FEVER

I. Definitions

  1. Fever = core temp 100.5' F or higher; threshold modified by clinical picture
  2. Night temp normally about 1.5' F higher than morning temp.

II. Mechanisms of fever

  1. IL-2 release stimulated by neoplasia, autoimmune disease, allergy, & infections
  2. Stimulates release of cytokines (PGs), monokines (IL-1, TNF) which produce fever
  3. Exogenous pyrogens: endotoxin, pepdidoglycan, Ag-Ab complexes stimulate monokine release
  4. Response of pt. to antipyretics gives no indication of the cause of the fever!

III. Use of antipyretics:

  1. In children, ibuprofen was more effective for fever (though no more effective for pain) compared with acetaminophen, according to a meta-analysis of 17 randomized trials in children < 18yo (Arch. Pediat. Adol. Med. 158:521, 2004--JW)
  2. n outpts, for comfort
  3. In hosp'd pts, avoid, because lose fever as marker for infection
  4. Specific indications:
  1. T > 106' F is deleterious in itself
  2. Pts with ischemic heart dis/bad mitral sten. (fever increases CO & can precipitate failure)
  3. T >101' F in kid<2yo (to avoid febrile sz)
  4. Old folks who get delirious when febrile
  1. DON'T GIVE ANTIPYRETICS "PRN FOR FEVER"!--causes sharp rises & falls in temp which is highly uncomfortable for pt; write for regularly administered antipyretics.

IV. "Fever w/u" in hosp'd pt:

  1. Hx, inc. medications (remember drug fever!)
  2. Px--source of infection
  3. Labs: CBC with diff (band count more important than total WBC); Blood cx x 2; clean catch U/A & C/S
  4. Microscopic urine: gm stain of unspun for bact; spun sediment for WBCs
  5. CXR (can always have asymptomatic pneumonia)
  6. By clinical indication, sputum gm stain/cx (within 20min of expectoration); LP; paracentesis; etc.

V. Causes of FUO (3wk with T>101'F & neg. fever w/u including cultures, CXR, abdominal imaging e.g. u/s):

  1. Infection 35-40% (TB, endocarditis, closed-space infection; Epstein-Barr virus; Cytomegalovirus; sinusitis; dental infection; Q Fever; HIV & opportunistic)
  2. Malignancy 25-35% (fever often secondary to infection of a blocked hollow organ)
  3. Collagen vasc. dis. 15% (esp. polymyalgia rheumatica, giant-cell arteritis)
  4. Misc 5-10% (drug fever, esp. sulfonamides; pulm. infarct; MI'; IBD; factitious
  5. Never dx'd 10%
  6. PET scanning or Gallium scanning can be helpful for dx (see Clin. Inf. Dis. 32:191, 2001--JW)