My Radial Access Technique in Oncologic Embolization Cases’ by Dr. Jason Iannuccilli

[Michael Barraza]
Jason, I know you said everybody has a different way of doing this, but would you mind walking us through your approach to radial access when you're doing IO procedures?

[Jason Iannuccilli]
Sure, absolutely. So obviously there are a bunch of technical aspects. Patient selection is key. And like I said, when you're first starting out you want to try to find the ideal patient that's going to have a suitable radial artery diameter, unlikely to have any plaque built up in the artery or any sort of unforeseen anatomic consideration as much as possible. It tends to be younger males that are the ideal candidates, particularly those that don't have all those risk factors. But since our patient population is pretty heavily weighted in the HCC realm, in IO we do get a lot of comorbid illness. So what we found is that as we have started going with this practice, even patients that we felt were not going to be candidates turned out to be good candidates.

And we can talk about some of the data toward the end of this discussion as far as the relative risk of vascular injury based on some of the pre-procedure testing stuff that we do. But what we found is that it's not as strict as what you initially think when you're starting. You don't have to be - I hate to say it - as careful as you really want to be in the beginning. There's a lot of leeway there and it's relatively rare that you're going to end up with a significant complication that's going to cause the patient long-term harm.

But in general, when we're talking about the technical aspects we always start off with an ultrasound to the forearm while the patient is in recovery. We'll check to make sure that the radial artery is sufficient diameter. I would set the threshold at two millimeters for a minimum diameter just based on the sheath size that we're putting in there, which we'll talk about. But in general there's also data to support that the complication rates are higher when the radial artery diameter is less than two millimeters. So we measure the artery, we do an ultrasound, we kind of follow the vessel up the forearm, make sure that we can't see any sort of radial loop or extreme tortuosity that might make it a difficult procedure. Even if you see a radial loop there are ways to overcome it, but again, it may sway you toward using a femoral access if it's a complete loop, for example.

So once we do the anatomic assessment with ultrasound we usually - you don't have to but we do - assess the completeness of the palmar arch by doing a Barbeau test. So the Barbeau test, I'm sure you guys are familiar with it, but it's basically an Allen's test used with a pulse oximeter that we place on either the thumb or the index finger or the hand. We compress the radial artery and observe the pulse ox's waveform. In general, the degree of depression of that waveform is going to tell you how well the ulnar artery is perfusing that superficial palmar arch. And there are various types of waveforms just based on the change. Type A or a type B is preferred. We have done a couple type Cs and haven't had any major issues with that yet but I would say that it's just a handful of patients that we run that risk with.

So that's sort of the overall assessment. If you've got a Barbeau type A or type B and the radial artery is two millimeters and the ultrasound at least to the forearm looks pretty good I'd say it's a go. And then we prep the patient up and bring him into the room.

[Jason Iannuccilli]
Once we get into the system and we've got good blood return through the sheath, we'll then put in a medicinal cocktail that is designed to reduce the risk of peri-sheath thrombosis and also stimulate some vasodilation. We use 2.5 milligrams of verapamil, 200 mics of nitro, and 5,000 units of heparin. We use a full dose heparin instead of the low-dose 3,000 units. There is some data to show that radial artery occlusion rates are a lot lower if you're using the full-dose heparin. So 5,000 units of heparin, 200 mics of nitro, 2.5 of verapamil, and then we hemodilute that. We will draw up in a 20 to 30 cc syringe, from the sheath, the patient's own blood to dilute the medication and then slowly administer that back through the sheath over the course of about two minutes. That's mainly to prevent that burning sensation that the verapamil can cause, that can incite some spasm, it can cause some anxiety in the patient who at this point is probably just crossing over that threshold into conscious sedation.

Once you've got the cocktail in you're kind of good to go at that point. I will mention that there is some data out there that instead of giving the nitroglycerin through the sheath some practices are using sublingual nitro. And they've shown that they can increase the radial diameter size by about 0.5 millimeters without a deleterious effect on blood pressure by giving it sublingual. It's an interesting point, we don't do that, but it's something that others have adopted in practice.