Dengue Hemorrhagic Fever

Dengue haemorrhagic fever is dengue infection with the four defining features of fever lasting 2 to 7 days, haemorrhagic tendency, thrombocytopenia (platelets 100 x 10^9/L or less) and objective evidence of plasma leakage (haematocrit rise of 20 percent or more, pleural effusion, ascites, hypoalbuminaemia). It is graded I to IV, with grades III and IV constituting dengue shock syndrome.

• Occurs mostly in secondary infection and in children, but affects adults and pregnancy.
• Caused by four serotypes transmitted by Aedes mosquitoes.

High fever, headache, retro orbital pain, myalgia, positive tourniquet test (20 or more petechiae in 2.5 cm square), petechiae, epistaxis, gum bleeding, melaena, hepatomegaly; plasma leakage appears as fever falls.

• Grade I: positive tourniquet test only; grade II: spontaneous bleeding; grade III: circulatory failure with narrow pulse pressure under 20 mmHg; grade IV: profound shock with unrecordable pressure or pulse.
• Differential diagnosis: malaria, typhoid, leptospirosis, meningococcaemia, Rift Valley fever and other haemorrhagic fevers, immune thrombocytopenia, leukaemia, sepsis, hepatitis, measles.
• Complications: shock, major haemorrhage, disseminated intravascular coagulation, fluid overload, hepatic and renal failure, encephalopathy, death.

Laboratory confirmation plus warning signs.

• NS1 antigen or PCR in the first 5 days; IgM from day 5; four fold rise of IgG in paired sera.
• Serial full blood counts and haematocrit (twice daily in the critical phase), liver enzymes, albumin, electrolytes, creatinine, coagulation tests, blood group and crossmatch.
• Ultrasound (gallbladder wall thickening, ascites, pleural effusion), chest radiograph.

Manage by grade with early fluids for leakage and prompt shock correction.

• Supportive: admission for grade II to IV and for any patient with warning signs, frequent monitoring of vital signs, haematocrit and urine output, rest, oral fluids (oral rehydration solution, juice, milk 50 mL/kg/day extra), avoid aspirin, NSAIDs and intramuscular injections.
• Pharmacological: paracetamol 10 to 15 mg/kg (adults 1 g) every 6 hours for fever. Grade I and II: oral fluids; IV Ringer lactate 5 to 7 mL/kg/h for 1 to 2 hours if haematocrit rising or intolerance of oral intake, then 3 mL/kg/h and reduce. Grade III and IV shock: Ringer lactate or 0.9 percent sodium chloride 10 to 20 mL/kg over 15 minutes (adults 500 mL), repeat up to 2 times; if still shocked with high haematocrit, give colloid 10 mL/kg (albumin or dextran 40) and reassess; if haematocrit has fallen, give packed red cells 5 to 10 mL/kg for concealed bleeding. Fresh frozen plasma 10 mL/kg for coagulopathy with bleeding; platelet transfusion for life threatening bleeding only. Omeprazole 40 mg IV daily for gastrointestinal bleeding. Furosemide 0.5 mg/kg IV for fluid overload after shock resolves.
• Procedures: arterial and central lines in refractory shock; ventilation for respiratory failure; avoid nasogastric tubes when possible, and avoid pleural or peritoneal drainage.
• Special groups: pregnancy, close obstetric monitoring and blood product availability, avoid tocolytics; infants and young children, accurate weight based fluids; elderly and cardiac disease, cautious volumes; haemoglobinopathy, avoid excessive transfusion.
• Red flags: pulse pressure under 20 mmHg, cold extremities, haematocrit rise with falling platelets, persistent vomiting, abdominal pain, bleeding, oliguria, altered consciousness.
• Follow-up: monitor 24 to 48 hours after defervescence; convalescent rash and fatigue are common; discharge when afebrile for 48 hours with improving platelets and stable haematocrit.