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Infectious Disease > Fever > Flashcards

Fever Flashcards

1
Q

What is the difference between fever and hyperthermia?

A

Fever is regulated by the hypothalamus in response to pyrogens resulting in rise of core temperature to >=37.8 degrees
NOTE: Fever needs to be qualified in notes

Hyperthermia is not regulated by the hypothalamus and is an uncontrolled body temperature rise

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2
Q

What is hyperpyrexia?

A

Extraordinarily high fever >=41.5

Type of hyperthermia

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3
Q

What is the normal body temperature and how is this regulated during the day?

A

36.8 +/- 0.8

Heat generated by metabolically active cells and lost from conduction, convection, radiation and evaporation

Hypothalamus tightly regulates core temperature at thermal setpoint

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4
Q

What components of the brain are involved in neurological thermoregulation?

A

Rostral hypothalamus (pre-optic area)

Limbic system + brain stem

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5
Q

What is fever?

A

Elevation of core body temperature above the daily range for an individual i.e. not shell temperature

Abnormal temperature= 37.8 degrees

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6
Q

What causes hyperthermia?

A

Loss of thermoregulatory compensatory mechanisms due to:
-heat stroke syndromes
-metabolic diseases
(Thyrotoxic storm/phaeochromocytoma/DKA)
-pharmacological agents
(Atropine/certain anaesthetics/neuroleptic malignant syndrome/serotonin syndrome)
-neurological injury
(Brain haemorrhage/hypothalamic stroke/status epilepticus)

Hypothalamic set-point remains the same

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7
Q

How can atropine cause hyperthermia?

A

Inhibits sweat production meaning there is a loss of compensatory mechanisms to control body temperature

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8
Q

How could identify someone with neuroleptic malignant syndrome?

A

Recently started on anti-psychotics

Autonomic dysfunction

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9
Q

What can cause serotonin syndrome?

A 
Cocaine 
NDMA
Amphetamines 
TCAs
SSRIs
MAOI
Lithium
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10
Q

How can you measure the core temperature? What are the potential problems with some of these routes?

A

Mouth
-can be affected by cold/warm drinks or foods

Rectum

  • has large arterial supply so can be considered representative of core temp
  • can give false low reading if patient in shock

Oesophagus

  • close to core
  • used in intensive care with hyperthermic

Tympanic membrane
-very reliable method

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11
Q

What are pyrogens? What are the 2 different causes?

A

Anything that causes a fever

Exogenous:

  • outside of host
  • microbes and their products

Endogenous:
-host-derived biologically active proteins = pyrogenic cytokines

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12
Q

What are the different exogenous pyrogens?

A

bacterial exotoxins
Eg TSST-1 toxin in Staph A + toxic shock syndrome
Eg Shiga toxin in shigella spp.

Bacterial endotoxins
Eg Lipopolysaccharide (LPS) on gram -ve enterobacteriaceae

Viral infection i.e. influenza and RSV

Fungal elements

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13
Q

Are gram +ve or -ve more pyrogenic? Why?

A

Gram -ve due to LPS on cell wall acting as an exogenous pyrogen to drive pyrexia due to being bacterial endotoxins

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14
Q

What are the different endogenous pyrogens?

A

TLRs activation leads to production of pyrogenic cytokines such as IL-1, IL-6 and TNF

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15
Q

How is prostaglandin E2 involved in thermostat control?

A

Increased PGE2 in hypothalamic tissue and 3rd ventricle during a fever

Causes neurontransmission via cAMP (not NTM in own right)

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16
Q

What are the stages of developing a fever?

A

Infectious agent (i.e. bacterial endo/exotoxins or viral RNA) OR damaged tissue act as TLR-ligands for dendritic cells and macrophages

Pyrogenic cytokines produced which enter the systemic circulation

Reach endothelium reticulum which causes an increase in PGE2

PGE2 induces fever via cAMP neurotransmitter and vasomotor centre

17
Q

What factors can affect the process of fever development?

A

Host genetic deficiencies

AI treatment i.e. Glucorticoids or Anti-IL-1 (anakinra) or Anti-TNF (infliximab)

Cytokine disease and non-infection fever
I.e lymphoma/leukaemia/systemic vasculitis

Brain injury
I.e. hypothalamic stroke/haemorrhage/status epilepticus

Use of anti-pyrexics
I.e. paracetamol/aspirin/NSAIDs

18
Q

Why might a person on infliximab not present with the classic signs of fever?

A

acts as an anti-TNF which is the one of the major pyrogenic cytokines which drive the process of fever

Therefore can have infection without the presentation of a fever

19
Q

What are the most common causes of fever in the returned traveller?

A

Pathogens endemic to other parts of the world i.e. malaria

Worldwide pathogens acquired by chance when travelling +/- added risk of drug-resistance i.e. primary EBV

20
Q

What is the criteria for pyrexia of unknown origin?

A

Fever >= 37.8 on several occasions

Duration of fever >= 21 days

Uncertain diagnosis after 1 week of investigations in hospital

21
Q

What are the 3 general classifications of PUO?

A

infections
Malginancies
Systemic rheumatic diseases

22
Q

What conditions should you be worried about if a traveller returns with a fever?

A

Falciparum malaria
Leptospirosis
Viral haemorrhagic fevers (VHF)

23
Q

What are the main areas which need to be assessed for risk of exposure with a returning traveller? Why is it important to ask about when the person travelled?

A

When and where they travelled

Activities whilst there i.e. animal or water contact, new sexual partner etc

Protection i.e. DEET

Immunity i.e. vaccination history or history of previous infection

It can be used to determine the possible incubation period which can indicate or exclude certain viruses
Eg. Falciparum malaria should have presented w/i 6 months

24
Q

How might a person suffering from falciparum malaria present?

A 
Impaired consciousness and seizures 
Renal impairement 
Hypoglycaemia 
Pulmonary oedema or ARDS
Low Hb 
Spontaneous bleeding 
Shock 
Haemoglobinuria
25
Q

How might a person with Middle East Respiratory syndrome present?

A

Severe respiratory infection
Symptoms of fever
Evidence of pulmonary parenchyma disease
History of contact with another known MERS-Cov infected person or been to area of high risk

Infectious Disease (19 decks)

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