ECMO circuit rupture!

Author: Chris Nickson
Peer reviewers: Aidan Burrell, Arne Diehl

Everything ECMO 017

You have just arrived at a regional hospital to retrieve a 35-year-old male who has had ECMO initiated. As you receive handover you notice that cable ties are missing from the ECMO circuit junctions.

All of a sudden the tubing ruptures at the site of one of the unsecured junctions.

Q1. Why is the location of the circuit rupture important?

Circuit rupture is a breach in any part of the circuit that results in blood loss from the circuit or air entrainment into the circuit. Which of these effects occurs depends on whether the site of the breach is pre-pump or post-pump.

During pump operation, the pre-pump-head region of the circuit has negative pressure. Any breach will result in rapid air entrainment that will stop (“de-prime”) the pump causing loss of ECMO support and potential massive air embolism.

On the other hand, the post-pump-head region of the circuit has positive pressure during pump operation. Any breach will result in forceful rapid blood loss until the breach is rectified, the pump is stopped or the patient has completely exsanguinated.

pre and post pump circuit pressures

Figure 1. Pre-pump (negative pressure) and post-pump (positive pressure) circuit regions.

 

Q2. What are your immediate actions if the location of the circuit rupture is PRE-pump-head?

This is the approach recommended by the Alfred ICU ECMO guidelines:

  • Clamp circuit and turn off pump. Apply a proximal clamp on the access cannula(e) and a distal clamp on the return cannula. The proximal clamp prevents bleeding from the ruptured circuit. The distal clamp prevents ongoing air embolism and “back bleeding” (retrograde blood flow) when the pump stops.
  • Call for help. Contact ICU Consultant and ECLS Coordinator.
  • If the patient was on VV ECMO, adjust the mechanical ventilation settings to ensure adequate oxygenation and ventilation (whilst ensuring safe lung ventilation)
  • Support the patient’s circulation (e.g. inopressors, ALS measures) if required (particularly important if the patient is on VA ECMO, has severe hypoxia on VV ECMO, or has circulatory collapse from an air embolism)
  • Patient management for air embolism (if required)
  • Exchange the ruptured circuit for a new circuit (see Everything ECMO 012) OR de-air current circuit via oxygenator and circuit ports (much slower!)

The main difference between VV and VA ECMO in this circumstance is that in VV ECMO additional ventilatory support is the priority during the emergency response, whereas additional circulatory support is the priority in VA ECMO.

Q3. What are your immediate actions if the location of the circuit rupture is POST-pump-head?

 

This is the approach recommended by the Alfred ICU ECMO guidelines:

  • If an open tap is the cause of the circuit rupture, it may be possible to rapidly control bleeding by securing the open tap manually and covering the breach. Following this, call for help and review the patient.
  • If bleeding is not controlled (e.g. if the tubing has completely separated at the site of a junction) them immediately clamp the circuit and turn off pump. Apply a proximal clamp on the access cannula(e) and a distal clamp beyond the rupture on the return cannula. The clamps primarily prevent bleeding from both the access and return sites.
  • Call for help and contact the ICU Consultant and ECLS Coordinator
  • If the patient was on VV ECMO, adjust the mechanical ventilation settings to ensure adequate oxygenation and ventilation (whilst ensuring safe lung ventilation)
  • Support the patient circulation (e.g. inopressors, ALS measures) if required (particularly important if the patient is on VA ECMO, had severe hypoxia on VV ECMO, or has circulatory collapse from an air embolism)
  • Repair breach if possible. Unless it is a simple tap or connection this will generally involve an immediate circuit change. If the return cannula or part of it is damaged, recannulation is required (see Everything ECMO 010).
  • Restart ECMO once the breach is repaired or overcome and all clamps are removed

Again, the main difference between VV and VA ECMO in this circumstance is that in VV ECMO additional ventilatory support is the priority during the emergency response, whereas additional circulatory support is the priority in VA ECMO.

Q4. What are the important causes of ECMO circuit rupture?

  • Improperly secured circuit tubing (e.g. cable ties not applied at all junctions, as described in this hypothetical case)
  • Broken or uncapped tap
  • Pump-head inlet and oxygenator inlet or outlet are susceptible to breaking off by external force
  • Accidental puncturing or cutting of ECMO circuit tubing (e.g. with a suture needle or blade (see Everything ECMO 018)

 

Q5. How is ECMO circuit tubing secured at the Alfred ICU?

All connections are secured with cable ties.

First, when making a connection to a cannula or ⅜ connector, ECMO circuit tubing should always be advanced past the second ridge (at minimum). The second ridge on the proximal end of an ECMO cannula is shown below:

ECMO cannula ridges for connection

Figure 2. The proximal end of an ECMO cannula showing ridges for connection.

 

Advancing the tubing over the connector can be helped by lubricating the joint with saline prior, and by gently rotating the tubing around the connector. To reinforce the connection, a cable tie is then applied around the ECMO circuit tubing. This should sit between the most ridges covered by the ECMO circuit tubing, like so:

Cable tie on ECMO cannula

Figure 3. Cable tie correctly place over connection between ECMO cannula and circuit tubing.

Reference

  • Pellegrino V, Sheldrake J, Murphy D, Hockings L, Roberts L. Extracorporeal Membrane Oxygenation (ECMO). Alfred ICU Guideline, 2012.

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