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Fever
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Outline
• Introduction
• Mean Normal Body Temperature
• Thermoregulation
• Approach to Febrile patient
• Outcome of untreated Febrile Patient
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Introduction: Mean Normal Body Temperature
• Mean Normal Body Temperature readings of common sites:
• Oral → 36.8 + 0.4 oc (with diurnal variations)
• Rectal → 37.3 + 0.5 oc
• Axillary → 36.8 + 0.7 oc
• Daily Diurnal Variations of 0.5oc: low levels at 6 am and high levels at
4-6 pm
• Thus mean Oral To of maximum 37.2oc (am) and 37.7oc (pm)
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Introduction: Mean Normal Body Temperature
• Oral & Rectal To better represent the core To
• Rectal ones are best but are inconvenient for daily use
• Lower oral readings are probably attributable to mouth breathing
• Axillary To is unreliable because
• It’s affected by external environment
• In hemiparesis pts, the affected site always exhibits significantly lower To
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Introduction:
Thermoregulation
• Setpoint & Control Center→ Hypothalamus
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Introduction: Terminologies
• Both Fever and Hyperthermia represent pathologically elevated
temperatures
Fever Hyperthermia
Elevated T due to an increase in the setpoint of
hypothalamus
Elevated T while the set point remains intact
Due to Pyrogens (e.g Endotoxins) May arise from changes within the body or by
change in the environment
Treatment with antipyretics and measure & drugs
to eliminate the cause
Treatment primarily involves rapid cooling of body
and certain muscle relaxants (depending on the
cause)
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Approach to Febrile patient
• Step 1: Characterization of Fever
• Step 2: Complete other parts of the History & Complete physical
examination
• Step 3: Pertinent Laboratory Investigations
• Step 4: Differential Diagnosis
• Step 5: Management
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Approach to Febrile patient
• Step 1:
Characterization of
Fever
• Inquire: Onset,
Duration, Progression
• Patterns of Fever may
then be elucidated
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Approach to Febrile patient
• Step 2: Complete other parts of the History (primarily establishing
associated symptoms) & Complete Physical examination
• Grading
• Low to Moderate vs High Grade → Above 39.4 oc high grade
• High grade suggestive symptoms → Chills & Rigor.
• Hyperpyrexia → T >41.5°C
• Can occur with severe infections but more commonly occur with CNS hemorrhages
• Localizing Fever Etiology
• Look at associated symptoms and Risk factors
• E.g. Recent Travel History → Malaria, TB, Yellow Fever, Ebola Fever
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Approach to Febrile patient
• Step 2: Complete other
parts of the History
(primarily establishing
associated symptoms) &
Complete Physical
examination
• Differentiating from
Hyperthermia (E.g. as in
patients in Heat Stroke):
• Signs of Hyperthermia:
Hallucinations, Delirium,
Dry Skin, Pupil Dilation
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Approach to Febrile patient
• Step 2: Complete other parts of the History (primarily establishing
associated symptoms) & Complete Physical examination
Danger Signs and Symptoms that promptly need treatment
o Severe headache
o Rash
o Unusual sensitivity to
bright light
o Stiff neck and pain
when you bend your
head forward
o Mental confusion,
strange behavior or
altered speech
o Persistent vomiting
o Difficulty breathing or
chest pain
o Severe Abdominal
pain
o Convulsions or
seizures
o Trauma
o Shortness of Breath
o Neonates and Infants
o Recent Surgical
History (Specially if it’s
moderate to high
grade fever)
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Approach to Febrile patient
• Step 3: Pertinent Laboratory Investigations
• Routine:
• CBC with differential
• Blood glucose
• LFT
• RFT
• Urinalysis
• Serum Electrolytes
• Additional test may be performed depending of the suspected Etiology and
the patient’s condition.
• E.g. Blood Culture, Chest X-Ray
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Approach to Febrile patient
• Step 4: Differential Diagnosis: Etiologies of Fever can be
• Infection (Systemic/Local)
• Autoimmune Diseases
• Cancer
• Allergies and Drug Reactions
• Dysmetabolic/Endocrine (e.g. Graves Disease)
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Approach to Febrile patient
• Step 5: Management
• Objective
• To reduce the elevated hypothalamic set point
• To facilitate heat loss
• This is done by treating underlying etiology and providing Antipyretic
Treatment
• Note: Hyperpyrexia should be promptly addressed and similar to
Hyperthermia it requires cooling the body (e.g. Bathing in cold water) in
addition to the routine fever treatment.
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Approach to Febrile patient
• Step 5: Management
• Antipyretic Treatment
• Use Antipyretic Treatment on regular schedule than intermittently
• Intermittent therapy aggravates chills and sweats.
• Chronic high-dose therapy with antipyretics (such as aspirin or nonsteroidalanti-
inflammatory drugs [NSAIDs] used in arthritis) does not reduce normal core body
temperature.
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Approach to Febrile patient
• Step 5: Management
• Antipyretic Treatment
• Choice of Medications: Acetaminophen followed by Aspirin, NSAID & Glucocorticoids
• Acetaminophen is preferred because it:
• Does not mask signs of inflammation
• Does not impair platelet function
• Does not adversely affect the GI tract
• Is not associated with Reye’s syndrome
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Outcomes of Untreated Fever
• In most cases, either the patient recovers spontaneously or the
history, physical examination, and initial screening laboratory studies
lead to a diagnosis.
• Untreated High Grade Fever how ever may worsen or linger and
significant health complications such as Febrile Seizures and various
degrees of protein damage specially Brain Damage.
• Note: Proteins such as Enzyme operate at a certain optimal temperature but if
it’s elevated significantly, they may stop or even denature.
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References
• Amboss (https://www.amboss.com/)
• Harrison's principles of internal medicine 19th Edition. (2015). New
York :McGraw Hill Education
• Lecture Notes on General Medicine For Dental Practice: A System
Based Approach with Dental Management Considerations. (2014).
Prabhu. Nova Science Publishers.
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