thermoregulation

• •Optimal physiological functioning of the human body occurs when a near-constant core temperature is maintained.
• Normal body temperature ranges from 36.2 °C to 37.6 °C (97.0 °F to 100 °F), or an average of 37 °C (98.6 °F)
• Thermoregulation is defined as the process of maintaining core body temperature at a near constant value
• Physiological adjustments to body temperature are controlled by the hypothalamus—often considered the thermostat center of the body
• Normothermia is normal body temperature (ranges between 36.5° C and 37.2° C
• Hyperthermia refers to a body temperature above normal range (>37.6°C
• Hyperpyrexia is an extremely high body temperature (above 41.5° C)
• Hypothermia is a body temperature below 36.2° C
• Infants •Thermoregulation is linked closely with metabolism and oxygen consumption •Brown fat •Non-shivering thermogenesis (involving increased metabolism and oxygen consumption) helps to offset heat loss •The flexed posture of newborns •Limited insulation due to a thin layer of subcutaneous fat
• Older Adults

  • Slower circulation

  • Reduced function of thermoregulatory capacity of the skin

  • Reduced heat production

  • Decreased shivering response

  • Reduced perception of environmental temperature
• Risk Factors •Infants & young children •Older Adults •Populations with altered cognition •Genetics •Recreational or occupational exposures •Health conditions
• Fever •A natural, adaptive response of the body, to physiological stress •An elevation in body temperature due to a change in the hypothetical set point (caused by inflammatory cytokines; hypothalamus is the “thermostat of the body”) •Can be caused by a vast range of conditions, both infectious and noninfectious. •This change in the set-point is mediated by the action of cellular messengers, known as pyrogens, on the hypothalamus. Pyrogens can either be endogenous (e.g.IL1, IL6, TNF ) or exogenous (e.g. bacterial/viral toxins)
• Fever: Signs & Symptoms

  • diaphoresis

  • irritability

  • lethargic

  • level of consciousness decreased

  • seizure activity

  • shivering

  • skin flushed

  • skin pale

  • skin warm to touch

  • Syncope
• Hyperthermia

  *Key difference between fever and hyperthermia – Hyperthermia is a body temperature above 37.6 ° C with an unchanged hypothalamic set point*

  •Excessive heat production, inadequate ability to cool, or hypothalamic

  regulator dysfunction

  •Hyperthermia can either be caused by excessive amounts of heat from the surroundings or due to an increase in the body’s internal heat production.

  •The heat produced overruns the body’s heat-loss capacity and causes a sharp spike in temperature, which often leads to severe complications and serious organ damage.
• Hypothermia

  •When the core body temperature declines below 36.2 °C and

  is further classified as mild (34 °C to 36 °C or 93.2 °F to 96.8 °F),

  moderate (30 °C to 34 °C or 86 °F to 93 °F), or severe (<30 °C or

  <86 °F).

  •Excessive heat loss, insufficient production of heat, or

  dysfunction of hypothalamic regulatory mechanisms
• Thin layer of subcutaneous fat


  • Blood vessels are close to the surface of the skin
• Changes in environmental temperature

  1. Alter the temperature of the blood

  2. Influence temperature regulation centres in the hypothalamus
• Infants

  • Larger body surface–to–body weight (Mass) ratios than children and adults
• Environmental influences

  • Temperature and humidity of the air
  • Flow and velocity of the air
  • Temperature of surfaces in contact with and around the infant
• Heat loss occurs in 4 modes

  • Convection
  • Radiation
  • Evaporation
  • Conduction
• Infant response to heat loss

  1. Increase muscle activity (Crying, appearing restless)

  2. Assume a flexed position

  3. Constrict peripheral blood vessels
• Thermoregulation: Pre-term Infant

  Maintaining appropriate body temperature in preterm infants
• Cold stress in preterm infants

  • Consequences: hypoxia, metabolic acidosis, hypoglycemia
• LBW infants


  • Smaller muscle mass, fewer deposits of brown fat, lack insulating subcutaneous fat, poor reflex control of skin capillaries
• Overheating in infants

  Increases oxygen and calorie consumption, jeopardizes infants in hyperthermic environment, can cause apnea and flushed colour
• Recommended axillary temperature range for healthy term infants

  36.5°C to 37.5°C (97.7°F to 99.5°F)
• Normal axillary temperature range for preterm or at-risk newborns

  36.3°C to 37.2°C
• Pre-term Infant: Nursing Interventions •Monitor axillary temperature every 30 min immediately postpartum until stable; then every 1–4hr depending on gestational age and ability to maintain thermal stability. •Provide skin-to-skin care in immediate postpartum period for stable infant. •Implement measures to avoid excess heat loss (adjust environmental temperature, avoid drafts). •Bathe only after thermal stability has been maintained for 1 h
• Care of the Hypothermic

  Infant

  •Should occur gradually, over a period of hours.

  •Rewarming can proceed at a rate of 1° to 2°C per hour.
• Hyperthermia

  • Can result from the inappropriate use of external heat sources such as radiant warmers, phototherapy, sunlight, increased environmental temperature, and use of excessive clothing or blankets
• Infants who are overheated because of environmental factors

  1. Skin vessels dilate

  2. Skin appears flushed

  3. Hands and feet are warm to touch

  4. Infant assumes a posture of extension
• Newborn who is hyperthermic because of sepsis

  • Vessels in the skin are constricted
  • Color is pale
  • Hands and feet are cool
• Hyperthermia


  Can cause cerebral damage from dehydration or even heat stroke and death