Background
Shoulder surgery is well recognized as having the potential to cause severe postoperative pain that may require opioid use for several days. Continuous Interscalene Blocks (CISB) using an indwelling catheter are safe and effective for analgesia after shoulder surgery. Another mode of analgesia is Periarticular Local Infiltration Analgesia (PLIA) of an “analgesic cocktail” consisting of a combination of local anesthetic, vasoconstrictor, opioid, and NSAID. This retrospective study examined the effectiveness of CISB compared to Single Shot Interscalene Block (SSISB) with PLIA. 

Materials and Methods
After approval from the Mayo Clinic Institutional Review Board (IRB), we performed a retrospective review of all patients who underwent shoulder arthroplasty by a single surgeon in a single institution between Jan 2014 and Oct 2016. Shoulder arthroplasty patients were divided into two groups based on postoperative analgesic modality; patients who received CISB (n=63) and patients who received SSISB with PLIA (n=53). We then conducted a retrospective chart review on each patient and identified pain scores (average and maximum) on Postoperative Day (POD) 0 and POD 1, intraoperative opioids given, and opioid consumption in Oral Morphine Equivalents (OME) on POD 0 and POD 1. Pain scores were collected using 0-10 Numerical Rating Scale (NRS). The results of the two groups were compared using one-way analysis of variance. 

Results and Discussion
CISB was associated with statistically significant decrease in opioid requirements in OME on POD 0 (3.89mg vs. 7.89mg, p<0.01) and POD 1 (7.02mg vs. 12.84mg, p<0.01) compared to SSISB with PLIA. There was no statistically significant difference in intraoperative fentanyl given (128mcg vs. 146mcg, p=0.24). Average and maximum pain scores on POD 1 were lower in CISB group compared to SSISB with PLIA. When compared to SSISB with PLIA, CISB was associated with a significant increase in patients who were opioid-free on POD 0 (44% vs. 2%) and POD 1 (35% vs. 0%). 

Conclusion
CISB for shoulder arthroplasty is a superior method for postoperative analgesia compared to SSISB with PLIA. CISB decreases, and has the potential to eliminate, opioid requirements in the immediate postoperative period. 


03 / Continuous interscalene block versus single shot interscalene block with periarticular injection for shoulder arthroplasty