Anterior suprascapular block a plausible alternative to intrascalene brachial plexus block

Anterior suprascapular nerve block (SSB) achieves a comparable level of analgesia to intrascalene brachial plexus block (ISB), but is better for preserving lung function, according to a new Singapore study.

“ISB had been considered the gold standard for perioperative analgesia for shoulder surgeries,” researchers said, noting that phrenic nerve paresis often occurs with the procedure. The present study aimed to assess anterior and posterior SSB as an alternative, with a primary focus on their effects on pulmonary function.

Sixty patients were enrolled, of whom 20 received ISB, 20 anterior SSB, and 20 posterior SSB. At baseline, all arms were comparable in terms of age, sex, and American Society of Anaesthesiologists (ASA) classifications. After 30 minutes of administration, all three groups saw generally successful blockade, with rates ranging from 90 percent to 100 percent. [Korean J Anesthesiol 2020;doi:10.4097/kja.20141]

Patients who were given ISBs showed significantly greater reduction in forced vital capacity (FVC) than their comparators who received the anterior and posterior SSB (31.2±17.5 percent vs 3.6±18.6 percent and 6.8±6.5 percent; p<0.001). Similarly, diaphragmatic excursion of the ipsilateral side saw greater reductions in the ISB group than in both anterior and posterior SSB arms (median, –85.7 vs –1.8 and –1.2; p<0.001).

These differences in pulmonary effects were not accompanied by discrepancies in analgesic effects. For example, 6-hour (p=0.256), 12-hour (p=0.768), and 24-hour (p=0.280) pain scores at rest were statistically comparable among the ISB and anterior and posterior SSB groups.

Some differences emerged, however, when pain scores during movement were evaluated. In particular, those who were given posterior SSBs showed significantly higher median scores at 6 hours (5 vs 0 and 1.8; p=0.003 vs ISB) and 12 hours (6 vs 2 and 4; p=0.018 vs ISB). No such difference was reported for 24-hour scores during movement.

Notably, aside from a significant spike in pain scores under movement at 1 hour (1.5 vs 0; p=0.027), researchers observed comparable analgesic performance between ISB and anterior SSB administrations. Moreover, intra-opioid consumption remained comparable across groups, as did the need for morphine during recovery. Oxycodone use within 24 hours was likewise similar across treatment arms.

“[A]nterior SSB was found to better preserve pulmonary function than ISB, and there were no statistically significant differences in analgesic effect,” the researchers said. “Therefore, we recommend performing anterior SSB in patients undergoing arthroscopic shoulder surgeries, especially in patients at high risk of respiratory compromise.”

Important limitations of the study include the failure to blind patients, which was due to the avoidance of using sham blocks, and lack of long-term assessment. Anaesthesiologists and outcome assessors, however, were blinded. Additionally, the effect of the single shot block might have worn off after 24 hours, according to the researchers.