Postoperative Analgesia After Shoulder Replacement

After IRB approval, 46 patients undergoing elective shoulder replacement surgery were recruited at Methodist Hospital (Philadelphia) for this single blind, randomized pilot study. Consented patients spent 48 hours in-house. They were randomly given either 0.5% or 0.75% ropivacaine via interscalene block (ISB) prior to surgery. After the operation, patients were transferred to the post anesthesia care unit (PACU) and placed on a patient controlled analgesia (PCA) morphine pump: basal rate of 0 mg; bolus of 1 mg; lock-out period of 10 min (maximum dose of 6 mg/hr). If the PCA did not provide adequate analgesia, subjects could also receive a bolus of morphine, 2 to 4 mg i.v., every fifteen minutes for several doses p.r.n. In addition, parameters of the PCA could also be modified in order to allow for increased delivery of morphine (e.g., lock-out of 6 min w/max dose of 10 mg/hr) for patient analgesia. PCA morphine therapy was continued after patient was transferred from the PACU to the patient's recovery room. PCA morphine therapy was discontinued the day after surgery and patients were given oral Percocet tablets for pain management. . Thirty-nine patients successfully completed this part of the study. There was no significant difference (p>0.05) between groups in amount of post-operative medications consumed (PCA morphine and oral analgesics) or post-operative pain.

Upon release, patients were given pain and medication diaries to complete for seven successive days. All patients recorded the total amount of Percocet tablets taken at home each day in addition to pain scores (0-10) in the morning, afternoon and evening. Twenty-seven patients successfully completed this part of the study. There was no significant difference (p>0.05)between groups in regard to pain; however, patients in the higher 0.75% group unexpectedly took more tablets (p<0.05).

Conclusion: The 0.5% ISB dose of ropivacaine was found to be equally efficacious as 0.75%; since this lower concentration would also reduce the risk of serious systemic toxicity, it is recommended for ISB prior to elective shoulder replacement.