Disease - Fever

Question 1

What part of the body regulates core temperature?

Answer 1

Preoptic area of Anterior Hypothalamus

Question 2

What things is the hypothalamus sensitive to in regulating temperature?

Answer 2

Blood temperature

• increase signal output on increased temp
• decrease signal output on decreased temp

Question 3

What is the temperature set point?

Answer 3

37. 1 C

- diurnal variation +/- 0.5 C

Question 4

What are the actions of hypothalamus if the temperature is above the set point?

Answer 4

Sympathetic inhibition

=> vasodilation of peripheral vessels via symp. adrenergic fibres, raises peripheral blood flow up to 30-fold

=> stimulation of sweat glands via symp. cholinergic fibres

Question 5

What are the actions of the hypothalamus if the temperature is below the set point?

Answer 5

Widespread sympathetic stimulation

=> peripheral vasoconstriction
=> piloerection (hair standing)
=> shivering
=> metabolic head production by liver

Question 6

What is a febrile response?

Answer 6

Elevation of set temperature in response to pyrogens

Question 7

What are the two types of pyrogens?

Answer 7

Exogenous

Endogenous

Question 8

How do exogenous pyrogens work and give some examples of them?

Answer 8

May work directly on hypothalamus

May work indirectly by causing release of pyrogenic cytokines by immune cells such as macrophages

Examples of exogenous pyrogens include:

• Lipopolysaccharide
• Strep/Staph toxins

Question 9

How do endogenous pyrogens work and give some examples of them?

Answer 9

Pyrogenic cytokines released by immune cells/tumours etc. work directly on hypothalamus

Examples include:
[] TNF-alpha
[] IL-1 and IL-6
[] Interferon-gamma

Question 10

What is prostaglandin E2 and how it it released?

Answer 10

A prostaglandin that induces fever by elevating the temperature set point

Released by the preoptic area of anterior hypothalamus via COX-2 enzyme when stimulated by pyrogens

Question 11

How is the temperature set point elevated?

Answer 11

The body used heat gain mechanisms to reach new set point

Question 12

What is fever?

Answer 12

Elevation of the hypothalamic set point

Question 13

What is hyperthermia?

Answer 13

Body temperature elevated above set point, usually due to hot environment or drug reaction

Question 14

What investigations should be done for elevated temperature?

Answer 14

S - sputum culture
U - urine culture and analysis
B - bloods: ESR, CRP, FBC, cultures, films, serology
E - ECG
X - X-rays and imaging: CXR, CT/USS for mass/abcess

Other: lumbar puncture

Question 15

How should raised temperature be managed?

Answer 15

General measures
- rest, oral rehydration, physical cooling

Supportive measures
- resuscitation, oxygen, restore circulation if necessary

Anti-pyretics
- paracetamol

Specific treatment
- antibiotics if infection

Question 16

How does paracetamol have an anti-pyretic effect?

Answer 16

COX inhibitor => reduced production of PGE2 => reduces set point

Question 17

Which antibiotics should be used to treat infections of the GIT?

Answer 17

Cefuroxime + Metranidazole

Question 18

Which antibiotics should be used to treat infections of the UT?

Answer 18

Quinolones

Trimethoprim

Question 19

What treatment should be given for suspected malaria?

Answer 19

Quinine (chloroquine)

Doxycycline

Question 20

Describe the symptoms according to fever stage

Answer 20

Prodromal stage
- non specific, headache, fatigue, malaise, aching

Chill stage
- shaking/rigors, vasoconstriction, piloerection, feel cold

Flush stage

• body temperature reached new set point
• shivering stops, sensation of warmth, flushed

Defervescence stage
- sweating to reduce heat as fever falls

Question 21

Which antipyretic drug can reduce antibody response to vaccinations?

Answer 21

Paracetamol