The anesthetic and recovery profiles of low-dose hypobaric mepivacaine and bupivacaine for spinal anesthesia in total hip and knee arthroplasty: a prospective observational study.

Purpose: Same-day mobilization and early hospital discharge is increasingly emphasized following hip and knee arthroplasty. One challenge of spinal anesthesia in this setting is achieving adequate block height while avoiding excessively large local anesthetic doses and prolonged motor and sensory blockade. Using a hypobaric local anesthetic solution is one potential strategy, as its intrathecal distribution can be reliably manipulated by patient positioning to achieve adequate block height independent of dose.

Methods: We conducted a prospective observational study to determine the clinical characteristics of spinal anesthesia with low-dose hypobaric mepivacaine and bupivacaine in patients undergoing hip and knee arthroplasty. Thirty patients scheduled for same-day discharge received 51 mg of hypobaric 1.5% mepivacaine and 30 patients scheduled for inpatient stay received 10 mg of hypobaric 0.33% bupivacaine.

Results: The mean (standard deviation) time to achieve sensory blockade at or above L1 and T10 in the operative limb was 5.7 (1.8) and 7.3 (3.3) min with mepivacaine and 6.2 (2.6) and 8.1 (4.8) min with bupivacaine, respectively. Anesthesia was adequate for surgical commencement in all patients regardless of spinal injection level. Four patients required anesthetic supplementation for surgical completion. Sensory block duration at or above T10 and L1 in the operative limb was 97 (27) and 115 (37) min with mepivacaine and 127 (32) and 161 (34) min with bupivacaine, respectively. Motor function returned by 145 (37) and 217 (43) min in mepivacaine and bupivacaine groups, respectively.

Conclusion: The anesthetic profiles of low-dose hypobaric mepivacaine and bupivacaine were favorable for fast-track hip and knee arthroplasty with short and predictable operating times.