Comparing Adductor Canal Blocks With Bupivacaine and Magnesium to Bupivacaine and Buprenorphine After Same-Day Discharge Total Knee Arthroplasty: A Prospective Randomized Controlled Trial.

Objectives Same-day discharge (SDD) total knee arthroplasty (TKA) can provide significant cost savings when compared to inpatient TKA. Advances in surgical techniques, early mobilization, and perioperative pain control have been the primary facilitators of this move toward SDD. Using adjuvant medications, such as magnesium and buprenorphine, along with local anesthetics in regional anesthetic techniques has been shown to be effective in prolonging analgesic effects. The objective of this study was to compare the effects of using magnesium and bupivacaine to buprenorphine and bupivacaine in adductor canal blocks (ACB) on postoperative pain, opioid consumption, nausea, and overall satisfaction. Methods A total of 105 adults undergoing elective unilateral SDD TKA were included. An a priori power analysis was conducted using G*Power 3.1.6 (Heinrich Heine University Düsseldorf, Düsseldorf, Germany) to calculate sample size. Patients were randomly assigned to receive ACB with magnesium and bupivacaine (n = 62) or buprenorphine and bupivacaine (n = 43). Primary outcomes were opioid consumption and pain scores for the first 48 hours after surgery. Secondary outcomes included the incidence of nausea in the first 48 hours after surgery and overall satisfaction with the surgical experience measured using a Likert scale from 0 to 10. Results There was no significant difference in pain scores in the magnesium group compared to the buprenorphine group over the first 24 hours (4.1 ± 1.8 vs. 3.7 ± 1.9, P = 0.375) and the second 24 hours (4.4 ± 2.2 vs. 4.2 ± 1.9, P = 0.637) after surgery. The difference in opioid consumption was also nonsignificant when comparing the magnesium group to the buprenorphine group over the first 24 hours (61.4 ± 50.6 vs. 47.4 ± 39.2, P = 0.108), the second 24 hours (33.0 ± 40.1 vs. 21.7 ± 20.8, P = 0.590), and the first 48 hours (28.0 ± 19.9 vs. 25.7 ± 21.2, P = 0.148) total after surgery. Secondary outcomes showed no difference in the incidence of nausea over the first 48 hours and overall satisfaction. Conclusion Magnesium and buprenorphine are comparable as adjuvants in their effects on postoperative pain and opioid consumption at 24 and 48 hours after SDD TKA, with similar incidences of nausea and vomiting.