About post-operative cognitive dysfunction

Post-operative cognitive dysfunction (POCD) is a state in which a patient’s memory and learning decline after surgery.

POCD is common:

• 1 in 3 patients will have POCD at discharge
• 1 in 10 patients will have POCD that lasts up to three months after surgery

All age groups are at risk – although those over 60 years of age are most commonly affected.

The symptoms of POCD vary amongst patients and can occur on a spectrum –some patients may experience many aspects of this disorder and have a severe presentation, while others may only notice mild differences.

Some common symptoms that have been reported include:

• Difficulty in remembering and recalling – misplacing things, entering a room and forgetting the reason why you are there, etc.
• Inability to complete tasks that were previously not difficult
• Issues with intellectual performance – no longer able to keep up with crosswords, reading
• Difficulty with combining tasks – multitasking, etc.
• Reduced psychomotor skills – challenges with fine movements
• Language comprehension difficulties
• Issues with social integration – problems following conversations, etc.

Often, patients may not overtly notice these changes immediately upon discharge, as they can be subtle. However, these changes to a patient’s brain function may have a significant negative impact on their ability to stay in the workforce and even live independently at home. Family and friends will often be the first to spot the changes, with patients becoming aware at later stages of the impairments.

POCD is measured using a series of tests called neurocognitive tests. These tests look at several important brain areas involved in learning and memory. Testing can be performance-based or it may involve completing a questionnaire to examine functional ability in memory, attention, language, motor function and other aspects of cognition. These tests are conducted before surgery to establish a baseline ‘score’ of how well the brain is functioning and are then repeated after surgery, to allow for measurement of any changes.

The exact cause of POCD is not known. Currently, researchers think that POCD is the result of an interplay between the stress and inflammation induced by surgery and anesthesia with the underlying sensitive brain of patients at risk. Inflammation is the body’s response to harmful stimuli such as bacteria and viruses that has a domino effect on one’s health.

Certain risk factors put patients more at risk for developing POCD:

Operative factors

• Certain types of surgery – cardiac surgery, major surgery (orthopaedic or vascular procedures, etc.)
• Post-operative complications (infection, respiratory complications)
• Multiple surgeries – particularly if they occur in a short period of time

Anesthetic factors

• Anesthetic technique – general anesthesia (being fully asleep during surgery) convey the most risk
• Prolonged and deep general anesthesia
• Intra-operative complications (low oxygen, low blood pressure)
• Poor pain management

Patient factors

• 60 years of age or older
• Pre-existing health conditions: cerebral, cardiac or vascular disease
• Pre-existing cognitive impairments
• Pre-existing depression, mood disorders, or other psychiatric conditions
• Sleep deprivation
• Low educational status
• History of alcohol abuse

Each of these risk factors individually may not result in the development of POCD. However, when combined, the chance of detrimental cognitive changes increases and can result in POCD.

POCD is different than dementia, as these cognitive impairments:

• Develop gradually over months to years
• Are progressive and irreversible

However, some studies do show that patients that develop POCD may be more likely to develop long term cognitive impairments in the future, indicating that POCD may occur in patients with already “sensitive” brains that are at risk for these types of disorders.

POCD is often compared to another common disorder called postoperative delirium. This form of cognitive dysfunction:

• Typically occurs immediately after surgery, in the recovery unit or 24-72 hours postoperatively.
• Presents with a fluctuating course, with patients having moments of disorientation, hallucinations and confusion interspaced with periods of being oriented and aware

The onset of POCD is usually more subtle and is diagnosed weeks to months following surgery. While delirium can be a precursor to POCD, its presentation is different in that patients with POCD are oriented to space and time. Those with POCD do not exhibit the extreme fluctuations in mood and behaviour but rather notice more elusive symptoms that are more likely to affect their abilities to perform daily tasks both in the workplace and at home.

Many of the risk factors associated with POCD are difficult to mitigate, in turn making this a hard condition to preventatively manage.

Some conservative strategies include:

Maintaining a healthy lifestyle

• Regular exercise, good eating habits and regular mental stimulation all help ensure that the body and brain are in the best shape before going into surgery

Taking prescribed medication regularly

• Good management of pre-existing health conditions is important prior to any surgical procedure

Ensuring good pre-operative compliance to any instructions provided by the health-care team

•  The health-care team aims to best prepare the patient for their upcoming procedure with clear instructions regarding medications and other suggestions for the pre-operative period

As well, engaging in mentally stimulating tasks, using all assistive devices such as hearing aids or glasses and getting sufficient sleep are all important in promoting good recovery and reducing cognitive dysfunction both pre- and post-operatively.

The surgical team, together with the anesthesiologist, will decide how to ideally optimize the patient to ensure the best possible outcome and to reduce the incidence of POCD – this can often include the use of minimally invasive surgery or ensuring all conservative measures have been attempted before recommending surgical treatments. Shorter durations of exposure to anesthesia can also diminish the risk of POCD, as can reducing exposure to certain medications such as benzodiazepines. Overall, the surgical team will pick the best techniques to both reduce negative post-operative outcomes, such as POCD, and to ensure any necessary procedure is well tolerated by the patient.

POCD can resolve itself without any treatment:

• Most patients’ brain function return to baseline (before surgery) within a few months following hospital discharge
• In a subset of patients, these cognitive changes can last several months and even years

Currently, there are no medications or treatments for POCD. However, promising research findings in this field have provided insight into some possible treatment strategies.

Since inflammation seems to be a key player in POCD, drugs that can modulate this step could provide some benefit to patients. Some studies have also started investigating the use of biologically active substances that have specific targets on certain binding regions in our brain cells involved in the development of cognitive impairments similar to POCD. These studies have shown promising results in pre-clinical models. Some studies also show behavioural modification – in particular ‘exercising’ the brain with tasks that require complex information processing and attention can also help with cognitive impairments in other forms of memory dysfunction, although this has not been tested in POCD.

Lastly, many of the conservative strategies used in delirium can also be applied to POCD:

Compliance with assistive devices

• Ensure patients use hearing aids, eyeglasses and all other assistive devices as necessary
• This can help lower confusion and stress during the sensitive post-operative period

Presence of supportive family members

• Regular, scheduled visits with family and friends can help reduce anxiety and provide support
• Family and friends can also help with cognitive reminders during difficult or confusing moments
• Ensuring the number of visitors is kept to a manageable number to avoid overwhelming the patient and distracting the health-care team is also important

Maintenance of normal routine in the post-operative period

• Minimizing confusion and creating a supportive environment for patients can be helpful during the post-operative period
• Ensuring sleep schedules are adhered to and meal times are not forgotten can also help create a sense of balance and routine

Compliance with medications and instructions provided by the health-care team

• Taking all prescribed medications correctly and following any other suggestions from the health-care team helps ensure the best recovery possible
• Any questions or concerns should be addressed with the appropriate health-care provider in a timely manner

The perioperative brain health centre at Sunnybrook Health Sciences Centre is a new initiative created for the purpose of providing more insight and information into brain disorders that occur during the perioperative period, including POCD. This centre is comprised of a multidisciplinary, interprofessional team that aims to address both the causes and cures for disorders such as POCD.

As mentioned, much of POCD remains unknown – for instance, while we know several factors are at play with this disorder, the exact contributions and their relative impact is unknown. Research done both at the pre-clinical and clinical stage at the Brain Centre will help answer questions such as these and many others. With the formation of a better understanding of POCD come the possibility for developing and testing possible preventative and healing strategies.