Revisiting dengue: Look for rise in hematocrit and not just falling platelets |
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Revisiting dengue: Look for rise in hematocrit and not just falling platelets
Dr KK Aggarwal,  13 October 2018
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Whenever dengue strikes, platelet counts along with shortage of platelets become the high point of discussion and panic sets in. Because it is presumed that platelet transfusion is the main treatment option for dengue. This is not so.


Platelet transfusions are not needed unless the platelet counts are less than 10,000 or there is active bleeding and thickening of blood.


Dengue causes low platelet count, but low platelet count by itself is never dangerous because patients with heart disease, diabetes are prescribed antiplatelets like aspirin, where they have a beneficial effect in preventing thrombotic complications. They are asked to report if they develop bleeding while on antiplatelets. Patients with idiopathic thrombocytopenic purpura (ITP) always have a low platelet count and they live a normal life on medication.


It’s not the platelet count alone with determines the prognosis of a patient of dengue.


More than the falling platelet count, it is the rapidity of fall in platelet count that is important. Even this does not alone is indicative of severity of illness.


Dengue not only causes low platelet count or destroys platelets, it also causes endothelial damage. Capillary leakage manifests as hemoconcentration and leads to increase in hematocrit and/or MCV and this is important. This is a medical emergency because a rising hematocrit means intravascular dehydration, which leads to multiorgan failure, hypotension and death.


Therefore, it is the rise in hematocrit along with rapid fall in platelets, which is the danger sign and is indicative of impending severe dengue.


Here is a simple Formula of 20 to identify high risk patients 


  1. Rise in pulse by 20
  2. Fall in upper blood pressure by more than 20
  3. Rise in hematocrit by more than 20%
  4. Rapid fall in platelets to less than 20,000
  5. More than 20 hemorrhagic spots on the arm in one inch after tourniquet test
  6. Difference between upper and lower BP is less than 20


Start fluid replacement at 20 ml/kg/hour immediately in such patients, and shift to nearest medical center for observation. 



Dr KK Aggarwal

Padma Shri Awardee

President Elect Confederation of Medical Associations in Asia and Oceania   (CMAAO)

Group Editor-in-Chief IJCP Publications

President Heart Care Foundation of India

Immediate Past National President IMA

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