236. Thermal Regulation Flashcards
Why are neonates particularly susceptible to temperature variability?
Due to environmental factors, anesthesia, and surgery promoting temperature instability.
What is the ratio of total body surface area to volume in neonates compared to adults?
Up to three times greater in neonates.
What percentage of total body surface area can the head of a neonate account for?
Up to 20%.
What factors predispose neonates to hypothermia?
- Thin skin
- Low subcutaneous fat stores
- Inability to shiver
- Immature autonomic nervous system
What is the primary method of thermoregulation in neonates?
Nonshivering thermogenesis.
What role does brown fat play in neonatal thermoregulation?
It generates heat through metabolism, accounting for up to 5% of body mass.
What is thermogenin’s role in brown fat metabolism?
It uncouples oxidative phosphorylation to generate heat when hypothermia occurs.
Where is brown fat primarily found in neonates?
- Between the scapulae
- Above the clavicles
- Throughout the mediastinum
- Surrounding the kidneys and trachea
What is a neutral thermal environment for neonates?
The ambient temperature at which a neonate can maintain normal temperature with minimal oxygen demand.
What is the first autonomic response to hypothermia in neonates?
Peripheral vasoconstriction.
What is the interthreshold range for internal temperatures in humans?
Approximately 0.4° in awake patients.
What are the stages of heat loss during anesthesia?
- Heat redistribution due to vasodilation
- Heat transfer from skin to environment
What is the major conduit of heat loss in newborns?
Radiation (39% of total heat loss).
How does the body conserve temperature when it falls below the interthreshold range?
- Vasoconstriction
- Nonshivering thermogenesis
- Shivering
What defines mild hypothermia in infants and children?
Core temperature ranging from 36.0°C to 36.4°C.
