Fever Evaluation and Management

Infectious Causes

The American College of Emergency Physicians suggests that bacterial infections, such as pneumonia, urosepsis, bloodstream/line infections, intra-abdominal infections, and meningitis, are the most common serious causes of fever in the range of 103-106°F, with a notable risk of occult bacteremia 1
Patients with diabetes mellitus are at increased risk of occult bacteremia, with a risk increase from 5% to 55% when multiple risk factors are present, including age ≥50 years, WBC ≥15,000/mm³, and ESR ≥30 mm/h 2
In children <3 years with fever ≥103.1°F and WBC ≥15,000/mm³, there is a 10% risk of occult pneumococcal bacteremia and a 0.3% risk of meningitis 1

The American Heart Association recommends considering hyperthermic syndromes, such as neuroleptic malignant syndrome, anticholinergic syndrome, and heat stroke, in patients with temperatures >106°F, which require immediate recognition and treatment 4
Drug-induced fever can occur, with a lag time averaging 21 days after drug initiation, and resolves within 1-3 days after discontinuation, with diagnosis of exclusion after ruling out infection 3
Infusion reactions can cause fever, and deep venous thrombosis and aspiration should be considered in the differential diagnosis 2

The American Stroke Association suggests that neurogenic fever, defined as core temperature >37.5°C from neurological dysregulation without sepsis, is common in patients with traumatic brain injury, stroke, or intracerebral hemorrhage, and requires controlled normothermia targeting 36.0-37.5°C regardless of ICP level 6
Fever from any cause can precipitate secondary brain injury, and pharmacologic treatment of elevated temperature may be reasonable to improve functional outcomes, though evidence is conflicting 2, 4, 6, 7

The American Academy of Pediatrics recommends obtaining a WBC count in children <3 years with fever ≥103.1°F, and considering empiric ceftriaxone if WBC ≥15,000/mm³, due to the risk of meningitis 1