Radial Artery Cannulation

The radial artery is cannulated for monitoring purposes. A catheter in the radial artery can be used for direct measurement of arterial pressure and for sampling arterial blood for blood gas determinations. It is almost always possible to cannulate the radial artery percutaneously, particularly if Doppler ultrasound guidance is used in difficult cases. Under rare circumstances, a patient with significant vascular disease or shock may require direct cutdown on the artery, with subsequent introduction of the catheter under direct vision. Both procedures are described in this chapter.

Steps in Procedure

Confirm Patent Palmar Arch by Allen Test

- Ask patient to clench fist
- Occlude both radial and ulnar arteries by direct pressure
- Have patient open hand, which should be blanched
- Release ulnar artery—hand should become pink within 3 seconds
- Alternatively, use Doppler ultrasound
Secure hand on armboard with wrist slightly cocked
Palpate radial artery
Inject lidocaine around artery
Introduce catheter at approximately 45-degree angle

If Cutdown is Necessary:

Transverse incision over radial artery
Isolate and elevate radial artery
Cannulate under direct vision

Hallmark Anatomic Complication

Ischemia of digits or hand due to lack of adequate collateral circulation

List of Structures

Radial Artery

Superficial palmar branch of radial artery
Principal artery of the thumb
Radial artery of the index finger

Deep Palmar Arch

Palmar metacarpal arteries

Ulnar Artery

Deep palmar artery
Superficial palmar arch
Common palmar digital arteries

Radius

- Radial styloid process
Ulna
- Palmaris longus tendon
- Brachioradialis tendon
- Tendon of the flexor carpi radialis
- Tendons of the flexor digitorum superficialis
- Tendon of the flexor carpi ulnaris
- Median nerve
- Ulnar nerve

Position of the Extremity and Identification of Landmarks (Fig. 35.1)

Technical Points

Before inserting an indwelling radial artery catheter, perform an Allen test to assess the adequacy of collateral circulation of the ulnar artery across the palmar arch. Because the arch is variable, the adequacy of circulation must be checked in each individual and in each extremity. Instruct the patient to clench the fist tightly. Use both of your hands to occlude both the radial and ulnar arteries. Then have the patient open the fist, which should be blanched. Release pressure on the ulnar artery and note the time required for the hand to become pink. The hand should become pink within 3 seconds after release of
occlusion. Alternatively, a Doppler ultrasound stethoscope may be used as a more objective means of determining the adequacy of circulation. Place the Doppler stethoscope over the palmar arch and do the test as previously described. In this case, use the appearance of Doppler flow in the palmar arch as evidence of collateral flow by the ulnar artery.