Fever in the ICU Christopher Kia

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

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)

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

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

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)

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

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

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

Diagnostic Approach to New Onset of Fever in ICU

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

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

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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