LEAD POISONING

What Is Lead Poisoning?• also known as saturnism, plumbism or painter’s colic• Cause by increased level of lead in blood• Lead can enter any cell so toxicity may occur in any tissue or

organ• Even small amount of lead can cause severe lasting harm, esp

to children• No level of lead exposure is safe• Level of concern is 10mcg/dL for children & 25mcg/dL for

adults

Main Causes Of Lead PoisoningAutomobile emission - In early 90’s ,tetraethyl lead added to gasoline. - nowadays gasoline usually lead free so drop in emission - however lead already deposited in soil after decades of burningDrinking water - lead was used in household plumbing material in earlier days. - older homes may have lead pipes & fixtures which may get corroded & contaminated the water.

Causes of Lead Poisoning- continued Agricultural soil - soil get contaminated with lead either fr lead dust dislodged fr

deteriorated paint or due to irrigation with water contaminated by lead pipes or lead mining.

- auto-emission also contributed a significant amount of lead in soil. - the lead get taken up by crops or may stick onto plants & get ingested. Lead paint - some paints may contain lead chromate & lead carbonate as it speeds

up drying & resist moisture. - children can be exposed to lead by eating & chewing an object painted

with these paints or swallow house dust that contain lead. Toys - toys may be painted or made up of plastic that contain lead.

What Happens When Lead Enters The Body ?

• Lead enters the blood stream & circulates throughout body

• Body tries to excrete the lead• Some deposits in soft tissues such as kidneys, lungs,

brain, spleen, muscles,& heart• Majority (95%) moves into bones & teeth ( some

into hair )• Lead is removed from the body extremely slowly

Effects Of Lead In The Body

Biochemical Effects• Lead inhibits or mimics the action of calcium• This can affect calcium-dependent or related

processes• Enzyme functions decreased as lead bind to protein

components of enzymes and interfere with their ability to catalyse their normal reactions

Effects Of Lead In The BodyNeurological/ Behavioral Effects• Encephalopathy – rare

BLL > 70-80 mcg/dL Signs & symptoms : hyperirritability, ataxia, convulsions,

stupor (near unconscious), coma, death• Disruption of balance• Impaired peripheral nerve functions• Hearing impairment• IQ loss• ADHD• Deficits in vocabulary, fine motor skills, reaction times, hand-eye

coordination• Delinquent & aggressive behaviour

Effects Of Lead In The BodyHematological Effects• Lead inhibits haemoglobin synthesis• This interferes with other haeme-dependent processes• Lead shortens the average lifespan of RBC’s

Cardiovascular Effects• Studies have linked lead to hypertension ( incl. low lead

exposure )• ECG abnormalities, degenerative changes in cardiac muscle

Effects Of Lead In The BodyRenal Effects• Proximal tubules of kidneys are sensitive to lead levels >

25mcg/dL• Lead forms protein complexes that lead to fibrous connective

tissue & goutGastrointestinal Effects• Colic is a consistent early symptom of exposure• Abdominal pain• Constipation• Cramps• Nausea & vomiting• Anorexia• Weight loss

Effects Of Lead In The BodyOther Effects• Auditory : negative impact on auditory functions• Endocrine : ↓ in human growth hormone• Vit D metabolism : interferes with the conversion of vit D to

its hormonal form• Growth : growth retardation in height, weight & chest

circumference• Reproductive : ↓ sperm count

↑ abnormal sperm ↑ miscarriages, stillbirth & premature birth Impotency

Why Are Children At Greatest Risk ?

• Greater exposure- high ‘hand-to-mouth’ activity- crawling, chewing & sucking- play in dirt and/or on floor

• Higher lead absorption rate – children absorb up to 50% of ingested lead , while adults only 10%

• Negative Impact on nervous system development

The Warning Signs Of Lead Poisoning• Lead poisoning is an invisible danger• Children with lead poisoning do not always look or act

sick• Signs & symptoms:

- general fatigue & lethargy- hyperactivity & ADHD (attention-deficit/ hyperactivity disorder)

- irritability- colic (abdominal pain )

- trouble sleeping-myalgia (pain in the muscle) or paraesthesia- headaches- tremor

Treatment Of Lead Poisoning– Chelation therapy is used if lead level is high– Chelation rapidly reduces the amount of lead stored in body. – Chelated lead is eliminated fr the body through the kidneys– EDTA ( ethylenediaminetetraacetic acid ) is given by IV – maybe

combined with dimercaprol– Prevention is the most effective means of reducing or

eliminating lead poisoning– This therapy may not reverse the damage that already occurred

in severe cases.– Children with lead toxicity may also be iron deficient so iron

supplements needed.

Chelating Agents

Dimercaprol ( British Antilewisite, BAL )• 1st chelator used in encephalopathic pt• Rapidly crosses the BBB• More effective at preventing lead from forming bonds with

tissue than reversing it• Usually used in combination with EDTA• Has a typical sulphide odour – pt often complain of bad taste

& feeling• A/E : fever, pain at injection site, N/V, headache• Dose : 3-5mg/kg IM q4h ( adults & children )

Chelating Agents

EDTA ( Edetate calcium disodium )• Nearly the perfect chelator• Is water soluble – can be used IV or IM• Allows lead to be renally excreted• It is not metabolised & have few s/e• IM – extremely irritating to muscle & painful

- can be used with lignocaine or procaine to lessen pain• Dose : 50-75mg/kg/d IV continuous infusion over 8-24 hr for

5 days or given IM in 2-6 divided doses

Chelating Agents

Succimer ( DMSA )• Only drug approved by FDA specifically for lead chelation in

children• Shown to be an effective oral chelator• Almost as effective as EDTA & BAL• Produce a rapid decline in lead levels & reverses many of the

biochemical indicators of toxicity