Dengue Shock Syndrome

Dengue shock syndrome is severe dengue with circulatory failure from plasma leakage, characterised by narrow pulse pressure (20 mmHg or less) or hypotension, cold clammy skin, and delayed capillary refill, together with thrombocytopenia and a rising haematocrit. It usually occurs in the critical phase, around the time of defervescence (day 3 to 7 of illness).

Epidemiology. Dengue infects an estimated 100 to 400 million people each year in tropical and subtropical regions, with severe disease in about 1 to 5% of cases. Risk is higher in secondary infection with a different serotype (antibody dependent enhancement), in children and young adults, in pregnancy, and in those with chronic disease (diabetes, obesity, hypertension, asthma).

Pathophysiology. Viral non-structural protein 1 and cytokine release damage the endothelial glycocalyx, causing increased capillary permeability and plasma leakage into the pleural and peritoneal spaces over 24 to 48 hours. Intravascular volume falls, causing shock and organ hypoperfusion. Thrombocytopenia and coagulation abnormalities lead to bleeding.

The febrile phase (days 1 to 3) has high fever, headache, retro orbital pain, myalgia, rash and positive tourniquet test. The critical phase (days 4 to 7) follows defervescence, with warning signs: severe abdominal pain, persistent vomiting, mucosal bleeding, lethargy or restlessness, liver enlargement over 2 cm, rising haematocrit with rapidly falling platelets, and clinical fluid accumulation.

Shock presents with tachycardia, cold extremities, narrow pulse pressure, then hypotension. Bleeding (gastrointestinal, vaginal), liver failure, encephalopathy, myocarditis and acute kidney injury may occur.

Red flags.

• Abdominal pain, persistent vomiting, bleeding or lethargy at defervescence.
• Narrow pulse pressure, cold extremities or delayed capillary refill.
• Rapidly rising haematocrit with falling platelet count (under 100 x 10^9/L).

Full blood count (leucopenia, thrombocytopenia, haematocrit rise of 20% or more over baseline), liver enzymes (raised aspartate transaminase), albumin, coagulation, urea, creatinine, lactate and glucose. Dengue diagnosis: non-structural protein 1 antigen or nucleic acid amplification testing in the first 5 to 7 days, and IgM antibody after day 5. Ultrasound or radiograph for pleural effusion, ascites and gallbladder wall thickening.

Differential diagnosis. Malaria, leptospirosis, typhoid, chikungunya, Zika, influenza, sepsis (including meningococcal), rickettsial infection and viral haemorrhagic fever.

Principles. Careful fluid replacement matched to leakage, with frequent reassessment. There is no specific antiviral.

Shock resuscitation.

• Isotonic crystalloid (0.9% sodium chloride or compound sodium lactate solution) 10 to 20 mL/kg (500 mL in adults) over 15 to 30 minutes, repeated up to 2 or 3 times, with reassessment of pulse pressure, capillary refill, urine output and haematocrit.
• If shock persists with a high haematocrit, give colloid (albumin 5% or a starch free colloid) 10 to 20 mL/kg.
• If haematocrit falls with unstable circulation, suspect concealed bleeding: transfuse red cells 5 to 10 mL/kg (or 1 to 2 units in adults) and fresh whole blood if available.
• After stabilisation, reduce fluid to 5 to 7 mL/kg/h for 1 to 2 hours, then 3 to 5 mL/kg/h for 2 to 4 hours, then 2 to 3 mL/kg/h, and stop 24 to 48 hours after leakage ends.

Vasopressors and ventilation. Noradrenaline 0.05 to 0.5 microgram/kg/min for persistent shock after adequate volume. Ventilatory support for respiratory failure.

Bleeding. Transfuse red cells for significant bleeding. Platelet transfusion is not given for the platelet count alone, but is used for active major bleeding (platelets under 50 x 10^9/L) or before procedures. Use plasma and cryoprecipitate for coagulopathy and bleeding.

Fever and pain. Paracetamol 500 to 1000 mg every 6 hours (maximum 4 g daily, 3 g with liver involvement). Avoid aspirin and non-steroidal drugs, and do not use corticosteroids.

Fluid overload in recovery (reabsorption phase). Stop IV fluids, give furosemide 0.1 to 0.5 mg/kg IV (adults 20 to 40 mg) for pulmonary oedema, and monitor potassium.

Organ involvement. Treat liver failure (N-acetylcysteine 150 mg/kg IV over 1 hour, then 12.5 mg/kg/h for 4 hours, then 6.25 mg/kg/h), acute kidney injury (early renal replacement therapy if indicated), myocarditis and encephalopathy.

Monitoring. Vital signs every 15 to 30 minutes in shock, haematocrit every 4 to 6 hours (or hourly in shock), platelets daily, urine output (aim for 0.5 mL/kg/h or more), glucose, lactate and liver tests.

Referral and escalation. Intensive care for shock, bleeding or organ failure, and infectious disease specialists. Notify public health. Vector control and bed nets for patients to avoid onward transmission.

Special groups. In pregnancy, close obstetric monitoring and expect higher bleeding risk at delivery. In infants and older adults, calculate fluid carefully. In obesity, use ideal body weight for fluids.