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General Anesthesia, Ketamine and Benzodiazepine Use May Influence Delirium Risk

Boston, MA—October 24, 2017

There are avoidable risk factors that may increase the odds of postoperative delirium in patients undergoing total hip and knee replacements, results of a study presented at the annual meeting of the American Association of Anesthesiologists on October 24, 2017, suggest.

Previous studies indicate a link between postoperative delirium and adverse outcomes such as more time spent in the hospital, higher medical care costs, and higher mortality rates. While some factors that have been found to increase the odds of postoperative delirium, many are unchangeable – including patient age and the burden of certain comorbidities, said Sarah Weinstein, lead author and data analyst within the Department of Anesthesiology’s Research Division. Several risk factors, however, are changeable, prompting the investigators to examine a potential association between them and the likelihood of developing postoperative delirium.

Weinstein and team, which was comprised of anesthesiologists at HSS and physicians from other hospitals, analyzed patient data from 41,766 unique patients who underwent unilateral total knee arthroplasties (TKA; n=20,744) or total hip arthroplasties (THA; n=21,022) at HSS from 2005 to 2014. They compared delirium rates among patients who received general anesthesia with those who received neuraxial anesthesia. The investigators also reviewed the rate of postoperative delirium in patients who were given benzodiazepines or ketamine during or after surgery to determine a potential link.

Of the patients, 2 percent had ICD-9 codes indicating postoperative delirium. Delirium was more common among patients undergoing TKA (3 percent) compared with patients undergoing THA (2 percent). Patients who underwent TKAs or THAs using general anesthesia as the primary anesthetic technique had a higher likelihood of developing delirium compared to patients who underwent their procedures using neuraxial anesthesia.

The researchers determined postoperative use of benzodiazepines and ketamine increased the odds of delirium by 2.81 and 12.66, respectively, compared to patients who did not receive each medication after surgery. Intraoperative ketamine and opioids also increased odds of delirium; intraoperative benzodiazepine use, however, was associated with a decreased risk of developing delirium after surgery. Indication bias may explain this finding, however.

"An anesthesiologist may be more reluctant to prescribe benzodiazepines to patients at higher risk for complications during surgery," noted Stavros Memtsoudis, MD, PhD, senior scientist, study author, and anesthesiologist at Hospital for Special Surgery.

"Given that some risk factors for delirium are not changable, [this] study provides vital insight for reducing the odds of this complication through modifications during the perioperative period," said Weinstein. More research is needed to validate and demonstrate the generalizability of the study findings among other orthopedic patients.


Weinstein SM, Cozowicz C, Moerwald EE, Pichler L, Baaklini LR, Poultsides L, Poeran J, Sharrock NE, Soffin EM, Memtsoudis, SG. “Delirium After Unilateral Total Hip and Knee Arthroplasty: A Retrospective Analysis of Modifiable Risk Factors.” Presented at the American Association of Anesthesiologists 2017 Annual Meeting; October 21-24.


About HSS | Hospital for Special Surgery
HSS is the world’s leading academic medical center focused on musculoskeletal health. At its core is Hospital for Special Surgery, nationally ranked No. 1 in orthopedics (for the ninth consecutive year) and No. 3 in rheumatology by U.S.News & World Report (2018-2019). Founded in 1863, the Hospital has one of the lowest infection rates in the country and was the first in New York State to receive Magnet Recognition for Excellence in Nursing Service from the American Nurses Credentialing Center four consecutive times. The global standard total knee replacement was developed at HSS in 1969. An affiliate of Weill Cornell Medical College, HSS has a main campus in New York City and facilities in New Jersey, Connecticut and in the Long Island and Westchester County regions of New York State. In 2017 HSS provided care to 135,000 patients and performed more than 32,000 surgical procedures. People from all 50 U.S. states and 80 countries travelled to receive care at HSS. In addition to patient care, HSS leads the field in research, innovation and education. The HSS Research Institute comprises 20 laboratories and 300 staff members focused on leading the advancement of musculoskeletal health through prevention of degeneration, tissue repair and tissue regeneration. The HSS Global Innovation Institute was formed in 2016 to realize the potential of new drugs, therapeutics and devices. The culture of innovation is accelerating at HSS as 130 new idea submissions were made to the Global Innovation Institute in 2017 (almost 3x the submissions in 2015). The HSS Education Institute is the world’s leading provider of education on the topic on musculoskeletal health, with its online learning platform offering more than 600 courses to more than 21,000 medical professional members worldwide. Through HSS Global Ventures, the institution is collaborating with medical centers and other organizations to advance the quality and value of musculoskeletal care and to make world-class HSS care more widely accessible nationally and internationally.


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