Mercury (quicksilver/para) may be a heavy, silvery liquid and volatile at normal temperature. It forms two series:

  1. Mercuric: which are soluble and highly poisonous
  2. Mercurous:  which are much less soluble and less    active.
MERCURY

Metallic mercury is not poisonous, if swallowed because it is poorly absorbed from the GIT.

POISONOUS COMPOUNDS OF MERCURY

  1. Mercuric chloride (corrosive sublimate): it occurs as Colorless, odorless, masses of prismatic crystals or white crystalline powder, but has a nauseous metallic taste. It is the foremost toxic salt and commonly the cause of acute poisoning.
  2.  Mercurous chloride (calomel): Heavy, amorphous white and tasteless powder.
  3. Mercuric sulphide (cinnabar or vermilion): It is not absorbed through skin and is as such nonpoisonous, artificial preparation occurs as red crystalline powder.
  4. Mercuric cyanide and iodide (scarlet red powder).
  5. Sulphate of mercury ( lemon- yellow powder)
  6. Organic compounds of mercury
  7. Mercuric nitrite
  8. Ammoniomercuric chloride

ACTION

The mercuric ion binds with sulphydryl groups of enzymes and cellular proteins, nucleic acids and mitotic apparatus interfering with enzymes and cellular transport functions.  It is rapidly converted to mercuric ions within the blood which cause renal tubular damage. In the CNS, mercury acts mainly upon cerebellum, temporal lobe, basal ganglia and callosum.

Fatal Dose

Mercuric chloride: 0.5–1 gm/70 kg. Mercurous chloride: 1.5–2 gm/70 kg.

Fatal Period

Death may occur within a couple of hours but is typically delayed for 3–5 days.

Signs and Symptoms

 Acute Poisoning:

Inhalation of mercury vapor causes chemical pneumonitis, pulmonary edema, gingivostomatitis and CNS symptoms, like ataxia, restriction of visual field of vision, paresis, delirium and polyneuropathy.

Ingestion of inorganic mercuric salts

It is divided into two phases.

First phase

System Signs and symptoms

GIT •Metallic taste, feeling of constriction within the throat, hoarse voice.

• Mouth, tongue and fauces become corroded, swollen and mucosa appears grayish white.

• Hot burning pain from the mouth to the stomach and pain radiating over the abdomen followed by nausea, retching and vomiting. Vomitus contains grayish slimy mucoid material with blood and shreds of mucousa.

• This is often followed by diarrhea, often bloody with tenesmus (gastroenteritis).

Renal: Oliguria, albuminuria and hematuria ending in kidney failure or nephritic syndrome.

CVS: Hypertension, difficulty in breathing and circulatory collapse.

Second phase: If patient survives, 2nd phase begins in 1-3 days.

  • Glossitis and ulcerative gingivitis appear in 1-2 days. Renal tubular necrosis produces polyuria, albuminuria, uremia and acidosis.
  • Recovery may occur within a fortnight, but membranous colitis may develop and produce dysentery, ulceration of colonic mucosa.

Postmortem Findings

  • Body looks emaciated.
  • GIT: Mucosa shows inflammation, congestion and grayish corrosion. Ulceration or may be gangrene of large intestine could also be seen.
  • Kidneys: Acute proximal tubular damage and glomerular degeneration or glomerular nephritis (membranous glomerulopathy) could also be seen.
  •  Liver: Congested and shows cloudy swelling of fatty change.
  •  Heart: Fatty degeneration and Subendocardial hemorrhage.

Diagnosis: Blood mercury level should not exceed 3.6 μg/dl, and 24 h urinary excretion of mercury > 15 μg/l indicates toxicity.

• Urine and blood mercury levels are assessed by atomic absorption spectroscopy.

• Mercury concentration of hair is best assessed by neutron activation analysis.

Treatment

  1. In case of inhalation, the patient is immediately removed from surroundings where he was  exposure to this poison and supplemental oxygen is given, and observed for the development of acute pneumonitis and pulmonary edema.
  2.  Egg whites, milk or animal charcoal which forms insoluble precipitate mercury. Emesis isn’t induced due to the risk of serious corrosive injury.
  3.  250 ml of 5% sodium formaldehyde sulphoxylate may be used for gastric lavage. A further of 100 ml of this solution may be left in the stomach. Lavage can be done with egg-white solution or 2-5% solution of sodium bicarbonate.
  4. Polythiol resins helps in binding mercury within the GIT.
  5.  BAL is that the chelator of choice.
  6. DMSA or succimer (10 mg/kg orally every 8 h foR 5 days and then 12 hourly for two weeks) may be a good alternative.
  7.  D-penicillamine is an alternate oral treatment, but it may be associated with side-effects and fewer efficient Hg excretions.
  8.  There’s no role of for dialysis, hemoperfusion or repeat dose charcoal in removing metallic mercury or inorganic salts. However, hemodialysis/peritoneal dialysis could also be just in case of kidney failure.
  9.  Maintain electrolyte and fluid balance.
  10. Symptomatic treatment.

Chronic Mercury Poisoning (Hydrargyrism)

Chronic poisoning results from:

  • • Continuous accidental absorption by workers
  •  • Excessive therapeutic use.
  • • Recovery from a large dose.
  • • If an ointment is employed as an external application for an extended time.

Signs and Symptoms

Chronic intoxication from inhalation of mercury vapor yields  a triad of tremors, neuropsychiatric disturbances and gingivostomatitis. Chronic ingestion causes:

  • Constant metallic taste, with signs of gingivitis,

    glossitis and loosening of teeth with blue line within the gum.

  • Loss of weight, anorexia, anemia and lymphocytosis, constipation or diarrhea, jaundice, increased urination and restricted field of vision.
  • Irritation of skin, sore mouth and throat.
  • Chronic inflammation of kidneys with progressive uremia and impairment of renal function.
  • CNS toxicity and impairment of motor speed, memory.

 Characteristic Features

  1. Intention tremors (Danbury tremors/shaking palsy) It occurs first within the hands, then progresses to the lips and tongue, and eventually involves arms                  and legs.

• Tremor is moderately coarse and is interspersed by jerky movements. The patient might not display much tremor during an accustomed job, but if he is being observed, he may begin to shake violently.

• Within the advanced stage, the person is unable to dress himself or walk properly. They are also called hatter’s shakes or glass blower’s shakes, as they are common in persons working with mercury in glass-blowing and hat industries. The most severe sort of tremors is understood as concussion mercurilis.

2. Mercurial erethism: Erethism is seen in persons working with mercury in mirror manufacturing firms. This cluster of symptoms was first described by Kussmahl and therefore the term is employed to refer to the neuropsychiatric effects of mercury toxicity.

These include:  Insomnia, Depression, anxiety, amnesia, timidity and shyness, frequent blushing, explosive irritability, Delusions and hallucisudden attacks of anger nations.

3.  Mercurialentis: It’s a peculiar eye change due the  exposure to mercury vapor.

• It is due to brownish deposit of mercury through the cornea on the anterior membrane.

• Slit-lamp examination demonstrates a malt-brown reflex from the membrane.   

• It is bilateral and has no effect on acuity.                   

3. Acrodynia or Pink disease: It is due to idiosyncratic hypersensitivity reaction to repeated ingestion or contact with mercury particularly seen in children. Signs and symptoms: There is pain within the extremities, flushing, itching, swelling, hypertension, excessive salivation or perspiration, weakness, irritability, pinkish morbilliform/acral rashes and desquamation of palms and soles.

ACRODYNIA

 4. Minamata disease is due to chronic mercury intoxication caused by eating contaminated fish and shellfish. Symptoms include disturbances in hand coordination, gait and speech, chewing and swallowing difficulties, visual blurring, tremors, rigidity, seizures and clouding of consciousness.

TEST:  if a piece of copper wire is introduced within the solution and a couple of drops of acid are added, a silver coating of mercury will be formed on the wire.

MEDICO-LEGAL ASPECTS OF POISONING

  1. Accidental poisoning by mercuric chloride may be due to use of strong solution in washing abscess cavities or irritating the vagina, uterus.
  2. Sometimes, it is introduced into a vagina as a contraceptive or for producing abortion.
  3. Homicidal or suicidal poisoning is rare.

For more metallic poisons, go through this link.

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