How to “Ace the Avalon”!

Author: Dominic Strachan
Peer reviewers: Aidan Burrell, Chris Nickson

Everything ECMO 021

A 35-year-old male with Pulmonary Fibrosis is admitted to ICU with rapidly deteriorating hypoxia. He does not improve with high-flow nasal oxygen and requires to be intubated. The patient is well known to the transplant team and is on the transplant list. VV-ECMO as a bridge to transplant is planned.

Q1. What are the options for cannulation in this patient?

VV-ECMO at the Alfred is usually initiated with the fem-fem configuration (see Everything ECMO 010: Keep calm and cannulate!). Other options include Femoral-Jugular cannulation, or a single vessel approach using a Dual-Lumen ECMO cannula (Avalon Elite® Bi-Caval Dual Lumen Catheter, Maquet).

It may be possible to insert femoral guidewires under local anaesthetic prior to intubation in case he becomes impossible to adequately oxygenate after induction, in which case he can be “crashed on” to VV ECMO. However, this depends on time and skill mix available and is not routine.

Q2. What is the benefit of using a dual lumen cannula in this patient?

ECMO as a bridge to transplant is a controversial technique, and patients are at risk of significant deconditioning in the time period spent waiting for suitable donor organs to become available. A dual lumen cannula inserted via the internal jugular vein may allow patients to not only wake from sedation and be extubated, but also mobilise and engage in physiotherapy in an effort to minimise the deconditioning process.

Q3. What are the main features of the Avalon Elite ECMO cannula?

The Avalon Elite® Bicaval Dual Lumen Catheter (DLC) is constructed of polyurethane/silicon and reinforced with stainless steel, making it flexible, kink-resistant and radio-opaque.

Avalon Elite Cannula

Avalon Elite® Cannula. Image source: Maquet. (Click image for source)

 

It is inserted via the right internal jugular vein, and exists in a range of sizes from neonatal to adult. It has drainage holes in the superior and inferior venae cavae, and a return hole which sits in the right atrium, and directs oxygenated blood across the tricuspid valve.

Avalon Elite bicaval dual lumen cannula in correct position. From Hirose et al, 20012. (Click image for source)

Avalon Elite® bicaval dual lumen cannula in correct position. From Hirose et al, 2012. (Click image for source)

Q4. What are the pros and cons of Avalon cannula insertion?

Pros:

  • Single vessel puncture
  • Potentially easier mobilisation and physiotherapy
  • Less recirculation

Cons

  • Reduced peak blood flows, especially in smaller sizes (23Fr and 27Fr)
  • Use limited to the right internal jugular vein (unable to use if this vessel is thrombosed, stenosed or has an overlying infection)
  • Contraindicated in superior vena cava stenosis (more common with long-term indwelling catheters)
  • Sensitive to changes in position (even small movements can reduce performance)
  • Insertion requires extra equipment and expertise (Image intensifier, transoesophageal echocardiography capability)

Q5. You decide to cannulate the patient using a dual lumen cannula. What size of Avalon cannula will you choose?

Typically, the largest cannula which can safely be inserted into the vessel will be used, in order to maximise the fraction of the cardiac output which enters the ECMO circuit.

The cardiac output can be estimated in various ways including with echo, and may be significantly increased from normal in patients requiring VV-ECMO. A 31F Avalon Elite® cannula will achieve up to 5-6L/min blood flow, and will usually be suitable for an average sized adult male. A 27F can achieve 4-5L/min and may be suitable for smaller male patients or females, depending on body size and estimated cardiac output.

Q6. What are the important differences between cannulation with an Avalon cannula and fem-fem cannulation?

Avalon Elite® cannulation requires the use of several techniques that differ from usual femoral or IJV cannulation, and it should always be done with continuous imaging of the wire. This can be done with trans-oesophageal echocardiography (TOE), obtaining a bicaval view at mid-oesophageal level (see Echo-guided bi-caval dual lumen ECMO catheter insertion (Avalon Elite®)).

If not available (e.g. during cannulation at a peripheral hospital), the guidewire placement can be viewed using the image intensifier. However; to ensure the optimal direction of the return jet the cannula position should be confirmed with echo as soon as it becomes available.

Q7. Should you use a floppy or stiff wire during the insertion?

Insertion of the Avalon Elite® cannula requires access to the inferior vena cava (IVC) from the right injugular vein (RIJV). The wire, therefore, needs to traverse the SVC and right atrium then enter the IVC.

The guidewire provided with the Avalon Elite® cannula is relatively soft and pliable – making it difficult to manipulate and also prone to migrating into the right ventricle. This can lead to the sharp introducer of the catheter being directed into the right ventricle, resulting in catastrophic RV perforation.

At the Alfred ICU, we initially gain access to the IVC with a floppy wire. We then place an exchange catheter, remove the floppy wire, and introduce a stiff wire into the IVC (e.g. Amplatz Super Stiff™ guidewire, Boston Scientific). This is all completed with continuous imaging as described in question 6.

Q8. How should the cannula be secured?

At the Alfred ICU we advocate a “no-suture” technique to avoid accidental cannula rupture. Instead, we secure all ECMO cannulae with GripLOKs (see Everything ECMO 018:ECMO Cannula Rupture!).

The Avalon Elite® cannula usually needs to be secured up and over the patient’s head and for this reason it may be necessary to shave the head. All pressure points should be padded to prevent pressure injuries.

Q9. What is the correct cannula position once secured?

As shown below, with the return limb positioned anteriorly and slightly rotated towards the patient. If it is rotated around the other way, the return jet will not be directed towards the tricuspid valve.

Daily nursing care of the cannula should also include a measurement from the skin in case the cannula migrates in or out.

Correct Avalon position

Correct position and orientation of the Avalon Elite cannula. Image Source: Maquet (Click image for source).

Q10. What major complication is this patient at risk for during the insertion of an Avalon Elite® with fem fem ECMO already in place? 

Care should be taken when inserting a DLC when femoral access cannulae are already in place (e.g. when existing fem-fem cannulae are to be replaced by a DLC to allow mobilisation). This is because the cannulae will be in very close proximity and the negative pressure created by the existing access cannula can entrain air through the exchange catheters or Avalon Elite® cannula itself, allowing air into the ECMO circuit.

This can cause massive air embolism to the patient, or significant air into the circuit which can cause it to stop (“air lock”) (see Everything ECMO 019: Bad Bubbles and VV-ECMO).

References

  • Banfi C, Pozzi M, Siegenthaler N, et al. Veno-venous extracorporeal membrane oxygenation: cannulation techniques. J Thorac Dis. 2016;8(12):3762-3773. [article]
  • Burrell AJC, Ihle J, Pellegrino VA, Sheldrake J, Nixon PT. Cannulation technique: femoro-femoral. J Thorac Dis 2018;10(S5):S616–23. [article]
  • Hirose H, Yamane K, Marhefka G, Cavarocchi N. Right ventricular rupture and tamponade caused by malposition of the Avalon cannula for venovenous extracorporeal membrane oxygenation. J Cardiothorac Surg. 2012 Apr 20;7:36. [article].
  • Pellegrino V, Sheldrake J, Murphy D, Hockings L, Roberts L. Extracorporeal Membrane Oxygenation (ECMO). Alfred ICU Guideline, 2012.

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“Pink fluid coming up the tube”.. ECMO, LV distention, and more!

Author: Shir Lynn Lim
Peer reviewers: Aidan Burrell, Arne Diehl, Chris Nickson

Everything ECMO 020

A 39-year-old male was commenced on peripheral fem-fem VA ECMO for cardiogenic shock following a late presentation of anterolateral STEMI. His ECMO flows had been stable at 3L/min. On the second day, he becomes progressively more difficult to ventilate and you notice a large volume of pink fluid coming up his endotracheal tube.

A chest x-ray is obtained:

EE 020 CXR

Figure 1. Chest x-ray. (Click to enlarge)

Q1. What are the potential causes?

The X-ray shows an enlarged heart, four quadrant infiltrates, and a multistage access cannula with the tip positioned in the superior vena cava.

Potential causes include acute pulmonary oedema. Other possibilities include primary lung pathologies, such as capillary leak syndromes, aspiration, or possibility ARDS with a high sputum/fluid load.

Given the clinical context and with fluid coming up the ETT, the picture is most suggestive of inadequate left ventricular (LV) unloading and progressive LV failure.

Q2. How will you confirm the diagnosis?

You arrange an urgent echocardiogram.

You look for the following features to confirm your diagnosis of inadequate LV unloading: distended and non-contractile LV, aortic valve opening only intermittently or not at all, bowing of the inter-atrial septum towards the right and severe mitral regurgitation.

Not all features LV distension are present in acute cardiogenic shock secondary to myocarditis or acute myocardial infarction, as LV dimensions remain within normal limits and significant mitral regurgitation may be absent.

EE 020 Echo 1 subcostal

TTE subcostal view of distended left ventricle on VA ECMO.

 

Q3. What are the mechanisms for LV distension?

VA ECMO supports the heart by draining venous blood which leads to a reduction in LV preload, and maintains aortic blood flow which can improve coronary perfusion. However cardiac function may be impaired by VA ECMO through several other mechanisms. There remains ongoing blood return to the LV via the bronchial, thesbesian and pulmonary circulations which are not captured by the circuit. VA ECMO also increases the afterload on the left ventricle via its return cannula pumping blood retrograde into the aorta. In each individual, different factors play a greater or lessor importance, and in a subgroup, inadequate LV unloading results. This can lead to cessation of native blood flow through the heart, LV stasis and LV distention.

Any aortic valve incompetence prior to ECMO tends to worsen with retrograde aortic flow as well, and this also contributes to the reduction in forward flow and left ventricular volume overload and distension.

Q4. What impact does LV distension have on the patient?

  • The distending LV causes a rise in intraventricular pressure and wall tension which can lead to increased oxygen consumption and can worsen ischaemic damage.
  • Increased shear stress to the infarct area could potentially result in ventricular free wall rupture.
  • Stasis in the LV can result in intra-cardiac thrombus formation.
  • Sustained LV distension can lead to severe pulmonary oedema and haemorrhage which can make ventilation almost impossible.

Q5. What can be done acutely?

Interventions include:

  • Increasing PEEP will reduce wall stress on the LV and may further reduce LV preload. It may have to be very high (ie >20cmH20) in order to overcome the extreme elevation in LAP and pulmonary oedema. Clamping the ETT is generally not recommended but has been described in the past to prevent uncontrollable pulmonary oedema from blocking up the ventilator circuit.
  • Increasing inotropic support improves myocardial contractility and promotes LV forward flow.
  • Adjusting ECMO flows may help or may make things worse. For example, increasing ECMO flows will direct a higher proportion of venous return into the circuit, and will reduce systemic venous return through the pulmonary circulation. But this may increase afterload on the LV and exacerbate the situation further.
  • Ensure proper positioning of access cannula in the right atrium. An inappropriately placed access cannula can result in inadequate drainage of the venous system and poor flows.
  • Manage systemic volume overload. If systemic volume overload is contributing to LV distension, this should be addressed by aggressive diuresis or hemofiltration.

TTE and CXR confirmed placement of access cannula in the right atrium. ECMO flows were increased to 3.5L/min. He had been on CRRT due to AKI, with aggressive fluid removal and milrinone was commenced for inotropic support. Despite these measures, pulmonary oedema persisted.

Q6. What other options are available for LV decompression?

Many methods have been described for LV decompression or venting – here are some examples.

Intraaortic balloon pumps

  • IABP reduce the LV afterload and thus potentially help LV ejection and emptying. Several non randomized studies have suggested the association of IABP and improved outcomes in VA ECMO.

Pigtail catheter in the LV

  • The LV can be directly vented through a percutaneous pigtail catheter that is inserted directly into the LV via the aorta and aortic valve. The proximal end is joined to the access limb of the ECLS circuit and usually enters via the femoral vein. Several experimental animal models reported a significant reduction in LV preload, total energy and work when comparing pre- and post-cannula insertion. Results in humans are largely limited to case reports and series. Fumagalli and colleagues described draining blood from the LV via a percutaneously inserted transaortic cannula directly into the femoral artery with normalisation of left heart filling pressures and resolution of pulmonary oedema. Hong et al published a series of 7 adult patients with transaortic catheter venting. They showed that survivors had reductions in LV size and that no procedural complications occurred.

Surgical access cannula in the LV

  • Surgical LV venting can be done via transapical cannulation under direct vision. This option is less attractive in settings where the chest is not already open. In such settings, decision for a centrally inserted vent should be weighed against the risk of bleeding complications due to systemic anticoagulation.

Percutaneous transseptal access cannula                  

  • Percutaneous transseptal venting of the left heart can be achieved via blade balloon atrial septostomy and transseptal cannulation. Due to difficulties in achieving unrestricted left-to-right flow with septostomy, transseptal cannulation is preferred as it is thought to provide better left heart decompression. The disadvantages of transseptal venting include septal injury and possible left-to-right shunt formation. Furthermore, there is no direct LV unloading in the absence of significant mitral insufficiency.

An example is shown of a pigtail catheter inserted into the LV via the transaortic route. This catheter can be incorporated into the access cannula of the ECLS circuit (see diagram below)

EE 020 CXR 2

Pigtail catheter venting the left ventricle (Click image to enlarge)

EE 020 LV vent in ECMO circuit diagram

Figure 3. ECMO circuit diagram showing how left ventricular “vent” can be incorporated in the circuit. In this diagram a transaortic catheter is used. Image from Hong et al, 2016. (Click image for source).

 

The pigtail catheter can be visualised on echo as well:

TTE subcostal view of distended left ventricle with transoaortic pigtail catheter in situ on VA ECMO.

 

EE 020 Echo 3 PLAX pigtail

TTE parasternal long axis view of distended left ventricle with transaortic pigtail catheter in situ on VA ECMO.

Q5. Discuss the likely outcomes for this patient?

There is no established method for assessing adequate LV decompression. Parameters which could be used include resolution of pulmonary oedema on chest x-ray and echocardiograhic indices such as aortic valve opening and left heart chamber dimensions.

Despite some promising methods for the decompression of the LV, many patients do not survive this condition.

At the Alfred ICU we have had cases of successful LV decompression with a pigtail catheter allowing successful bridging to LVAD insertion.

References

  1. Alkhouli M, Narins CR, Lehoux J, Knight PA, Waits B, Ling FS. Percutaneous Decompression of the Left Ventricle in Cardiogenic Shock Patients on Venoarterial Extracorporeal Membrane Oxygenation. J Card Surg. 2016;31(3):177-82. [pubmed]
  2. Baruteau AE, Barnetche T, Morin L, et al. Percutaneous balloon atrial septostomy on top of venoarterial extracorporeal membrane oxygenation results in safe and effective left heart decompression. Eur Heart J Acute Cardiovasc Care. 2018;7(1):70-79. [article]
  3. Fumagalli R, Bombino M, Borelli M, et al. Percutaneous bridge to heart transplantation by venoarterial ECMO and transaortic left ventricular venting. Int J Artif Organs. 2004;27(5):410-3. [article]
  4. Hong TH, Byun JH, Lee HM, et al. Initial Experience of Transaortic Catheter Venting in Patients with Venoarterial Extracorporeal Membrane Oxygenation for Cardiogenic Shock. ASAIO J. 2016;62(2):117-22. [article]
  5. Rihal CS, Naidu SS, Givertz MM, et al. 2015 SCAI/ACC/HFSA/STS Clinical Expert Consensus Statement on the Use of Percutaneous Mechanical Circulatory Support Devices in Cardiovascular Care: Endorsed by the American Heart Assocation, the Cardiological Society of India, and Sociedad Latino Americana de Cardiologia Intervencion; Affirmation of Value by the Canadian Association of Interventional Cardiology-Association Canadienne de Cardiologie d’intervention. J Am Coll Cardiol. 2015;65(19):e7-e26. [article]
  6. Soleimani B, Pae WE. Management of left ventricular distension during peripheral extracorporeal membrane oxygenation for cardiogenic shock. Perfusion. 2012;27(4):326-31. [article]
  7. Weymann A, Schmack B, Sabashnikov A, et al. Central extracorporeal life support with left ventricular decompression for the treatment of refractory cardiogenic shock and lung failure. J Cardiothorac Surg. 2014;9:60. [article]

 

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CICM Second Part Exam Practice SAQs 26042018

As prepared by Chris Nickson, here are the practice written questions from a recent CICM Second Part exam practice session at The Alfred ICU, with recommended reading from Lifeinthefastlane.com’s Critical Care Compendium and other FOAM sources:

Q1.

A 62-year-old male is admitted to the ICU post-operatively having undergone a transthoracic oesophagectomy for squamous cell carcinoma of the oesophagus. The patient was extubated at the end of the operation but requires re-intubation two days post-surgery due to respiratory failure.

 

  1. List the likely underlying causes of respiratory failure specific to this clinical situation (30%)
  2. List the pros and cons of non-invasive ventilation in this clinical situation (30%)
  3. Briefly outline the principles of management of an anastomotic leak in this patient (40%)

Learn more here:

CICM SAQ 2014.1 Q22

Q2.

A 45-year-old woman received a tracheostomy while she recovered from a cerebellar haemorrhage. She has made good progress and is deemed ready for decannulation.

1. What are your criteria for determining readiness for tracheostomy decannulation? (50%)

She develops laryngospasm immediately after decannulation.

2. Outline your approach to the management of this situation. (50%)

Learn more here:

Tracheostomy Decannulation Hot Case

Laryngospasm

Q3.

You are called to the Emergency Department to assist in the management of a 45-year-old man with respiratory distress. He is a known HIV patient with Pneumocystis jiroveci pneumonia and an allergy to sulphonamides.

On examination:

  • Temperature 38.8 C
  • Mucous membranes appear cyanotic Respiratory rate 35/min
  • Heart rate 125/min
  • Blood pressure 90/50 mmHg
  • SpO2 82% on 8L/min oxygen via Hudson mask

ABG

Initial arterial blood gas analysis (ABG) is as follows:

  1. Interpret the ABG report. (20%)
  2. What is the likely diagnosis? (10%)
  3. Outline your management of this patient (70%)

Learn more here:

CICM SAQ 2012.2 Q29

Pneumocystis pneumonia

Haemolytic anaemia

Methaemoglobinaemia

Methylene Blue


You can access all the previous practice questions since 2014 here:
https://docs.google.com/document/d/1_Ta8IvVaVtc5Il7-kJwj6qKGu54OmifJGRUWCXud8dY/edit
See this link on INTENSIVE for exam resources:
http://intensiveblog.com/resources/#3

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