Pyrexia: aetiology in the ICU

Abstract

Elevation in core body temperature is one of the most frequently detected abnormal signs in patients admitted to adult ICUs, and is associated with increased mortality in select populations of critically ill patients. The definition of an elevated body temperature varies considerably by population and thermometer, and is commonly defined by a temperature of 38.0 °C or greater. Terms such as hyperthermia, pyrexia, and fever are often used interchangeably. However, strictly speaking hyperthermia refers to the elevation in body temperature that occurs without an increase in the hypothalamic set point, such as in response to specific environmental (e.g., heat stroke), pharmacologic (e.g., neuroleptic malignant syndrome), or endocrine (e.g., thyrotoxicosis) stimuli. On the other hand, pyrexia and fever refer to the classical increase in body temperature that occurs in response to a vast list of infectious and noninfectious aetiologies in association with an increase in the hypothalamic set point. In this review, we examine the contemporary literature investigating the incidence and aetiology of pyrexia and hyperthermia among medical and surgical patients admitted to adult ICUs with or without an acute neurological condition. A temperature greater than 41.0 °C, although occasionally observed among patients with infectious or noninfectious pyrexia, is more commonly observed in patients with hyperthermia. Most episodes of pyrexia are due to infections, but incidence estimates of infectious and noninfectious aetiologies are limited by studies with small sample size and inconsistent reporting of noninfectious aetiologies. Pyrexia commonly triggers a full septic work-up, but on its own is a poor predictor of culture-positivity. In order to improve culturing practices, and better guide the diagnostic approach to critically ill patients with pyrexia, additional research is required to provide more robust estimates of the incidence of infectious and noninfectious aetiologies, and their relationship to other clinical features (e.g., leukocytosis). In the meantime, using existing literature, we propose an approach to identifying the aetiology of pyrexia in critically ill adults.

Targeted temperature management in patients with intracerebral haemorrhage, subarachnoid haemorrhage, or acute ischaemic stroke: consensus recommendations

“…16 Although the term fever is commonly understood, no universally accepted definition exists, and it is often used interchangeably with the terms pyrexia or hyperthermia. 2,17 Similarly, there is no accepted temperature threshold that defines the occurrence of fever, with between 5 and 14 different thresholds reported in various studies identified by a literature review. 2 A threshold of !38.3 C is often cited.…”

“…Fever is common in critically ill patients with neurological conditions. 2,3 In those with AIS or TBI, fever can contribute to secondary brain injury, and is associated with poorer functional outcomes and higher morbidity and mortality. 4e6 Fever has an infectious cause in about half of all cases.…”

“…4e6 Fever has an infectious cause in about half of all cases. 2,3,7,8 It has also been shown to have a strong independent association with poor outcomes. 7,9,10 Most evidence on fever prevention in patients in critical care is observational in nature, so the specific role fever plays in causing secondary brain injury is unclear.…”

A Practical Approach to Clinical Antibiotic Stewardship in the ICU Patient with Severe Infection

“…17 Nevertheless the diagnosis of hospital-acquired infections poses quite a challenge in the critically ill patient, as up to 50% of febrile episodes are of noninfectious origin, e.g., in burn patients, trauma patients, and patients with severe pancreatitis. 18 A daring quasi-experimental before and after study suggested that a restrictive antibiotic approach in hemodynamically stable patients might be beneficial with a 50% reduction in adjusted mortality, a shorter duration of therapy, and higher rates of appropriate initial therapy. 19 It should be emphasized that in this study only nonseverely ill patients were included.…”

Deterioro fisiopatológico y mortalidad, de pacientes críticos adultos sometidos a traslado por móviles del servicio de atención médica de urgencia del área metropolitana, Santiago de Chile

“…Una variación de la Tº corporal entre 0.5 y 1ºC, es considerada aceptable y dependiente de la temperatura ambiente que rodea el paciente, no entanto un aumento > de 1ºC, es asociado a mayor estrés fisiológico y a un incremento en la mortalidad del paciente crítico. La disminución de temperatura en el paciente en estado crítico, parece ser protectora hasta 1ºC, y son provocadas por el ambiente externo o por una patología propia del paciente ( neurológica) 67,68,69,70 .…”