In a dengue patient during the critical phase who is in shock, how do I differentiate cold shock from warm shock and what are the recommended fluid resuscitation and vasopressor treatments for each?

Differentiating Cold Shock from Warm Shock in Dengue Critical Phase

In dengue shock, assess capillary refill time, peripheral pulse quality, and extremity temperature: cold shock presents with capillary refill >2 seconds, diminished peripheral pulses, and mottled cool extremities, while warm shock presents with flash capillary refill, bounding peripheral pulses, and warm extremities. 1

Clinical Differentiation

Cold Shock Features

• Capillary refill time >2 seconds with poor peripheral perfusion 1, 2
• Diminished or weak peripheral pulses compared to central pulses 1, 2
• Mottled, cool extremities indicating high systemic vascular resistance 1
• Low cardiac index (<3.3 L/min/m²) with compensatory vasoconstriction 1, 3
• Central venous oxygen saturation (ScvO2) typically <70% reflecting inadequate oxygen delivery 1, 3

Warm Shock Features

• Flash capillary refill (<2 seconds) with rapid blanching 1, 2
• Bounding peripheral pulses with wide pulse pressure 1, 2
• Warm extremities despite hypotension 1
• Low systemic vascular resistance index (<800 dyne·s/cm⁵/m²) with vasodilation 3, 4
• Normal or high cardiac index initially, though may deteriorate 3, 4

Fluid Resuscitation Protocol

Initial Resuscitation (First Hour)

• Administer 20 mL/kg isotonic crystalloid boluses rapidly, repeating up to and over 60 mL/kg until perfusion improves 1
• Monitor for hepatomegaly and increased work of breathing as signs of fluid overload 1
• Correct hypoglycemia and hypocalcemia immediately during resuscitation 1
• Establish vascular access (peripheral or intraosseous initially, then central access if needed) 1

Monitoring During Fluid Resuscitation

• Target capillary refill ≤2 seconds, normal pulses, warm extremities, and urine output >1 mL/kg/h 1
• Maintain normal blood pressure for age as a minimum threshold 1
• Assess ScvO2 >70% if central venous access available 1

Vasopressor and Inotrope Management

Cold Shock Treatment (Low Cardiac Output)

Begin epinephrine 0.05-0.3 mcg/kg/min as first-line therapy for fluid-refractory cold shock to increase cardiac output and improve perfusion 1

Alternative initial approach:

• Dopamine 5-9 mcg/kg/min can be used initially at 15 minutes if shock persists after fluid resuscitation 1
• Add dobutamine up to 10 mcg/kg/min if dopamine alone insufficient 1
• Escalate to epinephrine 0.05-0.3 mcg/kg/min by 60 minutes if dopamine-resistant 1

If cold shock with normal blood pressure:

• Titrate fluid and epinephrine targeting ScvO2 >70% and hemoglobin >10 g/dL 1
• Add vasodilator with volume loading (nitrosovasodilators or milrinone) if ScvO2 remains <70% despite adequate cardiac index 1

If cold shock with low blood pressure:

• Titrate fluid and epinephrine as primary therapy 1
• Consider norepinephrine if hypotension persists despite adequate cardiac index 1

Warm Shock Treatment (Low Systemic Vascular Resistance)

Begin norepinephrine as first-line vasopressor for fluid-refractory warm shock to increase systemic vascular resistance and restore blood pressure 1

Dosing and escalation:

• Titrate norepinephrine to maintain mean arterial pressure (MAP) ≥65 mmHg in adults, age-appropriate MAP in children 1
• Add vasopressin (up to 0.03 units/min) if hypotension persists, to reduce norepinephrine requirements 1
• Consider vasopressin, terlipressin, or angiotensin for refractory warm shock with persistent low blood pressure 1

Catecholamine-Resistant Shock Management

Administer hydrocortisone if at risk for absolute adrenal insufficiency when shock persists despite catecholamines 1

Advanced monitoring targets:

• Maintain normal MAP-CVP (central venous pressure) gradient and ScvO2 >70% 1
• Target cardiac index 3.3-6.0 L/min/m² using advanced hemodynamic monitoring if available 1, 3

Critical Pitfalls and Caveats

Common Errors to Avoid

• Do not delay vasopressor initiation beyond 60 minutes if fluid resuscitation fails to restore perfusion 1
• Avoid excessive fluid administration once perfusion improves, as this increases complications in dengue 5
• Do not use dopamine as first-line in warm shock, as it is ineffective for vasodilation 1
• Recognize hemodynamic evolution: Children may transition between cold and warm shock patterns, requiring frequent reassessment and therapy adjustment 3, 4

Monitoring for Transition

• Reassess hemodynamics every 1-2 hours as dengue shock can evolve from one pattern to another 3
• Four of 21 warm shock patients developed low cardiac index requiring switch to epinephrine in one study 3
• Two of 15 cold shock patients required norepinephrine when systemic vascular resistance dropped 3

Dengue-Specific Considerations

• The critical phase typically occurs 3-7 days after fever onset when plasma leakage is maximal 5
• Monitor hematocrit closely as rising hematocrit with falling platelet count indicates plasma leakage 5
• Avoid excessive crystalloid as dengue shock involves capillary leak, making fluid overload particularly dangerous 5