Postoperative delirium after major orthopedic surgery.

Background: Postoperative delirium (POD) is one of the most common complications in older adult patients undergoing elective surgery. Few studies have compared, within the same institution, the type of surgery, risk factors and type of anesthesia and analgesia associated with the development of POD.

Aim: To investigate the following three questions: (1) What is the incidence of POD after non-ambulatory orthopedic surgery at a high-volume orthopedic specialty hospital? (2) Does surgical procedure influence incidence of POD after non-ambulatory orthopedic surgery? And (3) For POD after non-ambulatory orthopedic surgery, what are modifiable risk factors?

Methods: A retrospective cohort study was conducted of all non-ambulatory orthopedic surgeries at a single orthopedic specialty hospital between 2009 and 2014. Patients under 18 years were excluded from the cohort. Patient characteristics and medical history were obtained from electronic medical records. Patients with POD were identified using International Classification of Diseases, 9 Revision (ICD-9) codes that were not present on admission. For incidence analyses, the cohort was grouped into total hip arthroplasty (THA), bilateral THA, total knee arthroplasty (TKA), bilateral TKA, spine fusion, other spine procedures, femur/pelvic fracture, and other procedures using ICD-9 codes. For descriptive and regression analyses, the cohort was grouped, using ICD-9 codes, into THA, TKA, spinal fusions, and all procedures.

Results: Of 78492 surgical inpatient surgeries, the incidence from 2009 to 2014 was 1.2% with 959 diagnosed with POD. The incidence of POD was higher in patients undergoing spinal fusions (3.3%) than for patients undergoing THA (0.8%); THA patients had the lowest incidence. Also, urgent and/or emergent procedures, defined by femoral and pelvic fractures, had the highest incidence of POD (7.2%) than all other procedures. General anesthesia was not seen as a significant risk factor for POD for any procedure type; however, IV patient-controlled analgesia was a significant risk factor for patients undergoing THA [Odds ratio (OR) = 1.98, 95% confidence interval (CI): 1.19 to 3.28, = 0.008]. Significant risk factors for POD included advanced age (for THA, OR = 4.9, 95%CI: 3.0-7.9, < 0.001; for TKA, OR = 2.16, 95%CI: 1.58-2.94, < 0.001), American Society of Anesthesiologists score of 3 or higher (for THA, OR = 2.01, 95%CI: 1.33-3.05, < 0.001), multiple medical comorbidities, hyponatremia (for THA, OR = 2.36, 95%CI: 1.54 to 3.64, < 0.001), parenteral diazepam (for THA, OR = 5.05, 95%CI: 1.5-16.97, = 0.009; for TKA, OR = 4.40, 95%CI: 1.52-12.75, = 0.007; for spine fusion, OR = 2.17, 95%CI: 1.19-3.97, = 0.01), chronic opioid dependence (for THA, OR = 7.11, 95%CI: 3.26-15.51, < 0.001; for TKA, OR = 2.98, 95%CI: 1.38-6.41, = 0.005) and alcohol dependence (for THA, OR = 5.05, 95%CI: 2.72-9.37, < 0.001; for TKA, OR = 6.40, 95%CI: 4.00-10.26, < 0.001; for spine fusion, OR = 6.64, 95%CI: 3.72-11.85, < 0.001).

Conclusion: POD is lower (1.2%) than previously reported; likely due to the use of multi-modal regional anesthesia and early ambulation. Both fixed and modifiable factors are identified.