Anatomy of an Percutaneous ECMO Cannulation (Femoral Vein Cannulation)

Continuing our ECMO Education Series, below is a video from one of our recent ECMO cannulations along with an outline of the steps, pearls, and pitfalls when initiating ECMO.  This instructional video will focus primarily on VV-ECMO, stay tuned for a VA-ECMO cannulation soon!

Step 1: Get your gear – Initial Set-Up & Preperation

• Quiet down the room.
• Prep the patient with full-barrier, sterile scrub & drapes.
• Heparinize the patient: 3,000 – 5,000 units (100 units/kg).
• Fill a large, sterile bowl with NS & have a 60 cc bulb syringe ready for cannula irrigation and flushing.
• Initial Vascular Access
  • Be efficient: While setting up the circuit and the team is gathering supplies, start by obtaining vascular access
  • Initial access: Place a right femoral CVC, left femoral a-line, and a right IJ CVC under ultrasound guidance.  If you already have an a-line, you can suture a femoral arterial wire in place for future use.
  • Pitfall:  Not placing these lines under ultrasound guidance: As we all know, in the critically ill or critically hypoxic patient, arterial blood can look the same color as venous blood.  Don’t count on appearance alone.  Even using a pressure column can be misleading. 
  • Double-check: Confirm wire placement in the lumen of the vessel
• Cannulation Equipment
  • Cannulas
    • Venous Cannulas:Sizes range from 23 – 29 French steel wire reinforced
    • Arterial Cannulas: Sizes range from 19 – 21 French steel wire reinforced
    • Different insertion lengths: Range from 15 – 55 cm (depending on manufacturer)
    • Lock introducer
    • The size of the venous cannula directly determines blood flow.  The largest possible venous cannula should be used to maximize flow and easily achieve target output.
      • Some will choose cannula size on flow goals alone (See Cannula info)
      • Some data to suggest the use of US may be helpful to determine vessel lumen size and appropriate cannula size (Grasselli, 2010 PMID: 20872350)
    • Venous cannula length targets:
      • Femoral:  Distal tip rests in the IVC, generally at the level of T10 – T11.  You do not want to advance the cannula past the hepatic vein, as this can cause an obstruction and hepatic congestion.
      • Internal Jugular: Distal tip to rest in the SVC
      • Try to measure the lengths with the cannulas beforehand so when advancing you know when to stop!
    • Note: For venovenous ECMO, circuit of a femoral drainage (deoxygenated blood) and internal jugular return cannulas (oxygenated blood) believed to provide less recirculation than the reverse.
  • Dilators: Series of 8, 12, 16, 20, & 24 French dilators

Step 2: Dilate up the initial insertion sites

• Insert the 150 cm guide wire through the distal port of the femoral CVC.
• Remove the  CVC and hold pressure over the insertion site to prevent excessive bleeding.
• Load the 8 Fr dilator onto the introducer wire, & advance it just to the skin.
  • Prior to advancing the dilator you will have to extend your initial incision.
  • Extend the incision by about 1cm just smaller than the size of your dilator.
  • This will provide adequate hemostasis each time you dilate the soft tissue.
• Introduce the dilator in a corkscrew-wise fashion, advancing the dilator at the level closest to the skin
• As you advance the dilator, periodically check to make sure your guide wire freely moves within the dilator itself.  If you develop a kink or difficulty passing the dilator, you run the risk of lacerating the vessel. (GAME OVER)
• Repeat this step for each dilator up until you reach the appropriate size for your chosen cannula.

Step 3: Inserting the ECMO Cannula

• After your final dilation, load your introducer onto the 150 cm wire.
• Advance the introducer through the soft tissue, far enough that you actually dilate the wall of the femoral vein.
• Remove the introducer and hold lots of pressure.
• Load your venous cannula on to the introducer, then on to the 150 cm guide wire.
• Finally, advance your cannula to the pre-decided distance.
• Remove the dilator, wire, & double clamp the open end of the cannula.
• Flush your cannula with a copious amount of sterile saline.
• Pearl: There is a slight step-off between the cannula and the introducer due to the actual thickness of the wire-inforced cannula itself.  If your dilation is inadequate, this step off can get hung up on the soft tissue while attempting to insert it into the vessel.
• Pearl:  You can use your ultrasound to visualize cannula placement in the IVC!  Use it.

Step 4: Connect to the cannula to the circuit

• Check the circuit tubing: Remove all twists & coils.  Make sure that there is plenty of length between the circuit and the cannulas themselves.
• Irrigate the ends of the tubes:  As you attach the cannulas to the circuit tubing, use the bulb syringe to irrigate the ends to prevent air from getting trapped in the tubing

Step 5: The same steps above for the return cannula

Step 6: Turn on the circuit (we’ll add more about this in a separate post)

• Goal flow for VV ECMO (in adults) about 50-60 cc/kg/min.  You can start at round 2 liters and titrate up, usually to a goal of 4-5 liters per minute.
• Start the sweep at about 2 lpm (for CO2 clearance) and titrate.

Step 7: Clean up & confirmation

• Order a chest & abdominal XR to confirm cannula location
• While you are waiting, you can also perform a bedside ultrasound to visualize the cannula tip in the IVC.

• Make sure your cannulas are secure.  Usually, place at least 2 stabilizing sutures (for IJ’s) and 3-4 for the femoral cannulas with an 0 silk suture. Cover the sites with a sterile dressing.
  

Stay tuned as we continue to work our way through initiating ECMO and review the pearls & pitfalls of mechanical circulatory support!

 
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