The interscalene and supraclavicular nerves may be the blocks of choice in shoulder surgery, but both present the risk for respiratory distress. Ultrasound guidance provides a third option: the suprascapular block. Indeed, the suprascapular block provides analgesia similar to the other two blocks, but without compromise in pulmonary function.
“For years, the standard for shoulder surgery has been the interscalene block,” said David B. Auyong, MD, medical director of the Lindeman Ambulatory Surgical Center and section head of orthopedic anesthesiology at Virginia Mason Medical Center, in Seattle. “Now people have started using the supraclavicular block as well. The problem with either of these blocks is the risk of diaphragmatic paralysis. Even with ultrasound guidance, we continue to see patients struggling with respiratory function after interscalene blocks. …
“A few years ago, we presented ultrasound identification of the suprascapular nerve, which comes off the brachial plexus,” he continued. “Blocking this nerve allows us to provide very specific analgesia, [while] moving further away from a concomitant block of the phrenic nerve, which causes diaphragmatic paralysis.” Of the nerves enervating the glenohumeral joint, the suprascapular is responsible for as much as 70% of shoulder joint innervation. Yet no study to date has evaluated the blocks for analgesia and lung function.
To that end, Dr. Auyong and his colleagues enrolled 113 patients undergoing outpatient rotator cuff repair surgery into the trial. Patients were randomly assigned to receive one of the three nerve blocks, each of which comprised a 15-mL bolus of 0.5% ropivacaine.
“We have very strict intraoperative opioid regimens,” he said. “They’re only given for surgical stimulus intraoperatively.” Indeed, intraoperative fentanyl (25 mcg) was administered only for changes in heart rate more than 10 beats per minute or systolic blood pressure higher than 20 mm Hg due to surgical stimulus. Researchers collected data on numerical rating scale (NRS) pain scores in the PACU, total intraoperative and PACU opioid consumption, and vital capacity pre-block and in the PACU.
Results Were Comparable
As Dr. Auyong and anesthesia fellow Shine Lin, MD, reported at the 2016 annual spring meeting of the American Society of Regional Anesthesia and Pain Medicine (abstract 1403), postoperative pain scores (0-10 NRS) at 60 minutes after surgery were comparable between the three groups (2.1 interscalene, 2.2 supraclavicular and 1.9 suprascapular), as was worst pain recorded (2.4 interscalene, 3.1 supraclavicular and 3.0 suprascapular). Similarly, opioid consumption was not significantly different between the groups.
The researchers also examined the percentage of vital capacity preserved, finding that the suprascapular block was far superior to both the interscalene and supraclavicular blocks. While the interscalene block only saw 66.2% of vital capacity preserved, that number increased to 72.5% in supraclavicular patients and 92.5% in suprascapular patients (P<0.001, all groups).
“I would say that based on these data—if there’s concern about postoperative respiratory dysfunction—the option to move further away from the brachial plexus by doing a suprascapular block would be my first choice to provide similar analgesia, but with significantly improved lung function after surgery.”
Block Not More Difficult
One of the other benefits of the suprascapular block is that it is no more challenging to place than its counterparts. “That’s what’s exciting about the suprascapular approach,” he told Anesthesiology News. “The injection site is only a few centimeters away from the more familiar interscalene or supraclavicular block locations. In fact, the suprascapular nerve is actually quite shallow, and we’ve found that it was slightly easier to place in larger patients because the nerve is shallow and you have more room to manipulate an ultrasound transducer near the clavicle.” One potential drawback with the suprascapular block is the occasional requirement for a supplemental axillary nerve block to provide adequate postoperative analgesia.
“With the suprascapular block, it seems like we’re combining the knowledge of our forefathers,” he concluded. “We know that lung function is sometimes compromised with these traditional blocks. So using that knowledge and then adding ultrasound, we now have the ability to perform updated approaches to classic nerve blocks, and showing beneficial outcomes, too.”
Not for Anesthesia, However
Arthur Atchabahian, MD, professor of clinical anesthesiology at NYU School of Medicine, in New York City, commended the authors for their efforts. “The suprascapular nerve block—with its potential to offer analgesia following shoulder procedures—is indeed worth investigating, and its performance much easier with ultrasound guidance than when nerve stimulation was used,” Dr. Atchabahian said. “I would argue, however, that we see very few patients with clinically significant respiratory issues following interscalene or supraclavicular blocks.”
Dr. Atchabahian pointed out that the suprascapular block only provides analgesia, necessitating general anesthesia (or a short-acting interscalene or supraclavicular block) for the surgery. “In addition,” he said, “the suprascapular nerve does not innervate the anterior aspect of the shoulder joint, and thus the analgesia provided would be poor following anterior surgical procedures; those are the cases when an axillary block would need to be added.”