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A single shot of an anesthetic agent administered through an interscalene nerve block has been proven to provide pain relief in patients undergoing shoulder surgery. However, the effects typically last no more than 24 hours.

To extend pain relief another 6 hours, anesthesiologists at Hospital for Special Surgery (HSS) have been using perineural dexamethasone as an adjuvant to standard bupivacaine, based on several meta-analyses and systematic reviews supporting its safe and effective use in upper extremity blockade.

They wondered if replacing dexamethasone with liposomal bupivacaine – recently approved by the US Food and Drug Administration for interscalene nerve block – would provide even longer pain relief, possibly up to 72 hours.

The answer was unclear, however, as previous data were limited to comparisons of liposomal bupivacaine with placebo or standard bupivacaine.

Head-to-Head Comparison of Anesthetic Agents

To gain more clarity on the issue, the HSS investigators conducted the first randomized controlled trial of its kind to compare the use of standard bupivacaine with either dexamethasone or liposomal bupivacaine.

Their study included 112 patients who had undergone shoulder surgery at HSS on an outpatient basis between August 2019 and March 2021. Patients were randomized to receive 1 of the following:

• A mixture of 5 mL of 0.5% standard bupivacaine with 133 mg of liposomal bupivacaine (n=56)
• A mixture of 15 mL of 0.5% standard bupivacaine with 4 mg of dexamethasone (n=55)

The primary outcome measure was average numerical rating scale (NRS) score at rest for 72 hours after surgery, with the investigators hypothesizing that the NRS score for the liposomal bupivacaine group would be non-inferior to the NRS score for the dexamethasone group.

The secondary outcomes were:

• Duration of pain relief
• Duration of weakness and numbness
• Opioid consumption
• Pain scores at rest and with movement on POD1 through POD4 and POD7
• Patient satisfaction
• Readiness to leave the post-anesthesia care unit (PACU)
• Adverse events

Hypothesis of Non-Inferiority Confirmed

Primary investigator David H. Kim, MD, who specializes in regional anesthesia, said that the researchers saw, “no meaningful difference in duration of analgesia between the groups,” at 25.5 hours for the liposomal bupivacaine group versus 27.2 hours for the dexamethasone group (P= 0.851).

In addition, no statistically significant differences were observed between groups for:

• Average pain scores over 72 hours
• Duration of weakness and numbness
• Opioid consumption
• Readiness to leave the PACU
• Adverse events

“Liposomal bupivacaine is non-inferior to preservative-free dexamethasone when used as an adjuvant for the interscalene nerve block,” Dr. Kim said.

“Even though there was a statistically significant difference in the pain scores, the differences are unlikely to be clinically relevant. As practicing clinicians, it was important for us to investigate interventions that provide meaningful clinical differences, not to only look for statistical significance in numbers.”

The study findings were presented by Dr. Kim at the 47th Annual Regional Anesthesiology and Acute Pain Medicine Meeting. Dr. Kim and his HSS colleagues received 1 of 3 Best of Meeting Abstract Awards for their research.

Source

Kim D, Liu J, Beathe J, et al. Interscalene nerve block with liposomal bupivacaine versus bupivacaine with perineural dexamethasone: a noninferiority trial (Abstract 3229). Presented at the 47th Annual Regional Anesthesiology and Acute Pain Medicine Meeting, March 31-April 2, 2022, in Las Vegas, Nevada.