MCQs In Pediatric Toxicology

Q1 : 

A resident in continuity clinic approaches you to review the laboratory values obtained at a

patient’s 12-month health supervision visit. The fingerstick hemoglobin measurement was 10.5

g/dL (105.0 g/L), and the lead concentration was 11.0 mcg/dL (0.53 mcmol/L).

Of the following, the next BEST step for this boy is to

A. admit him to the hospital for chelation therapy

B. call child protective services to move him to a shelter

C. call the health department to arrange for an environmental investigation

D. measure the venous lead concentration

E. refer him for formal developmental evaluation and neuropsychometric testing

Answer:

D

The American Academy of Pediatrics policy statement recommends the use of venous
samples for initial screening whenever possible. If capillary testing is performed and the lead
concentration is greater than 10.0 mcg/dL (0.5 mcmol/L), the lead concentration must be
confirmed by a venous sample because microlead sampling is more likely to yield false-positive
results due to contamination from environmental lead.

Lead ingestion may cause a microcytic anemia by interfering with iron absorption and
utilization in heme production and can inhibit enzymes required for heme synthesis directly.
Children who have lead poisoning may have pica either as a cause or symptom of lead
poisoning. In these children, iron supplementation should be initiated until the presence or
absence of iron deficiency is determined.

Most asymptomatic children who have mildly elevated blood lead concentrations are not
candidates for chelation therapy with the currently available drugs because the toxicity of these
drugs outweighs the potential benefit of treatment, and chelation is unlikely to increase lead
excretion significantly. Chelation therapy should be considered, however, if lead concentrations
are higher than 44.0 mcg/dL (2.12 mcmol/L). The role of chelation is not clearly defined for
children whose blood lead concentrations range from 20.0 to 45.0 mcg/dL (0.97 to 2.17
mcmol/L). In this range, the clinician may choose to pursue further environmental screening,
attempt to eradicate lead from the child's environment, and measure blood lead concentrations
monthly. If the concentration remains in this range, despite successful eradication of the lead
source, the physician should institute behavior modification, nutritional sufficiency, or chelation
treatment.
Succimer is the drug of choice for children whose blood lead concentrations are 45.0 to
100.0 mcg/dL (2.17 to 4.8 mcmol/L). At values higher than 69.0 mcg/dL (3.3 mcmol/L), a second
drug, CaNa2EDTA, is added.

Blood lead concentrations fall precipitously after completion of chelation, but rebound within
weeks, even if there is no further exposure to lead, due to release of lead from bone stores. In
general, the concentrations do not return to the high values seen before chelation, and a second
course of chelation rarely is indicated.