Notes from REANIMATE (part II): Cannulation

More notes from REANIMATE. See Part I for patient selection, code flow, and pump setup.

Cannulation

Even if not in arrest, have pads in place in case wire provokes arrhythmia. Wear eye protection. Remember to heparinize before beginning stage II.

Initial vessel access tips

• A brief pause in compressions is okay to get your wire in place.
• If you have time, you can ultrasound both fems and pick the best side. The diameter in mm times 3 equals the largest French size you’re likely to be able to place (e.g. 7mm = 21 Fr).
• On ultrasound, the vein should be thin-walled, larger, and somewhat medial compared to the artery. But there is truly no perfect way to confirm an arterial stick versus vein in arrest, and even experts occasionally mix them up. Blood color, pressure, pulsatility are all useless. You can echo and do a flush test, or look for your wire in the right heart, if you have the time/skill.  The Alfred inserts both wires and then ultrasounds the IVC to confirm the presence of one wire (not two).
• Puncture just caudal to the inguinal ligament. This is usually higher than the inguinal crease and maybe higher than you’re used to; remember the ligament runs from ASIS to pubic tubercle. The CFA only runs a few cm below this, so sticking lower tends to get you SFA instead, which is small and not your goal. [In other circumstances, I often stick lower to make a cleaner site, but this is not okay for these large cannulas.]
• Using no syringe, and resting your hand on the leg, make make the puncture easier during CPR.
• Stick at the lowest angle possible. Steep angles will make dilation hard and dangerous. Use a longer needle if needed (e.g. take the introducer needle from a central line kit instead of from the art line kit).
• Do not do the technique of initially sticking at a steep angle, and then flattening out to facilitate wire passage. [I do this!] Your wire will not follow this path and will be prone to kinking. Pick one flat angle and maintain it during needle passage -> dilation -> cannulation.
• Patients on soft beds, especially if large, tend to fold in the middle (like a taco) and scrunch up the femoral area. Access is easier if you slip a backboard or a bump under the butt. If there are other anatomic abnormalities, make adjustments for those as well to straighten out the vessel.
• Stick the vessel once without backwalling. Bleeding is a big problem in ECMO patients and multiple sticks can really cause issues.
• Stick the artery first and place a 5 Fr sheath. (4 Fr might be better, but is uncommon.) Then place a 9 Fr sheath in the vein.

Cannula selection

Varies by institution. Basic approach:

• Venous cannula: 17–25 Fr, 60cm.
• Arterial cannula: 15–19 Fr; 20cm.
• Sharp tends to default to a 21 Fr venous and a 17 Fr arterial.
• Yannopoulous places a 25 Fr venous (after dilating with a 16 and 18). He places an arterial 15 Fr in women and 17 Fr in men, after dilating with a 12 and then 14.
• The Alfred places a 19 Fr venous and 15 Fr arterial, which is quick and allows low-ish initial flows (which they prefer) of 2.5–3 L/min

Once sheaths are in place from stage I and ready to proceed to ECMO, place Amplatz Super Stiff wire into first sheath. J-tip or floppy tip are okay. 180 cm is good; the 260 cm is obnoxiously long.

Wire tips

• Suggest doing vein first (the arterial cannula is more superficial and may get in the way of the vein). Can tailor this to the patient; e.g. you may want to hold onto one of the cannulae for BP monitoring, etc.
• May need some kind of “cheater” to open the hemostatic valve on sheath; can use almost anything, including one of your dilators.
• Wire should pass very easily. That said, some folks like to shove it in fast, as this may help ensure it stays in the major vessel (particularly with floppier wires). Nevertheless, must be careful, especially if you are placing Amplatz directly into a needle instead of starting with a sheath. If trouble passing wire, can consider switching to a softer wire, but beware kinks.
• Wire is not really marked, but you’re deep enough when the tail is at the patient’s feet.
• The Amplatz will fit down an 18 gauge arterial line, but not a 20. If you placed a 20, you can run down a micropuncture wire, place the microsheath, and put your Amplatz into that. Or put the smallest dilator over the microwire, then the Amplatz into that.
• Beware using a line or sheath placed previously by someone else; often they will be too low (not in the CFA).

Once wired…

1. Remove sheath
2. Skin nick. Plunging the full depth of a 11 blade should be adequate in most cases. If you are dilating and get stuck, you can always run the blade alongside to enlarge the nick. In small patients, nick at a shallow angle to ensure you don’t reach the vessel.
3. Begin dilation. The Maquet kits start at 12 Fr and go by even numbers, whereas the cannulae are odd numbers. Dilate up to 1 size below the cannula size (e.g. dilate to 18 Fr for a 19 Fr cannula). If you get stuck and need an “in between” dilator, take the inner stiffener out of the cannula and use that (you’ll still need to replace it in the cannula before inserting it.) This is particularly useful when the cannula is getting stuck on the “shoulder” where the stiffener merges into the cannula. In rare cases you will need to dilate to a size larger than your cannula, but in general this should be avoided as it causes bleeding.

Dilation tips

• Easy to get mixed up on dilators. Use both color codes and squinting at the numbers. Communicate closely between wire assistant and cannulator; you don’t want to accidentally dilate a much bigger hole than your catheter.
• Venous/art dilators are interchangeable, so you don’t need two kits, but it’s helpful if you drop something.
• We started at 12 Fr and used each dilator. Can skip dilations, but at your risk; you might get stuck. I’d stick to using each.
• Dilate at the flattest angle possible. Generally advance all the way to the hub.
• Use your wire assistant to mount your dilator and corral your long wire.
• As you dilate, wire assistant should continuously rack the wire back and forth. If they suddenly cannot, they immediately should tell you; this means your wire is about to kink. You will stop dilating and fix your angle until wire moves freely.
• If you have trouble advancing, use the twist & rip. Can widen the skin nick as well. Withdraw dilators with the pinch & pull.
• Wetting the dilator helps

Once fully dilated

1. Prepare cannula. Measure venous cannula from sheath to right nipple, or from groin–umbilicus–xiphoid. (Remember, measure to the end of the cannula, not the inner dilator, which is longer.) No need to measure arterial cannula.
2. Insert cannula using same technique as dilators. Wire assistant continues to rack.
3. For the venous side, once the last visible hole is inside vessel, withdraw the inner dilator to the marked line, which retracts the tip inside the cannula; this avoids harpooning the RA. For venous, advance to your measured depth; for arterial, advance nearly to the hub (stop before the flared endpiece; if this enters the vessel it will widen the hole and cause bleeding). Hold your cannula. in place.
4. Withdraw wire. Put thumb over end hole.
5. Wire assistant withdraws inner dilator. Blood will rise; clamp cannula to stop it. Clamp the soft portion, not the wire-wrapped tubing.
6. Optional: flush cannulae. The Alfred uses heparinized saline to flush each cannula x3 with 40ml. (Need to use underwater seal technique.)
7. Hook up to pump before securing, that way you can adjust depth if needed to improve flow. Use underwater seal technique, then “wring” the tubing to fully seat it onto the connector. Then cable tie it. Can confirm depth with CXR/US/fluoro before securing if you want.
8. Use 5-6 stitches on each cannula with a chest tube method (not all of them placed near the puncture; secure it down the leg). Putting a needle into the cannula would be bad (leakage and air entrainment), so aim away from it, or place your stitches parallel. The Alfred avoids sutures altogether for this reason and uses little griplocks. Weingart like the air knot method.

What about doing a cutdown?

The Parisians do this with excellent success (<1 minute to access), but it does take skill. At least, it may be a good backup in difficult cases.

Classic vascular surgery incision: Longitudinal

Parisian technique: Transverse/slash incision

1. Find inguinal ligament. Nothing important is superficial to this. The vessels will emerge deep and caudal to this.
2. Dissect down with fingers or by opening a Kelly clamp. (Don’t use scissor-opening, as you may accidentally cut a vessel while you close it.) A self-retaining retractor is helpful. Bleeding is usually minor.
3. Remember the NAVEL order. Common femoral artery should be somewhat more superficial than vein, rubber-band like, with no vessels emerging superficially; caudally it should bifurcate into the SFA and profunda. It will have fascia on it (can dissect this, but no need, and seems risky). The portion above the bifurcation is the CFA you want to stick.
4. Can directly insert needle, or insert it through the intact skin first, then guide it into the vessel within the incision. This helps stabilize it.

Big summary points

A few points were consistently emphasized by numerous speakers:

• Slow is smooth in cannulation. You waste more time goofing up than you save by rushing. Take your time.
• Access the common femoral artery. Going low and hitting SFA causes problems.

Continue to Part III for pump management and critical care.