Circuit rupture
Definition
This is a breach in any part of the circuit that results in blood loss from the circuit or air entrainment into the circuit.
Effects
The effects depend on whether the breach involves the circuit before or after the pump head.
Pre pump head circuit rupture
During pump operation, this region has negative pressure and any breach will result in rapid air entrainment that will stop (de-prime) the pump causing loss of ECMO support.
Post pump head circuit rupture
During pump operation, this region has positive pressure and any breach will result in forceful, rapid blood loss until the breach is rectified or the pump is stopped.
Causes
- Improperly secured circuit tubing (cable ties not applied at all junctions)
- Broken or uncapped tap
- Accidental puncturing or cutting of ECMO circuit tubing (e.g. suture needle or blade)
Response Pre pump-head circuit rupture
- Clamp circuit and turn pump off. Apply a proximal clamp on the access cannula(e) and a distal clamp on the return cannula
- Call for help. Contact ICU Consultant and ECLS Coordinator
- Ensure maximal safe lung ventilation (mechanical ventilation settings will need to be increased)
- Support patient circulation (ACLS measures) if required
- Patient management for air embolism (if required)
- Exchange circuit (new circuit) OR De-air current circuit via oxygenator and circuit ports
Response Post pump-head circuit rupture
- Secure any open tap or manually cover breach (if possible)
- If bleeding controlled, call for help and await medical review
- If bleeding is not controlled: Clamp circuit and turn off pump. Apply a proximal clamp on the access cannula(e) and a distal clamp on the return cannula
- Call for help. Contact ICU Consultant and ECLS Coordinator
- Ensure maximal safe lung ventilation (mechanical ventilation settings will need to be increased)
- Support patient circulation (ACLS measures)
- Repair breach if possible. Recannulation (over a guide-wire) will be required if the return cannula or distal perfusion cannula have been breached
- Restart ECMO once breach is repaired or overcome and all clamps are removed
Accidental decannulation
Definition
This is unintended partial or complete removal of either the ECMO access or return cannula from the patient during ECMO support resulting in bleeding or air entrainment.
Effects
There will be bleeding from the cannula insertion site. ECMO support will stop. In VV ECMO, if the respiration is largely supported by ECMO flow (minimal native lung function), this will be associated with severe acute hypoxia, hypercapnia and secondary haemodynamic effects. For VA ECMO organ perfusion and oxygenation will rely on the native cardiac function.
In addition, for:
Access cannula decannulation: air will rapidly enter and extensively de-prime the ECMO circuit and may reach the patient (see air embolism)
Return cannula decannulation
The patient’s blood volume will rapidly be lost from the circuit until the circuit is clamped.
Causes
- Tension on ECMO lines
- Inadequate dressing of ECMO lines
- Failure to monitor line position in day checks
Response
- Clamp circuit and turn off pump
- Call for help. Contact ICU Consultant and ECLS Coordinator
- If Decannulation is partial only: Reinsert cannula (if possible) and wait for medical review
- If Decannulation is complete: Control vessel bleeding with adequate pressure
- Ensure maximal safe lung ventilation (mechanical ventilation settings will need to be increased)
- Support patient circulation (ACLS measures)
- Patient management for air embolism (if required)
- Consider re-cannulation for ECMO (new circuit will be required)
Cannula site bleeding
This is preventable by using meticulous sequential dilatational technique during percutaneous cannula insertion and carefully securing the cannulae to prevent migration. Most commonly, cannula site bleeding is due to an arterial return cannula partially “sliding out”, leaving a narrower part of the cannula at the arterial entry point. Evaluation of arterial cannula site bleeding must include vascular ultrasound to exclude vessel injury, which will require vascular surgical input.
Management options include:
- Fully inserting the cannula to the taper
- Thrombotic (Kaltostat) dressings
- Pressure (sand bag)
- Cessation of heparin
- Vascular surgical review
- Repair and re-cannulation
“Purse-string” suturing should NEVER be attempted by ICU staff due to the risk of vessel or cannula damage and delayed skin necrosis which will complicate any eventual repair.
Dislodged backflow cannula
This is obvious when the cannula is entirely dislodged and there is continuous bleeding from the cannula tip. This can be aborted:
Immediately turn the 3-way tap in the distal perfusion circuit
(or apply an ECMO clamp on the distal perfusion circuit)
AND
Apply pressure over the anticipated entry point of the cannula into the common femoral artery (several centimeters distal to insertion point of ECMO return cannula)
Caution This is much more difficult to detect when this happens silently and the distal perfusion cannula dislodges into the subcutaneous tissue. This is more likely to happen with an increased depth of the SFA and there is also more tissue space to bleed into before becoming clinically apparent.
Do not apply a clamp anywhere on the circuit otherwise the patient will be off support and still continues to bleed through backflow in the arterial cannula.
For an interruption or breakage in the backflow circuit, clamp above and below that point.