Fever
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FEVER
•
An elevation of body temperature that exceeds the normal daily variation and occurs in conjunction with an increase in the hypothalamic set point
i.e. 37°C (normothermic) 39°C (febrile) Pyrogenic cytokines (IL-1, IL-6, TNF, IFN) and microbial toxins
Hypothalamus: increased PGE2 and cAMP
(+) Neurons in vasomotor center
Peripheral vasoconstriction and increased metabolic activity
Decreased heat loss peripherally (person feels cold)
“Shivering” heat production
FEVER
•
Decreased pyrogens/ antipyretic use reset hypothalamic set point vasodilation & sweating (heat loss)
Hyperpyrexia: fever of >41.5C (106.7F) resulting from severe infection or CNS hemorrhage Hypothalamic fever: elevated temperature caused by abnormal hypothalamic fxn Exogenous pyrogens • Microbial products • Microbial toxins o lipopolysaccahride endotoxin of G-negative bacteria o Staph aureus enterotoxin o GAS and GBS
• Whole microorganisms Endogenous pyrogens/pyrogenic cytokines • IL-1, IL-6, TNF, ciliary neurotropic factor (CNTF), IFN-α • Produced by monocytes, neutrophils, and lymphocytes • Production can be induced by infection, trauma, inflammation, and tissue necrosis Approach to patient with fever • Detailed history o Chronology of symptoms o Recently taken meds (prescribed or not) o Prosthetic or implanted devices o Occupational hazards o Recent travel o Unusual hobbies o Dietary preferences o Sexual practices o Exposure to animals o Drug use o Exposure to people with infection • Physical examination o Vital signs o Axillary temperatures are notoriously unreliable o Skin, eyes, lymph nodes, nail beds, cardiovascular system, chest, abdomen, musculoskeletal system, and nervous system o In women: do pelvic exam (possible PID) • Laboratory tests o Clinical Pathology
CBC with differential
(eosinophils, bands, toxic granulations, Dohle bodies) Neutropenia: parvovirus B19, typhoid, brucellosis, TB, histoplasmosis Lymphocytosis: typhoid, brucellosis, TB, viral disease Atypical lymphocytes: EBV. CMV, HIV, dengue,
o
o
o
rubella, measles, varicella, viral hepatitis Monocytosis: typhoid, TB, brucellosis Eosinophilia: parasitic infection Smear: malarial and babesial pathogens ESR Urinalysis with examination of sediment Chemistry Electrolytes Glucose BUN Creatinine Microbiology Gram stain Culture and sensitivity Radiology CXR
Patterns of Fever (http://www.fpnotebook.com/ID44.htm) 1. Remittent Fever: • Daily elevated temperature (>38 C or 100.4 F) • Returns to baseline but not to normal 2. Intermittent Fever (Periodic Fever) • Intermittently elevated temperature (>38 C, 100.4 F) • Return to baseline and to normal
•
Examples: PFAPA Syndrome: Fever every 3-4 weeks • Most common cause in children age <5 years 3. Relapsing Fever (Borrelia species): Every 2-3 weeks • Malaria: Fever every other or every third day • Rat Bite Fever: Fever every 3 to 5 days • Hodgkin's Disease: Pel-Ebstein Fever • Cyclic Neutropenia: Fever every 3 weeks 4. Hectic Fever • Daily elevated temperature (>38 C or 100.4 F)
•
Either remittent or intermittent pattern • Temperature excursion >1.4 C (2.5 F) • Examples: Intermittent bacteremia (dental abscess, UTI), Epstein-Barr Virus , Familial Mediterranean Fever , Crohn's Disease, Still's Disease (Juvenile Rheumatoid Arthritis) 5. Sustained or Continuous Fever • Daily elevated temperature (>38 C or 100.4 F) • Fluctuation of elevated temperature < 0.3 C (0.5 F) • Associated conditions: Drug Fever, Salmonella Mechanisms of antipyretic agents • Inhibition of COX • Acetaminophen: centrally-acting • Other antipyretics: ibuprofen, aspirin, indomethacin, glucocorticoids, phenothiazine gεnεЅϊЅ ϋ
•
An elevation of body temperature that exceeds the normal daily variation and occurs in conjunction with an increase in the hypothalamic set point
i.e. 37°C (normothermic) 39°C (febrile) Pyrogenic cytokines (IL-1, IL-6, TNF, IFN) and microbial toxins
Hypothalamus: increased PGE2 and cAMP
(+) Neurons in vasomotor center
Peripheral vasoconstriction and increased metabolic activity
Decreased heat loss peripherally (person feels cold)
“Shivering” heat production
FEVER
•
Decreased pyrogens/ antipyretic use reset hypothalamic set point vasodilation & sweating (heat loss)
Hyperpyrexia: fever of >41.5C (106.7F) resulting from severe infection or CNS hemorrhage Hypothalamic fever: elevated temperature caused by abnormal hypothalamic fxn Exogenous pyrogens • Microbial products • Microbial toxins o lipopolysaccahride endotoxin of G-negative bacteria o Staph aureus enterotoxin o GAS and GBS
• Whole microorganisms Endogenous pyrogens/pyrogenic cytokines • IL-1, IL-6, TNF, ciliary neurotropic factor (CNTF), IFN-α • Produced by monocytes, neutrophils, and lymphocytes • Production can be induced by infection, trauma, inflammation, and tissue necrosis Approach to patient with fever • Detailed history o Chronology of symptoms o Recently taken meds (prescribed or not) o Prosthetic or implanted devices o Occupational hazards o Recent travel o Unusual hobbies o Dietary preferences o Sexual practices o Exposure to animals o Drug use o Exposure to people with infection • Physical examination o Vital signs o Axillary temperatures are notoriously unreliable o Skin, eyes, lymph nodes, nail beds, cardiovascular system, chest, abdomen, musculoskeletal system, and nervous system o In women: do pelvic exam (possible PID) • Laboratory tests o Clinical Pathology
CBC with differential
(eosinophils, bands, toxic granulations, Dohle bodies) Neutropenia: parvovirus B19, typhoid, brucellosis, TB, histoplasmosis Lymphocytosis: typhoid, brucellosis, TB, viral disease Atypical lymphocytes: EBV. CMV, HIV, dengue,
o
o
o
rubella, measles, varicella, viral hepatitis Monocytosis: typhoid, TB, brucellosis Eosinophilia: parasitic infection Smear: malarial and babesial pathogens ESR Urinalysis with examination of sediment Chemistry Electrolytes Glucose BUN Creatinine Microbiology Gram stain Culture and sensitivity Radiology CXR
Patterns of Fever (http://www.fpnotebook.com/ID44.htm) 1. Remittent Fever: • Daily elevated temperature (>38 C or 100.4 F) • Returns to baseline but not to normal 2. Intermittent Fever (Periodic Fever) • Intermittently elevated temperature (>38 C, 100.4 F) • Return to baseline and to normal
•
Examples: PFAPA Syndrome: Fever every 3-4 weeks • Most common cause in children age <5 years 3. Relapsing Fever (Borrelia species): Every 2-3 weeks • Malaria: Fever every other or every third day • Rat Bite Fever: Fever every 3 to 5 days • Hodgkin's Disease: Pel-Ebstein Fever • Cyclic Neutropenia: Fever every 3 weeks 4. Hectic Fever • Daily elevated temperature (>38 C or 100.4 F)
•
Either remittent or intermittent pattern • Temperature excursion >1.4 C (2.5 F) • Examples: Intermittent bacteremia (dental abscess, UTI), Epstein-Barr Virus , Familial Mediterranean Fever , Crohn's Disease, Still's Disease (Juvenile Rheumatoid Arthritis) 5. Sustained or Continuous Fever • Daily elevated temperature (>38 C or 100.4 F) • Fluctuation of elevated temperature < 0.3 C (0.5 F) • Associated conditions: Drug Fever, Salmonella Mechanisms of antipyretic agents • Inhibition of COX • Acetaminophen: centrally-acting • Other antipyretics: ibuprofen, aspirin, indomethacin, glucocorticoids, phenothiazine gεnεЅϊЅ ϋ
