Thermoregulation in Human Biology

Thermoregulation

• Thermoregulation is the process of maintaining a constant core body temperature.
• Normothermia: Normal body temperature ranges between 36.2°C to 37.6°C (97.1°F to 99.6°F).
• Hyperpyrexia: Extremely high body temperature above 41.5°C (106.7°F)

Definitions

• Fever: Elevation in body temperature due to a change in the hypothetical set point.
  • Pyrexia
  • Malignant Hyperthermia
  • Hyperthermia
• Hyperthermia: Body temperature above 37.6°C (99.6°F).
• Hypothermia: Body temperature below 36.2°C (97.1°F).

Interventions for Hyperthermia

• Remove excess clothing
• Provide external cooling measures (cool packs, cooling blankets)
• Provide hydration (oral or IV)
• Give antipyretic drug therapy

Interventions for Hypothermia

• Remove person from cold environment
• Provide external warming measures
• Provide internal warming measures

Non-shivering Thermogenesis

• Increased temperature causes blood vessels to dilate (skin flushed), and sweat glands are activated.

Body Temperature Regulation

• Radiation: Heat transfer from one surface to another without direct contact.
• Conduction: Heat transfer from one object to another with direct contact.
• Convection: Heat transfer away by air movement.
• Evaporation: Heat transfer when a liquid changes to a gas.
• Diaphoresis: Visible perspiration, primarily on the forehead and upper thorax.

Methods of Temperature Measurement

• Three invasive core temperature sites.
  • Specific locations not provided.

Medications for Pyrexia/Fever

• Acetaminophen
• Ibuprofen
• Aspirin

Heat-Related Emergencies

Heat Cramps

• Brief and intense muscle cramps in large muscle groups.
• Inadequate fluid intake.
• Nausea, tachycardia, pallor, weakness, and profuse diaphoresis.
• Interventions: Rest, hydration, and pain relief.

Heat Exhaustion

• Prolonged exposure to heat, usually due to strenuous activity in hot, humid environments.
• Fatigue, nausea, vomiting, extreme thirst, hypotension, tachycardia, elevated body temperature, dilated pupils, and ashen coloring, and profuse sweating.
• Interventions: Fluid replacement, cool environment, and monitoring.

Heat Stroke

• Most serious heat-related emergency.
• Failure of hypothalamic thermoregulatory processes.
• Increased sweating, vasodilation, and increased respiratory rate deplete fluids and electrolytes.
• Sweat glands eventually stop functioning.
• Core temperature rises rapidly (above 105.8°F (41°C)).
• Altered mental status, confusion, coma, hypotension, tachycardia, tachypnea, weakness, hot dry skin, absence of sweating, and circulatory collapse.
• Interventions: Immediate medical attention via cool methods.

Cold-Related Emergencies

Frostbite

• Tissue freezing.
• Localized; typically affecting hands and feet (less commonly cheeks, nose, ears, penis).
• Superficial frostbite: involves the skin and subcutaneous tissue.
• Deep frostbite: involves muscle, bone, and tendon; skin will appear white, hard, and insensitive to touch. Can lead to gangrene (loss of blood circulation to the area and the skin tissue will die).
• Interventions: rapid warming by controlled circulating water immersion (99-102°F/37.2-38.9°C). No rubbing or massage of affected areas

Hypothermia

• Core body temperature below 95°F (35°C).
• Mild (93-95°F/33.9–35°C): Shivering, lethargy, confusion.
• Moderate (86-93°F/30-33.9°C): Rigidity, bradycardia, bradypnea.
• Severe (below 86°F/30°C): Life-threatening. Loss of consciousness, absent reflexes, and vital signs are difficult to detect.
  • Interventions: Passive or active external rewarming, correct dehydration and acidosis, and treat dysrhythmias.