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Starting ECMO - Preparation:

Preparation

If VA or VV ECMO is indicated in a patient, and the team decides to move ahead with cannulation, a well-coordinated plan must be put in place before it is safe to proceed.

It is important to know who to call. At TGH:

  • Initiation of V-V ECMO is performed by the lung transplant surgical team
  • Initiation of V-A ECMO is performed by the cardiovascular surgical team

Vascular Imaging

If the patient is stable enough, then vascular imaging is often ordered before cannulation. Vascular ultrasound is most frequently employed, and is used to assess:

  • Patency of blood vessels: patients will sometimes have thrombosis of large central veins which can make cannulation difficult.
  • I" Size of blood vessels: this can help the surgical team decide which size cannula to use ahead of time.

Vascular imaging is more commonly used in V-A ECMO, however it should be considered in V-V ECMO if there is suspicion of abnormal vasculature.

Location

The cannulation is performed in 3 main places, the operating room, the ICU at TGH, and in the field (usually an ICU at another hospital).

The operating room is the preferred venue for stable patients, especially those who require V-A ECMO. Advantages of the OR for cannulation over other locations are:

  • Sterile environment: ECMO cannulas are intended to stay in for a relatively long time, and so strict adherence to sterile protocol is necessary. This is much more easily accomplished in the OR.
  • Availability of fluoroscopy: confirming the correct placement of the ECMO cannula can be difficult without real time imaging available.
  • Availability of anesthesia: ECMO patients are inherently unstable, and having an anesthesiology team to monitor hemodynamics and offer TEE can be useful.
  • The OR is the only venue where central V-A ECMO can be initiated.

Disadvantages include:

  • Transportation is required to and from the OR, which can be dangerous in unstable patients.
  • Dependence on the availability of an operating room.

ECMO cannula may also be placed at the bedside in the ICU. Advantages of this technique include:

  • Minimizes transportation of an unstable patient.
  • Slightly less time to cannulation.

Disadvantages include:

  • Less than ideal sterile conditions.
  • Lack of real time imaging.

Personnel

The personnel required for ECMO cannulation include:

  • The surgical team: at TGH, cannulation is performed by the lung transplant surgical team for VV ECMO or the cardiovascular surgical team for VA ECMO.
  • The cardiovascular perfusionists: at TGH the ECMO circuit is controlled by perfusionists who have additional special training for ECMO.
  • The operating room nurses: regardless of where cannulation takes place, OR nurses are necessary as they have familiarity with the equipment and can adhere to sterile protocol.
  • The anesthesiologist: in the OR, the anesthesiology team is present, however in the ICU often the role of the anesthesiologist is assumed by the ICU team.
  • Respiratory therapist: if cannulation is taking place in the ICU, ventilator adjustments are often needed.
  • The ICU nurses: if cannulation is taking place in the ICU, then the ICU nurses play a central role in the care of the patient.

Equipment

Before the cannulation process begins, it is important to have all the necessary equipment available and ready.

  • The ECMO circuit.
    • Oxygenator, heat exchanger, blender, controller and cannulas must be connected.
    • The circuit must be primed: At TGH we use isolyte.
    • The circuit must be anticoagulated with 2500 units of heparin.
  • Surgical intruments:
    • The appropriate surgical intruments must be present (at TGH there is an ECMO OR package containing all the intruments).
  • Imaging:
    • An ultrasound machine must be available to assist in locating the blood vessels.
    • In the OR, fluoroscopy should also be available for real time imaging to assess the position of the cannula.
    • Transesophageal echocardiography is ideal to assess the position of the cannula.
    • In many cases transthoracic echocardiography can provide much of the same information where transesophageal echocardiography is either unavailable or contraindicated.
  • Monitors:
    • Standard monitoring of vital signs is necessary, as well as invasive arterial and central venous pressure monitoring.
    • Cardiac output monitoring is not necessary however it should be available.
    • An activated clotting time (ACT) machine is used in the operating room to measure the anticoagulation effect of heparin.

Patient Preparation

  • The patient should have central venous access prior to cannulation.
    • The right internal jugular vein is often used for cannulation, so another site must be used for central venous access in order to deliver medications and fluids.
    • It can save time to place a central line ahead of time in the vessels which the surgeons intend to use so that they can just change to their cannula over a wire.
  • The patient should have invasive hemodynamic monitoring prior to cannulation.
    • An arterial line is necessary.
    • In V-A ECMO, the arterial line should be placed in the right radial artery if possible. This will provide the best estimate of the blood pressure and oxygen saturation of the cerebral circulation.
    • A pulmonary artery catheter is not necessary, however cardiac output monitoring may be needed in certain situation.
  • Anesthesia:
    • Cannulation may be safely performed under local anesthesia alone.
    • Depending on the ability of the patient to cooperate, sedation and general anesthesia may be necessary.
    • For central V-A ECMO, general anesthesia is necessary.
  • Anticoagulation:
    • The patient must be systemically anticoagulated with heparin, typically a 5000 unit bolus.

Medication

The cannulation process may require additional medication to be administered as needed, and the following medication should be readily available:

  • Inotropes and vasopressors
  • Sedatives and analgesics
  • Heparin
  • Protamine
  • Large volumes of crystalloid
  • Blood products

Next page: Starting ECMO: Cannulation

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