Fever Flashcards
The thermostat in our bodies that determines temp. setpoint resides in the:
anterior hypothalamus and preoptic nucleus
A rich vascular network with fenestrated epithelium that is important in conveying blood-borne signals to the central thermostat.
OVLT
Exogenous pyrogens:
Bacterial exotoxins Bacterial endotoxins (LPS) Peptidoglycans
Endogenous pyrogens:
TNF-a, IL-1, CNTF, IL-6, PGE2
PGE2:
Central role in fever generation; accounts for teh efficacy of NSAIDs in fever treatment
Two ways that bacteria can induce fever:
Bacterial products in OVLT can directly stimulate fever via TLR on the endothelium
Bacteria can induce pyrogenic cytokines from leukocytes
The OVLT senses LPS through:
TLR-4 and CD-14
Cytokines and LPS both lead to elevated levels of (blank), which leads to elevated levels of (blank) in hypothalamic neurons, which increases the thermal setpoint.
PGE2
cAMP
Beneficial effects of fever:
Increased neutrophil motility
Increased immune surveillance
Increased adhesion and migration of lymphs
Lymph rolling, adherence, and emigration are increased through lymph venules
Fever may worsen:
acute lung injury in sepsis
Indications for symptomatic treatment of fever:
Temp >104 Age between 6 months and 3 yrs or less than 6 yrs w/ a hx of seizures. Cardiopulmonary, renal, or metabolic impairment Fluid-electrolyte problems Acute neurologic disease Sepsis and shock Impaired thermoregulation Environmental heat illness Sickle cell disease
How does acetaminophen reduce fever?
Inhibits COX3
How do glucocorticoids reduce fever?
Block transcription of pyrogenic cytokines
Inhibit PLA2, hence arachidonate release required for PGE2 synthesis
Fever of Unknown Origin:
Fever lasting at least 3 weeks
Temp greater than 101
Cause remains undiagnosed after 3 days of in-hospital testing or during two or more outpatient visits
Drugs implicated in fever:
beta lactam abx, alpha methyl dopa, isoniazid
