Pyrexia in ICU Lit review

Question 1

Body temperature measurement? and definitions?

Answer 1

Normal body temperature is between 36.0 and 37.5 °C,
with intraindividual variability of 0.5–1.0 °C depending
on the time of day (low in early morning, peak in early
afternoon/late evening) [1, 20]. Elevated body temperature
is classified as pyrexia or hyperthermia. Although these
two terms are often used interchangeably, their biological
mechanisms and response to therapy are different—thus
their distinction is important and will be maintained in
this article. Pyrexia, also referred to as fever, is an adaptive
response to a physiologic stress that is tightly regulated
through endogenous pyrogenic and anti-pyretic pathways,
and is associated with an increase in the hypothalamic set
point [18]. As such, the elevated body temperature in patients
with pyrexia responds to pharmacologic anti-pyretic
therapies such as acetaminophen. On the contrary, the
elevated body temperature that occurs in hyperthermia
syndromes often exceeds 41.0 °C, and reflects a pathologic
increase in body temperature that is not associated with
an increased hypothalamic set point [21]. This elevated
temperature in hyperthermia is therefore not responsive
to pharmacologic anti-pyretic therapy. For this article,
pyrexia and fever will be used interchangeably, but
hyperthermia will refer to the syndrome that accompanies
specific enviro

Question 2

To differentiate between pyrexia and hyperthermia ?

Answer 2

The absolute body temperature and the response to
pharmacological anti-pyretic therapy are often useful in
distinguishing between hyperthermia and pyrexia. A
temperature that exceeds 41.0 °C and is not responsive
to pharmacologic anti-pyretic therapy is more commonly
observed in patients with hyperthermia. Therefore,
patients with milder elevations in body temperature
and/or those whose temperature decreases when administered
pharmacologic anti-pyretic drugs are unlikely to
be suffering from a hyperthermia syndrome. On the
contrary, the absolute temperature is not as helpful in
differentiating between infectious and noninfectious
pyrexia. R

Question 3

Investigations in patients with hyperthermia or
pyrexia?

Answer 3

Guidelines recommend a clinically driven, cost-conscious
approach, rather than a protocolized, dogmatic approach,
to obtaining cultures and imaging studies in critically ill patients
with pyrexia [19]. Based on existing literature that
suggests a poor association between pyrexia and the likelihood
of a positive culture, yet a high likelihood that pyrexia
heralds the presence of an infection, most infections are
likely diagnosed based on clinical and radiographic findings.

Question 4

Summary of approach ?

Answer 4