Lead

It is a heavy steel-grey metal. All its salts are poisonous

Poisonous compounds:
1} Lead acetate {sugar of lead or salt of Saturn} white crystals
2} Lead carbonate{safeda} a white crystalline powder
3} Lead chromate – a bright yellow powder.
4} Lead monoxide {litharge, massicot} pale brick-red or pale orange masses
5} Lead tetroxide {Red lead, Vermillion, sindoor} scarlet crystalline powder
6} Lead sulphide is least toxic
7} Tetra-ethyl lead {added to petrol} It is lipid soluble and is highly toxic.

Route :
Ingestion
Fatal Dose :
about 20 g. of lead acetate, 40 g. of lead carbonate
Fatal Period :
One to two days
Clinical Picture :
• Acute Poisoning
It is extremely rare. The symptoms are: astringent and metallic taste, dry throat, thirst, burning abdominal pain, nausea, vomiting, peripheral circulatory collapse, headache, insomnia, paraesthesias, depression, coma and death. There is no diarrhoea unlike the case with other metallic poisons, but constipation is an invariable feature. Stools are bulky, dark or black – due to formation of lead sulphide.
Cerebellar ataxia is common in children in acute lead poisoning.

Action – At the cellular level, lead interacts with sulphydryl groups and interferes with the actions of enzymes necessary for haem synthesis, and for haemoglobin and cytochrome production. It causes haemolysis.

Laboratory Findings-
Porphyrinuria, mainly due to coproporphyrin III, is a valuable screening test. In the blood, levels above 0.07 mg percent and in the urine 0.15-0.3 mg, litre are diagnostic.

• Sub-Acute Poisoning
No specific signs and symptoms except for the formation of a pale blue line at the junction of the teeth and gums. To produce toxic symptoms dose should be More than 2.56 mg, kg.

• Chronic Poisoning
1} It occurs in people working in factories and industries using lead, due to inhalation of dust{ in paint industry, plumbing, glass-blowers, electric wire industries, batteries, toys, hair dye and gasoline industries}
2} Food contaminated with lead {stored or cooked in tins}
3} Water stored in lead vessels
4} Vermillion{sindoor} used in ladies, oil helps lead absorption.

Manifestations-
1} Hypochromic areticulocytic Anaemia with basophilic stipling of RBCs – multiple dark blue coloured pinhead sized spots in the cytoplasm of RBCs. {diagnostic}
2} Lead line- A stippled blue line called Burtonian line is seen on the gums in 50-70 percent of cases. It is more prominent when the teeth are dirty and disappears when the teeth are kept clean. Sometimes the lines are black or grey. A similar blue line may be seen in cases of poisoning by mercury, copper, bismuth, iron and silver.
3} Colic and Constipation {also known as dry-belly ache}- The colic is intermittent, spasmodic and relieved by pressure and is associated with constipation
4} Cardio-Renal manifestations- Lead causes vascular constriction, leading to hypertension and permanent arteriolar degeneration. Chronic arteriosclerotic nephritis and interstitial nephritis occur.
5} Lead Palsy – Wrist drop and Foot drop. There may be tremors, numbness, hyperaesthesia and cramps before the actual muscle weakness. It is commoner in adults than in children and men are particularly affected.
6} Encephalopathy- In some form it is present in almost every case of plumbism. It is commoner in children often associated with tetra-ethyl lead. The symptoms are vomiting, headache, insomnia, visual disturbances, irritability, restlessness, delirium, hallucinations, convulsions, coma and death. It is usually irreversible and about 85 percent have permanent brain damage. Death occurs in about 35 percent of cases.
7} Eye changes- retinal stippling and optic atrophy.
8} Facial pallor- due to vasospasm especially around the mouth.
9} Reproductive system- amenorrhoea, dysmenorrhoea, menorrhagia, sterility of both sexes and abortion are frequent. Abortion occurs in pregnant women between 3 to 6 months.
10} General Manifestations- weakness, anorexia, foul breath, dyspepsia, irritability and pain in joints.

Diagnosis:
1} History
2} Clinical Examination
3} Laboratory tests-
a. Coproporphyrin in urine{CPU}: in non-exposed persons it isles than 150 micrograms per litre
b. Aminolaevulinic acid in urine{ALAU}:more than 5 micrograms indicates poisoning.
c. Blood lead level more than 25 micrograms per 100 ml.
d. The presence of 0.25 mg of lead per litre of urine is also diagnostic.
e. X-ray evidence of increase radio-opaque bands or lines at the metaphyses of long bones is seen in children.
f. Basophilic stipling.
g. Zinc protoporphyrin and free erythrocyte protoporphyrin levels above 50 micrograms per 100 ml indicate poisoning.
h. X-ray may show radio-opaque material in the G.I. tract if lead is ingested in the preceding 36-48 hours.
i. Calcium disodium versenate provocation test is not recommended.

Treatment :
A. Severe acute poisoning with encephalopathy
1} BAL 4mg, kg immediately{in children}. Repeat the dose at 4 howebsitey intervals until blood lead levels fall below 40 micrograms per 100ml. Then reduce BAL to 12 mgkg, day in 3 divided doses.
2} CaNa2 EDTA 75 mg, kg, day i.v. infusion. Reduce EDTA to 50 mg, kg, day as condition improves.
3} The above regimen is continued until the patient is asymptomatic and can tolerate chelation with D-Penicillamine 10mg, kg, day or DMSA, 10mg, kg. dose t.i.d. for 20 days.

B. Severe poisoning without encephalopathy{BL more than 70 mg, 100 ml}
1} BAL 12mg, kg, day
2} EDTA 50 mg, kg, day
3} Discontinue BAL when blood level falls below 40 microgram per 100ml but continue EDTA for 5 more days.
4} Continue oral chelation until the BL falls below 15 micrograms per 100ml or for 3 months.

C. Moderate poisoning{BL between 45 to 75 micrograms per 100 ml}
1} EDTA 50 mg, kg, day
2} When BL falls below 40 begin oral chelation.

D. Mild poisoning{ BL 20 – 35 micrograms per 100 ml}
D-Penicillamine 30 mg, kg, day in 3 divided doses. Start with one-fourth of the calculated dose. Double this after one week. Double again after one week. Continue this until BL falls to below 15 micrograms per 100 ml or for 3 months.

Supportive measures include-
1. Thiamine 10-50 mg, kg to improve neurological manifestations.
2. Calcium gluconate i.v. for colic.
3. Magnesium or sodium sulphate 8 – 12 g. will change unabsorbed lead salts to highly insoluble lead sulphate and hasten its passage in stools.
4. Calcium versenate of disodium acts as an ion exchanger. EDTA 5 ml of 20 percent solution is diluted with 250-500 ml of normal saline or 5 percent glucose, and given by drip method over a period of one hour, twice daily for 5 days and can be repeated after an interval of 2 days.
5. BAL 4 mg, kg body weight every 4 hours is useful. In the presence of renal impairment BAL is the chelator of choice as its main route of excretion is bile. BAL should be given at least 4 hours before EDTA as EDTA mobilises lead from tissue stores and aggravates symptoms of lead poisoning.
6. Penicillamine 0.3-0.5 g. orally one to 5 times daily is effective in excretion of circulating lead but is not as effective as EDTA. This may be continued for 1-2 months.
7. DMSA{succimer} is superior to EDTA. 10 mg, kg orally every 8 hours for 5 days, followed by the same dose every 12 hours for 14 days.
8. DMPS
9. A diet poor in calcium, and ammonium chloride one g. ten times daily is given. By this lead deposited in the bones is mobilised into blood and excreted. High doses of parathormone have similar effects.
10. Treat symptoms on general lines.

Lead

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