A traveller returning from Phuket with defervescence, abdominal pain and rising haematocrit
Mr Ng, 34, returns to Hong Kong from Phuket five days ago and presents with a four-day history of fever up to 39 °C, retro-orbital headache and severe myalgia. He has been taking ibuprofen for the pain. Today the fever has settled to 37.8 °C and he says he feels better, but he has developed central abdominal pain and has vomited twice. Examination: mild epigastric tenderness, no rebound, BP 108/68 mmHg, HR 96/min, warm peripheries, no rash, no bleeding. Bloods: white cells 3.1 ×10⁹/L, platelets 92 ×10⁹/L, haematocrit 48% (documented baseline 42% two years ago), ALT 120 U/L, AST 160 U/L. Dengue NS1 antigen is positive. He lives with his parents and works as a chef.
1. He says he is over the worst because the fever has gone. Explain what is happening and why this is the dangerous phase.
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The fever settling around day 5 of illness marks the transition from the febrile phase to the critical (plasma leakage) phase of dengue, not recovery. Capillary permeability increases for about 24–48 hours, and this is when shock and bleeding occur. The clues here are a haematocrit that has risen from a baseline of 42% to 48% (haemoconcentration), a falling platelet count, leucopenia, transaminitis, and the warning signs of persistent abdominal pain and vomiting.
The apparent improvement in temperature is expected and is precisely why patients are sometimes inappropriately discharged. He needs admission for observation and serial haematocrit checks, not reassurance and outpatient paracetamol. Explain to him that the next 48 hours are the highest-risk period and that he must report dizziness, cold peripheries, bleeding or worsening pain immediately.
2. Set out your fluid plan and monitoring, including when you would escalate.
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Admit him for intravenous isotonic crystalloid (0.9% sodium chloride or Ringer's lactate) at about 5–7 mL/kg/hour for the first 1–2 hours, then reduce to 3–5 mL/kg/hour, titrated to a urine output of at least 0.5 mL/kg/hour, stable blood pressure and improving perfusion. Recheck the haematocrit every 4–6 hours, along with vital signs, urine output, and liver and renal function.
The aim is the lowest fluid rate that maintains perfusion. If the haematocrit is rising with a narrowing pulse pressure, rising heart rate, or falling urine output, increase the rate and reassess frequently; if shock persists despite crystalloid, consider colloid and involve senior or intensive care staff. Avoid over-resuscitation: once leakage resolves and fever has been absent for 24–48 hours, the haematocrit falls and excess fluid causes pulmonary oedema. Do not give platelet transfusions for a count of 92 without bleeding.
3. Which drugs and procedures must be avoided, and what must be true before he can go home?
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Stop ibuprofen and avoid all NSAIDs, aspirin and intramuscular injections, because of bleeding risk from thrombocytopenia and platelet dysfunction. Use paracetamol for pain and fever, and avoid unnecessary cannulation attempts. Dengue is notifiable in Hong Kong and should be reported to the Centre for Health Protection; he should use mosquito precautions to avoid onward transmission while viraemic.
Discharge is reasonable only when he has been afebrile for 24–48 hours, haematocrit is stable or falling, platelets are stable or rising, there are no warning signs, and he is eating, drinking and passing urine normally. Arrange early review, give written warning signs, and warn him not to take ibuprofen for the muscle aches, which is exactly the mistake he made this time.