Dual lumen cannula

Overview

Dual lumen cannulae are infrequently used and only serve a small subset of patients requiring VV ECMO support.

Used in patients

• Who are anticipated to mobilise and tolerate the IJ access awake AND are expected to require longer support
• Where maximal venous drainage (connecting both lumens together) is desired with large flow and exclusive neck access

Caution

Dual lumen cannula configuration is not suitable as the initial support if the trajectory and the level of support required for the patient are uncertain.

Only specifics to dual lumen cannula are mentioned here – for general aspects of peripheral cannulation advice see percutaneous cannulation.

The primary use of dual lumen cannulae at the Alfred ICU is in patients with cystic fibrosis who are being commenced on VV ECMO as a bridge to transplantation, facilitating patient mobilisation and allowing chest physiotherapy without movement restrictions.

However, in other patients where mobilisation and no femoral cannulae are desired this is an option. In discussing the advantages and disadvantages for individual patients, the following should be considered

• Femoral cannulae are NOT a contraindication for mobilisation or even to stand the patient up (if this is the main argument to change the configuration).
• Fixation of the cannula to the head requires shaving the hair and a compliant patient once awake
• Maintaining positioning of the cannula is crucial – for extended ECMO support, the neck insertion site is invariably prone to vertical movement and complications over time
• The cost of the cannula
• Overall higher rate of complications related to insertion and maintenance

Cannula specifications

Dual lumen cannula is a single cannula with two lumens. The access lumen of the cannula has two ports: the distal port at the tip and a proximal port at 14.7 cm from the tip. The distal tip needs to be placed in the IVC and the proximal port needs to be in the distal SVC. The return lumen of the cannula has a port at 9.4 cm (from the tip) which needs to be appropriately oriented for it to direct the return blood flow jet into the tricuspid valve. Hence, positioning is much more important with the dual lumen cannula.

Important specifications for the Avalon™ are displayed here:

Note: 27 and 31 Fr have the same insertion length 31cm [C] and distance from tip to infusion port of 9.4cm [F].

Prerequisites

Vessel assessment

Use ultrasound to assess the right internal jugular vein and the contralateral jugular vein to judge potential flow obstruction. Generally, contralateral internal jugular vein DVT is a contraindication, due to the risk of cerebral oedema through reduced venous drainage as the cannula will also block cerebral venous drainage.

If the patient has had long term indwelling catheters in the SVC, angiography needs to be done to rule out any SVC stenosis (not uncommon in CF patients). In SVC stenosis the possibility of stenting by interventional radiology can be explored.

Specific equipment required

• Avalon cannula
• Avalon dilator set with guidewire
• Guidewire exchange catheter
• Amplatz guidewire
• Echo – TOE probe and operator

Transition from femoral VV ECMO

If the patient is already on Femoro-Femoral VV ECMO configuration, the tip of the access cannula is withdrawn slightly and the RPM of the ECMO reduced as much as possible to prevent any inadvertent air embolism during the procedure. This is an important step.

Considerable further caution needs to be taken on insertion of the exchange catheter (sidearm closed) and advancing the actual cannula. At the point of withdrawing the introducer the circuit must be clamped temporarily to flush the cannula. The femoral support is withdrawn once established on double lumen catheter configuration.

Guidewire exchange

Post ultrasound-guided puncture low in the right neck (to allow space to position the cannula later), direct the guidewire into the IVC under TOE guidance (Avoid passing the guidewire into the right ventricle, as this will direct the cannula into the right ventricle with associated major complications).

The exchange catheter is then passed over the guidewire and also visualised in the IVC. It is imperative that the sidearm of the exchange catheter is closed to prevent catastrophic air embolism.

Once the exchange catheter is imaged well in the IVC, guidewire exchange to an Amplatz wire should proceed smoothly. The exchange catheter is then removed.

Dual lumen cannula positioning

The insertion should occur low in the neck to allow enough variation in insertion length (limited to 31 cm). Principles of dilatation are the same as described in the general cannulation section, but special attention to the control of guidewire insertion length is required. Note: only the Avalon dilator set contains the larger dilators up to size 30. These dilators are best dipped in saline as they are silicone and dilatation becomes easier.

Once the dilatation is complete, the metallic stiffener inside the catheter is taken out, the white obturator is coated with saline and reintroduced into the catheter. The catheter is then threaded over the guidewire. Ensure that the return port of the catheter is directed anteriorly while inserting it. This ensures that the return flow is directed towards the tricuspid valve. As the catheter tip enters the vein blood will come out of the SVC port necessitating rapid insertion with the obturator fully inserted. Once all of the catheter ports have entered the vein, the white obturator may be partially removed (up to the black arrow marked on the stiffener).

Note: the obturator could pass through the heart during initial insertion, which is why a stiff guidewire is MANDATORY to reduce the risk of RV perforation. The catheter is then pushed into position with the distal tip positioned in the IVC. This is done under echocardiography guidance, again to avoid right heart injury.

Ensure that the tip is not positioned in the hepatic vein. Once this is done, the access lumen is flushed with heparinised saline (3x) and clamped. See caution above if transitioning from femoral VV ECMO. The return port has a single cap that prevents blood flowing into the return lumen. Once the cap or valve is removed, the return lumen fills with blood retrogradely. A clamp is applied on the return limb and the cannula again flushed with saline. Ensure the cannula appears correctly positioned visually.

Once this is achieved, the return and access ports are connected to the circuit as described previously and ECMO commenced. TOE or TTE is used to see whether the return flow is directed towards the tricuspid valve. If not, adjustment is made under TOE / TTE guidance to ensure that most of the return flow enters the RV via the open tricuspid valve during diastole, thus minimizing recirculation.

TTE confirmation

Transthoracic echo, subcostal view. Confirmation of dual lumen cannula correctly positioned in the IVC and the returning oxygenated blood flows towards the tricuspid valve/right ventricle.

TOE confirmation

Transoesophageal echo, modified bi-caval view. Confirmation of dual lumen cannula correctly positioned in the right atrium and the return blood flow directed towards the tricuspid valve/right ventricle.

Cannula fixation

Post cannulation, a semi-occlusive dressing is applied at the cannulation site, then access and return limbs are wrapped around the patient’s shaved head and secured using Griplocks. It is very important that the cannula does not move during mobilisation afterwards, as even slight migration of the catheter can interfere with optimal delivery of oxygenated blood to the right atrium. Cable ties are applied at the sites where the circuit is connected with the limbs of the cannula. Clean up and documentation is as per usual ECMO cannulation.

Visual inspection of the Avalon cannula can reveal incorrect positioning. In the correct position, the return limb will sit anterior quite aligned with the skin. Also note the caudal migration of the incorrectly positioned cannula.

Recognition of malpositioning

Routine practice of caring for dual lumen cannulae includes vigilance regarding cannula position. Findings prompting revision of cannula position may include:

• Visual assessment, vertical or rotational movement (nursing routine)
• Sudden ALT rise with potential migration and blood flow directed into hepatic veins
• Marked change on CXR in correlation to adjacent organs
• Change of flow dynamics / profile that is not explained otherwise

The Gold standard for confirming correct positioning is echocardiography.