Low-dose hypobaric mepivacaine and bupivacaine provide adequate spinal anesthesia for hip and knee arthroplasty, with 93% of patients completing surgery without supplementation. Motor function returned by a mean of 145 minutes with mepivacaine and 217 minutes with bupivacaine.

"Practitioners should view our data on duration of surgical anesthesia and sensory and motor block as a reference from which to extrapolate LA [local anesthetic] dose adjustments based on their desired anesthetic goals. Where duration of surgical anesthesia above T10 exceeding two hours is desired, higher doses of mepivacaine (60-80 mg) or bupivacaine (12-15 mg) should be used," the authors of the study wrote.

The study was led by Joanne M.H. Tan, MD, of the Department of Anaesthesia, Pain and Hyperbaric Medicine at Royal Adelaide Hospital, in Adelaide, Australia, and was published online on December 10, 2024, in the Canadian Journal of Anesthesia.

Data regarding the duration of the sensory block at the T10 and L1 levels were missing for a significant proportion of patients, which could have led to an overestimation of the duration of the sensory block. The study did not formally measure the specific gravity of the LA solutions used in the study.

No funding source was disclosed. The authors reported no relevant conflicts of interest.