Lead (Pb)

Lead is absorbed into the body through both the respiratory and GI tracts. It also moves transplacentally to the fetus. Absorption through these different routes varies and is affected by age, nutritional status, particle size, and chemical form of the lead. Absorption is inversely proportional to particle size; this factor makes lead-bearing dust important. Adults absorb 6%–10% of dietary lead and retain very little of it; however, children from birth to 2 years of age have been shown to absorb 40%–50% and to retain 20%–25% of dietary lead. Spontaneous excretion of lead in urine by infants and young toddlers is normally about 1 μg/kg/24 hr, which may increase somewhat in cases of acute poisoning. Dietary intake of lead is less than 1 μg/kg of lead, which provides a margin of safety in the sense that a child goes into positive lead balance when intake exceeds 5 μg/kg of body weight.

Early symptoms of lead poisoning (plumbism) include anorexia, apathy or irritability, fatigue, and anemia. Toxic effects include GI distress, joint pain, colic, headache, stupor, convulsions, and coma. In adults, high levels of lead are caused mainly by industrial exposure to lead-based paints, gasoline, and ceramics. High-risk children are usually ages 3–12 years and live in or visit old or dilapidated housing with lead-based paint. A single paint chip can contain as much as 10,000 μg of lead.

The blood lead level (BLL) assay is used to screen adults and children for lead poisoning. Another, less sensitive test that may also be used to evaluate lead intoxication is free erythrocyte protoporphyrin. However, a BLL assay is the definitive test.

Normal Findings ⬆ ⬇

BLL:

<5 μg/dL or <0.24 μmol/L
24-hour urine: <80 μg/L or <0.39 μmol/L

Hair:

All ages: <3.9 μg/g

Clinical Alert

TOPIC HEADING-LEVEL="1" ID="Fischbach-ch006-topic153">Critical Values

Younger than 15 years, >20 μg/dL or >0.97 μmol/L; aged 15 years or older, >30 μg/dL or >1.45 μmol/L.
The Centers for Disease Control and Prevention (CDC) uses a blood lead reference value for children of 5 μg/dL (or higher) to identify children with elevated BLLs.
Patients with blood lead concentrations >80 μg/dL or >3.86 μmol/L (panic value) should be hospitalized immediately and treated as a medical emergency.
A single lead determination cannot distinguish between chronic and acute exposure.

Procedure ⬆ ⬇

Obtain a sample by finger stick using lead-free heparinized capillary tubes (capillary specimens are not considered diagnostic) or venous blood drawn in a 3-mL trace element-free tube. Label the specimen with the patient’s name, date and time of collection, and test(s) ordered. Place the specimen in a lead-free biohazard bag or container.
Do not separate plasma from cells. Refrigerate the sample.
24-hour urine specimens can also be collected.
Hair may also be used.
Observe standard precautions.

Clinical Implications ⬆ ⬇

BLLs in adults:

<5 μg/dL or <0.24 μmol/L: normal without occupational exposure
10 μg/dL or 0.48 μmol/L: BLL testing every 6 months
<20 μg/dL or <0.97 μmol/L: acceptable with occupational exposure
>40 μg/dL or >1.9 μmol/L: report to state occupational agency
>60 μg/dL or >2.9 μmol/L: remove from occupational exposure and begin chelation therapy

Table 6.6 lists the CDC classifications for levels of blood lead. Table 6.7 shows the effects of blood lead in children.

Interventions ⬆ ⬇

Pretest Patient Care

Explain test purpose and procedure.
Explain the importance of follow-up if lead levels are elevated.
Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

Posttest Patient Care

Have the patient resume normal activities.
Review test results, counsel, and monitor appropriately for elevated lead levels. Explain chelation therapy and possible need for further testing, such as iron deficiency and blood protoporphyrins. Modify the nursing care plan as needed.
1. Parental compliance is necessary. Parent education about lead poisoning can be given face to face, by pamphlet distribution, or in both ways.
2. The most important component of medical management is to facilitate reduction in the child’s exposure to the environmental lead. In providing intervention for the child with an elevated BLL, the initial step is to obtain a detailed environmental history. The causes of childhood lead poisoning are multiple and must take into account potential environmental hazards as well as characteristics of the individual child. Once a child is found to have lead intoxication, all potential sources must be identified and removed from the child’s environment.
3. The recommended diet for a child with lead toxicity is simply a good diet with adequate protein and mineral intake and limitation of excess fat. It is no longer necessary to exclude canned foods and beverages when the cans are manufactured in the United States because the manufacture of cans with lead-soldered seams ended in the United States in 1991.
4. Iron deficiency can enhance absorption and toxicity of lead and often coexists with overexposure to lead. All children with a blood lead concentration >20 μg/dL or >0.97 μmol/L whole blood should have appropriate testing for iron deficiency.
5. In class IV lead intoxication, chelation is necessary. Chelation therapy must be done in conjunction with eliminating the source of the lead poisoning. Chelation therapy, when promptly administered, can be lifesaving and can reduce the period of morbidity associated with lead toxicity.
6. Additional follow-up tests may be ordered, including free erythrocyte protoporphyrin, erythrocyte protoporphyrin, or zinc protoporphyrin.
Follow guidelines in Chapter 1 for safe, effective, informed posttest care.

Interfering Factors ⬆

Failing to use lead-free Vacutainer tubes invalidates results.
An elevated level should be confirmed with a second specimen to ensure that the first specimen was not contaminated.