Acute fever



  • Defined as temperature ≥38°C (100.4°F).
  • Peripheral temperature is not clinically accurate and central measurements are the preferred means of determining fever.
    • Rectal or oral
    • Rectal temperatures should not be performed in neutropenic patients[1]

Clinical Features

  • Fever directly causes an increase in:[2]
    • Heart rate: 10 beats per minute per degree centigrade
    • Respiratory rate

Differential Diagnosis




DDx by Heart Rate

Every 0.55°C increase in temperature should → increase HR by ~10BPM


See individual notes for specific workup:

  • Fever and Rash
  • Fever of Unknown Origin
  • Neutropenic Fever
  • AIDS Fever of Unknown Origin
  • Heat Emergencies
  • Fever in Traveler


  • Consider tylenol or ibuprophen for fever relief
  • Treat the underlying condition


  • Depends on underlying etiology

See Also


  1. Niven DJ, Gaudet JE, Laupland KB, Mrklas KJ, Roberts DJ, Stelfox HT. Accuracy of Peripheral Thermometers for Estimating Temperature: A Systematic Review and Meta-analysis. Ann Intern Med. 2015;163(10):768-777. doi:10.7326/M15-1150.
  2. Davies P, Maconochie I. The relationship between body temperature, heart rate and respiratory rate in children. Emerg Med J. 2009 Sep;26(9):641-3. doi: 10.1136/emj.2008.061598.
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