Definition
Entry of air in the circuit and potentially the patient.
Emergency intervention
Immediate
- Clamp circuit ideally closest possible to the patient near the return cannula
Significant air has entered the ECMO circuit, it was prevented returning to the patient by applying the clamp in proximity to the return cannula. The air rose subsequently from tubing below the level of the bed to this point.
Effects
Air rapidly enters the negative pressure side of the circuit even with small barely visible openings. The circuit empties (de-primes) the pump-head of blood that will stop the pump if the air bolus is large and result in pump failure (laboratory simulation) or greatly reduce circuit flow. Remaining air and blood in the pump-head will visibly froth. A large number of air bubbles will pass through the oxygenator and eventually overwhelm the oxygenator and enter the patient’s circulation. Within the patient’s circulation, bubbles can collect and can cause cardiac arrest, stop the flow (pulseless electrical activity) in VV ECMO and cause stroke or embolism to any other organ that is perfused by the ECMO blood flow.
Causes
- Circuit rupture/breach pre-pump head
(e.g. cap on the side-port of a jugular cannula during Hi-flow ECMO)
Central line insertion during ECMO
(e.g. during insertion of jugular line for conversion to Hi-flow ECMO)
Decannulation of access (venous) line during ECMO
Response
Immediate
- Clamp circuit and turn pump off
- Apply a distal clamp to the return cannula
- Call for help. Contact ICU Consultant and ECLS Coordinator
- Ask for ECPR circuit as emergency circuit change
Patient management
- Position head down (Trendelenburg position)
- ACLS management Inotropes and vasopressors for hypotension (bubble compression)
- Adequate lung ventilation with 100% oxygen
- Consider aspirating right atrium/ right ventricle (if VV ECMO)
- Consider lignocaine, thiopentone, hypothermia, steroids, mannitol (if VA ECMO)
ECMO circuit management
- Circuit exchange
- Ask for the emergency circuit in the storeroom and perform an emergency circuit change immediately if the patient deteriorates. Do NOT waste time aspirating air if the circuit was overwhelmed by air.
Only in exceptional circumstance de-airing of the existing circuit is recommended
- Small amount of air that is amenable to aspiration
- Patient reasonably stable
- Clarity where the air came from. In case of an unidentified circuit entrainment aspirating air does not solve the problem.
- Remove all clamps except distal clamp on return cannula (PUMP OFF). Remove pump head from pump and rotate pump head outlet at 12 o’clock. Ensure there is no air behind the pump. Attach a Luer Lock 50 ml syringe to venting port distal to the oxygenator and aspirate. Blood from the patient should re-prime circuit. You may, in addition, open the air vent on the oxygenator (YELLOW CAP) for barely visible air, however, this will only be effective very early in the circuit life before fibrin closes up the membrane.