Overview
The Configuration of ECMO refers to the cannula insertion site, type, tip position and size used in a particular mode. Commonly used configurations are described below.
There are many possible configurations due to the numerous possible approaches to accessing venous, arterial and cardiac sections of the circulation. The need to standardise nomenclature describing the configuration of any mode of ECMO has led to a Position Paper from Extracorporeal Life Support Organization (ELSO). The nomenclature used in this guideline is consistent with this Position Paper [1] and a further explanatory article [2].
[1] Conrad, S. A. et al. The Extracorporeal Life Support Organization Maastricht Treaty for Nomenclature in Extracorporeal Life Support. A Position Paper of the Extracorporeal Life Support Organization. Am. J. Respir. Crit. Care Med. 198, 447–451 (2018). [PMID 29614239]
[2] Broman, L. M. et al. The ELSO Maastricht Treaty for ECLS Nomenclature: abbreviations for cannulation configuration in extracorporeal life support – a position paper of the Extracorporeal Life Support Organization. Crit Care 23, 36 (2019). [PMID 30736845]
VV ECMO configurations
Femoro-femoral
Direction of flow is cavo-atrial to minimise recirculation
- The access cannula (long single stage, or multistage) is inserted via the femoral vein with the tip sited to drain blood from the hepatic inferior vena cava (IVC). Usual cannula sizes are 21-25 Fr.
- If a multistage access cannula is used to drain hepatic IVC blood, it is essential that the most proximal side drainage ports are located in the hepatic IVC. This means the tip of the cannula will be sited in the superior vena cava (SVC).
- If a single-stage cannula is used, then the tip must be sited at the inferior cavo-atrial junction.
- The return cannula (long single-stage) is inserted via the contralateral femoral vein with the tip sited within the right atrium. If the tip is advanced too far it will impinge on the interatrial septum. Usual cannula sizes are 21-23 Fr.
- The tip of the access cannula/ most proximal drainage hole is positioned about 5 cm lower than the tip of the return cannula to minimise recirculation.
Note: further description of the VV ECMO cannula position is provided in the procedure section.
Advantages
- Quick to insert (single anatomical region to prepare)
- Easy to secure cannulae
- Circuit pressures will allow connection to Continuous Renal Replacement Therapy (CRRT)
Disadvantages
- Limited maximum flow rates so may require conversion to a high-flow configuration
- Very limited ambulation and specific fixation required
- Risk of cardiac injury if cannulae introduced across the right atrium
Femoro-jugular
Direction of flow is cavo-atrial to minimise recirculation
- The access cannula (multi-stage) is inserted via the femoral vein with the tip sited in the SVC or at the superior cavo-atrial junction. Usual cannula size are 21-25 Fr
- The short return cannula (“arterial”) is inserted into the right internal jugular vein with the tip sited in the lower SVC (i.e. the tips may overlap or be very close without significant recirculation). Blood returning in this direction preferentially flows towards the tricuspid valve and right ventricle, which minimises recirculation. Usual cannula sizes are 19-23 Fr.
- It is also possible to have the access in the jugular position with a single-stage femoral return cannula (tip in the right atrium).
Advantages
- Nearly always can provide adequate support (4-6 L/min) without clinically significant recirculation
- Only two veins occupied
- Circuit pressures will allow connection to CRRT
Disadvantages
- Relatively difficult to secure and dress the jugular return cannula (compared to femoral)
- Requires two sterile fields to be applied during ECMO cannulation
- Specific securing of cannula required for ambulation
High flow
Uses the same bi-femoral cannula configuration as femoro-femoral (see above) with an additional short access cannula (“arterial”) inserted via the right internal jugular vein with the tip sited in the SVC. It is required when single access cannula circuit flow is inadequate to maintain sufficient levels of gas exchange in more severe cases of respiratory failure (i.e. where elevated cardiac output and oxygen extraction significantly exceed circuit delivery).
The optimal position of the tip is established after commencing full circuit blood flow. The tip is withdrawn sufficiently to prevent visible recirculation. Usual cannula sizes are 19-23 Fr. Direction of flow is bi-cavo-atrial to minimise recirculation
Advantages
- Allows higher circuit blood flows as two access cannulae draw patient blood from the great veins (SVC & IVC)
- Augments maximal blood flow by 1-2 L/min but does vary
- Reduces access insufficiency
- Can provide maximal oxygen delivery if configured correctly
- Circuit pressures will allow connection to CRRT
Disadvantages
- Occupies 3 veins
- Relatively complex to secure and dress the jugular cannula.
- Specific securing of cannula required for ambulation
- Side-port on the short (“arterial”) cannula is a potential source of air embolism and must remain tightly sealed during use; it is also a potential source of pressure injury.
Dual lumen cannula
For dual lumen or two-stage single cannula (e.g. Avalon ELITEⓇ Bi-Caval Dual Lumen Catheter) the direction of flow is bi-cavo-atrial to minimise recirculation.
- Single cannula with two lumens for access and return inserted via the right internal jugular vein.
- Two access stages (SVC and IVC)
- Return port emerges between the two access ports and is positioned at the level of the tricuspid valve.
Advantages
- Single vein cannulation
- Allows mobilisation and exercise of lower limbs and potential ambulation
Disadvantages
- Care on insertion to avoid right ventricular placement/rupture and hepatic vein cannulation. The cannula is large (31Fr for adults)
- Optimal positioning of return port towards the tricuspid valve generally requires echo guidance – may be difficult to maintain with head movement
- Difficult to run CRRT via the circuit due to high circuit pressures
- securing cannula to prevent catheter movement (or accidental decannulation) and pressure injury can be challenging
- Higher cost
More information on dual lumen cannulae and insertion.
VA ECMO configurations
Femoro-femoral
Standard Femoro-Femoral
The blood is accessed from the RA and returned to the arterial system through the femoral artery. Contralateral femoral cannulation is favoured to reduce the risk of leg hyperperfusion.
- Access Cannula (multistage) is inserted via the femoral vein with the tip sited within the SVC. Usual cannula sizes are 21-25 Fr
- Return cannula is a short “arterial” cannula inserted via the common femoral artery. This cannula is fully inserted to the taper, with the tip lying in the common iliac artery or lower aorta. Usual cannula sizes are17-21 Fr
- Additional distal perfusion cannula 6 or 8 Fr (“backflow cannula”) is inserted antegrade into the common femoral artery and directed into the superficial femoral artery. It is connected to the side port of the short “arterial” return cannula and adequately secured (link).
Advantages
- Provides full or partial cardiac support
- Can support CRRT circuit connection
Disadvantages
- Specific securing of cannula required for ambulation
- Risk of differential hypoxia with return of spontaneous circulation
- Risk of “A-V re-circulation” with return of spontaneous circulation (low O2 extraction from lower body with high O2 delivery (femoral artery return) associated with high IVC venous O2 saturation). Results in reduced ECMO oxygen delivery to patients.
Emergency Femoro-Femoral
Similar to standard femoro-femoral cannulation but uses smaller cannulae, which are quicker to insert in an emergency. Usual sizes are 19 – 21 Fr multi-stage venous and 15 – 17 Fr arterial return. Contralateral femoral cannulation is favoured to reduce the risk of leg hyperperfusion. The distal perfusion cannula is only inserted after ECMO is established.
Advantages
- Fast to insert
- Used for ECMO-CPR or in peri-arrest patients
Disadvantages
- High circuit pressures (smaller return cannulae) may not support CRRT
- Risk of differential hypoxia with return of spontaneous circulation
- Risk of “A-V re-circulation” with return of spontaneous circulation (low O2 extraction from lower body with high O2 delivery (femoral artery return) associated with high IVC venous O2 saturation). Results in reduced ECMO oxygen delivery to the patient.
Jugular-femoral
Blood is accessed from the RA with a short “arterial” cannula and returned into the arterial system via the femoral artery.
Advantages
- Leaves one femoral side free
- Access blood from RA/SVC. Reduces “A-V re-circulation” and improves O2 delivery
Disadvantages
- Neck cannula more challenging to fixate, particularly in awake patients
- Two sites need to be prepared for cannulation
Femoro-subclavian or Jugulo-subclavian
Blood is accessed from the right atrium and returned to the subclavian artery via a “tunneled” surgical grafted return. Distal subclavian artery banding is often required to mitigate arm hyperperfusion.
Advantages
- Allows longer support times with grafted arterial return
- Allows full lower limb mobility if combined with jugular access
Disadvantages
- Surgical procedure for cannulation and decannulation
- Bleeding from graft site undermining purpose of configuration
- Kinking of graft
High flow
Uses the same bi-femoral cannulation as standard femoro-femoral configuration (see above) with an additional short access (“arterial”) cannula inserted via the right internal jugular vein with the tip sited in the superior vena cava. Usual cannula sizes are 19 – 23 Fr
Advantages
- Used to minimise differential hypoxia when native cardiac function improves in the setting of significant respiratory failure in VA ECMO
- Increasing overall blood flow to improve oxygenation in VV ECMO
Disadvantages
- Additional cannula, with additional risks of infection and bleeding
- Potential for higher line associated thrombosis
LV drainage cannula
An LV drainage cannula is inserted surgically via a left mini-thoracotomy, through the apex of the heart with the tip placed in the mid cavity of the left ventricle. It may serve as a single access in the case of a temporary LVAD or as an LV decompression cannula (second access cannula) in any other VA configuration.
- Lighthouse cannulae are used which have a cone-shape tip with multiple drainage holes.
The apical LV cannula is inserted at the apex of the heart post dilation of the incision, secured with pledgeted sutures and brought out through the skin at the lateral chest wall.
Central ECMO
Uses specialised surgical cannulae. The access cannula is wire reinforced and malleable and is sited within the right atrium via the right atrial appendage. Itis then tunnelled out of the chest and the sternum closed. Usual cannula size is >30 Fr.
The return cannula is Dacron tipped and sewn directly onto the proximal aorta. The cannula is then tunnelled out of the chest and the sternum closed. Usual cannula size is >30 Fr.
Advantages
- Can provide full cardiac and respiratory support
- Not associated with differential hypoxia in the setting of combined cardiac and respiratory failure
- Optimal support for severe cardiac and respiratory failure in the immediate post cardiotomy setting
- Allows sternum to be closed and facilitates standard patient pressure area care
- Can provide support for up to 2 weeks
Disadvantages
- Requires sternotomy for institution and re-sternotomy for decannulation
- Bleeding is more common than in femoro-femoral configuration.
Central: Bypass cannulae
Uses existing bypass aortic and venous cannula which emerge via the open sternum
Disadvantages
- Increased bleeding
- Cannot support the patient safely beyond 3-5 days
- Open sternum prevents standard patient pressure area care
