Chapter 63 Poisoning
PATHOPHYSIOLOGY
Poisoning is defined as exposure to a potentially toxic substance and can occur by ingestion, inhalation, or absorption through the skin. The most frequent substances for poison exposures in the child less than 6 years of age are those that are readily available in the environment such as cosmetics, plants, cleaning supplies, pain medication, and cough and cold remedies. Pharmaceuticals are involved in a significant number of the fatalities resulting from pediatric poisonings. Poison control centers, safety education, and child-resistant packaging for drugs and hazardous chemicals have contributed to prevention of poisoning in children.
Childhood lead poisoning occurs when lead is absorbed, primarily through the gastrointestinal tract, after ingestion of lead-contaminated substances. Lead-based paint is the most common source and serious cause of lead poisoning. Children are exposed to lead-based paint when they ingest the fine dust particles from lead-based paint, paint chips from the walls of old homes, or lead-contaminated soil. Less common sources of lead include ceramics, hobby materials, and imported canned foods. Lead is a component of several folk remedies used in Mexico (azarcón and greta for digestive problems), the Middle East (farouk rubbed on gums to help teething, bint al zahib used for colic), and Southeast Asia (pay-loo-ah for fever and rashes). A high incidence of lead poisoning is associated with pica.
Lead poisoning is the excessive accumulation of lead in the blood. The majority of children with lead poisoning are asymptomatic, and diagnosis is often made as a result of screening. A lead level of less than 10 mg/dl indicates no lead poisoning; lead levels of 10 to 14 mg/dl are considered borderline; and lead levels of 15 mg/dl or higher require some degree of intervention. Acute symptoms of lead poisoning are generally not evident until the lead level reaches 50 mg/dl or higher.
Excessive amounts of absorbed lead accumulate in the bones, soft tissue, and the blood. Soft tissue absorption is of great concern because it can result in central nervous system (CNS) toxicity and irreversible renal failure. Late signs of lead toxicity include coma, stupor, and seizures. Lead poisoning is considered chronic if the lead has been accumulated over a period longer than 3 months. Lead interferes with heme synthesis and has a toxic effect on the red blood cells; this results in a decrease in the number of red blood cells and the amount of hemoglobin in cells, which leads to anemia.
INCIDENCE
1. Children under 6 years of age are more likely to have unintentional exposure to poisons compared to adolescents and adults. Adolescents are at risk for poisoning exposures both intentional and unintentional—about half of the poisoning exposures are considered suicide attempts in the adolescents.
2. Most poisonings take place in the home; the most common location is the child’s own residence, and the second most common is the grandparents’ home.
3. Times of peak incidence are evenings at mealtimes, weekends, and holidays.
4. The peak age of incidence for poisoning is between 1 and 3 years, when a child is autonomous and exploring.
5. Lead poisoning peak incidence occurs between 1 and 2 years of age. Children between the ages of 6 months and 6 years who live in poorly maintained older housing are at highest risk.
6. In the United States, about 2% of children less than 6 years of age have blood lead levels of 10 mg/dl or more.
Declines in the incidence are attributed to the elimination of lead from paint, gasoline, and food cans.
CLINICAL MANIFESTATIONS
The manifestations of poisoning depend on the agent that is ingested. The following are some examples:
Lead poisoning is detected during routine screening of high-risk children because most children are asymptomatic until the lead levels are high. Symptoms that may be seen as lead levels rise include the following:
1. Gastrointestinal: anorexia, constipation or diarrhea, nausea, vomiting, abdominal pain, or colic
2. Neurologic: irritability and malaise. When lead poisoning is chronic, increased incidence of learning disorders, behavioral disorders, perceptual deficits, and hyperactivity with decreased attention span can be seen
COMPLICATIONS
1. Pulmonary: respiratory arrest, acute respiratory distress syndrome, tracheal corrosion if a caustic substance is ingested
2. Cardiovascular: shock, cardiac arrest, congestive heart failure
3. Gastrointestinal: liver failure, esophageal corrosion if a caustic substance is ingested
