The management of poisonings in pediatric patients is based on an understanding of the basic supportive measures required for most ingestions. The epidemiology of pediatric ingestions is significantly different from that of adult ingestions. Because most are accidental and unwitnessed, the ability to manage ingestions of unknown substances before the results of specific testing are available is critical.
EPIDEMIOLOGY
The epidemiology of pediatric poisonings can be elicited by examining telephone calls made to poison control centers throughout the United States. More than 70% of calls to poison centers involve children under the age of 18 years. Data collected from these centers reveal that:
Of all pediatric poisonings, 85% involve children <5 years.
Most of these are unintentional and involve common household products and over-the-counter medications.
The mortality rate for children with ingestions is exceedingly low. Adolescent ingestions are more like adult ingestions:
The majority are intentional and involve either a suicide attempt or drug experimentation.
Because they are intentional, involve illicit drugs, or are an attempt at suicide, the rate of severe complications is much higher, and the associated mortality rate is 15 times that of younger children.
The most commonly ingested substances in young children in decreasing order of frequency include:
Cosmetics/hygiene products
Cleaning products
Analgesics
Plants
Cough and cold medications
Pesticides
Vitamins
Hydrocarbons
Fatalities from ingestion in children are extremely rare. Data from Poison Centers from 2003 revealed that of the approximate 2.5 million calls to these centers, there were 34 reported fatalities. In children <6 years of age, 12 deaths were associated with over-the-counter products, nine were unintentional, eight were therapeutic errors, seven were environmental exposures, and two were homicides. In adolescents, approximately 40% involved drug experimentation and 33% were suicides.
Plant exposures account for up to 10% of calls to poison centers. The vast majority do not involve more than minimal symptoms. However, because of the large number of these exposures, fatalities can occur. It is therefore useful to know which types of exposures have the potential to cause severe morbidity or mortality. These include:
Jimsonweed: a plant frequently ingested by adolescents for its hallucinogenic properties
Hemlock
Philodendron
Pokeweed
Holly
Castor beans
Mistletoe
Leaves and pits of several fruit trees can release cyanide
ROLE OF HISTORY AND PHYSICAL EXAMINATION
The history and physical examination are pivotal in the appropriate management of a child who presents after having ingested an unknown substance. Despite rapid advances in technology, a basic knowledge of the presenting features of the major categories of poisonings is critical to appropriate management because management decisions are routinely made before the results of laboratory tests become available. Most pediatric ingestions are unintentional, and in many cases, the poison is an unknown substance, so that it becomes necessary to elicit a thorough history from the parents. A standard history should be obtained, including what agent was ingested, how much, when, why, and under what circumstances. The location of the ingestion may also be helpful. For example, potential agents ingested in the kitchen may be different than those in the bathroom. It is often helpful to have the parents or caregiver bring in the substance. Many cleaning and household products contain multiple potential toxins, and reviewing the label may be useful. In cases of ingestion involving unknown products, the parents, with guidance, can often identify a list of potential toxins and medications in the home. A review of the activities of the past 24 hours can often provide a sense of when the ingestion took place, information that helps to determine the severity of exposure, and whether aggressive therapy is needed. It has been estimated that history is the most important factor in identifying unknown ingestions in up to 90% of cases. Information provided by an ado lescent who has had an intentional ingestion is often unreliable. Use of illicit drugs is typically underreported. A family history of drug use in an older sibling or par ent may often lead to unintentional ingestions in young children.
TABLE 59.2 CHARACTERISTIC ODORS THAT MAY SERVE AS CLUES TO AN UNKNOWN INGESTION
Odor
Substance/Toxin
Garlic
Arsenic
Organophosphates
Mothball
Camphor
Rotten eggs
Hydrogen sulfide
Wintergreen
Methyl salicylate
Bitter almond
Cyanide
Acetone
Salicylates
Isopropyl alcohol
Unfortunately, the history does not always identify the offending agent, especially in adolescents in whom the ingestion frequently is intentional and unwitnessed. In these situations, the physical examination and a knowledge of toxidromes is crucial because treatment often must be instituted before the results of any laboratory testing are known. Toxidromes can identify the ingested toxin or class of ingested agent in more than 80% of cases of ingestion of unknown toxins. The most commonly encountered toxidromes are summarized in Table 59.1.
Certain substances can be rapidly identified during the physical examination by characteristic odors (Table 59.2) or specific examination findings (Table 59.3). Frequent physical examinations may provide critical information about the evolution of poisoning and the need for aggressive interventions.
TABLE 59.3 GENERAL FINDINGS ON PHYSICAL EXAMINATION THAT MAY AID IN DETECTING AN UNKNOWN POISON
Physical Examination Finding
Substance/Toxin
Needle tracts
Drug abuse, particularly with narcotic agents
Gray cyanosis
Agents causing methemoglobinemia
Chocolate blood
Agents causing methemoglobinemia
Cherry-red mucous membranes
Carbon monoxide
ROLE OF LABORATORY TESTING
Screening laboratory tests are helpful in the management of ingestions because of their easy access and rapid turnaround times. The goal is often to identify the metabolic effects of the poison. However, few are specific.
In most cases, it is easy to calculate an anion gap from the electrolyte values in the emergency setting. The anion gap is calculated with the following formula:
Normal values are <16. An elevated anion gap represents an accumulation of organic acids, such as lactate or formate, which neutralize bicarbonate. However, a normal anion gap does not rule out the presence of organic acids.
An elevated anion gap can be caused by the ingestion of:
Alcohol
Toluene
Methanol
Paraldehyde
Ethylene glycol
Salicylates
Uremia, diabetic ketoacidosis, and lactic acidosis also can cause an elevated anion gap.
An osmolar gap can also be calculated easily from the laboratory values for electrolytes and renal function. An osmolar gap indicates the presence of low-molecularweight toxins, although the absence of an osmolar gap does not rule out the presence of these toxins. The following formula is utilized to calculate an osmolar gap: