Fever Flashcards
Fever
Body temperature >103 F
- pyrexia
What sets the thermoregulatory set point
Hypothalamus
Difference between hyperthermia and fever
Hyperthermia: hot animal that wants to be cooler
Fever: hot animal that wants to be warmer
Pyrogens
Reset thermoregulatory set point via local prostaglandins (PGE2)
Exogenous pyrogens
- organisms
- antigens
- foreign substances
- drugs
Endogenous pyrogens
Cytokines
- IL-1, IL-6, TNF
Pyrogen process
- IL-1 secreted by phagocytes travels in blood to hypothalamus
- hypothalamus secretes prostaglandin, which resets hypothalamic thermostat
- nerve impulses cause shivering, higher metabolic rate, inhibition of sweating, and vasoconstriction
- these increase body temperature to the point set by the hypothalamic thermostat
Endogenous pyrogens cause a _____ response
Non-specific response to infections, inflammatory and neoplastic diseases
- mediators of systemic inflammatory response
Signs of hyperthermia
Demeanor: excited, agitated, distressed
Behavior: panting, vasodilation, sweating, cold-seeking
Body temp: up to 110 F or greater
Signs of fever
Demeanor: lethargic, depressed, anorectic
Behavior: shivering/huddling, vasoconstriction, piloerection, heat-seeking
Body temp: rarely > 106-107 F
Is infection the only cause of fever?
No
- could be inflammatory, immunologic, neoplastic, or drug-associated
Fever as a protective mechanism
- enhances host immunity
- inhibits bacterial growth by reducing serum iron concentration
- contributes to neoplastic cell death
- encourages rest in affected animal
Inflammation
Complex reaction in vascularized connective tissue
- leads to accumulation of fluid and WBCs in extravascular tissues
Inflammation as a protective mechanism
- cause of cell injury: organism/toxin
- consequences of cell injury: dead cells/debris
Harmful consequences of inflammation
- hypersensitivity
- chronic inflammatory disease
- immune-mediated disease
- scar tissue/fibrosis
- systemic inflammatory response*
Inflammatory mediators
Entire inflammatory process is mediated by chemcials derived from plasma and cells
5 cardinal signs of inflammation
- redness (rubor)
- swelling (tumor)
- heat (calor)
- pain (dolor)
- loss of function
Types of inflammatory mediators
- vasoactive amines (histamine, serotonin)
- plasma proteases
- arachidonic acid metabolites (prostaglandins, leukotrienes)
- platelet activating factor
- nitric oxide
- oxygen-derived free radicals
- cytokines (IL-1, IL-6, TNFa)
Inflammatory cytokines are produced by ____
Macrophages, lymphocytes, and EC
Systemic inflammatory response
Cytokine mediated
- fever
- anorexia/cachexia
- lethargy/malaise
- acute phase proteins
- neutrophila
- anemia of chronic disease
- glucocorticoid release
Lab results in patient with fever
- inflammatory or stress leukogram
- anemia of chronic disease
- mild hypoalbuminemia
- mild to marked hyperglobulinemia
Physical cooling
Contraindicated
- stresses and distresses patient
- if needed, use NSAIDs instead
