Pyrexia: aetiology in the ICU.

Area of Science:

• Critical Care Medicine
• Internal Medicine
• Pathophysiology

Background:

• Elevated core body temperature is a frequent sign in adult ICUs, associated with increased mortality.
• Definitions of elevated body temperature (commonly ≥38.0°C) and related terms (hyperthermia, pyrexia, fever) vary and are often used interchangeably.
• Hyperthermia results from non-hypothalamic set point changes, while pyrexia/fever involve a hypothalamic set point increase due to various stimuli.

Purpose of the Study:

• To review the incidence and causes of pyrexia and hyperthermia in adult ICU patients.
• To differentiate between pyrexia and hyperthermia in critically ill populations.
• To propose a diagnostic approach for pyrexia in critically ill adults.

Main Methods:

• Comprehensive review of contemporary literature on pyrexia and hyperthermia in adult ICUs.
• Analysis of studies investigating incidence, aetiology, and clinical features.
• Examination of temperature thresholds differentiating pyrexia and hyperthermia.

Main Results:

• Pyrexia is common in ICUs, often triggered by infections but also noninfectious causes.
• Temperatures >41.0°C are more indicative of hyperthermia than pyrexia.
• Current studies have limitations in sample size and reporting of noninfectious aetiologies, impacting incidence estimates.
• Pyrexia alone is a poor predictor of culture-positivity, necessitating improved diagnostic strategies.

Conclusions:

• Distinguishing hyperthermia from pyrexia is crucial for appropriate patient management in ICUs.
• Further research is needed to accurately estimate the incidence of infectious and noninfectious pyrexia causes.
• An evidence-based approach can improve the diagnosis of pyrexia aetiology in critically ill adults.