Lecture Summary: Monitoring Patients on VV ECMO

Learning Objectives

  • Understand the goals of VV ECMO monitoring.

  • Systematically assess the patient and ECMO circuit.

  • Identify key parameters to monitor in both patient and machine.

  • Recognize early signs of complications and readiness for weaning.

Principles of VV ECMO Monitoring

  • Monitoring must be divided into three components:

    1. Patient – ICU assessment (organ function, hemodynamics, sedation, fluid balance).

    2. ECMO Circuit – ensuring correct function of pump, oxygenator, and cannulas.

    3. Interaction – harmony between patient’s cardiopulmonary system and ECMO.

  • Multidisciplinary team (nurses, intensivists, perfusionists, surgeons, respiratory physicians) plays a critical role through daily rounds and checklists.

Patient Monitoring

  1. Respiratory System

    • Clinical exam, chest imaging, ventilator settings.

    • Key variables: tidal volume, compliance, gas exchange.

  2. Hemodynamics

    • MAP, HR, fluid status (ultrasound, balance chart, exam).

    • Volume overload → may delay ECMO weaning.

    • Thermodilution is unreliable on ECMO.

  3. Neurological Status

    • Vigilant monitoring for intracranial bleeding, sedation depth, pupillary reactions.

  4. Renal Monitoring

    • Urine output, urine color, interaction with RRT.

  5. Drug Effects

    • Pharmacokinetics altered by ECMO → focus on effect, not just dose.

  6. Hematology & Anticoagulation

    • Daily targets for Hb, platelets, and anticoagulation adjusted to bleeding/thrombosis risk.

ECMO Circuit Monitoring

  • Cannulas: location (radiology + clinical), tip position, migration risks, infection/bleeding/DVT at site.

  • Blood Gases:

    • Pre-oxygenator: represents venous return/CvO₂ (consumption vs drainage adequacy).

    • Post-oxygenator: represents oxygenator function (baseline reference after initiation).

  • Pressures: Pre-pump and post-oxygenator pressures for circuit integrity.

  • Alarms: Set high/low flow alarms early for safety.

Patient–ECMO Interaction

  • Gas exchange depends on 3 components:

    1. Oxygenator performance.

    2. Native lung contribution (from full shunt → partial recovery).

    3. Proportion of undrained venous blood mixing with ECMO return.

  • ABG monitoring:

    • Arterial blood gas = final interaction of patient + ECMO.

    • Compare with pre- and post-oxygenator gases to troubleshoot.

Complications to Detect Early

  • Cannula displacement or malposition.

  • Bleeding (internal/external).

  • Oxygenator dysfunction (falling post-oxygenator PaO₂).

  • Infection or clot formation.

Key Takeaway Framework (ABC of Monitoring)

  • A – Assess the patient.

  • B – Assess the ECMO circuit.

  • C – Assess their interaction.

Conclusion

Monitoring VV ECMO patients requires:

  • Continuous vigilance,

  • Structured assessment (patient, circuit, interaction),

  • Multidisciplinary collaboration,

  • Early recognition of complications and recovery to guide management and weaning.

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