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Lead Poisoning

- Severe toxicity: three major clinical syndromes: - Alimentary type: anorexia, metallic taste, constipation, severe abdominal cramps due to intestinal spasm and sometimes associated with abdominal wall rigidity - Neuromuscular type (characteristic of adult plumbism): peripheral neuritis, usually painless and limited to extensor muscles - Cerebral type or Pb encephalopathy (more common in children): seizure, coma, and long-term sequelae, including neurologic defects, delayed mental development, and chronic hyperactivity

- Significant possible interactions - Vitamins should not be given concurrently with oral chelation. - BAL may precipitate hemolytic crisis in a patient with glucose-6-phosphate dehydrogenase deficiency.

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  • Children are at increased risk because of incomplete development of the blood " “brain barrier at <3 years of age, allowing more Pb into the CNS; ingested Pb has 40% bioavailability in children compared with 10% in adults.
  • Common childhood behaviors such as frequent hand-to-mouth activity and pica (repeated ingestion of nonfood products), greatly increase the risk of ingesting Pb.

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GENERAL PREVENTION

  • Family should receive counseling on potential sources of Pb and methods to decrease Pb exposure. Children at high risk should receive blood Pb screening (1)[C].
  • Warn parents about the dangers posed by unsafe renovation methods.
  • Wet mopping and dusting with a high-phosphate solution (e.g., powdered automatic dishwasher detergent with 1/4 cup/gallon of water) will help to control Pb-bearing dust. But high-phosphate detergent is no longer available in some states.
  • Pregnant women with community-specific or any individual risk factor for Pb poisoning should be screened for Pb toxicity (2)[C].

COMMONLY ASSOCIATED CONDITIONS

Iron-deficiency anemia ‚

DIAGNOSIS

HISTORY

  • Often asymptomatic
  • Mild-to-moderate toxicityMay cause myalgia or paresthesia, fatigue, irritability, lethargyAbdominal discomfort, arthralgia, difficulty concentrating, headache, tremor, vomiting, weight loss, muscular exhaustibility
  • Severe toxicity: three major clinical syndromes:Alimentary type: anorexia, metallic taste, constipation, severe abdominal cramps due to intestinal spasm and sometimes associated with abdominal wall rigidityNeuromuscular type (characteristic of adult plumbism): peripheral neuritis, usually painless and limited to extensor musclesCerebral type or Pb encephalopathy (more common in children): seizure, coma, and long-term sequelae, including neurologic defects, delayed mental development, and chronic hyperactivity
  • Chronic exposure may cause renal failure.

PHYSICAL EXAM

Often normal, but abdominal tenderness may be severe. Neurologic exam may reveal neuropathy or encephalopathy. ‚

DIFFERENTIAL DIAGNOSIS

  • Alimentary type may be confused with acute abdomen.
  • Neuromuscular type may be confused with other polyneuropathies.
  • Cerebral type may be confused with ADD, mental retardation, autism, dementia, and other causes of seizures.
  • Elevated erythrocyte protoporphyrin may be caused by iron-deficiency anemia or, less commonly, hemolytic anemia.
  • Erythropoietic protoporphyria produces a very high erythrocyte protoporphyrin level.

DIAGNOSTIC TESTS & INTERPRETATION

  • Blood Pb >5 Ž ¼g/dL (0.24 Ž ¼mol/L) collected with Pb-free container
  • Use a laboratory that can achieve routine performance within 2 Ž ¼g/dL.
  • In 2012, CDC recommended using a reference value as the basis for management, currently >5 Ž ¼g/dL
  • Screening capillary Pb levels >5 Ž ¼g/dL (0.24 Ž ¼mol/L) should be confirmed with a venous sample.
  • Hemoglobin and hematocrit slightly low; eosinophilia or basophilic stippling on peripheral smear may be seen but is not diagnostic of Pb toxicity.
  • Renal function is decreased in late stages.
  • Abdominal radiograph for Pb particles in gut if recent ingestion is suspected.
  • Radiograph of long bones may show lines of increased density in the metaphyseal plate resulting from growth arrest but does not usually alter management and is not routinely recommended.
  • X-ray fluorescence for the total body burden of Pb is experimental.

TREATMENT

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View LargeBlood level ( Ž ¼g/dL)Time to confirmation testing ≥ref value " “91 " “3 month10 " “441 week " “1 month45 " “5948 hours60 " “6924 hours ≥70Urgently as emergency test

ALERT

  • For any blood Pb levels persistently >15 Ž ¼g/dL, contact local public health department for home inspection.
  • If Pb level is between 5 and 45 Ž ¼g/dL, the higher the Pb level, the more urgent the need for confirmation testing.
  • For all elevated levels: Educate family on sources of Pb (3)[C].
  • Pb level > ref level to <45: Complete history and physical exam, follow-up Pb monitoring; complete inspection of home or workplace to determine source of Pb and Pb-hazard reduction; neurodevelopmental monitoring: iron status, Hgb, or Hct (4)[C]
  • Pb level 45 to 69: Actions for lower level plus free erythrocyte protoporphyrin, oral chelation therapy, or hospitalization if Pb-safe environment cannot be ensured (4)[C]
  • Pb >70: Hospitalize for chelation therapy (5)[C]

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MEDICATION

  • Consider oral chelation for asymptomatic and Pb >45 and <70; chelation (preferably parenteral) for Pb >70 or symptomatic Pb <70 (5)[C].
  • Do not begin chelation until Pb particles present in gut are cleared (5)[C].

First Line

  • Oral chelation: Succimer (Chemet), dimercaptosuccinic acid (DMSA) 10 mg/kg q8h for 5 days; then 10 mg/kg q12h for 2 weeks. This may be repeated after 2 weeks off if Pb levels are not stabilized at <15 Ž ¼g/dL (<0.72 Ž ¼mol/L) (5)[C].
  • Parenteral chelation (begin after establishment of adequate urine output):Dimercaprol (British anti-Lewisite [BAL]) 75 mg/m2 given deep IM; then BAL 450 mg/m2/day divided q4h for 5 days plus Ca edetate calcium disodium (EDTA) 1,500 mg/m2/day continuous IV infusion for 5 days. If rebound Pb level ≥45 Ž ¼g/dL ( ≥2.17 Ž ¼mol/L), chelation may be repeated after 2-day interval if symptomatic or after 5-day interval if asymptomatic.Ca EDTA 1,000 mg/m2/day for 5 days; may be repeated after 5 to 7 days
  • Diazepam for initial control of seizures; further control maintained with paraldehyde
  • Contraindications: BAL should not be given to patients allergic to peanuts (the drug solution contains peanut oil).
  • PrecautionsSuccimer: GI upset, rash, nasal congestion, muscle pains, elevated liver function testsCa EDTA: renal failure, increased excretion of zinc, copper, and ironBAL: nausea, vomiting, fever, headache, transient hypertension, hepatocellular damage
  • Significant possible interactionsVitamins should not be given concurrently with oral chelation.BAL may precipitate hemolytic crisis in a patient with glucose-6-phosphate dehydrogenase deficiency.

Second Line

Oral chelation with penicillamine (D-penicillamine, Depen, Cuprimine) (5)[C] ‚

  • Penicillin-allergic patient should not receive penicillamine (cross-sensitivity is common).
  • 10 to 15 mg/kg/day given BID mixed in apple juice/sauce on empty stomach (not approved by the FDA)
  • Penicillamine may cause GI upset, renal failure, granulocytopenia, liver dysfunction, iron deficiency, and drug-induced lupus-like syndrome.

ISSUES FOR REFERRAL

Consider consultation if parenteral chelation is required. ‚

ADDITIONAL THERAPIES

Remove patient from potential source of Pb or Pb level >45 until complete home inspection is performed. ‚

INPATIENT CONSIDERATIONS

Admission Criteria/Initial Stabilization

  • Blood Pb level >70 Ž ¼g/dL
  • If symptomatic, blood Pb level >35 Ž ¼g/dL
  • Outpatient care unless parenteral chelation is required or immediate removal from contaminated environment.

Discharge Criteria

  • If Pb source is in the home, the patient must reside elsewhere until the abatement process is completed.
  • Avoid visit to any site of potential contamination.

ONGOING CARE

FOLLOW-UP RECOMMENDATIONS

Patient Monitoring

  • After chelation, check for rebound Pb level in 7 to 10 days. Follow with regular monitoring, initially biweekly or monthly.
  • Correct iron deficiency or any other nutritional deficiencies present.
  • Once Pb <35 Ž ¼g/dL, repeat testing every 1 to 3 months until level <25 Ž ¼g/dL is achieved. Then monitor every 3 to 6 months until level <10 Ž ¼g/dL. Once <9 Ž ¼g/dL, test every 6 to 9 months (4)[C].

DIET

  • If symptomatic, avoid excessive fluids.
  • Avoid pica.
  • Adequate calcium, iron, zinc, and vitamin C to reduce absorption and retention of Pb (6)[B]

PATIENT EDUCATION

  • Needleman HL, Landrigan PJ. Raising Children Toxic Free: How to Keep Your Child Safe From Lead, Asbestos, Pesticides, and Other Environmental Hazards. New York, NY: Farrar, Straus and Giroux; 1995.
  • National Lead Information Center, 422 South Clinton Avenue, Rochester, NY 14620; 800-424-5323; www.epa.gov/lead/
  • National Safety Council, 1121 Spring Lake Drive, Itasca, IL 60143-3201; 800-621-7615; http://www.nsc.org/learn/safety-knowledge/Pages/Lead-Poisoning-Prevention.aspx

PROGNOSIS

  • Symptomatic Pb poisoning without encephalopathy generally improves with chelation, but subtle CNS toxicity may be long lasting or permanent.
  • If encephalopathy occurs, permanent sequelae (e.g., mental retardation, seizure disorder, blindness, and hemiparesis) occurs in 25 " “50%.

COMPLICATIONS

  • CNS toxicity may be long lasting or permanent.
  • Long-term Pb exposure may cause chronic renal failure (Fanconi-like syndrome), gout, or Pb line (blue " “black) on gingival tissue.
  • Pb exposure in pregnancy is associated with reduced birth weight and premature birth.
  • Pb is an animal teratogen.

REFERENCES

11 Wengrovitz ‚ AM, Brown ‚ MJ. Recommendations for blood lead screening of Medicaid-eligible children aged 1 " “5 years: an updated approach to targeting a group at high risk. MMWR Recomm Rep. 2009;58(RR-9):1 " “11.22 Centers for Disease Control and Prevention. Guidelines for the Identification and Management of Lead Exposure in Pregnant and Lactating Women. Atlanta, GA: Centers for Disease Control and Prevention; 2010.33 Binns ‚ HJ, Campbell ‚ C, Brown ‚ MJ, et al. Interpreting and managing blood lead levels of less than 10 microg/dL in children and reducing childhood exposure to lead: recommendations of the Centers for Disease Control and Prevention Advisory Committee on Childhood Lead Poisoning Prevention. Pediatrics. 2007;120(5):e1285 " “e1298.44 Centers for Disease Control and Prevention. Low Level Lead Exposure Harms Children: A Renewed Call for Primary Prevention. Atlanta, GA: Centers for Disease Control and Prevention; 2012.55 American Academy of Pediatrics Committee on Drugs. Treatment guidelines for lead exposure in children. Pediatrics. 1995;96(1, Pt 1):155 " “160.66 Woolf ‚ AD, Goldman ‚ R, Bellinger ‚ DC. Update on the clinical management of childhood lead poisoning. Pediatr Clin North Am. 2007;54(2):271 " “294, viii.

ADDITIONAL READING

  • American Academy of Pediatrics Committee on Environmental Health. Lead exposure in children: prevention, detection, and management. Pediatrics. 2005;116(4):1036 " “1046.
  • Chandramouli ‚ K, Steer ‚ CD, Ellis ‚ M, et al. Effects of early childhood lead exposure on academic performance and behaviour of school age children. Arch Dis Child. 2009;94(11):844 " “848.
  • Senut ‚ MC, Cingolani ‚ P, Sen ‚ A, et al. Epigenetics of early-life lead exposure and effects on brain development. Epigenomics. 2012;4(6): 665 " “674.

SEE ALSO

Anemia, Iron Deficiency ‚

CODES

ICD10

  • T56.0X4A Toxic effect of lead and its compounds, undetermined, init
  • T56.0X1A Toxic effect of lead and its compounds, accidental, init

ICD9

  • 984.9 Toxic effect of unspecified lead compound
  • 984.0 Toxic effect of inorganic lead compounds

SNOMED

  • 38342005 toxic effect of lead compound (disorder)
  • 72446009 Toxic effect of inorganic lead compound
  • 216662006 Accidental poisoning by lead paints (disorder)

CLINICAL PEARLS

  • The following children should have Pb screening:6 to 11 months of age with ≥1 risk factors:Live in or visit a house built before 1960 with peeling paint or recent renovationSibling/playmate with elevated PbLive with adult with job or hobby involving PbLive near industry likely to release PbChildren living in high-risk communities (>12% elevated Pb) should be tested yearly from ages 1 to 5.Newly arrived refugeesChildren in low-risk areas should be screened by a questionnaire containing the above risk factors.
  • There is no clear safe Pb level. Many experts consider Pb levels >4 Ž ¼g/dL as elevated.
  • There are no studies that show benefit of chelation for asymptomatic children with Pb <45. Removal of sources of Pb is paramount.