In this post, I link to the Internet Book of Critical Care‘s chapter, Approach to new fever or rigors in the ICU patient, July 29, 2021 by Dr. Josh Farkas.
What follows are the direct links to the section and subsection headings of the chapter.
CONTENTS
All that follows is excerpted from the chapter.
rapid reference
approach to fever or rigors in ICU
history
- Any localizing symptoms? Diarrhea?
- Recent procedures or transfusion?
- Indwelling devices?
exam
- Respiratory (if intubated: Sputum? Increasing ventilator support?)
- Abdominal tenderness?
- Skin exam (focus on surgical incisions, line/drain sites).
evaluation (more)
- Basic evaluation:
- Chest X-ray (unless not intubated & no respiratory symptoms).
- Blood cultures x2 plus additional culture of any line placed >48 hours ago.
- Additional tests only if indicated:
- C. Difficile, if diarrhea.
Sputum culture only for patients diagnosed with probable VAP.
- i) Urinary symptoms & no foley catheter.
- ii) Urologic issue (e.g., obstruction/surgery/renal transplant).
management (more)
- Treat any identified source of infection.
- D/c lines, as able.
- D/c drugs, if possibly causing drug fever.
- Acetaminophen only if:
- (a) Neurological injury.
- (b) Severe fever (>40C/104F).
- (c) Fever causing clinical deterioration (e.g., delirium).
fig1 when available.
definition & classification of fever
definition of a fever
- Fever is a bedrock concept in medicine, yet its precise definition remains a bit elusive.
- The Infectious Disease Society of America defined fever in the ICU as a temperature above 38.3/101.(18379262) This is generally a useful rule of thumb. However, a lower threshold for fever (>38/100.4) may be appropriate in some patients:
- Immunocompromised patients (e.g. neutropenic).
- Elderly patients.
- Patients on scheduled acetaminophen or NSAIDs.
- Precise temperatures may vary, depending on the site and the technique of measurement. Ideally, core temperature should be measured (e.g., rectal or esophageal temperature). However, in practice this is not routinely performed.
- Once patients have been in the ICU for a few days, their fever curve may be more informative than any single measurement. A consistent trend over multiple time-points may be more likely to reflect a true event. Alternatively, a one-time fever spike which is below 38.9/102 and immediately disappears is less likely to represent infection.(23878765)
fig2 when available
definition of a fever
- Fever is a bedrock concept in medicine, yet its precise definition remains a bit elusive.
- The Infectious Disease Society of America defined fever in the ICU as a temperature above 38.3/101.(18379262) This is generally a useful rule of thumb. However, a lower threshold for fever (>38/100.4) may be appropriate in some patients:
- Immunocompromised patients (e.g. neutropenic).
- Elderly patients.
- Patients on scheduled acetaminophen or NSAIDs.
- Precise temperatures may vary, depending on the site and the technique of measurement. Ideally, core temperature should be measured (e.g., rectal or esophageal temperature). However, in practice this is not routinely performed.
- Once patients have been in the ICU for a few days, their fever curve may be more informative than any single measurement. A consistent trend over multiple time-points may be more likely to reflect a true event. Alternatively, a one-time fever spike which is below 38.9/102 and immediately disappears is less likely to represent infection.(23878765)
recognition of hyperthermia
- Hyperthermia is defined as elevated temperature resulting from extreme heat generation, rather than from an alteration of the hypothalamic set point.
- Hyperthermia is suggested by the following clinical features:
- Extreme temperature elevation (temperatures above roughly ~41/105.8).
- Skin may be hot and dry (but not always!).
- Antipyretics are ineffective.
- Hyperthermia has its own differential diagnosis and requires specific treatment.
- More on the critical distinction between fever versus hyperthermia:
fig3 when available.
appreciation of spontaneous rigors as a fever-equivalent
- Rigors are shaking chills, which which can be very dramatic. They represent an aggressive attempt by the hypothalamus to rapidly increase body temperature. A rigor will often precede development of a fever.
- Rigors are closely linked to bacteremia.(24298435) Although not supported by evidence specific to the ICU environment, it’s logical to investigate a patient with new-onset rigors in the same fashion as a patient with new-onset fever. Overall, evidence linking rigors to bacteremia is probably more persuasive than evidence linking fever to bacteremia.
common causes of fever in the ICU patient
start here.
