Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content +++ DEFINITIONS ++ Fever is an increase in the body core temperature due to elevation of the hypothalamic set point triggered by pyrogens. It should be differentiated from hyperthermia, which results from overwhelming of the body’s thermoregulatory mechanisms without elevation of the hypothalamic set point. Fever of unknown origin (FUO) was traditionally defined as a fever >38.3°C on several occasions over a period longer than 3 weeks with an uncertain diagnosis after 1 week of evaluation in the hospital. Due to changes in model of healthcare and advances in outpatient testing facilities, the 1-week inpatient evaluation criterion is no longer required. +++ CAVEATS ++ A temperature of 37.5°C constitutes a fever in normal adults. However, immunocompromised hosts, e.g. the elderly, cancer patients on chemotherapy, transplant patients on immunosuppressants, retroviral patients, etc., may not be able to mount a fever. The magnitude of temperature and response to antipyretics generally do not correlate with the severity of illness. There are many causes of fever, but infections remain the most common cause (see Table 1). ++Table Graphic Jump LocationTABLE 1Causes of fever or hyperthermiaView Table||Download (.pdf) TABLE 1 Causes of fever or hyperthermia Causes Types Infections By microbial agent: Viral, bacterial, fungal or parasitic By common vs occult anatomical sites: Respiratory tract Genito-urinary tract Intra-abdominal (including hepatobiliary tract) Musculoskeletal and cutaneous skin infection Central nervous system Cardiovascular (including endocarditis, mycotic aneurysms) Iatrogenic, e.g. central line-associated bloodstream infections Metabolic Gout Hyperthyroidism Neoplasms “Tumour fever” Solid tumours Leukaemia, lymphoma Collagen vascular diseases Systemic lupus erythematosus Rheumatoid arthritis Central nervous system lesions “Central fever” Stroke Intracranial bleeding, e.g. subarachnoid haemorrhage Drugs Toxicology: serotonin syndrome, neuroleptic malignant syndrome, salicylate overdose, anticholinergic overdose, sympathomimetic use The remainder are diagnoses of exclusion as a cause of fever: Antibiotics, e.g. penicillins, sulphonamides Anticonvulsants, e.g. carbamazepine, phenytoin Others, e.g. antihistamines, ranitidine Miscellaneous Heatstroke Thromboembolic disease, e.g. pulmonary embolism ++ SPECIAL TIPS FOR GPs Antibiotics should not be prescribed indiscriminately for non-specific viral fevers or upper respiratory tract infection. Delayed antibiotic prescriptions is a reasonable approach to shared decision making in use of antibiotics for upper respiratory tract infections. It is important to refer febrile unwell patients to hospital immediately for evaluation and management. +++ CLINICAL ASSESSMENT +++ History ++ Duration and pattern of fever Associated localising symptoms, e.g. cough, dysuria, vomiting/diarrhoea Presence of constitutional symptoms, e.g. loss of weight, night sweats Past medical history, especially immunocompromised states Recent institutionalised care for possible nosocomial infection Recent invasive procedures, e.g. urinary catheterisation, IV cannula insertion Travel history/recent febrile contacts Occupation and special hobbies, e.g. animals, freshwater exposure Vaccination history (especially in children) Previous treatments for current illness Medication history +++ Physical examination ++ General appearance, including mental status and hydration status. Vital signs. (Note: The pulse should increase by 10 beats ... Your Access profile is currently affiliated with [InstitutionA] and is in the process of switching affiliations to [InstitutionB]. Please select how you would like to proceed. Keep the current affiliation with [InstitutionA] and continue with the Access profile sign in process Switch affiliation to [InstitutionB] and continue with the Access profile sign in process Get Free Access Through Your Institution Learn how to see if your library subscribes to McGraw Hill Medical products. Subscribe: Institutional or Individual Sign In Error: Incorrect UserName or Password Username Error: Please enter User Name Password Error: Please enter Password Sign in Forgot Password? Forgot Username? Download the Access App: iOS | Android Sign in via OpenAthens Sign in via Shibboleth You already have access! Please proceed to your institution's subscription. Create a free profile for additional features.