Mepivacaine is found to be an effective spinal anesthetic for knee replacement surgery

A numbing medicine largely abandoned decades ago for pain control during surgery could be making a comeback as an effective spinal anesthetic for today's modern-day knee replacement.

In two companion studies by Henry Ford Health System, mepivacaine was found to be as effective for controlling pain with less side effects as bupivacaine, which for years has been the standard spinal anesthetic favored by anesthesiologists and orthopedic surgeons. Patients who received mepivacaine recovered normal function faster, which allowed for a quicker recovery and shorter hospital stay.

While the results proved promising, researchers say more research is needed to evaluate mepivacaine's effectiveness on a larger scale for medium length surgery. The findings – one study was published recently in The Journal of Arthroplasty – add to a growing body of research involving similar shorter acting medications with improved results.

"Our studies suggests that mepivacaine has multiple advantages and few drawbacks compared to bupivacaine as a spinal anesthetic in knee replacement surgery," says Jason Davis, M.D., a Henry Ford joint replacement surgeon and the study's senior author. "It shows promise as an ideal anesthetic by working long enough for most knee replacements without the excessive duration that can delay patients' recovery."

As the popularity of bupivacaine was established in the 1990s, mepivacaine use became limited after research showed it had a higher incidence of post-surgery complications like nerve irritation. More recent studies have refuted those previous concerns and shown improved side effects, while allowing for a faster return of nerve function.

Total knee replacement is one of the most commonly performed orthopedic procedures. It's estimated that the number of knee replacements is expected to increase by nearly 700 percent by 2030 as the population ages. Recent studies show up to 25 percent or more of these patients may benefit from a partial knee replacement, an alternative to total knee replacement, making the potential for outpatient surgery even more feasible.

During a knee replacement procedure, the surgeon replaces the damaged joint surface with a knee implant to restore the alignment and function of the knee. More than 90 percent of knee replacements are functioning 15 years and more after surgery, according to the American Academy of Orthopaedic Surgeons.

In the Henry Ford studies, researchers sought to evaluate the safety and effectiveness of mepivacaine compared to bupivacaine as a spinal anesthetic for pain control during surgery. One involved a retrospective review of the clinical results of 156 knee replacement patients. The second involved a smaller randomized study of 32 patients that looked specifically at the timing of nerve recovery in the legs and for urinary control.

In both, Dr. Davis noted patients who received mepivacaine had better urinary control, faster recovery of nerve function and accelerated recovery compared to those who received bupivacaine. Patients fared no worse with other side effects like nerve complications, pain control or nausea.

"Advances in surgical technique and pain control have made for improved early outcomes in recent years," Dr. Davis says. "Choosing the right anesthetic may now be the key to attain a faster recovery with a lower risk of complications after surgery. Such shorter acting medications have the potential to become the new standard for regional anesthesia during the migration to outpatient joint replacement."