History

An accurate history is vitally important in the diagnosis of unknown poisoning. Surprisingly, the physician in the intensive care unit (ICU) may be the first health professional who can sit with parents and carefully review the possible circumstances of the exposure. Poisonings may occur by various routes including ingestion, inhalation, ocular exposure, dermal exposure, mucous membrane involvement, or parenteral exposure. Once the child’s condition has been stabilized, the pediatrician should query the family about the incident, with particular attention to the environmental, patient, and toxic agent factors as outlined in Table 105-2. In acute, unintentional exposures in young children, the time of exposure and toxin involved frequently are accurately known. The importance of obtaining the precise ingredients in the suspected toxic agents cannot be overemphasized. Parents should bring the product containers or medication labels. For estimations of liquid toxins, the average swallow of a young child is approximately 5 to 10 mL while that of the older child and adolescent is 10 to 15 mL. The clinician must appreciate the fact that parents frequently minimize the child’s exposure to a toxin in an attempt to deny the threat of injury or to assuage their guilt that such an episode occurred. Therefore it is prudent to assume the worst possible scenario in calculating the maximum dose of a drug or household product a child could have swallowed in a poisoning and to treat the patient accordingly. Calculation of the dose the child might have received is sometimes helpful, using the maximum number of missing tablets or amount of liquid, the concentration of the drug or chemical, and the child’s weight.

Table 105–2 History Taking and Unknown Poisoning in the Pediatric Patient

The latency between the time of ingestion and the onset of symptoms is important. The tempo of progression of symptoms and signs also may help the clinician gauge the severity of the intoxication and the urgency with which intervention is necessary. However there are some exceptions to this rule. Patients poisoned by some toxins, such as paraquat and the Amanita mushroom toxin, classically have a relatively asymptomatic period of 12 hours or more but then manifest life-threatening pulmonary or hepatic toxicity, respectively.^2,3 Some drugs, such as sulfonylurea hypoglycemics and valproic acid, can also have similar latency periods prior to the onset of severe toxicity.^4,5 Adolescent poisonings are confounded by the intentionality of the episode and the frequent unreliability of the adolescent’s history. Adolescents in distress may be evasive, misleading, or otherwise uncommunicative. Their ability to remember or provide a coherent account of what happened may be distorted by the effects of the drugs taken. The clinician cannot assume that the time of exposure, the dose, or even the toxic agents themselves are accurately recounted.

Physical Examination

The physical examination is crucial for assessment of the patient’s medical stability and for identification of the unknown poison. Specific changes in vital signs and symptoms are associated with likely toxins or groups of toxins. Such characteristic clinical patterns of illness are sometimes termed toxidromes. Table 105-3 lists some of the more common toxidromes important in pediatric poisoning. Families are using herbs and diet supplements with increasing frequency to treat their children’s illnesses or simply to promote their general well-being. However, serious poisonings in which herbs and dietary supplements are implicated are appearing in the medical literature.⁶ Table 105-4 lists some examples of toxicities associated with particular herbal remedies.

Table 105–3 Common Toxidromes in Pediatric Poisoning

Table 105–4 Herbs Associated with Toxicity

Frequently, the gastrointestinal tract is involved early in a poisoning. Nonspecific findings after a drug or chemical overdose include nausea, vomiting, abdominal pain, and loose stools. A variety of drugs can cause fever. Overdoses with cocaine, phenothiazines, atropine, or salicylates often are associated with an elevated temperature. For specific discussions of the effects of toxins on other selected organ systems, the reader is referred to the general reviews listed in the additional readings at the end of this chapter and to other chapters in this textbook on toxicology and poisonings.

Table 105-5 lists examples of drugs and toxic agents associated with specific effects on the cardiovascular system. Drugs with cardiotoxic effects, especially those with membrane stabilizing activity, are among those most commonly associated with life-threatening toxicity. In one 10-year retrospective study, 15 out of 17 poisoned patients requiring extracorporeal life support measures for refractory shock or prolonged cardiac arrest had overdosed on cardiotoxic agents.⁷ Toxins may cause hypertension or hypotension by direct effects on vascular smooth muscle, neurogenic effects on autonomic nervous centers governing vascular innervation, direct effects on the heart, or renal effects. Specific agents associated with hypertension include adrenergic stimulants, such as amphetamines, cocaine, phencyclidine, phenylpropanolamine, ephedrine, and phenylephrine. Although the hypertension caused by sympathomimetics frequently lasts only a few hours, it may be associated with acute encephalopathy and/or intracranial hemorrhage.

Table 105–5 Toxins Associated with Cardiovascular Findings

Sign

Agents

Tachycardia

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