Author: Patrycja Olszynski, MD
A newly described infraclavicular approach to the brachial plexus may provide additional potential benefits over the traditional technique. According to the sonoanatomy of this approach, the shorter distance between the upper part of the artery and cutaneous surface and the clustering of cords lateral to the artery could lead to a decreased incidence of inadvertent vessel punctures.
“With this new technique, the brachial plexus is closer to the skin, so you have less depth to pass the needle through and therefore potentially less risk of vascular puncture,” said Patrycja Olszynski, MD, a resident in anesthesiology and perioperative and pain medicine at Stanford University School of Medicine, in California. “Given that the cords are bunched lateral to the artery, it may be a better placement for the catheter, too. Overall, we propose this as a variation to the traditional technique, not necessarily to replace it.”
As Dr. Olszynski reported, the traditional approach to the infraclavicular nerve block involves placing the ultrasound probe in the parasagittal plane medial to the coracoid process and inferior to the clavicle. The needle is then inserted cephalad to the probe, in-plane and directly caudad.
“This approach can be challenging to perform because the brachial plexus is located very deep, and the cords surround an artery in a ‘U’ shape,” Dr. Olszynski said. “In addition, the angle needed to reach the target can be steep, and local anesthetic must be posited around the artery.”
New Approach Allows Better Positioning
With this new approach, however, the ultrasound probe is placed in the oblique plane, directly parallel to the clavicle, where the cords of the brachial plexus lie lateral to the axillary artery, and the needle is directed from lateral to medial. There’s also a difference in the positioning of the patient’s arm, Dr. Olszynski noted. With the traditional technique, the arm is abducted and flexed at the elbow, with the patient supine. With the new technique, however, the arm is positioned at the patient’s side.
“If patients have injuries, this is potentially a better position,” she said.
Following institutional review board approval, 25 patients underwent ultrasonography at her institution’s outpatient surgical center. The volunteers were scanned bilaterally on hospital gurneys using both the new and traditional techniques.
The following measurements were obtained:
distance between artery and cutaneous surface of skin;
distance from artery to pleura;
number of visible veins; and
topography of the cords.
Bunching of Cords a Plus
As Dr. Olszynski reported at the 2017 annual meeting of the American Society of Regional Anesthesia and Pain Medicine (abstract 3320), the sample population (16 men, nine women) had a mean age of 42.8 years and a body mass index of 28 kg/m2.
With the traditional technique, the average distance between the upper part of artery and cutaneous surface was 31.3±7.4 mm. With the new technique, however, this distance was only 27.0±6.8 mm, which was significantly shorter, Dr. Olszynski said (P=0.0032).
According to Dr. Olszynski, the pleura also was in closer proximity to the axillary artery with the new technique (P<0.0001), and there was more variability in the number of veins visualized (P=0.0281). Also, the cords, although not individually identifiable, were “bunched laterally to the axillary artery as opposed to clustered around it,” Dr. Olszynski said.
“This bunching of the cords could potentially decrease the incidence of inadvertent vessel punctures,” she observed. “The new approach to infraclavicular nerve block may also benefit from the plexus being a closer target from the skin.”
Nevertheless, there are potential disadvantages associated with this technique. Because the pleura is closer to the brachial plexus with the newer approach, there could be more risk for pneumothorax, Dr. Olszynski noted. Given that there are more veins visible with the new technique, there could also be more risk for vascular puncture, but further studies are needed in the clinical setting to compare both techniques, Dr. Olszynski concluded.
Danielle B. Ludwin, MD, assistant professor of anesthesiology and associate fellowship director for regional anesthesia at NewYork-Presbyterian/Columbia University Medical Center, in New York City, asked whether this block is being used at Dr. Olszynski’s institution.
“Dr. Jean-Louis Horn, an anesthesiologist at our institution, does all his blocks this way,” Dr. Olszynski said.
“Regional Anesthesia and Pain Medicine published a paper by Karmakar’s group (2015;40:287-288) about the use of ultrasound-guided costoclavicular brachial plexus block in patients scheduled for hand or forearm surgery, so that’s an interesting resource,” Dr. Ludwin said. “There were no complications related to the technique, but they mentioned that the cords of the brachial plexus were clustered together lateral to the axillary artery in the costoclavicular space, which would be directly in the path of your needle. That’s something to be cautious of, but clearly there are clinical applications for this block.”