T13: Pyrexia of unknown origin Flashcards
What is the normal temperature in a healthy 18-40-year-old?
36.8 +/- 0.4 degrees Celsius
List 3 causes of physiological elevations in body temperature
- postprandial
- pregnancy
- Menstruation
List 4 ways through which we measure temperature
- Oral
- Rectal
- Axillary
- Tympanic membrane
The least reliable way of measuring temperature
Axillary
The most commonly used but less reliable in respiratory diseases way to measure temperature
Oral
How does rectal temperature differ from oral temperature?
It is > 0.4 degrees Celsius
How does the tympanic membrane method work and how does it differ from the oral method?
It measures heat radiation from the tympanic membrane. It is more variable than oral.
PHYSIOLOGY OF THERMREGULATION: There is an ongoing balance between heat loss and production. List 4 ways through which heat is produced
- Oxidation of nutrients
- Cellular metabolism
- Blood circulation
- Involuntary contraction of muscles
PHYSIOLOGY OF THERMREGULATION: There is an ongoing balance between heat loss and production. List 4 homeostatic mechanisms of heat regulation (excluding hypothalamic thermoregulation center)
Autonomic- sympathetic nerves
Endocrine- adrenal, thyroid, sweat gland
Metabolic- skin arterioles
Behavioral - take clothes on/ off (skeletal muscles- voluntary)
Name the 3 endocrine organs involved in thermoregulation
- Thyroid.
- Adrenal
- Sweat glands
State whether this refers to fever or hyperthermia:
- Setpoint remains unchanged
Hyperthermia
State whether this refers to fever or hyperthermia:
- Caused by: Neuroleptic malignant syndrome, Malignant hyperthermia, and serotonergic syndrome
Hyperthermia
State whether this refers to fever or hyperthermia:
- Pathogenesis: Heat conservation and thermogenesis
Fever
State whether this refers to fever or hyperthermia:
- Caused by infection, inflammation, cancer, medications, Thrombosis
Fever
State whether this refers to fever or hyperthermia:
Pathogenesis: Exogenous heat exposure or endogenous heat protection (can rapidly become fatal)
Hyperthermia
PATHOGENESIS OF FEVER: State whether the following refers to endogenous or exogenous pyrogens:
Derived from bacteria, viruses, parasites, fungi»_space; stimulate other pyrogens via immune activation
Exogenous pathogens
PATHOGENESIS OF FEVER: State whether the following refers to endogenous or exogenous pyrogens:
Pyrogenic cytokines: IL-1, IL-6, TNF, IFN-y, monocytes, lymphocytes, neutrophils. Stimulated by: inflammation, tissue necrosis, immune complexes
Endogenous pyrogens
CONSEQUENCES OF FEVER:
At which temperature (rectal) do you get permanent brain damage?
> 41 degrees Celcius
CONSEQUENCES OF FEVER:
Up to which temperature can you be spared from thermal injury?
41 degrees Celcius
CONSEQUENCES OF FEVER:
At which temperature can you get: heat stroke and death
> 43 degrees Celcius
We use the Durack and Street classification for Fever of Unknown Origin (FUO). List the 4 categories we look at
- Classical FUO
- Nosocomial FUO
- immune-deficient FUO
- HIV-related FUO
Immunodeficient FUO is:
- Also called?
- Sources?
- 4 Causative Organisms
- Management?
- Neutropenic FUO
- Focal bacterial/ fungal bacteraemia/ catheter-related/ perianal
- S.aureus, TB, Gram negatives, HSV, CMV,fungal
- Broad spectrum A/B
True or false:
More than 50% of nosocomial FUO is non-infectious and ~ 25% is infectious
false
Which 7 groups of patients are at risk of Nosocomial infectious FUO?
- Original surgical field
- U-catheter
- Intubated
- Diarrhoea
- IV lines
- Prostheses
- Source control
What are some non-infectious causes of nosocomial FUO? (8)
- 24 hours post-op
- DVT
- MI
- Drug fever
- Transfusion reaction
- Neoplasm
- Drug/ ETOH withdrawal
- Acalculous cholecystitis
Classical FUO has 4 categories (nature of pathology) with a mnemonic: INCUM. Name these
Infection Neoplasm Collagen vascular disease Undiagnosed Miscellaneous
Account, in 4 ways, for the changing epidemiology of classical FUO
- Ubiquitous use of A/B
- Imaging
- Tests: immunological, tumour antigen assays
- Increased detection of rheumatologic diseases
Rheumatological causes of classical FUO: List the causes in the following groups of patients:
- Young patients
- Old patients
- Still’s disease, SLE
2. Temporal arteritis, polymyalgia rheumatica
The modifying factors of classical FUO are age- and geographic location-related. explain.
Elderly= more neoplastic or multisystem disease causes
Young= most no case identified (good prognosis, less likely underlying disease)
LMI countries= more infections, HIC= more evenly distributed causes
Explain, in 3 steps, your approach to FUO
Step 1: History, Physical exam, non-specific tests
Step 2: More detailed Ix (decide on which organ/ system is involved)
Step 3: Definitive Ix to confirm Dx
True or false
Fever patterns are of great help in the diagnosis of FUO conditions
False
Diagnose this patient:
- Patient looks well
- Temperature normal under supervision
- Bizzare temperature chart > 41 with no diurnal variations and no correlation between pulse rate and temperature
- No sweating when fever resolves
- Evidence of self harm, injection
- Normal ESR/CRP
Factitious fever
