Risk Factors for Postoperative Delirium in Elderly Patients Undergoing Major Non-Cardiac Surgery in Singapore

The primary aim is to establish the risk factors, in particular the modifiable risk factors, for the development of POD in elderly patients undergoing major non-cardiac surgery in a tertiary hospital in Singapore.

The secondary aims are:

1. To establish the incidence of POD in elderly patients in Singapore, including the proportions that develop hypoactive, hyperactive and mixed delirium, as well as dementia within a one-year follow-up period;
2. To understand the timeline of the development and peak incidence of POD, from the post-anaesthesia care unit till 3 days postoperatively;
3. To compare the utility and accuracy (sensitivity and specificity) of two simplified delirium detection tools, 3D CAM and NuDESC, against the gold standard DSM-5 criteria, in our population as a means for monitoring POD as standard of care in the future;
4. To collect data for holistic evaluation of neurobehavioural and daily functioning status

Singapore's population is growing older and increasingly burdened with systemic disease. It is estimated that over 320 million people underwent surgery worldwide in 2010, with Asia being the fastest growing region. Elderly patients aged \>65 years are presenting for surgery at an ever-increasing rate. In the United States, studies have estimated that approximately 53% of all surgical procedures are performed on patients over the age of 65. Projections estimate that approximately half of the population over the age of 65 will require surgery once in their lives.

We often hear from our elderly patients that they value their quality of life more than prolonging it. Therefore it is essential that we optimize the care in the perioperative period to allow patients to fully benefit from surgery, as this period profoundly impacts survival and quality of life of patients after surgery. There is a current focus on enhanced recovery after surgery (ERAS) where surgeons implement protocols such as improved analgesia, less invasive procedures and early mobilisation to encourage earlier discharge of post op patients. In the best practice guidelines for care of elderly surgical patients put forward by the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) and the American Geriatrics Society (AGS) published in 2012, anaesthesia plays a role in more than half of the 13 recommendations put forward.

One of these recommendations is to reduce postoperative delirium (POD). The anaesthetic agents we use is toxic to the brain, and deep anaesthesia causes POD, which is linked to increased hospital length of stay, increased 30-day mortality, and dementia. POD is one of the leading causes of why patients fall at home after surgery. Up to 10% will develop long-term neurocognitive deficits, which in turn diminish the quality of life and levy a tremendous socio-economic burden on family and care-givers, and shortens life. The topic of POD has dominated the anaesthesia literature in the last year, with both the US and European societies issuing best practice guidelines such as the Brain Health Initiative and the Safe Brain Initiative, as well as harmonization of the definitions of postoperative neurological outcomes with that used by neurologists in compliance with DSM-5 definitions to allow for collaborative solutions.

Awareness of POD remains poor amongst both doctors and the public. The reason for this is that POD requires specialized neurological testing and currently, there are no established biomarkers or monitors to detect it. Yet when patients are assessed for POD, it has been reported that it occurs in as many as 11-50% of patients undergoing major non-cardiac surgery. Studies have shown that up to 40% of POD is preventable. Anecdotally, POD is one of the leading reasons for in-hospital (blue letter) psychiatric referrals after surgery in NUHS, as delirious patients will refuse to comply with physiotherapy, medications and wound care, leading to delayed healing, infection and delayed discharge. Patients are not routinely assessed for POD, and can be discharged with it. Patients who are still delirious can end up with poor feeding and self-care, and even hurt themselves leading to rehospitalisation. In short, POD is a common yet under-diagnosed, and potentially preventable, complication of anaesthesia and surgery in the elderly that has significant long-term effects on the independence of patients after surgery and their quality of life.

Eligibility Criteria:
Inclusion Criteria:

* Elderly patients aged 65 years and above
* Undergoing major non-cardiac surgery, defined as surgery that is predicted to be at least 2 hours and requiring at least 1 day postoperative stay in the hospital
* English, Chinese or Malay speaking

Exclusion Criteria:

* History of psychiatric disease
* Unable to provide informed consent for surgery
* Illiterate
* An active history of substance abuse
* Undergoing neurosurgical procedures
* Undergoing emergency surgeries
* Has a second surgery within 5 days of index surgery
* Non-resident of Singapore
* Severe hearing and/or speech impairment