Lead intoxication

Question 1

Form entering the body?

Answer 1

• Inorganic lead oxides and salts
• Organic (tetraethyl lead)

Question 2

Source of intoxication?

Answer 2

• Occupational, environmental (batteries, paints, ceramics, …)
• Antiknock agent in gasoline (organic)

Question 3

Routes of absorption?

Answer 3

• GI tract (organic)
  
  • _~ 10% in children
  • 40% enhanced in case of reduced Fe or Ca
• Respiratory tract (organic)
• Crosses the placenta

Question 4

Pharmacodynamics?

Answer 4

• Inhibits enzymes via sulfhydryl binding
• Interferes with action of Ca, Fe, Zn
• Alters the structure of membrane and receptors

Question 5

Distribution?

Answer 5

• 1st it is bound to erythrocytes
• Inorganic: soft tissues, redistribution in bones
• Organic: especially liver and CNS

Question 6

Elimination?

Answer 6

Elimination via kidney:

• Elimination half-life:
  
  • Tissue - 12 months
  • Bones - 20 years
• Mobilization from bones enhances in case of:
  
  • Hyperthyroidism
  • Prolonged immobilization
  • During pregnancy and lactation
  • Postmenopause

Question 7

Acute clinical features?

Answer 7

Acute intoxication is rare (difficult diagnosis)

• Encephalopathy
• Colic
• Spastic ileus
• Hemolytic anemia

Question 8

Chronic lead intoxication affects which systems?

Answer 8

• Blood
• GIT
• Nervous system
• Kidney
• Cardiovascular
• Bones

Question 9

Blood chronic clinical features?

Answer 9

Blood:

• Interferance of heme synthesis (inhibits the incorporation of Fe into protopophyrin)
• Increases membrane fragility of RBCs
• Anemia
• Basophilic stippling
• Hemolysis (high exposure)

Question 10

GIT chronic clinical features?

Answer 10

• Smaller doses:
  
  • Loss of appetite
  • Constipation
• Higher dose:
  
  • Bouts of abdominal pain (lead colic)
• Gingival lead lines (deposits on gingiva)

Question 11

Nervous system chronic clinical features?

Answer 11

Children:

• Minimal brain dysfunction
• Decrease hearing acuity

Adults:

• Slowed reaction time
• Insomnia
• Anorexia
• Irritability
• Peripheal neuropathy (weakness of extensors) months or years after high-dose exposure

Question 12

Kidney chronic clinical features?

Answer 12

• High dose
  
  • Interstitial fibrosis
  • Nephrosclerosis
• Decreased uric acid excretion
  
  • Symptoms of gout

Question 13

Cardiovacular system chronic clinical features?

Answer 13

Hypertension

Question 14

Bones chronic clinical features?

Answer 14

Children growth retardation (lead deposits in epiphysis)

Question 15

Acute intoxication therapy?

Answer 15

• Supportive care
• EDTA calcium disodium (IV infusion for 5 days) OR
• 1st dimercaprol –> 4h later, EDTA calcium disodium
• Afterwards oral succimer or penicillamine

Question 16

Chronic intoxication therapy?

Answer 16

Oral chelators

Question 17

Clinical features and therapy of organic lead poisoning?

Answer 17

Clinical features:

• CNS effects: hallucination, delirium convulsions, brain edema, death

Therapy:

• Decontamination from skin
• Symptomatic treatment
• NO chelators (not effective)!!!