Sodium Nitrite Poisoning

Introduction

  • Sodium nitrite is also known as nitrous acid sodium salt.
  • Sodium nitrates is inorganic poison
  • It is a white and yellow crystalline substance or powder.
  • It is odourless.
  • It is like table salt in taste.
  • Sodium nitrite acts as antimicrobial agent and also acts as powerful oxidizing agent.
  • It is readily soluble in water as well as in alcohol and is hygroscopic.
  • The chemical formula of sodium nitrite is NaNO2.
  • The melting point of sodium nitrite is 271 degree Celsius.
  • The density of sodium nitrite is 2.168 g/cm3 .
  • It has hypotensive effects.

Uses

  • It is largely used in dyeing industry.
  • It is also used as preservatives for some foods.
  • It acts as microbial agent for preserving meat, fish and hot dog.
  • It is widely used in industry as well as in construction.
  • It is used as herbicides, organic insecticides.
  • It is also used as intravenous mixture with sodium sulfate to treat cyanide poisoning.

Fatal Dose

  • The usual fatal dose for sodium nitrite is about 200mg to 600 mg.
  • In adults, the estimated lethal dose is approximately 2600mg.

Fatal Period

The fatal period of sodium nitrite is 20 mins to 3 hours after ingestion.

Mode of Action

  • Nitrites are the actual toxic compound.
  • Firstly, Circulatory haemoglobin is converted into methaemoglobin.
  • Secondly, 1 mole of absorbed nitrites reacts with 2 moles of haemoglobin. In this process, ferrous form of iron in haemoglobin is converted to ferric form which results in methaemoglobin forms.
  • Nitrites can cause methaemoglobinaemia which is unusual and potentially fatal condition in which haemoglobin is oxidized to MHb, reducing the amount of oxygen that is released from haemoglogin.
  • Nitrites are also a potent vasodilator.
  • It can cause coronary ischemia and stroke as a result of hypotension, tachycardia and hypoxia.
  • Nitrites induce methaemoglobinaemia which causes the detachment of cyanide from the haeme group of cytochrome oxidase.

Sign and Symptoms

  • Giddiness
  • Headache
  • Vomiting
  • Purging
  • Weakness
  • Hurried breathing
  • Anxiety
  • Agitation
  • Vasoldilation
  • Anoxia
  • Abdominal pain
  • Diarrhoea
  • Muscular weakness
  • Accelerated heart rate
  • Cyanosis which is first visible as bluish discolouration of the mucous membrane
  • Respiratory grasping is also seen.
  • Confusion
  • Convulsions
  • vertigo,
  • Tremors
  • Weakness
  • Fatigue
  • Dizziness,
  • Tachycardia and hypertension
  • Bradycardia and hypotension
  • Ventricular dysrhythmias.
  • Hypoxia
  • Coma
  • Pupils are often dilated and sluggish in reaction.
  • Unconsciousness followed by death

Post Mortem Findings

  • Dark brown or coffee coloured blood which clots improperly.
  • Brown staining of tissues have been reported.
  • Congestion of the intra-abdominal organs is also seen.
  • Peteicheal haemorrhages on the serious surfaces may be seen.
  • Dilation of blood vessels.
  • Generalized cyanosis and blood stained pericardial fluid are commonly seen.

Treatments

  • Methylene blue intravenously at the rate of 4-8 mg/kg.
  • Ascorbic acid is also effective.
  • Stomach wash.
  • Haematologic evaluation.
  • Diazepam for convulsions.
  • Determine the methaemoglobin concentration, and evaluate the patient for clinical effects of methaemoglobinaemia.
  • Treat patients with symptomatic methaemoglobinaemia with methylene blue (this usually occurs at methaemoglobin levels above 20 to 30%, but may occur at lower methaemoglobin levels in patients with anaemia, or underlying pulmonary or cardiovascular disorders). Dose: 1 to 2 mg/kg/dose (0.1 to 0.2 ml/kg/dose) IV over 5 minutes, as needed every 4 hours.
  • If kidney function is normal, administer 0.45% sodium chloride in D5W, and a diuretic such as furosemide 1 mg/ kg to a maximum of 40 mg/dose to obtain a urine flow of 3 to 6 ml/kg/hr to increase renal excretion. For anuria or agranulocytosis, dialysis and/or isolation should be considered.
  • Supportive measures.
  • Haemodialysis may be beneficial.

Test for Detection or Forensic Examination

  • Bedside Test: Place 1 drop of patient‚Äôs urine on wood pulp (lignin) or pulp paper (newspaper), and add to it 1 drop of concentrate HCl. Normal urine stains yellow, methaemoglobin gives Dark chocolate coloured or coffee coloured indicates the nitrites poisoning.
  • Quantitation in serum can be done with High Performance Liquid Chromatography.
  • Urine levels can be estimated by Gas Chromatography /Mass Spectrophotometer.
  • Titration test
  • Nitrite test kit

Medico Legal Aspects

  • On account of its easy availability, the cases of nitrite poisoning are more frequent in areas near the dyeing industries.
  • Food poisoning has been reported due to accidental use of sodium nitrite.
  • Abortion in pregnant animals.
  • Sometime unintensional exposures can also lead to sodium nitrite poisoning.
  • It is commonly used to kill cattle to take revenge.
  • Homicidal poisoning may be occurred.
  • Suicidal cases are rarely encountered.

References

  • Dr. K.S. Narayan Reddy. The essential of forensic medicine and toxicology.34th edition.
  • VV Pillay. Modern medical toxicology.4th edition.
  • R.K.Sharma. Concise textbook of forensic medicine and toxicology. 3rd edition.
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