Lecture 24: Boy with a Fever

Question 1

What is a fever?

Answer 1

• It is a state of elevated core temperature, which is often part of the defensive responses of multicellular organisms (host) to the invasion of live or inanimate matter recognised as pathogenic or alien by the host.
• In other words, it is a host defensive response to a foreign pathogenic object

Question 2

What ist he normal human temperature?

Answer 2

The normal human body goes through a range of temperatures (35.6 to 38.2 with mean of 36.8, only 8% recordings were 37) throughout 24 hour time period.

• Humans have their highest core body temperature in the afternoon/evening, and they are coldest in the morning (6am nadir and 6pm peak).
• They also found that women (36.9) had a marginally higher core body temperature compared to men (36.7), and also that the core body temperature of women increased slightly around the time of ovulation.

Question 3

What is involved in regulating and producing the body temperature?

Answer 3

Biochemical reactions make heat (organs, muscle and brown fat). The heat is distributed by the circulatory system.

• It is controlled by change in cutaneous blood flow (vasodilation mediates loss of heat, and vasoconstriction preserves heat).
• It is under the influence of thermoregulators in the hypothalamus. There are core (myocardium and aorta) and cutaneous (skin) thermosensors, which transmit signals to thermoregulators.

Question 4

Describe the Febrile Response

Answer 4

Febrile response is a sign that the innate immune response is triggered.

Exogenous payrogens or cellular damage within body activates white cells, mediates cytokine release (IL-1, TNF-a, IFN-g), which release IL-6.

IL-6 affects septal and preoptic nuclei of anterior hypothalamus (receives input from thermosensors, coordinate febrile response).

• Hypothalamic nuclei release various vasoactive molecules (cryogens) such as ADH, a-MSH and CRH, which acts on effector organs (limit febrile response).
• It also has temperature dependent feedback on cytokine production.

Question 5

Why do people get fever?

Answer 5

Theories

No one really knows why humans and other animals get fever. There are two main theories (likely both true):

• The first theory is that people get fever for behavioural reasons.
  
  • Change in body temperature triggers brain pathways and changes behaviour in animals.
  • Therefore, they undertake sickness behaviour, e.g. become lethargic, not wanting to do anything but rest, want to be looked after by others.
• The first theory is that people get fever for physiology reasons.
  
  • In vitro enhanced phagocytosis (improve the ability to ingest bacteria)
  • In vitro decreased stability of neutrophil granules
    
    • When temperature is elevated, it is more likely to fuse with phagosome to release contents and kill ingested bacteria, therefore more effective bacteria lysis,
    • When normal, non-febrile body temperature, neutrophils are kept in a stable state.
  • Enhanced antibody function

Question 6

When should fever be investigated rigorously?

Answer 6

Investigate a fever rigorously if:

1. Age under 3 months
2. Unwell
3. Immunocompromised
4. It has a duration longer than 10 days (very unusual for a self-limiting infection to continue for this long).

• A common finding is glandular fever (EBV infection).
• When the fever has continued for this long, the risk of diagnosing more serious infections rises

Question 7

What is the most likely cause of serious illness in primary care?

Answer 7

Pneumonia

Meningitis, infection of the limbs, pyelonephritis is super rare.

Question 8

What are the 3 most common causes of acute pharyngitis? (bacteria/viruses)

Answer 8

(Often find staphloccoccus aureus in a throat, but often don’t cause sore throats) = carrier.

1) Stretooccocus pyogenes
2) Rhinovirus
3) No cause identified

Question 9

Streptococcus pyogenes is the most important cause of pharyngitis because…

Answer 9

1) It is the most common cause of pharyngitis/rheumatic fever

Question 10

What antibiotics can be prescribed for S.pyogenes if the patient is allergic to penicillin?

Answer 10

Erythromycin

Question 11

What are the stereotypical symptoms of Meningitis? (5)

Answer 11

1) Fever
2) Headache
3) Photophobia
4) Neck stiffness
5) Rash

Question 12

Should you treat a fever in a well child?

Answer 12

The major role of a doctor should be diagnosis and reassurance (tell the patient that it is nothing serious, it is benign, and that you will recover).

If you believe fever is harmful and that lowering fever will reduce harm (e.g. malignant hyperthermia), then use anti-pyretics.

No studies have ever shown benefit in anti-pyretic therapy. Controlled clinical trials have not shown symptomatic benefit in treatment of treatment.

No studies have shown fever to be harmful

Anti-pyretics have not been shown to prevent febrile seizures