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What are effect of fever on body?

Fever can have effect on various systems in the body
Effect on cardiovascular system
With every 1°F rise of temperature above 100°F the following changes are observed 
1.The pulse rate increases by 10 
Relative bradycardia means there is no proportionate increase in the pulse rate with rise in temperature
This is seen in 
  • Any viral fever.
  • First week of enteric fever.
  • Sometimes in pyogenic meningitis.
  • Brucellosis and psittacosis
Relative tachycardia there is disprortionate increase in the heart rate compared to rise in body temperature
The rise is more than  10/degree F 
  • Actute rheumatic carditis.
  • Tuberculosis.
  • Diphtheritic myocarditis.
  • Polyarteritis nodosa.
2.High volume pulse and wide pulse pressure is seen in febrile patients because of vasodilatation

Effect of fever on respiratory system 
There is rise in respiratory rate by 4degree F with rise of temperature above 100 degree F
Tachypnea is seen especially in pneumonia

Effect of fever on central nervous system
  • There is headache due to vasodilatation
  • Febrile convulsion can occur especially in children
  • Acute confused state and delirium  may be seen in febrile patients called and is called as toxic encephalopathy
Effect of fever on gastrointestinal system
These manifestations include anorexia. constipation and herpes labialis
These are especially seen in patients with pneumonia and malaria (rare in enteric fever),  

Effect of fever on skin
  • Cutaneous manifestations are seen with fever 
  • Miliaria is due to sweat retention rash
  • Rash in exanthematous fevers link
Dehydration is common in febrile patients due to increased sweating, vomiting and decreased fluid intake.