A teenager with fever and a low blood pressure

A 17 year old boy was admitted in a state of peripheral circulatory failure with cold clammy hands and feet and a blood pressure of 78/60mm Hg. He had been unwell with fever, headache and aches in various parts of his body for 5 days but had not sought medical treatment. He had noticed slight bleeding from his gums when he brushed his teeth. He did not complain of abdominal pain, nausea and vomiting or cough and breathlessness. Initial investigations in the A&E showed that he had a hemoglobin value of 11.2gm/dL, a total white cell count of 4200/uL and a platelet count of 68000/uL. He was diagnosed with dengue shock syndrome and treated intensively with intravenous fluids while the results of further tests were awaited.

Discussion

Can dengue shock syndrome be diagnosed in a patient like this without any obvious excessive bleeding?
Yes, we can. Dengue shock syndrome occurs in Dengue hemorrhagic fever (DHF), not in classical dengue fever. The distinction between these two types of dengue fever does not lie in the degree of bleeding but in the presence or absence of plasma leakage from the vessels. Having said this, I must also state that generally, one expects a greater degree of bleeding in DHF than in classical dengue. 

How do you recognise capillary leakage of plasma in a patient with dengue fever?
The clues to this are: 
1.An increase of 20 percent in hematocrit from the previous value, or the reverse - that is, a fall in hematocrit by 20 percent after hydration is initiated.
2. A pulse pressure less than 20mm Hg 
3. A low serum protein level 

We know that fluids are the mainstay of treatment for dengue shock syndrome. How do you initiate fluids and when will you consider colloid infusions?
Crystalloids - normal saline or dextrose saline or Ringer Lactate - can be initiated at 6ml/kg per hour for 2 hours. If the blood pressure does not increase, we can infuse at 10ml/kg per hour for another two hours. If the BP is still low at this point, colloids (like Dextran 40) can be considered. 

IgM antibodies to the dengue virus are generally detected after 5 days of the illness. Is there any test that can detect the dengue virus in the first one or two days of illness?
Yes, there is a commercial test kit for the NS 1 viral antigen (Non Structural viral protein). This test can help to confirm dengue infection within 24 to 48 hours of the onset of fever.