Increased duration of hip fracture surgery appeared to increase risk for postoperative delirium, a retrospective Canadian analysis suggested.
Longer surgery duration was associated with a higher likelihood of postoperative delirium, with a 6% increase in delirium risk for each additional half hour of surgery (adjusted OR 1.06, 95% CI 1.03-1.08, P<0.001) after controlling for variables like age, sex, comorbidities, and type of anesthetic, according to Bheeshma Ravi, MD, PhD, of Sunnybrook Health Sciences Centre in Toronto, and colleagues.
Receiving general anesthesia also was associated with a slightly higher rate of postoperative delirium than not receiving general anesthesia (11.0% vs 10.2%, P=0.001), they reported in JAMA Network Open.
“Elderly patients are prone to delirium after surgery; this contributes significantly to postoperative morbidity and can also lead to long-term disability,” Ravi told MedPage Today. “It is also associated with increased healthcare costs. Postoperative delirium is a complex problem, with many contributing factors.”
Hip fracture repair is the most common reason for urgent surgery in elderly patients, accounting for more than 300,000 hospital admissions in the U.S. each year. Hip fracture can signify a premorbid decrease in function, and a subsequent episode of perioperative delirium can lead to lifelong functional impairment and increased mortality.
In this retrospective population-based cohort study, researchers looked at patients ages 65 and older who had hip fracture surgery from 2009 to 2017 at 80 hospitals in Ontario from the Canadian Institute for Health Information Discharge Abstract Database, and the Ontario Health Insurance Plan Claims History database and Registered Persons database from Health Quality Ontario.
In total, 68,131 patients underwent hip fracture surgery; they had a median age of 84 and 71.7% were women. Overall, 26,853 patients received general anesthesia and a total of 7,150 people experienced postoperative delirium. Delirium was identified using validated definitions with high specificity but poor sensitivity (35%), the authors noted.
The incidence of postoperative delirium associated with general anesthesia was 11%, consistent with some previous reports, although other studies such as the STRIDE randomized trial of deep versus light sedation in hip fracture repair patients have shown substantially higher delirium rates.
The work by Ravi and co-authors is “primarily hypothesis-generating work, not work that should be taken as a formal test of whether longer surgery is worse or whether general or spinal anesthesia is better,” noted Mark Neuman, MD, MSc, of the University of Pennsylvania in Philadelphia, who was not involved with the study.
“When you use registry data, you’re relying on what’s picked up by the people who look at the discharge abstract. The problem with that is that you’re never quite sure that’s capturing all of the people who might have an important outcome. This is particularly important for delirium because it’s the kind of thing that’s pretty hard to diagnose,” Neuman explained.
“The actual effects they found were quite small,” he added. “In a study like this, when you’re not sure whether you’re capturing all the cases, small effects are pretty hard to interpret.”
The impact of delirium postoperative is likely higher than what this study showed, added Rebecca Mitchell, PhD, of Macquarie University in Sydney, Australia, who also was not part of the research.
“Identification of delirium in hospitalization records can be a challenge, as it can be difficult to distinguish from dementia, and often only the most severe forms of delirium are recorded,” Mitchell told MedPage Today. It also can be difficult to identify preoperative delirium in hospitalization data, she added.
The authors noted other limitations to their work. The study defined surgical duration as time between entry and exit from the operating room, not the time between incision and closure, which was not captured. They also were unable to differentiate between incident (postoperative) and prevalent (preoperative) delirium cases reliably.
Two randomized controlled multicenter trials — the REGAIN trial in the U.S. and Canada and the RAGA-delirium trial in China — are underway and will shed more light on the effect of anesthesia on postoperative delirium among hip fracture repair patients, they added.
This research was supported by the Marvin Tile Chair in Orthopaedics at Sunnybrook Health Sciences Centre and the Institute for Clinical Evaluative Sciences, a nonprofit research institute funded by the Ontario Ministry of Health and Long-Term Care.
One researcher reported receiving in-kind donation for no-cost use of perioperative cognitive testing software from Cogstate Ltd. No other disclosures were reported.