Key Learning Points
1. ECMO Blood Flow Depends on Venous Return
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ECMO blood flow is preload-dependent.
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Venous return = (Mean systemic filling pressure – Right atrial pressure) / Resistance.
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Determined by venous tone, intravascular volume, cannula position/diameter, and pump speed.
2. Chattering: Causes and Interpretation
Chattering (cannula swing or collapse) occurs when venous return is insufficient for set pump speed. Causes include:
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Hypovolemia (absolute or relative)
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Cannula malposition
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High intrathoracic/intra-abdominal pressures
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Patient-ventilator asynchrony or agitation
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Circuit thrombus or obstruction
3. Management Algorithm
Step 1: Decrease pump speed — “low and slow” approach to avoid suction and hemolysis.
Step 2: Inspect circuit and cannula — confirm no kinks, clots, or malposition.
Step 3: Optimize sedation — reduce coughing, straining, or spontaneous breaths if premature.
Step 4: Address mechanical complications — rule out tamponade, pneumothorax, IAH.
Step 5: Consider fluid bolus — only if other causes excluded.
Step 6: Add drainage cannula — in refractory cases, increase drainage capacity
Volume Resuscitation: Rational Approach
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Avoid reflex fluid boluses for chattering.
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Clinical signs
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Lactate
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TTE/echo
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Passive leg raise (PLR)
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Capillary refill time (CRT)
Evaluate need based on:
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Start with crystalloids (e.g., Ringer’s or NS).
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Albumin and PRBCs only in specific indications.
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Avoid excessive fluid — positive fluid balance on ECMO day 3 correlates with increased mortality.
Fluid type:
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Special Scenarios Discussed
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Double-lumen cannula: Requires meticulous positioning due to single drainage port.
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Septic patient on VV ECMO with high flow needs: Consider VVA configuration or adding drainage cannula.
Final Message
Chattering ≠ immediate fluid bolus.
Use a structured, physiological approach.
Tailor interventions based on timing, aetiology, and patient-specific context.