## Livor Mortis (Post-mortem Hypostasis) — Fixation Timeline **Key Point:** Livor mortis is a purple-red discoloration of dependent areas caused by gravitational pooling and deoxygenation of blood in capillaries and venules. It becomes **fixed** (non-blanching) when haemoglobin denatures and leaks into surrounding tissues. ### Progression of Livor Mortis | Stage | Time Post-mortem | Appearance | Blanching | Mechanism | |-------|-----------------|-----------|-----------|----------| | **Early** | 0.5–2 hours | Faint purple-red | Blanches on pressure | RBC pooling, reversible | | **Intermediate** | 2–8 hours | Darker purple-red | Partially blanches | Haemoglobin deoxygenation | | **Fixed** | 8–12 hours | Deep purple-red | Non-blanching | Haemoglobin denaturation, tissue infiltration | | **Late** | 12–24+ hours | Dark purple-brown | Completely fixed | Advanced tissue changes | **High-Yield:** Livor mortis becomes **completely fixed and non-blanching at 8–12 hours** post-mortem under normal conditions. This is a critical forensic marker for timing of death. **Clinical Pearl:** Factors affecting fixation time: - **Accelerate fixation:** High ambient temperature, thin skin, dehydration - **Delay fixation:** Cold environment, obesity, thick skin **Mnemonic:** **FIX at 8** — Fixation of livor mortis occurs at approximately 8–12 hours post-mortem. **Warning:** Early livor mortis (0.5–2 hours) blanches on pressure and may be mistaken for living bruising; fixed livor (8–12 hours) does NOT blanch and is diagnostic of post-mortem origin.
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.