowel Irrigation

Whole bowel irrigation uses isosmotic cathartic solutions to flush and cleanse the bowel. It is potentially beneficial in patients who have ingested substances that are not well-absorbed by activated charcoal and/or are not amenable to lavage. Examples of such substances include iron, lithium and slow-release potassium, and packets or vials containing cocaine and other drugs. Commonly used irrigants (Golytely, Colyte) contain a polyethylene glycol electrolyte solution that is not absorbed from the gastrointestinal tract and does not cause significant fluid or electrolyte imbalances. The solution is administered orally or through a nasogastric tube at the rate of 2 L per hour in adults and 0.5 L per hour (or 25 to 40 mL per kg per hour) in children until the rectal effluent is clear.^8,12,13 Patients tolerate the procedure best when alert and sitting on a commode; supine patients are best managed by placing a rectal tube. Contraindications to whole bowel irrigation include mechanical obstruction, ileus, perforation and gastrointestinal bleeding.

Antidotes

Table 4 lists antidotes to several of the common and dangerous poisons. Antidotes are typically given once the patient has been stabilized, usually within a few hours of the ingestion. Unless clinicians are familiar with the use of an antidote, it is probably wise to contact a certified poison control center regarding the specifics of its use. In addition, many antidotes have a short duration of action relative to the effects of the ingested poison, and observation in a specialized hospital unit following administration of the antidote is advisable.

Disposition

Management and disposition of patients following decontamination is toxin- and patient-specific, occasionally requiring interventions such as dialysis, hemodialysis and hemoperfusion. Fortunately, most poisoned patients require only minor supportive care and recover without sequelae. Patients treated over the telephone without being seen should have close telephone follow-up, within two to three hours of initial contact and as indicated thereafter. Many patients seen in an emergency department can be discharged without concern about toxicity from the ingestant(s) and require only routine outpatient follow-up with their primary care provider.

Patients treated for intentional poisonings should undergo psychiatric evaluation before the final decisions regarding disposition are made. Patients admitted to the hospital should be placed on units able to closely monitor their condition; those treated with antidotes usually require admission to intensive care or step-down units, where monitoring and close observation are possible. Finally, a certified poison control center should be consulted if questions arise about the disposition of a poisoned patient.