Anesthesia type affects outcomes of bilateral knee replacement surgery

Currently, the majority of bilateral knee replacements in the United States (as well as single knee replacements) are performed under general anesthesia, and researchers say that a regional anesthesia known as neuraxial anesthesia should be promoted for these procedures.

"The use of neuraxial anesthesia may not always be feasible in every patient, but it should be considered more frequently," said Stavros Memtsoudis, M.D., Ph.D., director of Critical Care Services at Hospital for Special Surgery (HSS) in New York City, who led the study. "You shouldn't be asking doctors who don't use neuraxial anesthesia in their daily practice to suddenly switch over and start doing it, but there is a lot of education that needs to be done in terms of training residents and orthopedic surgeons to point out the impact of the choice of anesthetic technique on outcomes beyond the operating room." The study appears online ahead of print in the journal Regional Anesthesia and Pain Medicine.

Despite its advantages, bilateral knee replacement is associated with an increased risk of complications, compared with the alternative of operating on one knee at a time. Neuraxial anesthesia involves injecting medication into the fatty tissue that surrounds the nerve roots in the spine (known as an epidural) or into the cerebrospinal fluid that surrounds the spinal cord.

For the last two decades, HSS has increasingly used regional anesthesia for orthopedic procedures, because of a growing body of evidence showing favorable results compared with general anesthesia.

Because the influence of anesthesia on perioperative outcomes after bilateral total knee replacement is unknown, researchers at Hospital for Special Surgery conducted a retrospective review of all bilateral knee replacements performed between 2006 and 2010 using Premier Perspective. This administrative database contains discharge information from approximately 400 acute care hospitals located throughout the United States. The study population included 22,253 patients, but the type of anesthesia used was unclear in 6,566 of the patients. Of the 15,687 patients where anesthesia type could be identified, 6.8% received neuraxial anesthesia, 80.1% received general anesthesia, and 13.1% received a combination of both. The three groups had similar comorbidity burdens.

The investigators discovered that patients receiving neuraxial anesthesia were less likely to receive blood transfusions (28.5%) than patients receiving general anesthesia (44.7%) or the combination (38.0%) (P<0.0001). The researchers identified a trend toward a reduction in major complications, such as pulmonary embolism and mechanical ventilation, with the use of neuraxial anesthesia compared with the other two groups, but this was not statistically significant. The investigators say it is possible that the sample size was too small to find other differences in complication rates, with only 1,066 patients receiving neuraxial anesthesia.

"This study shows the important role that anesthesia plays in terms of perioperative outcomes and that people need to start looking at interventions to reduce complications of bilateral knee replacements, not just patient selection, which is basically the only thing that doctors have been advocating in the last ten years," said Dr. Memtsoudis.

In recent years, clinicians have been selecting younger patients for bilateral procedures, a practice that by itself may unfortunately be limited in its impact on complications, as it is counteracted by increasing rates of comorbidities, such as obesity, present in orthopedic patients and in the population in general [put link to other Memtsoudis press release]. "You can try to choose healthier people, but that is only going to get you so far," said Dr. Memtsoudis. "Implementing active interventions, such as selecting a specific anesthetic in order to improve outcomes may be something that we need to do more of."

Dr. Memtsoudis pointed out that communication with patients is key. "Many patients don't like the idea of having an injection in their back and their legs being numb, and they are worried about paralysis. There is a lot of misinformation out there," he said. "You have to take into account comorbidities, patient preferences and other practice specific factors, such as the choice for anticoagulation, but neuraxial anesthesia should at the very least be considered in every patient."

The price tags associated with neuraxial and general anesthesia are similar. Anesthesia medications used during surgeries are a small fraction of overall health care costs.

More work is needed to identify ways to prevent complications in patients undergoing bilateral knee replacement and a recent conference at Hospital for Special Surgery, chaired by Dr. Memtsoudis, is aiming to do just that. The Consensus Conference on the Creation of Guidelines for Bilateral Knee Arthroplasty involved 40 experts from 16 institutions. The guidelines coming out of this conference, which are expected to be published within the next six months, address issues such as selecting appropriate candidates, determining the appropriate workup and management for a patient undergoing bilateral knee replacement, and how long doctors should wait between procedures if a patient undergoes two operations.

Provided by Hospital for Special Surgery