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.
SCORE™, the Surgical Council on Resident Education, classified arterial line placement as an “Essential Common” procedure.
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 arm board with wrist slightly cocked
Palpate radial artery
Inject lidocaine around artery
Introduce catheter at approximately 45-degree angle using an over-the-needle system or a special arterial cannulation system incorporating a guidewire
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, Identification of Landmarks, and Cannulation of Artery (Fig. 37.1)
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 the 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.
Place the patient’s hand on an arm board with a roll under the wrist and secure the hand in a slightly wrist-cocked position. Palpate the radial pulse. Prepare the area over the radial pulse with povidone–iodine (Betadine) about 1 to 2 cm proximal to the crease in the wrist. Infiltrate the area with 1% lidocaine (Xylocaine).
Several systems are available for cannulation. They differ in whether or not a guidewire is used as an intermediary in catheter placement. The simplest system uses a small gauge (20G for the average adult) over-the-needle catheter similar to those used for intravenous access. The advantage of this system is that the equipment is readily available in all hospital settings.
Take care to identify the spot where the pulse is most prominent and feels closest to the skin. Then palpate the patient’s pulse just proximal to this site with the fingers of your nondominant hand while gently introducing the needle–catheter assembly at an angle of about 45 degrees. The goal is to pierce the anterior wall of the artery and then have nearly tangential access to the artery to advance the catheter (Fig. 37.1B). Pass the needle–catheter assembly into the artery under palpation guidance. As soon as pulsating arterial blood is obtained from the needle, slide the catheter over the needle into the artery. The catheter should pass easily and pulsating blood should exit the catheter freely after the needle is removed. To stop the flow, simply occlude the radial artery proximal to the catheter entry site. If you encounter difficulty passing the catheter or accessing the artery, try moving proximal a centimeter or two. The artery will be generally larger, but may be deeper and more mobile. If necessary, ultrasound can be used as an aid or
a cutdown can be performed. Secure the catheter in place and secure the extremity.
a cutdown can be performed. Secure the catheter in place and secure the extremity.