L14: Lead Flashcards
Sources of Lead
toxic compounds of Lead
Mode of poisoninig by Lead
- Mostly accidental
Absorbtion of Lead
- Lead is absorbed through GIT, respiratory tract and skin.
what increases/decreases Lead absorbtion?
Increased by
- Iron deficiency
- Low dietary calcium
Decreased by
- co-ingestion with food
Distribution of Lead
Metabolism of Lead
Lead metabolism is typically as Ca metabolism
what increases Deposition of lead in bone?
- Alkalis as K citrate, Na citrate
- Ca rich diet and Vitamin D
Execretion of Lead
- It is mainly excreted through urine (70%).
- Smaller amounts are eliminated via feces and scant amounts via the hair, nails and sweat.
what increases Mobilization of lead from bone?
- Acids as NH3 chloride
- lodides
- Chelators
- Parathormone.
Mechanism of Toxicity by Lead
Types of Lead toxicity
- Acute Poisoning
- Chronic Poisoning
Incidence of Acute Lead Poisoning
relatively uncommon
CP of Acute Lead Poisoning
- Local (GIT)
- Remote (CNS, Blood & Renal)
Remote effects of Acute Lead Poisoning
CNS
- Headache, lethargy, insomnia, paresthesia.
- Lead encephalopathy: It is commonly preceded by several weeks of prodromal complaints, Including irritability, headache and sleep disturbance, Encephalopathy characterized by Ataxia, seizures, delirium, stupor and coma.
Toxic hepatitis
Haemolytic angemia.
Local effects of Acute Lead Poisoning
- Metallic taste
- Dry throat, thirst
- Nausea, vomiting, cramping abdominal pain
- Constipation.
Effects of Chronic Lead Exposure
- Low levels may be associated with subslinical effects as Impairment of visualmotor dexterity, reaction time Slowing of motor nerve conduction velocity.
- But Higher levels Cause chronic poisoning
Facial pallor in Chronic Lead Poisoning
- Earliest sign around the mouth,
- Due to vasospasm and produced by contraction of capillaries at arterial side.
CP of Chronic Lead Poisoning
- Facial pallor
- Hematological effect
- GIT
- Neurological effect
- Reproductive system effects
- Effects on the eye
- CVS effects
- Renal effects
- Bones
- Carcinogenic effect
Hematological effects in Chronic Lead Poisoning
- Hypochromic anemia with normocytic or microcytic indices.
- Reticulocytosis due to anemia
- Punctuate basophilia (basophilic stippling of erythrocytes): early sign as consequences of lead-induced inhibition of pyrimidine-5 nucleotidase or cellular ribonucleases.
GIT effects in Chronic Lead Poisoning
- Burton’s/Burtonian (lead line)
- Colic
- constipation
Burton’s/burtonian (lead line)
- Incidence
50-70% cases
Burton’s/burtonian (lead line)
- Description
- A stippled blue line on gingival surface due to subepithelial deposit of granules at junction of teeth, especially near dirty or carious teeth.
Burton’s/burtonian (lead line)
- Causes
- Due to formation of lead sulphide (reaction of circulating leadt sulfur ions released by oral microbial activity) especially near dirty or carious teeth.
- Seen in poisoning with copper, iron.
Burton’s/burtonian (lead line)
- Specifity
Not specific, Seen in poisoning with copper, iron.
Incidence of colic in patients with Chronic Lead Toxicity
85% cases
Characters of colic in patients with Chronic Lead Toxicity
- The pain is spasmodic, paroxysmal, occurs at night may be very severe.
- Pain is slightly relieved by application of pressure over abdomen.
Neurological effects of Chronic Lead Toxicity
- Deficits in cognitive function
- Irritability, fatigue, headache, sleep disturbance and depressed mood
- Lead palsy (peripheral neuropathy, Mainly Motor)
- Lead. encephalopathy
Deficts in cognitive functions in Chronic Lead Toxicity
IQ decreased and attention impairment especially in Children
Local encephalopathy in Chronic Lead Toxicity
Symptoms include
- Changes in personality
- Restlessness, hyperkinetic and aggressive behavior disorders
- Mental dullness,
- Learning disorders
- Refusal to play
- Headache and insomnia.
Lead palsy in Chronic Lead Toxicity
- a late and uncommon phenomenon
- There may be tremors and cramps before the actual muscle weakness.
- Later the extensor muscles of wrist (Wrist drop) and anterior tibial muscles (foot drop) are affected.
- it may occur in male adults” workers exposed chronically to high lead levels.
Reproductive system effects of Chronic Lead Toxicity
Effects of Chronic Lead Toxicity on eyes
- Optic atrophy in severely intoxicated patients.
- Retinal stippling noticed by ophthalmoscope with grayish glistening lead particles, in early phase of chronic lead poisoning.
CVS effects of Chronic Lead Toxicity
Hypertension (vasoconstriction)
Renal effects of Chronic Lead Toxicity
- Interstitial nephritis.
- Renal insufficiency.
- Decreased renal clearance of uric acid.
- Fanconi-like syndrome (aminoaciduria, glucosuria, hypophosphatemia, hyperphosphaturia).
Carcinogenic effects of Chronic Lead Toxicity
- Lead is considered a probable human carcinogen.
- Clinical presentation of lead toxicity (listed in approximate order of appearance).
Bones affection in Chronic Lead Toxicity
Lead osteopathy in children and young adults,
- It is deposited beyond the epiphysis of growing long bones leading to abnormal development.
why are children more susceptible to Chronic Lead Toxicity?
Dx of Chronic Lead Toxicity
Depends on
- History of exposure
- Blood lead level.
Investigations for Chronic Lead Toxicity
Emergency TTT of Lead Toxicity
- Maintain airway, breathing and circulation.
- Provide adequate fluids to maintain urine flow.
Decontamination in Lead Toxicity
- Remove the patient from the sourco of exposuro.
- Gastric lavage and whole bowel irrigation.
- For Lead-containing shots, shrapnel, or bullets in or adjacent to a synovial space or CSF, should be surgically removed if possible.
Antidotes in Lead Toxicity
- Edetate calcium disodium (CaNa2EDTA)
- BAL (British Anti-Lewisite, dimercaprol)
- Succimer (dimercaptosuccinic acid DMSA)
- Antidoes for asymptomatic patients
Edetate calcium disodium (CaNa2EDTA)
- As 30 mg/kg/day in 4-6 divided doses or as a continuous infusion for 5 days.
- Prolonged dosing has risk of nephrotoxicity.
BAL (British Anti-Lewisite, dimercaprol)
- An oily solution.
- The most effective in preventing renal damage if administrated within 4 hours after acute ingestion of lead salts.
- Dose 3-5 mg/kg IM every 4-6 hours for 3 days.
- Side effects: HTN, nausea, vomiting, headache, pain at the injection sites, priapism and convulsions.
Succimer (dimercaptosuccinic acid DMSA)
oral, IM, IV
In severe acute poisoning
- 3-5 mg/kg every 4 hours by IV infusion over 20 min in the first day then continue orally
In chronic poisoning
- 10 mg/kg orally every 8 h for 5 days, Every 12 h for 2 weeks.
Antidotes (Chelation Therapy) For asymptomatic patients
- Children with blood lead concentration ≥ 45 ug/dl or Adults > 80-100 ug /dl
- Administer oral succimer.
- There is no consensus regarding the value of chelation at lower levels.
Enhanced Elimination in lead toxicity
There is no role for enhanced elimination of lead.
Symptomatic TTT in Lead Toxicity
