NRSG258 Principles of Nursing: Surgical - Thermoregulation and Fever

Thermoregulation

• Achieved by balancing heat production, conservation, and loss.
• Optimal range: 37^oC (35.8^oC – 38.2^oC range).
• Mediated by the hypothalamus, endocrine system, and sympathetic nervous system.
• Thermoreceptors in skin and hypothalamus provide temperature information.
• Hypothalamus triggers heat production, conservation, or loss mechanisms.

Hypothermia

• Core temperature less than 36^oC (96.8^oF).
  • Mild: 34^oC to 35^oC (93.2^oF to 95^oF).
  • Moderate: 30^oC to 34^oC (86^oF to 93.2^oF).
  • Severe: Less than 30^oC (86^oF).
• Heat promoting mechanisms:
  • Constriction of cutaneous blood vessels.
  • Increase in metabolic rate (non-shivering thermogenesis).
  • Shivering.
  • Enhanced release of thyroxine.
  • Behavioral modifications (e.g., warmer clothing, hot fluids).

Hyperthermia

• Elevated body temperature.
• Fever: Abnormally high body temperature, a systemic response to invading microorganisms.
• Heat loss mechanisms:
  • Dilation of cutaneous blood vessels.
  • Enhanced sweating.
  • Behavioral modifications (e.g., reducing activity, seeking cooler environment).

Pathogenesis of Fever

• Leukocytes and macrophages exposed to exogenous pyrogens.
• Triggers release of endogenous pyrogens.
• Endogenous pyrogens act on hypothalamus.
• Prostaglandins raise body temperature.
• Heat production activated via vasoconstriction and shivering.

Fever - Risks vs Benefits

• Benefits:
  • Inhibits growth and replication of microorganisms.
  • Decreases serum levels of iron, zinc, and copper.
  • Prevents viral replication.
  • Improves immune response.
  • Enhances phagocytosis and interferon production.
• Risks:
  • Stress on the body.
  • Brain damage if sustained temperature > 41^oC.
  • Death > 43^oC.
  • Febrile seizures (>39^oC) in children.