Discuss the clinical features, management and post-mortem findings in a case of cyanide poisoning.

Clinical Features

The clinical presentation of cyanide poisoning depends on the dose, route of exposure, and speed of onset. Symptoms progress rapidly, making early recognition vital.

Early Symptoms (Mild Exposure)

• Hyperventilation: Initial response to cellular hypoxia.
• Dizziness, headache, and weakness.
• Nausea and vomiting.
• Anxiety and restlessness.

Moderate Exposure

• Rapid breathing and heart rate.
• Confusion and disorientation.
• Weakness and incoordination.
• Methemoglobinemia: Cyanide converts hemoglobin to methemoglobin, impairing oxygen carrying capacity.

Severe Exposure

• Loss of consciousness.
• Seizures.
• Respiratory failure.
• Cardiac arrest.
• Pupils may be fixed and dilated.
• Characteristic bitter almond odor on breath (not always present, as the ability to detect it is genetically determined).

Management

Management of cyanide poisoning is a multi-step process focused on removing the patient from exposure, providing supportive care, and administering specific antidotes.

First Aid & Supportive Care

• Remove the patient from the source of cyanide exposure.
• Ensure adequate ventilation and oxygenation.
• Decontamination: Remove contaminated clothing and wash skin thoroughly.
• Monitor vital signs continuously (ECG, blood pressure, pulse oximetry).
• Establish intravenous access.

Definitive Treatment – Antidotes

• Hydroxocobalamin: The preferred antidote. It binds to cyanide, forming cyanocobalamin (Vitamin B12), which is excreted in the urine. Dosage: 5mg IV initially, may repeat.
• Cyanide Antidote Kit (CAK): Contains amyl nitrite, sodium nitrite, and sodium thiosulfate.
  • Amyl Nitrite: Inhaled for 10 seconds, followed by 10 seconds of room air. Induces methemoglobinemia, which competes with cyanide for binding to cytochrome oxidase.
  • Sodium Nitrite: Administered IV to further induce methemoglobinemia.
  • Sodium Thiosulfate: Enhances the detoxification of cyanide by converting it to thiocyanate, which is less toxic and excreted by the kidneys.

Additional Considerations

• Gastric lavage and activated charcoal are generally not effective due to rapid absorption.
• Consider hyperbaric oxygen therapy (HBOT) in severe cases, although evidence is limited.

Post-Mortem Findings

Post-mortem examination in cases of cyanide poisoning reveals characteristic findings, aiding in diagnosis.

• Smell of Bitter Almonds: Often present in the stomach contents and blood, but not always reliable.
• Bright Red Skin: Due to the inability of tissues to utilize oxygen, resulting in a cherry-red coloration.
• Venous Congestion: Particularly in the brain and lungs.
• Pulmonary Edema: Fluid accumulation in the lungs.
• Histological Findings: Cytopathic changes in the liver, heart, and brain.
• Blood Analysis: Elevated cyanide levels in blood can confirm the diagnosis, but levels decline rapidly post-mortem.
• Gastric Contents: Analysis for cyanide presence.

Finding	Description
Skin Color	Bright red (cherry-red) due to oxygen deprivation.
Smell	Bitter almond odor (variable).
Venous Congestion	Prominent in brain and lungs.
Blood Cyanide Level	Elevated (but declines rapidly post-mortem).