Pyrexia of Unknown Origin & Bloodborne Infections Flashcards
What is pyrexia?
Fever
How is someone diagnosed with pyrexia of unknown origin (PUO)?
Investigations into a sick patient with fever
Fever > 38C
No localising signs
Initial investigations are negative for > 3 weeks
What investigations are done for sick patients with fever?
Most patients will have resolution without diagnosis
For others - rapid identification of focus and cause e.g. pneumonia, cellulitis
What percentage of PUOs are caused by infections?
16%
What percentage of PUOs are caused by malignancies?
7%
What percentage of PUOs are caused by inflammatory conditions?
22%
What percentage of PUOs have miscellaneous causes?
4%
What percentage of PUOs causes remain unknown?
50%
What are principal infectious causes of PUO?
TB and other mycobacteria
Endocarditis
Osteomyleitis
Deep abscesses - spine, liver, pelvic, retroperitoneal
Brucellosis
Typhoid fever
Malaria
What are principal inflammatory causes of PUO?
SLE
Rheumatoid arthritis
Giant cell arthritis and other vasculitis
Sarcoid
What malignancies can cause PUO?
Lymphoma
Myeloma
Renal cell carcinoma
Lung cancer
What are some miscellaneous causes of PUO?
Factitious fever
Drug fever - inc antibiotics
Genetic e.g. FMF (family Mediterranean fever)
What are some factors that may change the likely causes of PUO?
Geography - especially recent travel/migration
Smoking
HIV
Other immunosuppression
Age
Family history
Drug history
Animal contact
Occupation
What is bacteraemia?
Bacteria in bloodstream
Not a single disease but an endpoint of different disease processes
How is bacteraemia detected?
Blood cultures
What is true bacteraemia often associated with?
Illness - fever, hypotension, organ failure, skin features (sepsis, septicaemia, septic shock)
What infections can bacteraemia cause?
Tissue based infection
Device related infection
Endovascular infection
Give examples of tissue based infections
UTI
Pneumonia
Peritonitis
Meningitis
Osteomyelitis
Cellulitis
Spinal abscess
Brain abscess
Give examples of device related infections
Central line
Peripheral cannula
Pacemaker
Vascular graft
What is endovascular infection?
Endocarditis
What does bacteraemia result in?
Septicaemia and septic shock - fever, hypotension, multi-organ failure
Describe endocarditis
Before antibiotics, virtually all patients died
Has many cardiac and non-cardiac features
Central lesion is the cardiac vegetation
What are vegetations?
Masses composed of fibrin, platelets and infecting organisms, held together by agglutinating antibodies produced by the bacteria
Usually on valves
What do vegetations lead to?
Valve destruction, perforation
Valve ring abscess
Chordae tendinae rupture
Myocardial abscess with/without pericarditis
How are infected vegetations caused?
Bacteraemia provide a means of bacteria sticking to the endocardium, causing infected vegetation
What are the main causes of bacteraemia in endocarditis?
Poor denitation with or without dental procedures - oral Streptococci
Intravenous drug abuse (IVDA)
Intravascular lines - e.g. for dialysis, parenteral nutrition (Staphylococci)
How do bacteria stick to the endocardium?
Endocardium is damaged
vWF adhered
Platelets adhere
Platelets bind fibrin
Bacteria adhere
More platelets and fibrin laid down, forming a vegetation
What leads to a damaged endocardium?
Rheumatic heart disease
Congenital heart disease
Degenerative/calcific valves
Prosthetic valves
These all cause turbulence, which leads to a damaged endocardium
What are clinical consequences of vegetations?
Infected vegetation leads to cardiac murmurs, valve rupture, regurgitation and heart failure
Also causes bacteraemia and features of sepsis -> septic emboli -> lung abscess, brain abscess/stroke, spinal abscess, skin emboli, retinal emboli
What is strep endocarditis often associated with?
Poor oral hygiene
How is endocarditis diagnosed?
Blood culture and echocardiography
Describe basic principles of treatment of endocarditis
If the bug is protected within the vegetation then high dose IV antibiotics, combination, prolonged treatment (3-6 weeks)
If valve damage then surgery
If prosthetic valve then surgery
There is often high operative risk
