Fever is an adaptive response to infection or injury that is coordinated by the hypothalamus. Cytokines released during inflammation, like IL-1, IL-6, and TNF-α, cause the release of prostaglandins that act on the hypothalamus to increase the body's temperature. In the ICU, identifying the cause of a fever is important, as it could indicate serious infections like ventilator-associated pneumonia, catheter-related bloodstream infections, or fungal infections. For acute undifferentiated fevers, factors like thrombocytopenia, hepatorenal dysfunction, or altered sensorium may provide clues to infectious diseases like malaria, leptospirosis, or typhoid

2. Fever is a co-ordinated neuro endocrine,
autonomic and behavioral response that is
adaptive, and an essential part of the acute-
phase response to immune stimulus or tissue
injury
Co-ordinated by the hypothalamus
Neural input from peripheral thermoreceptors
Humoral cues from inflammation or infection

3.  Cytokines released by monocytic cells play a central role in
the genesis of fever. IL- 1, IL-6, and(TNF)-a.
 the cytokine receptor interaction activates phospholipase
A2, resulting in the liberation of plasma membrane
arachidonic acid as substrate for the cyclo-oxygenase
pathway.
 Some cytokines appear to increase cyclo-oxygenase
expression directly, leading to liberation of prostaglandin
E2. This small lipid mediator diffuses across the blood
brain barrier, where it acts to decrease the rate of firing of
preoptic warm-sensitive neurons, leading to activation of
responses designed to decrease heat loss and increase
heat production.
 In a small proportion of hospitalized patients,
hyperthermia may result from increased sympathetic
activity with increased heat production.

4.  Enhances parameters of immune function
 Improves antibody production
 Activates T-cells
 Produces cytokines
 Enhances neutrophil and macrophage function

5.  Hot baths for malaria fever for treatment of syphilis
 Positive correlation between maximum temperature
on the day of bacteremia and survival
 Temperature > 38 °C improved survival in patients
with SBP
 In children with chicken pox, treatment with
acetaminophen increased time to crusting of skin
lesions

6. Increased cardiac output
Increased oxygen consumption
Increased carbon-di-oxide production
Increased basal metabolic rate

7. Poorer neurological outcomes in patients with
stroke and traumatic brain injury who manifest
temperature
Fever poorly tolerated in patients with reduced
cardio-respiratory reserve
Maternal fever cause of fetal malformations as
well as spontaneous abortions

8.  Peripheral temperature measurements
 Measured in the outer 1.6 mm of skin or mucus
membranes
 Considered unreliable as influenced by environmental
temperatures, mouth breathing etc.
 Examples – oral temperature, axillary, skin
temperature
 Core temperature measurements
 Not influenced by external factors
 More accurately reflects temperature in the internal
organs
 Examples – pulmonary, rectal, esophageal, urinary,
tympanic

10. Normal temperature
 98.2O F (36.8OC)
 Diurnal variations of temperature with evening rise
up to 100O F (37.8O C)

11. Society of Critical Care Medicine (SCCM)
and Infectious diseases society of America
recommend investigations in the ICU if
temperature is above
 101O F (38.3OC)

12. Patient who
comes in with a
febrile illness
Cause of fever need
to be ascertained
Patient in the ICU
develops fever
What is causing this
fever?

13. Patient with an
obvious focus of
infection
Where is the
focus?
Acute un-differentiated
fever
What is causing this
fever?

14. Community acquired pneumonia
Acute CNS infection
Urinary tract infection
Abdominal focus of infection
Wound infection / Pus collections
Trauma with infection

15. And why do they come to the ICU
 Ventilatory support – respiratory failure –
pneumonia
 Hemodynamic support – shock
 Renal replacement therapy – renal failure, severe
acidosis
 Monitoring, Neurological dysfunction,
Hematologic

16. Patients
presenting with
a febrile illness
Patient developing fever
in the ICU
Is there a focus
of infection?
Acute undifferentiated
fever√

17. Where no specific focus identified
Look for specific clues to guide in the
diagnosis

18. Fever with thrombocytopenia
Fever with hepato-renal dysfunction
Fever with pulmonary renal syndrome
Fever with altered sensorium

19. Fever with thrombocytopenia
Malaria (notably falciparum)
Dengue
Leptospirosis
Rickettsial infections
Viral fevers

20. Fever with hepato-renal dysfunction
Malaria (falciparum)
Leptospirosis
Scrub typhus
Fulminant hepatic failure with hepatorenal

21. Fever with pulmonary-renal dysfunction
Malaria (falciparum)
Leptospirosis
Scrub typhus
Hantavirus infection
Severe legionella / pneumococcal pneumonia

22. Fever with altered sensorium
Malaria – cerebral malaria
Encephalitis
Meningitis
Typhoid fever
Septic encephalopathy
Brain abscess

23. Patients
presenting with
a febrile illness
Patient developing fever
in the ICU
Is there a focus
of infection?
Acute undifferentiated
fever√ √

24. Infectious causes
Where is the focus?
Non-infective causes
What is causing this
fever?

25.  most noninfectious disorders usually do not
lead to a fever> 38.9°C (102°F); therefore, if
the temperature increases above this
threshold, the patient should be considered
to have an infectious etiology as the cause of
the fever However, patients with
 drug fever may have a temperature >102°F
Similarly, fever secondary to blood
transfusion maybe >102°F.

26. Ventilator associated pneumonia
Catheter related blood stream infections
Urosepsis
Intra-abdominal infections
Sinus infections
Diarrhoea

27. Fungal infections including candidemia
Surgical wound infections
Acalculous cholecystitis
Endocarditis
Meningitis

29. Patients
presenting with
a febrile illness
Patient developing fever
in the ICU
Is there a focus
of infection?
Acute undifferentiated
fever
Infective
Causes
Non-infective
Causes

57. Should I be worried?
YES
 In an immunocompromised
patient
 If hemodynamic instability
 Decreasing UOP
 Increasing lactate
 Worsening conscious state
 Falling platelet counts
 Worsening coagulopathy
NO
 Small spike
 No hemodynamic instability
 Carefully examine clinically
for an obvious focus of
infection

61. Bloods – counts, procalcitonin
Imaging – CXR, Scans as indicated
(abdomen, sinus, CT brain)
Cultures as appropriate – ETA, BAL,
Urine, Blood cultures (peripheral and
through lines), cultures from pus,
wound etc, Stool for clostridium