LEAD TOXICITY
Acute = ingestion = rare
Chronic = exposure (still relatively uncommon)
Absorption:
Oral: ingestion, bioavailability: children >> adults
Topical: through intact skin
Inhaled: fumes (smelting, dust)
Foreign Bodies
Distribution
Bound by RBC – transported around body
Deposited in:
BONE – can remobilise decades after exposure
CNS
Kidneys
Spleen
Easily crosses placenta
Excretion:
Urinary
CLINICAL:
ACUTE
Abdo pain, N/V, hepatitis
CNS: cerebral oedema, encephalopathy, seizures, coma (pre-terminal)
CHRONIC:
Vague, multi-system complaints:
GIT:
Anorexia, vague abdo pain, wt loss,
NEURO:
 concentration, emotional lability,  coordination
Peripheral neuropathies (wrist drop) = rare but classical
Subclinical effects on higher functions/IQ
RENAL:
Chronic interstitial nephritis
OTHER:
Arthralgia
PREGNANCY
Major malformations
CHILDREN:
Neurotoxic – developmental delay
ANY level of exposure = bad (ie no “safe” lower limit)
Ie DON’T BUY LEAD TOYS FROM CHINA!
LEVELS:
Acute OD severe enough to cause CNS Syx/death = level > 100mcg/dL (4.8umol/L)
INVESTIGATION:
General:
ECG, BSL, Paracetamol
Specific:
Whole blood lead level: most useful indicator of exposure
FBE: Anaemia
U&E, LFT
FEP (Free Erythrocyte Protoporphyrin)
Surrogate marker of total body lead level
AxR: lead ingestion
Chronic:
Nerve conduction studies
Psychomotor testing
MANAGEMENT:
1) Risk assessment:
High Risk
Acute ingestion
Children
Pregnant
Altered conscious state/CNS Syx
2) Resuscitation:
ABC/IV/O2/monitor
Cerebral oedema: mannitol/steroids
Seizures: treat as per usual
Supportive care and monitoring
3) Decontamination
Above Gastro-oesophageal junction
Endoscopic removal
Below Gastro-oesophageal junction
Asymptomatic
High fibre diet
Laxatives: polyethylene glycol
Repeat AxR every 24hrs  aim passage <72hrs
If still present at 72hrs:
Admit
Whole bowel irrigation (polyethylene glycol)
4) Enhanced Elimination
Not clinically useful
5) Antidotes = CHELATION:
General Idea:
IF ICU sick (can’t tolerate oral therapy)
Dimercaprol + EDTA
Don’t give EDTA alone (can cause redistribution of lead to CNS)
IF able to tolerate oral therapy
Succimer
1) Dimercaprol
Adjunct to EDTA
But best if given few hours before
Only used in ICU due to
1) Side effects
2) Severity of condition
Also used in: Arsenic, Mercury, Gold, other heavy metal toxicity
Given IM, 4 hourly, started 4 hrs before EDTA
Binds metals  excreted in urine (and also removed by dialysis)
Formulated in peanut oil (CI – peanut allergy)
SE:
Nephrotoxicity (due to dissociation of metal in kidney)
alkalinise urine to  this effect
Pain/sterile abscess at injection site, fever, myalgia, CP/HT/HR, headache,
N/V, paraesthesia, burning lips, lacrimation/salivation
Haemolysis in G6PD
Tips:
NEVER GIVE IV
Most effective ASAP afer exposure
Treatment with Succimer always preferable
Difficult to obtain  only stocked at a few hospitals
2) EDTA (Na+/Ca2+ Edetate)
Indication:
Lead Encephalopathy
Severely symptomatic and/or Level > 100mcg/dL
Mild/no Syx & level >70mcg/L
2nd line if DMSA not available/tolerated
Other heavy metal poisoning (efficacy unknown)
Contraindication (relative) = anuric renal failure
Given IV
Infusion runs over 24hrs, starting 4hrs after Dimercaprol
Max 5 days
Once clinically improved can switch to oral Succimer
Binds metals  excreted in urine (and also removed by dialysis)
SE: pain phlebitis, fever, chills, myalgia, headache, anorexia….lots more
Nephrotoxicity (due to dissociation of metal in kidney)
Minimise by adequate urine flow, max 5 days, monitor Cr/RF
3) Succimer (DMSA)
Indications:
Able to tolerate oral therapy
Symptomatic + no encephalopathy (ie not needing ICU)
Asymptomatic + level > 60-70mcg/dL (adult) >45mcg/dL (child)
Other heavy metals: arsenic, bismuth, copper
Water soluble analogue of Dimercaprol
Binds heavy metals  excreted in urine
Lead poisoning:
Can give as outpatient
Oral dose (10mg/kg) tds for 5 days
Check levels after treatment  treat again if levels rise
Can use after IV treatment in sever poisoning
SE: Foul smelling – GIT upset, Hypersensitivity, others
May be difficult to acquire – only available under “Special Access Scheme”