Fever in the ICU

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Fever in the ICU

• Christopher Kia

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Outline

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

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Definition of Fever

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

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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

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Why Fever in the ICU is Important (11)

• In one observational study of 24,204 adult ICU
  admissions, high fever (39.5C) 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

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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)

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Etiology

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

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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
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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
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Diagnostic Approach to New Onset of Fever in ICU
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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

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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

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Recap

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

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QUESTIONS?