Overview of Fever Physiology
Definition of fever
aka Pyrexia
Raised core temperature matching a new set point caused by action of
thermoregulatory pyrogens on the hypothalamus.
Defined as core temperature >38.2°C = >100.8°F
Fever can be due to endogenous pyrogens and exogenous pyrogens
Exogenous pyrogens
Infection with bacteria or viruses.
Microbial toxins and superantigens.
Endogenous pyrogens
Immune complexes
Malignant cells
Trauma and central fever due to intracranial hemorrhage
Inflammation
FUO
Fever of Unknown origin.
, No clues to cause, but:
Causes correlate with the mediators of fever.
1. Infection
2. Malignancy
3. Rheumatologic or Inflammatory diseases
Hyperthermia
Temperature above the hypothalamic set point due to heat
exposure or unregulated heat production in excess of heat loss.
Hyperpyrexia
very high fever exceeding 41.5C or 106.7F)
Seen with Severe infection (sepsis) usually via bacteria or some viruses
like Rubeola, Roseola and enteroviruses.
But also associated with CNS hemorrhage, or hyperthermia associated
conditions like hyperthyroidism or thyroid storm
or due to introduction of exogenous substances or drugs like cocaine,
amphetamines,
Methods of obtaining temperature
Most accurate is the rectal temperature.
Fever Cascade
Overview of the Fever Cascade
:
Stimulation of sentinel cells by exogenous pyrogens produces endogenous
Definition of fever
aka Pyrexia
Raised core temperature matching a new set point caused by action of
thermoregulatory pyrogens on the hypothalamus.
Defined as core temperature >38.2°C = >100.8°F
Fever can be due to endogenous pyrogens and exogenous pyrogens
Exogenous pyrogens
Infection with bacteria or viruses.
Microbial toxins and superantigens.
Endogenous pyrogens
Immune complexes
Malignant cells
Trauma and central fever due to intracranial hemorrhage
Inflammation
FUO
Fever of Unknown origin.
, No clues to cause, but:
Causes correlate with the mediators of fever.
1. Infection
2. Malignancy
3. Rheumatologic or Inflammatory diseases
Hyperthermia
Temperature above the hypothalamic set point due to heat
exposure or unregulated heat production in excess of heat loss.
Hyperpyrexia
very high fever exceeding 41.5C or 106.7F)
Seen with Severe infection (sepsis) usually via bacteria or some viruses
like Rubeola, Roseola and enteroviruses.
But also associated with CNS hemorrhage, or hyperthermia associated
conditions like hyperthyroidism or thyroid storm
or due to introduction of exogenous substances or drugs like cocaine,
amphetamines,
Methods of obtaining temperature
Most accurate is the rectal temperature.
Fever Cascade
Overview of the Fever Cascade
:
Stimulation of sentinel cells by exogenous pyrogens produces endogenous
