Fever Flashcards
Diurnal changes in body temperature are dependent on
Sleep-wake cycle
and
How you measure temperature - oral most variable
What is febrile neutropenia
greater than 38.3 orally or more than 38 for more than hour
Fever of unknown origin
more than 38 on multiple readings over 3 weeks
- No cause after initial investigation
FUO is not applicable when
FN, HIV, HSCT, nosocomial acquisition
or to returned travelers or children
Normal body temp
between 36.5-37
how does the hypothalamus cool body temp
- Inreases cutaneous blood flow
- Sweating
- Decreases GI blood flow
how does the hypothalamus increase body temp
- Shivering
- Decrease Cutaneous blood flow
Fever results in
An increase in the hypothalamic set point
4 Pyogenic cytokines
IL-1
TNF-a
IFN
IL-6
The release of pyogenic cytokines results in
PGE2 increase
What leads to the increase in the hypothalamic set point?
PGE2 secretion
What does the hypothalamus do when set point goes up
Wants to cool body down
- Decrease cutaneous blood flow
- Chills
- Shivering to generate heat match rise in setpoint
- Thermogenesis of brown fat
Evolutionary advantage of fever
Increase survival against Gram negatives and peritonitis?
With antipyretics you get
prolonged viral shedding
Fevers are almost always…..
<41
Disadvantages to having a fever are
symptoms - chills and rigors - sweats TACHy cardia, TACHypnea - delirium - arthralgias/myalgias (due to PGE2)
Children may develop…… from fever?
Febrile seizures >39
What 2 things are NOT fever
Hyperthermia
Hyperpyrexia
What is hyperthermia
- inability to lose heat
- UNCHANGED hypothalamic set point
- heat stroke, malignant hyperthermia, neuroleptic
What is hyperpyrexia
> 41 temp
CNS Hemorrhage
Nowadays what are some causes of FUO
- malignancy
- autoimmune disease
certain infections
How do antipyretics work?
Block COX - block production of prostaglandins
What are some common antipyretics?
ASA salicylates
- tylenol
- NSAIDs
- CORTICOSTEROIDS - (dont use!!)
When to use anti-pyretics?
- fever is prolonged/severe
- Hyperpyrexia - external cooling as well
When should you NOT use anti-pyretics?
- Hyperthermia!
When during the day is your temperature the lowest?
2 and 6 am - as long as that is during your sleep cycle
What cells do the pyogenic cytokines interact with?
Vascular endothelium - circumventricular
