The Infraclavicular Brachial Plexus Block
The infraclavicular block is late in coming to the Neuraxiom website and, I must admit, it is about time.
I have had a bias against the infraclavicular block in the past, I think, because I have been so enamored of the other brachial plexus blocks. Between them, the interscalene, supraclavicular, and axillary approaches, have almost always seemed to fill the needs of most practices. The rule here has generally been;
- shoulder to mid humerus get interscalenes,
- mid-humerus to mid-forearm get supraclaviculars, and
- mid forearm down through the hand is axillary.
In reality the useful areas of coverage among the blocks aren't nearly that clear. There is a good deal of overlap in the areas covered by the different approaches.
For my money the most utilitarian of the brachial plexus blocks is the supraclavicular. Most of the time it will cover most any procedure. Still, there are times when casting, immobilizers, injuries, or other “conditions” prevent one or another of the “standard” approaches.
Enter the Infraclavicular approach. So it's time to pay attention to this useful little court of last resort, the venue of access, and maybe make it the front runner for a few more blocks.
The nerve roots comprising the brachial plexus exit the spinal cord from C2 to T1 and descend in a sheath, between the anterior and middle scalene muscles
After passing the 1st rib the cords or branches of the plexus follow closely the subclavian artery and then the axillary artery. The axillary artery and the nerves pass outside of the thoracic cavity to the arm.
The infraclavicular approach is through the anterior wall of the shoulder girdle. The skin, subcutaneous tissue, pectoralis major and minor muscles overly the space containing the neurovascular bundle to the arm.
Technique and Landmarks
Place the transducer over the upper, outer area of the anterior shoulder, perpendicular to the suspeccted path of the axillary vessels. A useful lateral boundary is the medial margin of the deltoid muscle. The axillary artery will be seen as a round pulsating echo-lucent (dark) circle at a depth of about 3-4 cm. You will probably also be able to see ribs and the chest cavity at the inferior pole of your survey window. If you have trouble identifying the artery, turn on the color Doppler to help identify the artery.
The nerves of the brachial plexus are arranged radially around the axillary artery in the infraclavicular space.
In order to effectively bring the local anesthetic into contact with the nerves it is enough to aim your needle tip to the 12 o'clock and 6 o'clock positions next to the artery and inject 5 - 15 ml at each position, depending upon how you observe the solution spreading around the circum-arterial space. It may be necessary to re-position the needle more than once to assure a good spread of the solution.
The needle approach to the nerves surrounding the artery can be either in-plane or -out-of-plane, depending upon personal preference. However, there may be some advantage to the out-of-plane approach for this block because the injection point targets are at opposite poles of an artery which is larger than the nerve targets. Because of this the artery will be in the way of the needle for the second target position.
By placing the transducer in an orientation which is perpendicular to the suspected path of the axillary vessels, over the upper outer area of the shoulder girdle, the axillary artery will appear on ultrasound as a dark pulsatile circle at 3-4 cm in depth. If there is trouble visualizing the artery, turn on the color or power Doppler to hi-light the position.
Aspirate frequently during the injection to prevent inadvertent intravascular injection. There should be no reason to approach the ribs or the pleura during this block.