Sodium Nitrite Poisoning - Forensic's blog

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 NaNO_2.
The melting point of sodium nitrite is 271 degree Celsius.
The density of sodium nitrite is 2.168 g/cm^{3 .}
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 fatal period of sodium nitrite is 20 mins to 3 hours after ingestion.

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.

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.

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

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.34^th edition.
VV Pillay. Modern medical toxicology.4th edition.
R.K.Sharma. Concise textbook of forensic medicine and toxicology. 3^rdedition.