Fever is an elevation of body temperature regulated by the hypothalamus in response to pyrogens. It is a common symptom of infection or inflammation. Fever has various stages as temperature rises and falls, and can be classified by pattern of temperature changes. Fever benefits the immune response by enhancing immune cell activity and inhibiting microbial growth at higher temperatures. Management involves identifying and treating the underlying cause while controlling temperature.

1. FEVER

2. • Most common presenting symptom to
clinician.
• May associated with other symptom eg
chills, rigor ,bodyache, generalised
weakness, headache, anorexia etc

3. • Pyrexia –Greek- pyr meaning fire.
• Febrile- Latin- febris meaning fever.

4. Normal temperature regulation
in body
Normally heat is continuously produced in
body and being lost to surroundings.
Rate of heat production= rate of heat loss,
person is said to be in heat balance.
When there is disturbance of equilibrium
between the two, then body temperature may
rise-fever, or fall-hypothermia.

5. • No single core temperature can be
considered normal, there is always a
range.
Core temperature is normally maintained
within a range of 36.0 C-37.5C(97 F-99.5
F).

7. • At 6 AM 37.0C(98.6 F)
• At 6 PM 37.6 C(99.6F)- increased BMR &
muscle activity.
• An a.m. temperature of >37.2°C
(>98.9°F)
• An p.m. temperature of >37.7°C
(>99.9°F) defines a fever

8. • Normal diurnal variation-1 F
-Temperature
Rectal>Oral>Axillary

9. • Temperature regulation-Preoptic area of
anterior hypothalamus
• Physiological thermostat

12. Factors Determining Rate of Heat
Production
• a. Basal metabolic rate of body
• b. Muscle activity
• c. Effect of thyroid hormones
• d. Effect of epinephrine and
norepinephrine.

13. Method of Heat Loss from Body
• a. Radiation: Loss of heat from body in
form of infrared rays.
• b. Conduction: Heat is conducted from
body to objects in contact with it, e.g.
chair, bed, etc.

14. • c. Convection: Heat is lost from body by
air currents surrounding it.
• d. Evaporation: Evaporation of water
(sweat) from body surface serves as an
important protective mechanism in
reducing body temp.

16. • Fever:- Is an elevation of body
temperature above normal circadian
variation as a result of change in
thermoregulatory centre, located in
anterior hypothalamus.

17. Relation with Pulse, Resp. , BMI
• With every 1°F rise of temp >100 F
Pulse rate increases 10,
Respiratory rate by 4
BMR by 7
Oxygen consumption increases by 13%.

18. Stages of fever
4 successive stages -
1. Prodrome
• nonspecific complaints, mild headache,
fatigue, general malaise, aches and pains.
2. Temperature rises
• generalized shaking with chills and feeling
of being cold
• Vasoconstriction, piloerection precede
onset of shivering
• skin is pale

19. –3. Flush
• cutaneous vasodilation occurs and
skin becomes warm, flushed
4. Defervescence
• Initiation of sweating.

22. Pathogenesis of fever
• Pyrogen-Any substance that cause fever
• Exogenous pyrogens -derived from
outside the patient: microbial products,
microbial toxins, or whole microorganisms

23. Eg - Lipopolysaccharide (endotoxin) of
gram-negative bacteria.
-Enterotoxins of Staphylococcus aureus
They induce host cells, i.e, blood
leukocytes, tissue macrophages to
produce endogenous pyrogens (e.g.,
interleukin-1).

24. Pyrogenic cytokines- include IL-1, IL-4, IL-6,
TNF, ciliary neurotropic factor (CNTF),
IFN-alpha.
Endogenous pyrogens increase set point
hypothalamic thermoregulatory center
through prostaglandin E2.

26. Mechanisms of fever

27. The effects of fever
• Metabolic effects:
– Increased need for oxygen
• Increases heart rate
• Increases respiration
– Increased use of body proteins as an energy
source
– During fever body switches from using
glucose (an excellent medium for bacterial
growth) to metabolism based on protein and
fat breakdown

28. The effects of fever
It enhance immune function
– Increases motility and activity of WBC
– Stimulates the interferon production and
activation of T cells
• Inhibits growth of some microbial agents:
– Many microbial agents that cause infection
and grow at normal body temperatures.

29. Celcius Fareinheit
Hypothermia <35 C <95 F
Subnormal 35-36.7 95-97
Normal 36.7-37.2 98-99
Mild Fever 37.2-37.8 99-100
Moderate Fever 37.8-39.4 100-103
High Fever 39.4-40.5 103-105
Hyperpyrexia >40.5 >105

30. Types of fever
• Continous fever
-Temperature remains above normal
throughtout the day
-Does not fluctuate more than 1 C in 24 hrs.
Eg lobar pneumonia, UTI, infective
endocarditis, brucellosis

31. • Remittent fever
Temperature remains above normal
throughout the day
Fluctuate more than 1 C in 24 hrs.
Eg typhoid ,viral upper respiratory tract,
legionella, and mycoplasma infections

32. • Intermittant fever
Temperature is present for some hours in a
day and remits to normal for remaining
time.
Daily spike-Quotidian
Every alternate day-Tertian
Every third day-Quartan
Eg malaria , kala-azar, septicemia

33. • Hetic/Septic
Temperature variation between peak and
nadir is more than 5 C.
Eg septicemia

34. • Pel Ebstein fever
Bouts of febrile and afebrile periods
Temperature takes 3 days to rise, remains
high for 3 days and remits in 3 days,
followed by apyrexia for 9 days.
Eg Hodgkin lymphoma

35. • Low grade fever
Temperature present daily, mainly in evening
for several days but usually does not
exceed 37.8 C.
Eg tuberculosis

38. • Aseptic fever-
Malignancies
Acute Myocardial Infacrtion
Sarcoidosis,
Chronic renal failure
Collagen vascular diseases
Drug fever
Radiation sickness
Post surgical patients

39. • Drug fever
Prolonged fever
Relative bradycardia and hypotension
Perisist 2-3 days even after drug is
withdrawn
Eg penicillins,procainamide,propylthoiuracil,
sulphonamides,anticonvulsant

40. • Fever with Relative Bradycardia
1. Typhoid fever
2. Meningitis
3. Viral fever (Influenza)
4. Brucellosis
5. Leptospirosis
6. Drug induced fever

41. • Fever with rigors
Malaria
Kala azar
UTI
Septicemia
Infective endocarditis
Collection of pus in body
Lobar pneumonia
Cholangitis
pyleonephritis

42. • Fever with rash
1. Rash appearing on 1st day of fever—
Chicken pox.
2. Rash appearing on 4th day of fever—
Measles.
3. Rash appearing on 7th day of fever—
Typhoid.

43. • Fever with membrane in throat
Diphtheria
Infectious mononucleosis
Agranulocytosis

44. • Fever with delerium
Encephalitis
Tyhpoid
Meningitis
Hepatic encephalopathy

45. Hyperpyrexia
• When body temperature > 105 F.
• Cause
1 Pontine haemorhrage
2 Rheumatic fever
3 Menigococcal meningitis
4 Cerebral malaria
5 Septicimia
6 Enchephalitis

46. Pyrexia of unknown origin
• Persistance of temperature > 101.2 F
• > 3 weeks duration
• Faliure to reach diagnosis even after 1
week of evaluation

47. • Causes
Abcesses- subphrenic/liver/retroperitoneal
UTI
Endocarditis, hepatobiliary infections, osteomylitis
HIV
Parasitic infections
Malignancy
Collagen vascular disease
Factitious fever
Hyperthyroidism
Sarcoidosis

48. • Malignancies associated with PUO
Hodgkin’s disease
NHL
Leukaemia
Hepatoma
Renal cell carcinoma
Ca colon

49. Neuroleptic malignant syndrome
Characterized by-
-Lead pipe muscle rigidity
-Extrapyramidal side effects
-Autonomic dysregulation
-Hyperthermia.

50. Cental D2 receptor blockage - elevated
hypothalamic set point.
Block of nigrostriatel pathway - muscle
rigidity.

51. • Cause
Succinylcholine
Phenothiazines
Haloperidol
Fluoxetine, loxapine
Tricyclic benzodiazepines
Metoclopramide, domperidone

52. Management by cold sponging
Dantrolene(central muscle relaxent)
Drug of choice-bromocriptene