Approach to Fever in the Intensive Care Unit Patient
Sonia N. Chimienti
Richard H. Glew
I. GENERAL PRINCIPLES
A. Definition.
1. Normal average body temperature is 37.0°C (98.6°F); this may vary by 0.5°C to 1.0°C depending on time of day, activity level, and environmental and hormonal factors.
2. Fever in a normal host is defined as a single core temperature ≥38.3°C (≥101.0°F).
3. Fever in a neutropenic or otherwise immunosuppressed patient is defined as a single core temperature of >38.0°C (100.4°F) for >1 hour.
4. Hypothermia is defined as a temperature of <36.0°C in the absence of another explanation (cooling blanket, environmental, hypothyroidism).
5. The patient’s overall clinical picture (e.g., trends in temperature, septic physiology) is more important than the absolute temperature.
B. Description.
1. Body temperature may be measured in a variety of ways.
a. Pulmonary artery catheter thermistor most accurately assesses core body temperature, but generally is impractical.
b. Rectal temperatures are reliable but have some disadvantages.
i. They may be perceived as invasive and uncomfortable by patients.
ii. They may cause the spread of enteric pathogens (via the device or care provider).
iii. They should not be used in neutropenic patients.
c. Oral temperatures generally are reliable and safe but also have disadvantages.
i. They may be erroneous in patients who are mouth breathers.
ii. They may be erroneous in patients who are not sufficiently alert to cooperate.
iii. They may be erroneous in patients who just drank hot or cold liquids.
d. Axillary temperatures are less reliable and generally should not be used.
2. The febrile response may be blunted or absent in certain patient populations (i.e., the elderly, and patients with open abdominal wounds, azotemia, congestive heart failure, end-stage liver disease, large body surface area burns, and those who are receiving antipyretics or corticosteroids).
3. Environmental factors (i.e., specialized mattresses, hot lights, ambient temperature, continuous venovenous hemofiltration/continuous venovenous hemodiafiltration, peritoneal lavage) can influence a patient’s measured body temperature.
4. Central and autonomic nervous system disruption can affect thermoregulatory responses.
5. Hypothermia may also be a sign of severe systemic infection.
6. Appropriate, timely, resource-conscious evaluation to determine the etiology of fever is important in order to initiate targeted treatment, to limit the utilization of laboratory tests, and to minimize the exposure of patients to unnecessary radiation and invasive procedures.
C. Epidemiology.
1. Fever is common in the ICU.
a. May occur in up to one-third of hospitalized medical patients.
b. May occur in up to 50% of ICU patients.
2. Fever in adult medical ICU patients is associated with increased mortality.
3. Rational and efficient evaluation of the etiology of fever is imperative.
II. ETIOLOGY
A. Common infectious causes of fever in the ICU.
1. Intravascular catheter-related bloodstream infections (CRBSI) (see Chapter 64).
a. Risk of infection varies with a given device.
i. Short-term, noncuffed central venous catheters (CVCs) (i.e., those used for hemodialysis)—2.7/1,000 catheter-days.
ii. Peripherally inserted CVCs—2.1/1,000 catheter-days.
iii. Arterial catheters—1.7/1,000 catheter-days.
iv. Surgically implanted long-term central venous devices.
(a) Cuffed and tunneled catheters—1.6/1,000 catheter-days.
(b) Central venous ports—0.1/1,000 catheter-days.
v. Small peripheral intravenous catheters—0.5/1,000 catheter-days.
vi. Midline catheters—0.2/1,000 catheter-days.
b. Consider endovascular focus (central venous septic phlebitis, endocarditis, graft infection) in the setting of persistent fever on effective antibiotic treatment, especially if positive blood cultures persist after removal of the implicated intravascular catheter.
a. Acute infectious pneumonia.
i. Severe community-acquired pneumonia (CAP).
ii. Ventilator-associated pneumonia (VAP).
iii. Health care-associated pneumonia (HCAP) in patients not ventilated.
iv. Aspiration pneumonia/pneumonitis.
b. Nosocomial sinusitis: Consider in patients with:
i. Transnasal intubation (prevalence of 33% after 7 days of intubation).
ii. Maxillofacial trauma with obstruction of nasal drainage.
a. Causes 10% to 25% of all cases of antibiotic-associated diarrhea and almost all cases of antibiotic-associated pseudomembranous colitis.
b. May occur following treatment with virtually any antibiotic (most common precipitants are the fluoroquinolones, cephalosporins, and clindamycin).
a. Acute cholecystitis: calculous and acalculous.
b. Ascending cholangitis.
c. Diverticulitis, intra-abdominal abscess.
d. Mesenteric infarction.
e. Acute appendicitis.
f. Acute necrotizing pancreatitis.
5. Urinary tract infection (UTI) (see Chapter 65).
a. UTI is the most common nosocomial infection in the United States.
b. Catheter-associated UTI (CAUTI) in the ICU setting often due to nosocomial, multiple antibiotic-resistant gram-negative aerobic bacteria.
c. Candiduria associated with urinary catheters may represent colonization, but occasionally can be a clue to disseminated candidiasis in high-risk patients.
6. Skin and soft tissue infections.
a. Surgical site infections/wound infections.
