Dengue and other arboviral infections: SAQ

This boy has dengue with warning signs progressing into the plasma-leak critical phase. His travel to Bali without mosquito precautions, the defervescence of his fever with clinical deterioration, his abdominal pain, persistent vomiting and lethargy, his rising haematocrit with a falling platelet count, and the positive NS1 antigen together meet WHO 2009 criteria for dengue with warning signs, and his borderline perfusion places him at risk of severe dengue. He needs immediate admission for group B management with titrated isotonic crystalloid and serial monitoring. ^[2]

Question 1 (10 marks)

Outline the WHO 2009 classification of dengue, classify this child, and justify your disposition. (6 marks for the classification and its application; 4 marks for the disposition and the immediate plan.) ^[2]

The 2009 WHO scheme divides dengue into three categories: dengue without warning signs, dengue with warning signs, and severe dengue. Dengue without warning signs is a probable acute febrile illness with two or more supportive criteria (nausea or vomiting, rash, aches, leucopenia, positive tourniquet test) and no warning signs. Dengue with warning signs requires any one of the seven warning signs: abdominal pain, persistent vomiting, clinical fluid accumulation, mucosal bleeding, lethargy or restlessness, hepatomegaly greater than two centimetres, and a rising haematocrit with a falling platelet count. Severe dengue is defined by plasma leakage causing shock or respiratory distress, by severe bleeding, or by organ impairment. ^[2]

This child meets dengue with warning signs: he has abdominal pain, persistent vomiting, lethargy, and the characteristic rising haematocrit with a falling platelet count. He is not yet in severe dengue because he has no shock, respiratory distress, severe bleeding or organ impairment, but his pulse pressure has narrowed to 22 mmHg and his capillary refill is prolonged, so he is at the boundary of compensated shock. A systematic review confirmed that combinations of these warning signs each roughly double the odds of progression to severe disease. ^[3]

The disposition is WHO group B: admission for close monitoring and titrated isotonic crystalloid. The immediate plan is to establish intravenous access, send a baseline full blood count, haematocrit, platelets, electrolytes, liver function, albumin, coagulation, lactate and glucose, repeat the haematocrit every six to twelve hours, monitor perfusion hourly, and titrate fluid (0.9 per cent saline or Hartmann's) at 5 to 7 mL/kg per hour initially, reducing as the haematocrit stabilises. Aspirin and non-steroidal anti-inflammatories are avoided and paracetamol alone is used for fever. ^[2]