0:01

So, what are the two main sources

0:02

of blood supply to the hand?

0:04

Well, you tell me.

0:07

The radial and the ulnar artery.

0:09

And these actually form a particularly

0:11

complete and robust collateral pathway

0:13

via the deep and superficial arches.

0:16

Where is the deep and where

0:17

is the superficial arch?

0:19

Well, here we have the deep palmar arch

0:22

at the base of the metacarpal heads, the

0:25

superficial palmar arch around the mid

0:27

metacarpal heads, and we have the radial artery.

0:31

And anastomosing and collateralizing

0:33

with the ulnar artery.

0:34

And then we have the common digital

0:36

arteries, which also arise, that I think

0:38

are particularly important to keep track of.

0:41

So, what do we intend to do here?

0:43

Well, we're including the radial artery.

0:46

And why would we do that?

0:47

How do we assess for patency of both radial

0:49

and ulnar artery prior to radial access?

0:51

Well, there's the modified Allen test.

0:53

So the operator applies pressure to both

0:55

the radial and ulnar arteries in the hand.

0:59

It sort of turns a bluish hue.

1:01

And then the ulnar artery is released.

1:05

So now the radial artery is still occluded

1:07

as it is in this particular setting.

1:09

And if the hand achieves normal sort

1:10

of color and hue after 9 seconds, then

1:14

the ulnar artery is actually patent.

1:15

Because that means that the occluded radial

1:17

artery, the blood from the heart is not

1:19

reaching the hand from the right

1:21

lateral region, but it's now coming from

1:24

the ulnar artery and collateralizing

1:25

through the superficial and deep palmar arches.

1:27

to the radial artery that now fills that region.

1:30

If only this medial portion

1:33

of the hand is perfused, and this

1:36

portion of the hand is not,

1:39

then you know that perhaps those collateral

1:42

arches are not perfused.

1:46

In place, or dysfunctional, or diminutive.

1:50

So this Allen test is particularly important.

1:52

And sometimes it can actually result

1:54

in high false positive or negative

1:56

results because of the subjective nature of the exam.

1:58

So there are other tests that are used.