Prevent Perioperative Hypothermia: Retain Heat
Highlights
- Heat loss is proportional to the temperature difference by a power of 4 (View Highlight)
- Convection is the direct transfer of heat to moving currents of air or water surrounding the body. It’s proportional to air velocity (View Highlight)
- Infants and young children are much more likely to get hypothermic in a cold environment because of significantly higher surface to volume ratio (toddlers 2X and infant 3X the adult ratio) and little muscle mass or fat insulation (View Highlight)
- Cover the head. About 7-10% of heat loss occurs through the exposed head. (View Highlight)
- Perioperative hypothermia is defined as a core body temperature below 36°C (96.8°F) (View Highlight)
- Perioperative hypothermia can cause:
• cardiovascular complications
• delayed wound healing
• altered states of consciousness
• increased infection rate
• increased blood loss
• prolongation of drug effect. (View Highlight)
- Anesthesia disrupts normal thermoregulation by:
• changing the brain’s thermal regulatory set points
• decreasing metabolic rate,
• altering the distribution of blood flow (View Highlight)
- Sinking below the lower threshold triggers vasoconstriction and shivering to retain heat and to increase heat production.
Anesthesia resets those thresholds by 2-3°C, making perioperative hypothermia more likely. (View Highlight)
- Intraoperative vasodilation is caused by both:
• the direct effect of anesthetic agents
• the indirect consequences of a lowered vasoconstriction threshold. (View Highlight)
- As the hypovolemic patient rewarms, the patient will vasodilate, potentially causing hypotension.
In a severely hypothermic patient, such as from cold water emersion, rapid rewarming can precipitate cardiovascular collapse and possible cardiac arrest for the same reason. (View Highlight)