What are the clinical criteria to distinguish dengue shock?

Distinguishing Dengue Shock Syndrome

Dengue shock syndrome is distinguished by the presence of all dengue hemorrhagic fever criteria (thrombocytopenia, hemorrhagic manifestations, and plasma leakage) plus hypotension or narrow pulse pressure (<20 mmHg). 1, 2

Clinical Criteria for Dengue Shock

The diagnosis requires meeting all of the following components:

Core Hemodynamic Criteria

• **Systolic blood pressure <90 mmHg** for >30 minutes, OR
• Pulse pressure <20 mmHg (narrow pulse pressure is the defining feature distinguishing shock from dengue hemorrhagic fever alone) 1, 2, 3
• These hypotensive parameters must persist despite initial fluid resuscitation 4

Required Underlying Features (Dengue Hemorrhagic Fever Criteria)

• Thrombocytopenia (platelet count typically <100,000/mm³) 1, 3
• Evidence of plasma leakage, demonstrated by:
  • Rising hematocrit (≥20% increase from baseline) with concurrent thrombocytopenia 1, 3
  • Pleural effusion on chest radiograph 3
  • Ascites or thickened gallbladder wall on ultrasound 3
• Hemorrhagic manifestations (minor or major bleeding phenomena) 1, 3

Signs of End-Organ Hypoperfusion

• Cold, clammy extremities or livedo reticularis 4
• Capillary refill time ≥3 seconds 4
• Altered mental status (lethargy or restlessness) 1, 2
• Urine output <0.5 mL/kg/hour 2
• Elevated lactate >2 mmol/L 4

Distinguishing Dengue Shock from Other Shock States

Dengue shock behaves differently from bacterial septic shock and requires distinct management considerations 4:

Key Differentiating Features

• Plasma leakage is the primary mechanism in dengue shock (not distributive vasodilation as in septic shock) 5, 6
• Hemoconcentration with rising hematocrit is pathognomonic for dengue shock and distinguishes it from dengue fever with bleeding 3
• Timing: Shock typically occurs around days 3-7 of illness, coinciding with defervescence (the critical phase) 1
• Microvascular dysfunction: Preliminary evidence shows lower reactive hyperemic index and reduced perfused vessel proportion in severe dengue compared to uncomplicated cases 5

Distinguishing from Dengue Fever with Unusual Bleeding

• Patients with dengue fever may have significant bleeding and mild thrombocytopenia but lack hemoconcentration 3
• Absence of plasma leakage evidence (no rising hematocrit, no effusions) excludes dengue shock syndrome 3

Warning Signs Preceding Shock

Recognition of warning signs allows intervention before progression to shock 1, 2:

• Persistent vomiting 1, 2
• Severe abdominal pain or tenderness 1, 2
• Clinical fluid accumulation (ascites, pleural effusion) 1
• Mucosal bleeding 1
• Hepatomegaly >2 cm 1
• Hematocrit rise concurrent with rapid platelet decline 1, 2

Critical Pitfalls to Avoid

• Do not wait for blood pressure collapse: Narrow pulse pressure (<20 mmHg) is an earlier and more sensitive indicator than absolute hypotension 1, 2
• Do not confuse with "severe febrile illness": The FEAST trial definition (impaired consciousness, respiratory distress with impaired perfusion) is broader and includes conditions where fluid boluses may not be beneficial 4
• Avoid over-resuscitation: Dengue shock requires careful fluid management with frequent reassessment, as excessive fluids can worsen outcomes given the underlying plasma leakage pathophysiology 4, 2
• Monitor for recurrent shock: The compensatory reserve index can predict recurrent shock within 12 hours (cutoff 0.4 provides sensitivity 0.66, specificity 0.86) 7

Initial Management Once Diagnosed

When dengue shock is confirmed, administer an initial fluid bolus of 20 mL/kg with subsequent patient reassessment 4, 2. Consider colloid solutions for severe shock when available, though evidence is limited 2. Continuous monitoring with cardiac telemetry and pulse oximetry is recommended 2.