Thermoregulation and Body Temperature

Thermoregulation

• Thermoregulation is constantly maintaining a stable core body temperature
• Normothermia: 36.2°C-37.6°C
• Hypothermia: Below 36.2°C
  • Mild: 34°C-36.2°C
  • Moderate: 30°C-34°C
  • Severe: 30°C
• Hyperthermia: Above 37.6°C-41.5°C
  • Hyperpyrexia: Extremely high body temperature (41.5°C)
• Fever is a rise in body temperature due to a change in the hypothetical setpoint due to foreign antigens (e.g., pyrogens)

Temperature Balance

• Basal Metabolic Rate (BMR): The rate of energy the body uses for essential activities like breathing
  • Can increase or decrease body heat production
  • Higher metabolic rate in younger people
• Muscle Activity (e.g., shivering): Produces heat
• Thyroxine output: Hormone produced by the thyroid gland; crucial for regulating metabolism
  • Increased thyroxine = increased epinephrine production
• Epinephrine and Norepinephrine: Hormones and neurotransmitters that increase metabolism and cause vasoconstriction, increasing body temperature
• Stimulation/Stress Response: Increase in these hormones and neurotransmitters
• Vasoconstriction: Narrowing of blood vessels; increases body temperature
• Convection: Transfer of heat from warm to cool air
• Conduction: Direct contact heat transfer from warm to cool surfaces
• Radiation: Heat transfer from warm to cool objects without direct contact
• Evaporation: Transfer of heat from water droplets to vapor (e.g., sweat)

Methods of Heat Loss

• Includes convection, conduction, radiation, and evaporation

Fever

• 4 Methods of Heat Loss: Convection, conduction, radiation, evaporation

Hypothalamus

• 3 Primary Components: Sensors, Hypothalamus, Effectors
  • 1. Sensors:
    • Detect temperature changes
    • Mostly in skin, detect cold more efficiently than warmth
    • Neurological and hormonal control mediated by hypothalamus
  • 2. Hypothalamus:
    • Receives signals from sensors
    • Sends signals to release hormones to stimulate or reduce heat production, cause shivering, and increase muscle tone.
  • 3. Effectors/Response to sensors
    • Once body temperature is within normal range, the hypothalamus stops these responses.

Risk Factors of Thermoregulation

• Age (old and very young): Infants and the elderly have different thermoregulation capacities.
• Other factors: Subcutaneous fat, body surface area, blood vessels, racial disparities, social determinants, alcohol consumption, medical conditions, homelessness, mental health.

Interrelated Concepts

• Concepts interconnected with thermoregulation, including infection, intracranial regulation, traumatic brain injury, nutrition, perfusion, tissue integrity, fluid & electrolytes.

Hypothermia Assessment

• Vasoconstriction—cool and clammy skin, pale, slow capillary refill, muscle rigidity, shivering
• Poor perfusion
• Decreased urinary output
• Cognition changes
• Dysrhythmias leading to cardiovascular collapse

Hyperthermia Assessment

• Vasodilation—flushed, warm or hot skin, diaphoresis, decreased urine output, dry mucous membranes, decreased cognition, seizures, coma

Prevention Strategies

• Wear appropriate clothing, moisture wicking clothing, no alcohol consumption, adequate nutrition.

Clinical Judgment

• The 6 functions of clinical judgment: recognize cues, analyze cues, prioritize hypotheses, generate solutions, take action, evaluate outcomes
• The Nursing Process and its integration with clinical judgment

Hypothermia S/S and Interventions (Mild, Moderate, Severe)

• Detailed symptoms and interventions for each stage of hypothermia, including blood pressure changes, dehydration effects, and rewarming techniques.

Warming the Core of the Body First

• Interventions for severe cases