fever and PUO Flashcards
what is the definition of pyrexia of unknown origin
- prolonged illness
- fever on several occasions
- no diagnosis after intelligent investigations
what is the “normal” oral temp range
35.8-37.8
what is the diurnal variation in body temp
lowest in the morning
highest in the afternoon
in which part of the hypothalamus are the temp sensitive neurons
anterior - pre optic region of the hypothalamus
how do we loose heat in the body
peripheral vasodilation
sweating
reduced physical activity
how is heat conserved in the body
peripheral vascoconstriction
piloerection
warmth seeking behaviour
how is heat produced in the body
shivering
release of thyroid hormone, Glucocorticoids and catecholamines
what is classified as a fever
early morning oral temp >37.2
oral temp >37.8 at any other time of the day
which noninvasive way of measuring temperature is probably the most accurate
ear probe
why is a fever sometimes “good”?
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
what is the downside of maintaining a fever during infection
it is expensive to maintain the level of metabolic activity
explain the mechanism for fever
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
what are the signs of a true rigor
- feeling of intense cold
- uncontrollable shivering
- striking pallor face and limbs
- pilo-erection
- leaves sufferer exhausted with high fever
what is the most common cause of fever of short duration
infection
which types of patients are “at risk” for severe illness
patient with recent overseas travel asplenic patients neutropaenic patients elderly diabetcs IVDU
what are the extra symptoms that are warning bells when someone presents with acute fever
- rapid onset
- rigors
- severe muscle pains
- impaired conscious state
- vomiting
- severe headache
- rash
- jaundice
what is the management of acute fever
- investigate
- empirical IV antibiotics if bacterial infection likely
- admit
- instructions and early review next day
which investigations would you order for a patient who presents with acute fever
FBE CRP renal function liver function blood/urine cultures CXR
why is a normal WCC and CRP in a patient who presents with acute fever not necessarily a good thing
because they may not have had time yet to make an immune response
what things should you ask the patient if they present with prolonged fever
- occupation/animal exposure
- country of origin
- travel
- contact with toddlers
- risk for SBE
- new sexual contacts
- new medications
which infection is likely if a patient presents with prolonged fever and they have a toddler
acute CMV infection
which infection is likely if a patient presents with a prolonged fever and they have travelled within the last 2 years
vivax malaria
which investigations should you order in a patient who presents with prolonged fever
FBE ESR CRP LFTs CXR serology blood and urine cultures
what information does the ESR give you when investigating for prolonged fever?
high in prolonged bacterial infection or vasculitis
what information can the FBE give you when investigating for prolonged fever?
- atypical lymphocytosis - infectious mononucleosis syndrome
- neutrophilia - bacterial/inflammatory process
- exclude malaria
what information can the CRP give you when investigating for prolonged fever?
if very high - suggests bacterial infection/inflammation
what information can a CXR give you when investigating for prolonged fever?
can rule out pneumonia
what are the differential diagnoses for pyrexia of unknown origin
infections - 20%
CT disorders - 35%
malignancies - 35%
other - 10%
what are the three main infections that cause PUO
subacute bacterial endocarditis by viridans strep
tuberculosis
intra-abdominal abscess
