1. Fever in the ICU
Christopher Kia

2. Outline Definition of fever Why fever in the ICU is important
Temperature measurement
Etiology - infectious and noninfectious causes
Diagnostic approach

3. Definition of Fever
Normal body temperature = 37.0°C, varying with the time of day and measurement method
Definition of fever is arbitrary
Fever = body temperature of 38.3°C or higher, while acknowledging that this threshold may need to be lowered in immunocompromised patients (ACCCM/IDSA joint task force definition)

4. Why Fever in the ICU is Important (1)
Fever complicates 70% of all ICU admissions
Often represents a serious underlying condition, but may propagate a series of unnecessary investigations and lead to inappropriate antibiotic use
Fever is associated with increased length of stay in ICU, increased cost of care, poorer outcomes in certain patient groups e.g. traumatic head injury, SAH, pancreatitis

5. Why Fever in the ICU is Important (11)
In one observational study of 24,204 adult ICU admissions, high fever (≥39.5°C) alone was associated with a significant increase in mortality (20% vs 12%)
Clinical assessment of ICU patients is often hampered by invasive medical technology e.g. CRRT and ECMO can modify the febrile response or mask it completely

6. Temperature Measurement
Conventional: intravascular, intravesical, rectal, oral, cutaneous, tympanic
Axillary, temporal artery, tympanic and chemical dot monitors are inaccurate in critically ill patients
Gold standard: thermistor on a pulmonary artery catheter (infrequently placed and may be unreliable if PAC used for rapid volume administration)

8. Etiology Infectious and Noninfectious causes
Distinguishing between both causes can be challenging, requires careful clinical assessment, both causes may coexist
Fever ≥41.1°C usually noninfectious in origin
Temperatures between 38.9 and 41.0°C can be assumed to be infectious in origin

9. Infectious causes of fever
Common causes
Other causes
Bacteraemia
Intravascular catheter-related infection
Surgical site infection
Ventilator-associated pneumonia (VAP)
Cellulitis
Cholangitis
Diverticulitis
Empyema
Endocarditis
Intra-abdominal abscess
Meningitis
Myonecrosis
Necrotising fasciitis
Pseudomembranous colitis
Septic arthritis
Sinusitis
Thrombophlebitis
Urinary tract infection
Viral

10. Noninfectious causes of fever
Important causes
Other causes
Acalculous cholecystitis
Adrenal insufficiency
Benign post-operative fever
Drug fever
Pancreatitis
Thyroid storm
Transfusion reaction
Acute respiratory distress syndrome (late) Burns
Drug overdose (e.g. aspirin, anticholinergic drugs)
Drug withdrawal
Gout
Heat stroke
Intracranial haemorrhage
Ischaemic colitis
Malignancy
Malignant hyperthermia
Myocardial infarction
Neuroleptic malignant syndrome
Pheochromocytoma
Seizures
Serotonin syndrome
Thromboembolic disease
Vasculitis

11. Diagnostic Approach to New Onset of Fever in ICU

12. Serum markers (1)
CRP: Acute phase protein secreted by liver, marker of inflammation, can be affected by significant liver disease, more sensitive marker of sepsis than either body temperature or WCC but lacks specificity
Procalcitonin: More specific marker of bacterial infection than CRP, levels rise earlier than CRP and correlate more closely to severity of disease, however its utility in distinguishing infection from other causes of SIRS in older patients conflict in studies

13. Serum markers (11)
An endotoxin activity assay has shown encouraging results, excluding Gram- negative infections with a 98.6% negative predictive value in one observational study
Use of both procalcitonin and this endotoxin activity assay are supported by American College of Critical Care Medicine and Infectious Diseases Society of America as adjunctive tools in discriminating infection from other causes of SIRS

15. Recap Definition of fever Why fever in the ICU is important
Temperature measurement
Etiology - infectious and noninfectious causes
Diagnostic approach and management

16. QUESTIONS?