Time of return of neurologic function after spinal anesthesia for total knee arthroplasty: mepivacaine vs bupivacaine in a randomized controlled trial

BACKGROUND: Mepivacaine as an intermediate-length spinal anesthetic for rapid recovery in total knee arthroplasty (TKA) has not been fully described. We compared spinal mepivacaine vs bupivacaine for postoperative neurologic function in patients undergoing primary TKA. METHODS: Thirty-two patients undergoing primary TKA were enrolled. Primary outcome measure was return of motor and sensory function. Secondary outcome measures included assessment of urinary function, pain via visual analog scale (VAS) scores, opioid usage, distance walked and pain with physical therapy, time to discharge readiness, and complications. RESULTS: Patients with mepivacaine spinal anesthetic had faster return of sensory function (164 ± 38.6 vs 212 ± 54.2 minutes, P = .015), return of motor function (153 ± 47.4 vs 200 ± 45.2 minutes, P = .025), and time to straight leg raise (148 ± 43.5 vs 194 ± 50.8 minutes, P = .023). The mepivacaine group experienced significantly fewer episodes of urinary retention and shorter time to urination (344 ± 154.4 vs 416 ± 96.3 minutes, P = .039). Patients exhibited slightly higher VAS pain scores in the postanesthesia care unit (1.0 ± 1.7 vs 2.7 ± 2.3, P = .046) with no difference in opioid consumption. There were no differences in VAS scores or opioid use on the inpatient ward. Patients achieved discharge readiness 71 minutes faster in the mepivacaine group. There was no need to convert to general anesthesia or transient nerve symptoms in either group. CONCLUSIONS: Patients undergoing TKA with mepivacaine spinal anesthetic had a reliably more rapid neurologic recovery after TKA compared to bupivacaine.