Critical Care Training, MD - Internal Medicine, MBBS
Dengue - Important Information
Dengue fever is a painful mosquito-borne disease. It is caused by any one of four types of dengue virus, which is transmitted by the bite of an infected female Aedes aegypti mosquito.
Previous dengue infection with similar serotype provides immunity but different serotype causes more severe infection.
Common symptoms of dengue include high fever, runny nose, a mild skin rash, cough, and pain behind the eyes and in the joints. However, some people may develop a red and white patchy skin rash followed by loss of appetite, nausea, vomiting, etc.
Patients suffering from dengue should seek medical advice, rest and drink plenty of fluids. Paracetamol can be taken to bring down fever and reduce joint pains. However, aspirin or ibuprofen should not be taken since they can increase the risk of bleeding.
The risk of complications is in less than 1% of dengue cases and, if warning signals are known to the public, all deaths from dengue can be avoided.
Best test is NS1, specific
Cannot be false +ve
Is + from day 1 to 7 ideally.
If on day 1 is -ve, repeat it next day.
Always ask for ELISA based NS1 tests as card tests are misleading.
IgG & IgM dengue
In a pt with reduced platelets and looking "sick" on day 3 or 4 of illness, a very high titre of IgG with borderline rise in IgM signifies secondary dengue. These pts are more prone to complications.
In primary dengue IgG becomes + at end of 7 days, while IgM is + after day 4.
Immature Platelet fraction (IPF)
A very useful test in Dengue for patients with thrombocytopenia.
If IPF in such a pt is > 10%, despite a platelet count of 20, 000, he is out of danger & platelets will rise in 24 hrs.
If its 6%, repeat the same next day. Now if IPF has increased to 8% his platelets will certainly increase within 48 hrs.
If its less then 5%, then his bone marrow will not respond for 3-4 days & may be a likely candidate for platelet transfusion.
Better to do an IPF even with borderline low platelet count.
A low Mean Platelet volume or MPV means platelets are functionally inefficient and such patients need more attention.
The primary cause of death in patients suffering from dengue is capillary leakage, which causes fluid deficiency in the intravascular compartment, leading to multi-organ failure. Platelet deficiency is not the cause of death in most of the patient suffering from Dengue .
According to International guidelines, unless a patient’s platelet count is below 10,000 or there is spontaneous, active bleeding, no platelet transfusion is required. The outbreak of dengue in the City and Hospital beds are full and families are seen running around in search of platelets for transfusion. However what most people do not realize is that the first line of treatment for dengue is not platelet transfusion. In fact, it does more harm than good if used in a patient whose counts are over 10,000.
At the first instance of plasma leakage from the intravascular compartment to the extravascular compartment, fluid replacement amounting to 20 ml per kg body weight per hour must be administered. This must be continued till the difference between the upper and lower blood pressure is over 40 mmHg, or the patient passes adequate urine. This is all that is required to treat the patient. Giving unnecessary platelet transfusion can make the patient more sick.
“While treating dengue patients, physicians should remember the ‘Formula of 20' i.e. rise in pulse by more than 20; fall of BP by more than 20; difference between lower and upper BP of less than 20 and presence of more than 20 hemorrhagic spots on the arm after a tourniquet test suggest a high-risk situation and the person needs immediate medical attention.”
Read WHO guidelines for further fluid management strategies & Hematocrit monitoring.