Paper Highlights Link Between Preoperative Depression and the Increased Risk of Delirium After Major Surgery

A recent paper has revealed a link between preoperative depression and the significantly higher risk of developing postoperative delirium in surgical patients. The findings of the systematic review and meta-analysis suggest that individuals who exhibit depressive symptoms before undergoing major surgery are nearly twice as likely to experience this complication, which can impede recovery and affect overall outcomes.

Following the publication of the article, lead author and anesthesia resident, Dr. Calvin Diep, discussed the impact of the research with the communications team.

1. Your research focuses on the relationship between preoperative depression and postoperative delirium. What sparked your interest in this area?

I’ve always had an interest in mental health, although I didn’t choose a career in psychiatry. In anesthesiology, we learn to provide care for patients with a wide breadth of chronic medical conditions and acute illnesses, but these are largely focused on physical ailments. In comparison, there’s much less known about how patients’ psychological states and mental health might interact with their anesthetic care and impact outcomes. Considering that about one-quarter of all adult patients presenting for major surgery endorse clinically important depressive symptoms when asked, many of the patients we provide care for every day stand to potentially benefit from their psychological states being more well studied and considered.

Under the mentorship of Dr. Duminda Wijeysundera and Dr. Karim Ladha, I set out during my graduate training in clinical epidemiology to begin to identify for which adverse perioperative outcomes patients with depression or depressive symptoms might be at increased risk. Prior observational studies had suggested these patients are at increased risk of delirium (amongst other adverse perioperative outcomes such as acute and chronic pain, delayed neurocognitive recovery, and poor surgical recovery), which we wanted to confirm in a systematic review and meta-analysis.

2. What were you hoping to achieve with this systemic review and meta-analysis?

Our primary goal was to describe the pooled incidence (risk) of postoperative delirium for patients with preoperative depression or depressive symptoms. We then compared this to the risk of postoperative delirium for patients without preoperative depression. Through these two objectives, we confirmed this is indeed an unaddressed problem and an area in which the prediction or mitigation of adverse outcomes might be improved.

3. Your analysis showed that patients who already had a depression diagnosis or showed clinically important depressive symptoms before surgery had a much larger risk of experiencing delirium after surgery. Were these results expected? What did your analysis show contribute to this increased risk?

Based on the existing primary literature showing a link between depression and delirium and the known overlap in their pathophysiology, our findings were as expected. However, the magnitude of this association was much greater than we had anticipated. Surgical patients with pre-existing depression or depressive symptoms had nearly twice the risk of postoperative delirium compared to other patients; this is certainly worthy of greater attention and further exploration.

While patient-level risk factors or modifiers for the development of postoperative delirium could not be identified in our meta-analysis, this is one of the next steps in this line of work. We’re planning to do this by conducting a secondary analysis of the Functional Improvement Trajectories After Surgery cohort, which is a prospective observational study of older Canadian adults undergoing major surgery, led by my graduate supervisor, Dr. Wijeysundera. I suspect factors such as surgical stress (type and length of surgery), uncontrolled pain, and postoperative complications will be implicated in the causal pathway between preoperative depressive states and postoperative delirium.

4. Which implications do you see for these findings?

While we continue to improve our understanding of the causal pathway between preoperative depression and postoperative delirium, we can begin informing perioperative clinicians (e.g., physicians, nurses, physiotherapists, dietitians, and social workers) as well as affected patients and their family members of the increased risks of postoperative delirium. However, this is only the first step in translating these findings to the clinical setting.

The next (and much more challenging) steps involve developing, testing, and implementing interventions to mitigate the risks of—and perhaps one day even treat—postoperative delirium. There are currently no known effective treatments for postoperative delirium, so we rely on preventative measures such as ensuring patients have their usual visual or hearing aids, reducing perioperative benzodiazepine and opioid use, providing adequate analgesia for pain, encouraging mobilization, promoting sleep, and adequate nutrition. The first step to improve outcomes might simply be to embark on quality improvement initiatives to ensure these measures are routinely and immediately employed for all patients throughout their surgical admissions.

The more targeted approach for patients with preoperative depression or depressive symptoms would be to try to reduce patients’ depressive symptom burdens before coming for surgery. When we talk about “prehabilitating” patients for the anticipated stresses of surgery and anesthesia, most patients (and clinicians) think about improving exercise tolerance and adopting a healthy diet, but often forget the third key component: a well-prepared psychological state. There are some interesting pilot trials currently being conducted by anesthesiologists in the United States in which affected patients connect to psychiatrists and pharmacists to optimize their non-pharmacologic and pharmacologic antidepressant therapies before and after surgery. Findings from these pilot studies may help develop new approaches to how we provide holistic perioperative care for patients with pre-existing psychological concerns.

I intend to continue carving out a research program focused on the intersections between mental health, anesthesia, and perioperative outcomes. As our specialty continues to look for ways to expand our mastery of perioperative care, consideration of patients’ psychological factors represents an unexplored and exciting frontier for both research and the provision of clinical care.