fever and PUO

Question 1

what is the definition of pyrexia of unknown origin

Answer 1

• prolonged illness
• fever on several occasions
• no diagnosis after intelligent investigations

Question 2

what is the “normal” oral temp range

Answer 2

35.8-37.8

Question 3

what is the diurnal variation in body temp

Answer 3

lowest in the morning

highest in the afternoon

Question 4

in which part of the hypothalamus are the temp sensitive neurons

Answer 4

anterior - pre optic region of the hypothalamus

Question 5

how do we loose heat in the body

Answer 5

peripheral vasodilation
sweating
reduced physical activity

Question 6

how is heat conserved in the body

Answer 6

peripheral vascoconstriction
piloerection
warmth seeking behaviour

Question 7

how is heat produced in the body

Answer 7

shivering

release of thyroid hormone, Glucocorticoids and catecholamines

Question 8

what is classified as a fever

Answer 8

early morning oral temp >37.2

oral temp >37.8 at any other time of the day

Question 9

which noninvasive way of measuring temperature is probably the most accurate

Answer 9

ear probe

Question 10

why is a fever sometimes “good”?

Answer 10

because a rise in core temp “switches on” a range of immune, endocrine and physiological mechanisms where there optimum temp for activity is 39.5 degrees

Question 11

what is the downside of maintaining a fever during infection

Answer 11

it is expensive to maintain the level of metabolic activity

Question 12

explain the mechanism for fever

Answer 12

something activates macrophages/monocytes/neutrophils –> releases cytokines which induce COX-2 expression –> this causes the production of PGE2 –> activates E-prostanoid receptor in hypothalamus –> fever

Question 13

what are the signs of a true rigor

Answer 13

• feeling of intense cold
• uncontrollable shivering
• striking pallor face and limbs
• pilo-erection
• leaves sufferer exhausted with high fever

Question 14

what is the most common cause of fever of short duration

Answer 14

infection

Question 15

which types of patients are “at risk” for severe illness

Answer 15

patient with recent overseas travel
asplenic patients
neutropaenic patients
elderly
diabetcs
IVDU

Question 16

what are the extra symptoms that are warning bells when someone presents with acute fever

Answer 16

• rapid onset
• rigors
• severe muscle pains
• impaired conscious state
• vomiting
• severe headache
• rash
• jaundice

Question 17

what is the management of acute fever

Answer 17

• investigate
• empirical IV antibiotics if bacterial infection likely
• admit
• instructions and early review next day

Question 18

which investigations would you order for a patient who presents with acute fever

Answer 18

FBE
CRP
renal function
liver function
blood/urine cultures
CXR

Question 19

why is a normal WCC and CRP in a patient who presents with acute fever not necessarily a good thing

Answer 19

because they may not have had time yet to make an immune response

Question 20

what things should you ask the patient if they present with prolonged fever

Answer 20

• occupation/animal exposure
• country of origin
• travel
• contact with toddlers
• risk for SBE
• new sexual contacts
• new medications

Question 21

which infection is likely if a patient presents with prolonged fever and they have a toddler

Answer 21

acute CMV infection

Question 22

which infection is likely if a patient presents with a prolonged fever and they have travelled within the last 2 years

Answer 22

vivax malaria

Question 23

which investigations should you order in a patient who presents with prolonged fever

Answer 23

FBE
ESR
CRP
LFTs
CXR
serology
blood and urine cultures

Question 24

what information does the ESR give you when investigating for prolonged fever?

Answer 24

high in prolonged bacterial infection or vasculitis

Question 25

what information can the FBE give you when investigating for prolonged fever?

Answer 25

• atypical lymphocytosis - infectious mononucleosis syndrome
• neutrophilia - bacterial/inflammatory process
• exclude malaria

Question 26

what information can the CRP give you when investigating for prolonged fever?

Answer 26

if very high - suggests bacterial infection/inflammation

Question 27

what information can a CXR give you when investigating for prolonged fever?

Answer 27

can rule out pneumonia

Question 28

what are the differential diagnoses for pyrexia of unknown origin

Answer 28

infections - 20%
CT disorders - 35%
malignancies - 35%
other - 10%

Question 29

what are the three main infections that cause PUO

Answer 29

subacute bacterial endocarditis by viridans strep
tuberculosis
intra-abdominal abscess