Approach to FEVER

Dr.Bilal Natiq Nuaman

Lecturer at Ibn-Sina Medical College

C.A.B.M. ,F.I.B.M.S. ,D.I.M. ,M.B.Ch.B.

2013-2014

Thermoregulation

• Because Temperature affects how the enzymes work in your

body , People should maintain a normal body temperature of

about 37°C despite wide variations in both their metabolic

activity and the temperature of their environment. Enzymes are

proteins that catalyze chemical reactions in living cells.

• Almost all enzymes have an "optimal" temperature. For

example, most human derived enzymes will function best at

around 37 ° C .If it gets too hot or cold the enzymes might

denature and lose the shape of their active site, which means

the substrate may no longer fit and this decreases the rate of

the chemical reactions.

HOMEOSTASIS

• The body keeps its core temperature constant at about 37 C by

physiological adjustments controlled by the hypothalamus

(Thermostat Center) where there are neurons sensitive to

changes in skin and blood temperatures. The temperature-

regulating centers are found in the Preoptic Area (the anterior

portion of the hypothalamus). This area receives input from

temperature receptors in the skin and mucous membranes

(Peripheral Thermoreceptors) and from internal structures

(Central Thermoreceptors), which include the hypothalamus

itself.

Normal Features of Body

Temperature

1-the mean oral temperature is 36.8° ± 0.4°C

2-The normal diurnal variation is typically 0.5°C

(6 A.M. readings < 6 P.M. readings by 0.5 °C)

Fever

definition:-

Fever is an elevation of body temperature that exceeds the normal daily range and occurs in conjunction with an increase in the hypothalamic set point—for example,from 37 ˚ C to 39 ˚ C .

an A.M. temperature of >37.2 ˚ C(98.9F ) or a P.M. temperature of >37.7 ˚ C (99.9F)

Mechanisms of fever• (1) Exogenous pyrogens (micro-organism , toxin …)

induce host cells, such as blood leukocytes and tissuemacrophages, to produce fever-producing mediatorscalled Endogenous pyrogens (e.g., interleukin-1).

• (2) resetting of hypothalamus thermostatic set point to ahigher level through the action of prostaglandinE2.(prodrome);

• (3) generation of hypothalamic mediated responses thatraise body temperature (chill);

• (4) development of fever with elevation of body to newthermostatic set point;

• (5) production of temperature lowering responses(defervescence-sweating) and return of bodytemperature to a lower level.

• Exogenous pyrogens induce host cells, such as bloodleukocytes and tissue macrophages, to produce fever-producing mediators called endogenous pyrogens (e.g.,interleukin-1).

• The endogenous pyrogens mediate a number of otherresponses. For example, interleukin-1 is aninflammatory mediator that produces other signs ofinflammation, such as leukocytosis, anorexia, andmalaise.

• The phagocytosis of bacteria and breakdown products ofbacteria that are present in the blood lead to the release ofendogenous pyrogens into the circulation.

• The endogenous pyrogens are increase the set point of thehypothalamic thermoregulatory center through the actionof prostaglandin E2.

• In response to the sudden increase in set point, thehypothalamus initiates heat production behaviors(shivering and vasoconstriction) that increase the corebody temperature to the new set point, and fever isestablished.

This shift of the set point from “normothermic” to

febrile levels very much resembles the resetting of

the home

thermostat to a higher level in order to

raise the ambient temperature in a room.

Benefits of fever

• 1-It enhance immune function;

• Increases motility and activity of the white blood cells

(T cells and B cells ).

• Stimulates the interferon production .

• Increase phagocytic activity

• 2-Inhibits growth of some microbial agents:

• Many of the microbial agents that cause infection grow

best at normal body temperatures, and their growth is

inhibited by temperatures in the fever range

Adverse effects of fever• Dehydration occurs because of sweating.

• Metabolic effects:

• Increased need for oxygen (13 % for every 1 ˚ C increase

in body temp.).

• Increases the heart rate (10 /min. for every 1 ˚ C increase

in body temp.).

• Increases the respiration rate (4/min. for every 1 ˚ C

increase in body temp.).

• Increased use of body proteins as an energy source

(catabolism)

• With prolonged fever, there is increased breakdown of

endogenous fat stores .(metabolic acidosis)

• Precipitates febrile convulsions

Some Features of Fever

Relative bradycardia:(rising of HR <5 /min. for each 1˚C rise )

Causes : Typhoid,Brucellosis,Leptospirosis,and Factitious fever

Relative tachycardia (rising of HR >15/min. for each 1˚C rise )

Causes :Myocarditis, rheumatic fever

Reversed diurnal pattern :(AM Temp. >PM Temp.)

Causes: Typhoid , disseminated TB

Failure to have fever

Cause: Elderly,CRF,Corticosteroid

components of fever

1-Onset of fever : (warming – chill phase )

Sudden rise : pneumonia,malaria,meningitis (associated with oral herpes simplex).

Gradual rise : typhoid fever (step-ladder) .

2-Main (pattern-plateau phase)

Continuous: fever does not fluctuate more than 1˚C during 24hrs, but at no time touches the normal.e.g.pneumonia,typhoid fever, urinary tract infection, brucellosis

Remitent : daily fluctuations exceed 2˚C but at no time touches the normal.

It is associated with viral upper respiratory tract, legionella, and mycoplasma infections

Intermittent : fever reaches normal level

Quotidian :wn. Paroxysms of fever occur daily(P.Falciparum)

Tertian : wn. Paroxysms of fever on alternate days(P.Vivax,Ovale)

Quartan :every 72 hrs (P.Malaiae)

3-End of fever :

Crisis (sudden reduction ){associated with sweating}

e.g. pneumonia

Lysis ( gradual reduction)

e.g. Typhoid

Approach to patient with fever • 1- History taking

1)Onset (sudden vs. gradual)

2) grade (High vs. low grade)

Low grade : temp.<38.5 , not associated with rigor (but chills ) ,

relieved by antipyretics or sponging , not interfere with usual

activity .

High grade : temp.>38.5 , associated with rigor and sweating , not

relieved by antipyretics or sponging , interfere with usual

activity.

• Rigors.

profound chills accompanied by chattering of the teeth and severe shivering, implies a rapid rise in body temperature. Can be produced by :

• 1) brucellosis , malaria , pyelonephritis , Pneumonia

2) abscess ,cholangitis , septic arthritis

3) lymphoma

3)Duration of the fever

4)Fever pattern (Remittent fever, Intermittent, continuous fever)

5)Timing (through out the day, at night, day time)

6)Severity

interfere with sleep , interfere with usual activity

7)Relieving and aggravating factors

8)Treatment received or/and outcome

9)Associated symptoms

Complete review of systems a) Upper respiratory tract infection (sore throat, coryza)

b) Lower respiratory tract infection (cough, chest pain,

shortness of breath)

c) GIT symptoms (diarrhea; watery or mucous, abdominal pain,

constipation)

d) GUT (Pain on micturation, hesitancy, urgency)

e) Skin lesion (rash, infection), night sweat.

f) Musculoskeletal pain,

Excessive sweating.

Night sweats are characteristic of tuberculosis, brucellosis , endocarditis ,lymphoma

Drug and allergy History

Drug fever is a disorder characterized by a febrile response coinciding temporally with the administration of a drug in the absence of underlying conditions that can be responsible for the fever. A key feature that differentiates drug fever from fever of other causes is that it disappears once the offending drug is discontinued. Drug fever tends to be a diagnosis of exclusion, often suspected in patients with otherwise unexplained fevers.causes :

antibiotics (penicillin) ,anticonvulsants(phenytoin) , and some cardiac drugs

Blood transfusion.

Immunization and vaccinations .

Personal and Social History

• Smoking history - amount, duration & type

• Alcohol history - amount, duration &type

• Occupation, social & education background, family social support& financial situation, Social class.

• Home conditions-Water supply, Sanitation status in his home & surrounding, Geographic area of living, fresh-water swimming.

• Animals / birds in his/her house- exposure to birds (psittacosis) or animals (,avian flu , toxoplasmosis, brucellosis, rabies….)

• Consumption of unpasteurized milk or milk products (tuberculosis, brucellosis and Q fever).

• Sexual History- Unprotected exposure to sexual partner with

STD, HIV,syphilis…

• Illicit drug usage- injections and sharing of needles (HIV,

hepatitis B &C, infective endocarditis), site of injection (e.g

Femoral vein-septic arthritis, ilio-psoas abscess)

Travel History

Travel to an area known to be endemic for certain disease:

• Name of the area, duration of stay

• Onset of illness- (incubation period)

If the patient has been in an endemic area

The most common diagnoses :

Malaria, Typhoid fever, Viral hepatitis .

2-Complete Physical Examination

FEVER AND SKIN RASH (EXANTHEM)

o DAY1 Chicken pox

o DAY2 Scarlet fever

o DAY3 Rubella

o DAY4 Measles

o DAY5 Typhus

o DAY6 Typhoid

(rose spot)

FEVER AND MUCUS MEMBRANE RASH

(ENANTHEM)

• Koplik's spots in measles

• Forchheimer spots in rubella

• FEVER AND LYMPHADENOPATHY

Brucellosis

Cytomegalovirus

Epstein-Barr virus

Human immunodeficiency virus(AIDS)

Lymphoma

Syphilis (secondary)

Toxoplasmosis

Fever and Jaundice :

Cholangitis , Hepatic abscesses, Malaria , Viral

hepatitis , Yellow fever

• Fever and pulmonary involvement :

Influenza

Pneumonia

Severe acute respiratory syndrome (SARS)

3-Full Investigations

Lab.

A-Bld.film :

1-DÖhle bodeis , toxic granulation , band form : bacterial inf.

2-neutropenia :viral inf.,SLE ,typhoid , brucellosis , and b.marrowinfiltration(lymphoma,TB,leukemia

3-lymphocytosis : typhoid , brucellosis , TB ,viral inf.

4-Atypical lymphocyte :viral inf.

5-monocytosis: typhoid , brucellosis , TB ,lymphoma

6-eosinophilia : drug reactions ,hodgkin s dis.,adrenal insufficiency

7-thich and thin bld film for malaria

B-Biochemical

urea and electrolytes, liver function tests (LFTs), blood glucose ,

GUE, GSE,

Sputum for routine microscopy and culture, and microscopy and

culture for mycobacteria ,

Culture of blood , urine .

inflammatory markers, erythrocyte sedimentation rate (ESR) and

C-reactive protein (CRP)

autoantibodies, including antinuclear antibodies (ANA)

C- Radiology

CXR, Abdominal US , Echocardiogram , CT/MRI of thorax and

abdomen

Treatment of fever

Fever must be reduced in some groups of patients :

1- Patients with preexisting cardiac disease (IHD)

2- Patients with cerebrovascular disease

3- patient with preexisting pulmonary disease

4-Children with a history of seizure

5-Pregnants

6-Elderly.

Oral aspirin and NSAIDS (paracetamol, ibuprufen …)

effectively reduces fever.

Also reduce systemic symptoms of headache, myalgias,

arthralgias due to reduction of PGE2 production.

Questions??

Thank you