ECMO is indicated when there is a reasonable expectation of long-term survival without severe disability, and the risks of less invasive support are considered greater than the risks of ECMO. It is always applied at the discretion of the managing Intensivist or Cardiac Surgeon. All ECMO admissions to ICU are at the discretion of the ICU ECMO Clinical Service.
Selecting the right patient for ECMO at the right time is frequently complex. It involves weighing up multiple different factors (see table below). Team-based decision making, where decisions to commence or withhold ECMO are discussed with senior ECMO-experienced colleagues is essential to ensure maximal success of the program.
Important factors for consideration when initiating ECMO
Diagnosis & clinical state
Reversibility of disease
Duration of disease
Speed of disease progression
Number of organ failures
Need for interhospital transfer
Acute physiology and shock status
Patient age is important, mortality increases and physiologic reserve reduces similar to any other patient in intensive care. Caution to employ ECMO in patients greater than 65 years of age (relative contraindication). We consider age greater than 75 a contraindication.
Body size will make procedures in particular cannulation more difficult. Traversed soft tissue thickness has to be taken into account to determine the actual length of the cannula that is intravascular. This is of particular importance for the distal perfusion cannula.
However, apart from these practical challenges, weight in itself is not a dominant factor. In fact, outcomes may be favourable for respiratory disease requiring VV ECMO. Some obese patients will deteriorate with lesser respiratory disease burden (compared to normal size individuals) due to their reduced respiratory reserve. Obesity may preclude patients with severe chronic heart failure from VA support (as it may exclude long term mechanical support).
Clinical judgment on co-morbidities and their implications for the individual patient is crucial. It is important to assess the chronicity and make an informed bedside assessment analogous to any other intensive care patient.
In general terms, additional advanced chronic organ failures rule patients out for ECMO support. Non-responsive malignancy represents an absolute contraindication.
Reversibility of conditions
Paramount to successful patient selection is a reversible condition where appropriate organ support leads to recovery of the patient. This at times is more challenging to judge and rightly the question about the acuity of the condition and the possibility of underlying chronic disease is a very valuable question.
If the condition is considered to be chronic or an end-stage process of lung or cardiac disease, ECMO requires careful consideration. Patients with preserved overall condition, listed for organ transplantation, clear communication with the patient and the involved specialties may allow ECMO support to be offered. ECMO is not offered to patients with end-stage heart or lung failure without acceptance by relevant transplant services. In exceptional circumstances, without prior confirmed listing for organ transplantation (Bridge to decision) this may occur. Even if the patient is on an established pathway for organ transplantation by no means ECMO is an automated pathway, communication with the patient, family, ECMO team and the specialty unit before initiating the support is required.
Caution is to be exercised once organ failure develops. Whilst early organ failure may reverse with ECMO support, established multi-organ failure represents a contra-indication to ECMO. If the patient is judged to have early organ failure, it is important to take into account the acuity of onset, progression and the possibility of unrecognised chronic disease. The clinician should also make a judgment about the specific organ failure and the patient-specific circumstances e.g. early acute renal failure in the setting of cardiac failure is almost anticipated and does not represent a contra-indication. Whereas severe brain injury represents an absolute contra-indication.
Patients in a shock state at the time of assessment for ECMO should be carefully assessed for concurrent sepsis. This is not a contra-indication however requires management in terms of cultures, source control, and antibiotics. It also increases the risk of multiorgan failure. Predominant vasoplegic shock as result of sepsis en large presents an absolute contraindication to ECMO to this date.
Suitable anatomy for ECMO support
Detailed review both of the patient’s medical history, as well as assessment at the bedside, may reveal vital information that may rule them out for emergency femoral cannulation and/or require a change in the approach.
Important information to seek include
- Known significant aortofemoral disease, placement of stents or vascular bypass surgery
- Long term presence of central venous cannulae (Hickmann’s, Portacath ect)
- Chronic SVC or IVC occlusion or stenosis
- Presence of IVC filters
- Abnormal anatomy e.g. tortuous pelvic vessels
At the bedside
- Proximal femoral or external iliac vein thrombus on US
- Right or bilateral internal jugular venous thrombus
- Abnormal vessels size or anatomy
Scoring systems that predict hospital mortality may be used by clinicians to facilitate decision-making and patient selection. These include the SAVE score for VA ECMO, the ENCOURAGE score for patients on VA ECMO post-AMI, the RESP score for VV ECMO and the ECMONet score for H1N1 related VV ECMO. However, these scores have been developed from patients that have received ECMO (and have excluded patients that have not received ECMO) and therefore function better as risk of death prediction tools.
Scoring systems objectively weigh each mortality predictor in the model and therefore may predict outcomes better than individual clinicians. Caution should be exercised when interpreting scoring systems however as they only include patients who are already on ECMO. Many models have not been validated to work on an individual patient level, and they have mostly been used to target hospital mortality rather than longer term patient-centred outcomes.