During stabilization, information should be obtained from family members, friends, or paramedics who have transported the patient to the hospital about the possible agent, the mode of intoxication, the maximum potential dose, and the time since exposure. If poisoning is suspected, but the history is not confirmatory, information regarding different drugs in the home should be obtained by inquiring about illnesses of the patient and other family members. A determination that an ingested compound is nontoxic (Box 119.1) can enable the provider to avoid subjecting the child to invasive therapies and even admission. Alternatively, a determination of the specific compound early in the course of treatment can help focus treatment. In particular, determination that a compound highly toxic to a child in small quantities (Box 119.2) can heighten concern and the intensity of intervention. The products listed in Box 119.2 have the potential to be fatal in children less than 2 years of age with as little as 1 to tablets or 1 to tablespoons of liquid ingested. Determining the amount of a toxin ingested can be difficult, although estimates of pills ingested from those remaining can be helpful as a starting point. For an estimation of liquid ingestion, the volume of a swallow has been calculated to be approximately 0.27 cc/kg body weight.

The physical examination can be particularly helpful in the case of a questionable exposure to a toxic agent. Certain constellations of symptoms and physical findings may suggest a specific ingestion (Table 119.1). However, children who arrive in the emergency department with a diagnosis of poisoning frequently are asymptomatic. Of those who do present with clinical findings, gastrointestinal tract symptoms (e.g., nausea, vomiting, diarrhea, cramps) and central nervous system depression (e.g., drowsiness, coma) are most common. Other common findings are referable to the respiratory tract (e.g., cough, dyspnea, respiratory depression), cerebellum (e.g., ataxia, nystagmus), central nervous system (e.g., hyperactivity, tremor, convulsions, confusion, delirium, hallucinations), and cardiovascular system (e.g., heart rate, cardiac arrest).

Routine laboratory tests also can aid in the diagnosis and management of poisoned patients. Decreased hemoglobin saturation with a normal or increased arterial oxygen partial pressure is found in patients with carbon monoxide poisoning or in methemoglobinemia. Serum metabolic acidosis with an increased anion gap suggests the ingestion of methanol, ethylene glycol, paraldehyde, toluene, iron, isoniazid, or salicylates. An elevated measured serum osmolarity compared with a calculated osmolarity indicates the presence of low-molecular-weight and osmotically active compounds, such as methanol, isopropyl alcohol, and ethylene glycol. Hypoglycemia can be seen in patients intoxicated by ethanol, methanol, isopropyl alcohol, isoniazid, acetaminophen, salicylates, and oral hypoglycemic agents. Serum pregnancy testing also should be obtained in pubertal females as a possible etiology for intentional ingestion.

Toxicology testing may be helpful in confirming the clinical diagnosis of drug intoxication. However, identifying all available drugs with a high degree of specificity and sensitivity is impossible because of time limitations. Instead, a drug screen
is performed. Because drug screens vary among institutions, the physician should know exactly which drugs can be detected. Generally, toxicology screening tests detect a wide range of narcotics, analgesics, barbiturates, antidepressants, tranquilizers, sedative-hypnotics, and various other drugs and abused substances. Ethylene glycol, lithium, iron, cyanide, lead, and other heavy metals usually are not included in drug screening tests. Some centers have access to rapid, comprehensive drug screening using high-performance liquid chromatography methodology. In general, the history and physical examination are more important in the acute management of drug overdose than is a comprehensive drug screen. Positive drug screen findings merely confirm exposure to that substance, and such an exposure should not be assumed to be responsible for the clinical findings of the moment.

Attention to basic life support and emergency cardiorespiratory support must precede any diagnostic studies in the poisoned child. Respiratory failure can result from upper airway obstruction, central nervous system depression, continuous convulsions, neuromuscular blockade, increased oral and airway secretions, aspiration, and pulmonary edema. An adequate airway is the first priority. Airway patency can be accomplished by jaw-thrust or chin-lift maneuvers or by the placement of an oral or nasopharyngeal airway or an endotracheal tube. Only endotracheal intubation protects from the hazards of aspiration in the airway of a comatose patient lacking a gag reflex.

Usually, hypotension in poisoned children is associated with hypovolemia from excessive volume losses or is considered secondary to vasodilation or capillary leak with third-space losses. Guidelines for fluid resuscitation in hypotensive patients can be applied (see Chapter 453, Shock). The insertion of a central venous line or pulmonary arterial catheter to measure cardiac output and left ventricular filling pressure may be necessary, if hypotension continues despite aggressive fluid administration and inotropic agents.