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Fever

Krista A. G randey, DO

Key Points

• Fever is a symptom, not a disease.

• Fever should not be confused with hyperthermia.

Temperatures higher than 41 oc (1 05.8°F) are almost

always due to hyperthermia and not fever.

• Be thoughtfu l in your eval uation of fever to avoid

misdiagnosing a serious bacterial illness as "just

another viral syndrome."

INTRODUCTION

The human body temperature is controlled within a narrow range between 36 and 37.8 °C (96.8 -100.4°F). Fever is

defined as a core temperature >38° C (100.4 °F) in infants

and >38.3°C ( 100.9°F) in adults. It is the result of the body

resetting the temperature control center, the hypothalamus, in response to infection. Endogenous ( cytokines) and

exogenous (bacterial and viral) pyrogens trigger production of prostaglandin E2 (PGE2) in the hypothalamus.

PGE2 raises the hypothalamic temperature set point. The

body then generates and conserves heat to reach this new

hypothalamic set point, thereby raising the body temperature. Fever is sustained as long as the levels of pyrogens and

PGE2 are elevated. Cyclooxygenase inhibitors decrease

fever by blocking the production of PGE2.

Fever is one of the most common presenting complaints in the emergency department (ED). It accounts for

So/o of adult visits, 15o/o of elderly visits and 40o/o of pediatric visits to the ED. The most important thing to recognize

about fever is that it is a symptom, not a disease, and it

represents an underlying problem that must be evaluated

and treated. The most common sites of infection vary

based on age and immune system status. In the elderly and

immunosuppressed, respiratory, genitourinary, and bacterial

• Provide empiric antibiotics early for moderate to

severely ill patients with a possible infectious etiology.

Give directed antibiotic treatment in the emergency

department to patients with serious foca l bacterial

infections.

skin infections predominate. In younger patients the cause

of fever is often self-limited and benign (eg, upper respiratory infection), but serious focal bacterial infections (eg,

meningitis) requiring antibiotics, diagnostic procedures,

and admission, must be detected.

CLINICAL PRESENTATION

� History

The differential diagnosis for fever is quite broad, but in 85o/o

of cases the cause is identified by a thorough history and

physical examination. Important historical information

includes the onset, magnitude, duration, pattern, any associated symptoms, travel within the past year, chronic illnesses,

recent medication changes, recent hospitalizations, chemotherapy, radiotherapy, or the presence of indwelling vascular

access devices or artificial heart valves. The age and overall

health of the patient must be taken into account when taking the history and making medical decisions.

� Physical Examination

The site of temperature recording should be noted, as rectal temperatures are more accurate and usually 1 oc higher

than oral temperatures. Rectal temperature should be

1 38

Table 33-1. Physica l examination in fever.

General

Neurologic

Ear, nose, and

throat

Chest

Abdomen

Skin