- 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.
- 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.
- The usual fatal dose for sodium nitrite is about 200mg to 600 mg.
- In adults, the estimated lethal dose is approximately 2600mg.
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
- Hurried breathing
- Abdominal pain
- Muscular weakness
- Accelerated heart rate
- Cyanosis which is first visible as bluish discolouration of the mucous membrane
- Respiratory grasping is also seen.
- Tachycardia and hypertension
- Bradycardia and hypotension
- Ventricular dysrhythmias.
- 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.
- 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’s 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.
- 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.