A 35-year-old man is found dead in a house fire. On autopsy, the body shows extensive charring of the skin, but the lungs are pale pink with frothy fluid in the airways. Which of the following is the most common cause of death in ante-mortem burns?

Explanation

## Most Common Cause of Death in Ante-mortem Burns **Key Point:** Carbon monoxide (CO) poisoning is the most common cause of death in ante-mortem burns, accounting for approximately 50–80% of fire-related deaths. ### Mechanism 1. **CO Production in Fires**: Incomplete combustion in oxygen-poor environments (common in enclosed spaces) produces large quantities of CO. 2. **Binding to Hemoglobin**: CO binds to hemoglobin with an affinity 200–250 times greater than oxygen, forming carboxyhemoglobin (COHb). 3. **Tissue Hypoxia**: Even at low concentrations, CO causes severe tissue hypoxia and death before significant thermal injury occurs. ### Autopsy Findings in CO Poisoning | Feature | Finding | |---------|----------| | **Skin color** | Cherry-red or pink (due to COHb) | | **Lungs** | Pale pink with frothy fluid (pulmonary edema) | | **Blood** | Bright red (high COHb saturation) | | **Cause of death** | Asphyxia from CO, not thermal injury | **Clinical Pearl:** The pale pink lungs with frothy fluid in this case are classic for CO poisoning, not thermal injury. Thermal injury to airways typically causes charring of the mucosa and hemorrhage, not pale lungs. **High-Yield:** In fire deaths, victims often die from CO poisoning *before* the body is significantly burned. This is why ante-mortem burns show evidence of CO in blood and tissues (COHb levels >10% indicate ante-mortem exposure). ### Why Other Causes Are Less Common - **Thermal injury to airways**: Occurs but is usually secondary to CO poisoning; victims are already unconscious from CO. - **Hypovolemic shock**: Develops over hours; most fire victims die within minutes from CO. - **Electrolyte imbalance**: A late complication, not a primary cause of death. [cite:Reddy Forensic Medicine 34e Ch 12]