Question

Define hypothermia. What are the different phases of heat loss under anaesthesia?

Hint:

Hypothermia during anaesthesia is common but preventable. Warming the patient early and maintaining a warm operating room can reduce heat loss.

Answer 1

Step 1: Definition of hypothermia.
Hypothermia is a medical condition characterized by a core body temperature below 35°C. It occurs when the body loses heat more quickly than it can generate, resulting in an abnormally low body temperature. Hypothermia can range from mild (32-35°C) to severe (<28°C), with symptoms increasing in severity as the temperature drops.

Step 2: Phases of heat loss under anaesthesia.
During anaesthesia, heat loss can occur in different phases:
- Phase 1 (Initial phase, 0-1 hour): Rapid heat loss due to redistribution of heat from the core to the periphery of the body. This is primarily due to vasodilation induced by anaesthetic agents.
- Phase 2 (Intermediate phase, 1-3 hours): Moderate heat loss occurs due to a combination of heat loss through radiation, conduction, and convection. This phase also includes evaporative heat loss through insensible perspiration.
- Phase 3 (Late phase, >3 hours): Prolonged exposure to cold environments leads to a steady state of heat loss, which can be worsened by prolonged exposure to cold operating room temperatures, poor insulation, and inadequate warming measures.