Cardiac arrest on VV-ECMO

Author: Virginia Newcombe
Reviewers: Chris Nickson, Sacha Richardson

Everything ECMO 005

You are in the ICU tea room when an emergency buzzer is activated.

You race into the unit to find that the 26 year-old man from Everything ECMO 001 and 003, who is on VV ECMO for severe ARDS due to influenza, is in cardiac arrest!!!

Q1. How is cardiac arrest defined for VV ECMO?

Sudden loss of native cardiac output during ECMO support, typically due to a dysrrhythmia.

Q2. What are the common rhythm disturbances seen during an arrest in a VV ECMO patient?

  • Ventricular fibrillation or tachycardia
  • Ventricular standstill
  • Asystole

Q3. How does cardiac arrest affect VV ECMO support?

Unlike VA ECMO, where the ECMO circuit flow should maintain organ perfusion even in cardiac arrest, in VV ECMO cardiac output is entirely dependent on native cardiac function. In the event of cardiac arrest there will be no cardiac output and no systemic oxygen delivery. The absence of cardiac output means venous return is similarly affected, causing access insufficiency on the ECMO circuit and impairing VV ECMO flow.

Q4. Should you do chest compressions in a VV ECMO cardiac arrest?

YES!

In a VV ECMO cardiac arrest cardiac compressions must be commenced according to the normal ACLS pathway. With good quality CPR enough venous return can be produced for VV ECMO to continue at low flows.

VV ECMO patients typically have major problems with lung gas exchange so conventional methods to oxygenate will likely fail. Thus it is important to continue ECMO circuit flow, even at low flows, otherwise hypoxaemia will worsen, exacerbating the cardiac arrest and making ROSC (return of spontaneous circulation) less likely.

Q5. What is your approach to management of cardiac arrest in a VV ECMO patient?

Important steps in management of cardiac arrest in a VV ECMO patient include:

  • Call for help
  • Commence chest compressions (100-120/minute)
  • Assess the ECMO circuit flow
    • If there is access insufficiency reduce pump speed (e.g. by 500 rpm increments)
  • Treat specific arrhythmias as per the ACLS pathway
    • VF/VT:
      • rhythm check and defibrillation q2min
      • adrenaline 1mg IV after the 2nd shock then every 2nd cycle
      • amiodarone 300 mg IV after the 3rd shock
    • PEA/asystole:
      • 1mg adrenaline IV immediately then every 2nd cycle
  • Turn up ventilator FiO2 to 1.0 to guard against hypoxaemia if VV ECMO support is inadequate
  • Seek and treat underlying causes

After return of spontaneous circulation (ROSC) ECMO pump speed (RPM), ventilator settings and inotropes/vasopressor support may need to be adjusted.

Q6. What are the important triggers of cardiac arrest in a patient receiving VV ECMO?

Always exclude, or identify and treat, the following important causes:

  • Hyper/hypokalemia
  • Pneumothorax
  • Cardiac tamponade
  • Haemorrhage
  • Air embolus

The patient was established on VV ECMO with an adequate PaO2 three hours prior to the arrest when you took them for a CT scan. However, it seems hypoxia was the trigger.

Q7. What are the likely explanations?

If the patient was previously well supported on VV ECMO then the circuit needs to be carefully checked for problems.

Issues that may cause hypoxaemia in a previously well supported ECMO patient include:

  • Power supply failure
    • the “not-so-subtle” alarm will be a clue to this!
  • Lack of oxygen supply
    • this can occur if the O2 cylinder runs empty after transport and connection of the oxygenator to the wall supply is forgotten
  • Oxygenator failure
    • this is usually a gradual process characterised by gradually decreasing post-oxygenator PaO2 and an increasing pressure drop (the difference between pre-oxygenator pressure and post-oxygenator pressure)
  • Cannula migration
    • causing either low flows or significant recirculation

 

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