Comparison of Analgesic Efficacy Between of Interscalene Block With Liposomal Bupivacaine With Bupivacaine and Dexamethasone

Pain management after shoulder surgeries poses a unique challenge to the surgeon as well as the anesthesiologist. Regional anesthesia in the form of interscalene approach to the brachial plexus as an adjunct to general anesthesia or as a sole primary technique comes to one's rescue. Interscalene block either as single shot or as a catheter is an established modality for effective analgesia which facilitates early mobilization helping in physical therapy and early discharge.

With the help of local anesthetic injected as a single shot, analgesia usually lasts less than 24 hours. Recent research in regional anesthesia is advancing towards adjuvants which will prolong the duration of local anesthesia. This has introduced the concept of "multimodal perineural analgesia (MMPNA)" whereby multiple agents with differing mechanisms of action are used with the goal of providing perineural analgesia while avoiding exposure to high and potentially toxic levels of individual agents. Some of the commonly used adjuvants in clinical studies are fentanyl, buprenorphine, morphine, tramadol, magnesium, epinephrine, ketamine, non-steroidal anti-inflammatory drug (NSAID), midazolam, parecoxib, ketorolac, clonidine, dexmedetomidine, dexamethasone, neostigmine and potassium. They find a distinct place in wide spread clinical practice as an off-label use.

Steroids have a long history of safe use in epidural space for treatment of radicular pain due to nerve irritation. Dexamethasone is used routinely as a part of anti- emetic prophylaxis and anti-inflammatory effect. Methyl prednisone was the first steroid to be used as an adjuvant. Dexamethasone was first used as an adjuvant in 2003.

It has been hypothesized that steroids induce a degree of vasoconstriction, thereby reducing local anesthetic absorption, tend to have an opioid sparing effect. Another theory suggests that it increases the activity of inhibitory potassium channels on nociceptive C-fibers (via glucocorticoid receptors), thus decreasing their activity.

Several studies have demonstrated promising results with the use of 8mg of perineural dexamethasone. No neuronal injury has been reported in in vivo studies. Though there are several studies which report usage of dexamethasone in varying doses of 2mg to 8mg, the optimal effective dose of dexamethasone as an adjuvant for nerve block remains unknown. Some studies have suggested perineural is more effective than IV as an adjuvant .

Liposomal bupivacaine, a formulation where bupivacaine is encapsulated into multivesicular liposomes, making it a slow and controlled release from the liposomes, was originally indicated for wound infiltration at the surgical site to provide post-surgical analgesia. Studies have demonstrated efficacy up to 24 hours in femoral nerve block in total knee arthroplasty. Recent approval of liposomal bupivacaine in interscalene block for shoulder surgeries by FDA opens an arena unexplored in the world of regional anesthesia.

Current opioid epidemic, a crisis in health care forces healthcare providers to consider alternate analgesic modalities without compromising patient comfort. Regional anesthesia has revolutionized peri-operative pain management by avoiding opioids and their side effects. Use of adjuvants to the current regional techniques holds promise in postsurgical analgesia.

The researchers propose to compare the analgesic efficacy of liposomal bupivacaine to bupivacaine with dexamethasone as an adjuvant in interscalene block with catheters for shoulder surgeries. Till date, there is not a single study comparing the three in current literature.