Many efforts are made between orthopedic surgeons and anesthesiologists to improve the perioperative pain control of patients undergoing shoulder surgery. Use of local anesthetics has become common, used both for nerve blocks and locally about the shoulder, and continuous infusion catheters are frequently employed. Placement of these catheters has been described both perineurally around the brachial plexus, typically placed by an anesthesia provider trained in regional anesthesia, or locally around the shoulder, typically placed by the surgeon intraoperatively. A common choice for shoulder surgery is the interscalene brachial plexus block, which has been shown to reduce pain scores for at least 8 h postoperatively and decrease opioid consumption [1]. Despite success with pain management, complications have been noted with their use, and block placement requires a skilled regional anesthesiologist, who may not be routinely available at smaller institutions [2,3].

Due to these inherent challenges, some surgeons have opted for continuous pain catheters for pain control. These catheters can be relatively easily inserted by the surgeon upon conclusion of the procedure and have been shown to be effective in pain management [4,5]. Initially these catheters were used both intraarticularly and subacromially based on the nature of the shoulder surgery performed [4,5]. However, animal studies have revealed the deleterious effects of bupivacaine on hyaline cartilage [6,7]. Additionally, due to increased chondrolysis in younger patients following shoulder surgery and its potential association with high volume intraarticular pain pump use, placement of these catheters within the glenohumeral joint has markedly decreased. The perineural space and the subacromial space [8,9] remain common placement options, although local toxicity concerns remain. There is evidence of cytotoxicity of local anesthetics to nerve cells [10,11], potentially complicating perineural placement, and there may also be unfavorable effects at the cellular level on postoperative healing, potentially complicating subacromial placement.

Given the known harmful effects of local anesthetics on hyaline cartilage, neurons, and other cell types, we sought to further assess the toxicity of local anesthetics to fibroblasts, which may have an important impact on the healing process after shoulder surgery, particularly in cases involving tendon repairs or tendon transfers, and which may also play a role in persistent neurological dysfunction and pain due to effects on perineural fibroblasts [12]. We evaluated the effect of various concentrations of local anesthetics on fibroblasts in vitro to determine whether caution should be advised when placing these catheters during or following surgery. We hypothesized that greater anesthetic concentration, longer exposure to the anesthetic, and greater time between exposure and assessment of fibroblast mortality would result in lower fibroblast survival.