fever,pyrexia,

1. APPROACH TO CASE
OF PYREXIA
DR.MOHAMAD HUSAIN
PGJR-2
DEPARTMENT OF MEDICINE
TOTAL NO. OF SLIDE-28
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2. OVERVIEW
• INTRODUCTION
• MECHANISM
• HYPERPYREXIA VS HYPERTHERMIA
• PATHOGENESIS
• PATTERN OF FEVER
• APPROACH TO A PATIENT
• TREATMENT 2

3. INTRODUCTION
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4. 4
Tympanic membrane Thermometers:
• use an otoscope-like probe that is inserted into the
external auditory canal to detect and measure thermal
infrared energy emitted from the tympanic membrane.

5. Menstruating Females: the morning
temperature is generally lower during the 2
weeks before ovulation.
it then rises by ~0.6°C (1°F) with ovulation
and stays at that level until menses occur.
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6. MECHANISM OF FEVER
• Fever occurs in conjunction with an increase in the
hypothalamic set point (e.g., from 37°C to 39°C).
• Once this hypothalamic center is active the
neurons and vasomotor center are activated which
leads to vasoconstriction of peripheral circulation
(hand & feet cooling). 6

7. Mechanisms to raise the core temperature to new set
point in hypothalamus.
(heat conservation) by Cutaneous Vasoconstriction
 (heat production)
• Shivering
• Non shivering Thermogenesis
• Behavioural Adjustments (like putting more clothes)
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8. When the hypothalamic set point is again reset
downward:
• Vasodilation
• Sweating
With every 1°F rise of temperature, above 100°F,
• the pulse rate increases by 10, the respiratory rate
by 4,and BMR by 7.
• Oxygen consumption increases by 13%.
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9. PATHOGENESIS
Pyrogens
• Any substance that causes fever.
1. Exogenous Pyrogens:
• Derived from outside the patient.
• Microbes or their Products.
• eg-(endotoxin) of Gram-ve bacteria, Enterotoxins of S. aureus.
2. Pyrogenic Cytokines
• Cytokines which cause fever aka Endogenous Pyrogens IL-1, IL-
6, TNF, IFN a, Ciliary Neurotrophic Factor.
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10. • Can be induced by:
• Infective Cause: Bacterial, Fungal, Viral
Infection
• Non Infective Cause: Pericarditis, trauma,
Stroke, Vaccination.
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12. HYPERPYREXIA VS HYPERTHERMIA
HYPERPYREXIA:
It is an elevation of body core temperature, above 41°C
(106°F), due to inadequate dissipation of heat.
HYPERTHERMIA:
Hyperthermia is characterised by an unchanged setting of
the thermoregulatory centre with an uncontrolled increase in
body temperature that exceeds body’s ability to lose heat.
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13. HYPERPYREXIA HYPERTHERMIA
CAUSE Cns haemorrhage (pontine
hemorrhage)M/C
Microbes
Toxin
Increase environmental
temp.(heat stroke)
Or
Increase heat production by
muscle(malignant hyperthermia)
MECHANISM Increase hypothalamic set point
(Increase PGE2)
Hypothalamic set point normal
SWEATING Present (cold skin) Hot &dry skin
VALUE >41.5 c(>106.7 F) >40.5 C
TREATMENT Underlying cause + NSAID Water therapy 13

14. • Causes of Hyperpyrexia
• 1. Pontine haemorrhage
• 2. Rheumatic fever
• 3. Meningococcal meningitis
• 4. Septicaemia
• 5. Cerebral malaria.
• Treatment It is treated with parenteral anti-
pyretics to set the elevated thermostat set point
to a lower level. 14

15. Malignant hyperthermia
• Is an inherent abnormality of skeletal muscle
cell sarcoplasmic reticulum which is unable to
store calcium ion.
• There is an increase in the intracellular
myoplasmic calcium, leading to activation of
myosin ATPase.
• which converts ATP to ADP there by producing
hyperthermia. 15

16. • Hyperthermia is triggered by use of inhalation
anaesthetics (Halothane, Cyclopropane) and muscle
relaxants (Succinylcholine).
 Seratonin syndrome:
It is seen with selective serotonin uptake inhibitors –
monoamine oxidase inhibitors and other seratonergic
medications.
It consists of hyperthermia, diarrhoea, tremor and
myoclonus.
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17. PATTERNS OF FEVER
1. Continuous Fever
• The temperature remains elevated above normal without
touching the baseline and the fluctuation does not exceed 0.6°C
(1°F) (diurnal variation).
 Lobar pneumonia.
 Infective endocarditis.
 Enteric fever.
2. Remittent Fever
• The temperature fluctuation exceeds 0.6°C (1°F), but without
touching the baseline. 17

18. 3.Intermittent fever
• The elevated temperature touches the baseline in
between.
• In hectic or septic type of intermittent fever, the diurnal
variation is extremely large, as occurs in septicaemia.
4.Relapsing Fever
• Febrile episodes are separated by normal temperature
for more than one day,
e.g. Borrelia infection, rat bite fever.
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19. Tertian fever - occurs on the first and third day,
e.g. Plasmodium vivax, ovale, falciparum.
 Quartan fever - occurs on first and fourth day,
e.g. Plasmodium malariae.
 Pel-Ebstein fever- Is a type of fever lasting
for 3–10 days followed by an afebrile period of
3–10 days.
e.g. Hodgkins and other lymphomas.
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20.  Saddle back fever: Initially fever lasts for 2–3
days followed by a remission lasting for 2 days
and the fever reappears and continues for 2–3
days.
e.g. Dengue fever.
 Cyclic neutropenia: Cyclic neutropenia
accompanied with fever occurs every 21 days.
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22. Fever with Relative Bradycardia
1. Typhoid fever
2. Meningitis
3. Viral fever (Influenza)
4. Brucellosis
5. Leptospirosis
6.Drug induced fever
Fever with Exanthems
1.Rash appearing on first day of fever—Chickenpox.
2.Rash appearing on fourth day of fever—Measles.
3.Rash appearing on seventh day of fever-Typhoid. 22

23. DRUG FEVER
• It is prolonged fever and may belong to any febrile
pattern.
• There is relative bradycardia and hypotension.
• Pruritus, skin rash and arthralgia may occur.
• It begins 1–3 weeks after the start of the drugs
and persists 2–3 days after the drug is withdrawn.
• Eosinophilia may be present.
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24. • Almost all drugs can produce fever.
• Important commonly used drugs producing fever are:
Sulphonamide
Procainamide
Penicillins
Iodides
Anti-TB drugs
Propylthiouracil
Methyldopa
Anticonvulsants
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25. • Fever can Subside in the Following Ways
Crisis - Elevated temperature settles down to
the baseline immediately after starting
treatment. It may be accompanied by
diaphoresis, diarrhoea or diuresis, e.g.
Pneumonia.
Lysis : Elevated temperature settles down to
the baseline in a step ladder fashion, after
starting treatment, e.g. Typhoid fever. 25

26. APPROACH TO PATIENT
 Physical Examination:
• Same site should be used consistently to monitor
the temperature
• Active Infection in the absence of fever can be
present in
• Newborns & Elderly
• Chronic Hepatic or Renal failure
• Patients taking Glucocorticoids or Anticytokine
therapy.
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27.  Laboratory Tests
• CBC with Differential Count
• C Reactive Protein
• Erythrocyte Sedimentation Rate
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28. TREATMENT
 Most fevers- self limited infections (viral)
• With holding Antipyretics can be helpful:
• For evaluating the effectiveness of Antibiotic &
• Pattern of certain diseases helpfull for
diagnosis.
• Treat underlying cause of Fever.
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