Early Opioid Use and Postoperative Delirium Following Open Abdominal Aortic Aneurysm Repair

Postoperative delirium is a common complication following open abdominal aortic aneurysm repair (OAR). Opioids have been found to contribute to delirium, especially at higher doses. This study assessed the impact of early postoperative opioid analgesia on postoperative delirium incidence and time to onset. We hypothesized that higher early postoperative opioid utilization would be associated with increased postoperative delirium incidence.

This was a retrospective analysis of OAR cases at a single quaternary care center from years 2012-2020. The primary exposure was oral morphine equivalents use (OME), calculated for postoperative days 1-7. A cut point analysis using a receiver operator curve for postoperative delirium determined the threshold for high OME (OME>37 mg). The primary outcome was postoperative delirium incidence identified via chart review. Multivariable logistic regression was performed for postoperative delirium and adjusted for covariates meeting P < 0.1 on bivariate analysis.

Among 194 OAR cases, 67 (35%) developed postoperative delirium with median time to onset of 3 days (IQR = 2-6). Patients with postoperative delirium were older (74 years vs. 69 years), more frequently presented with symptomatic AAA (47% vs. 27%) and had a higher proportion of comorbidities (all P < 0.05). Cases with high OME utilization on postoperative day 1 (55%) were younger (69 vs. 73 years), less frequently had an epidural (46% vs. 77%), and more frequently developed delirium (42% vs. 25%, all P < 0.05). Epidural use was associated with a significant decrease in OME utilization on postoperative day 1 (33 vs. 83, P < 0.01). Postoperative delirium onset was later in those with high OME use (4 vs. 2 days, P = 0.04). On multivariable analysis, high OME remained associated with postoperative delirium (Table II).

High opioid utilization on postoperative day 1 is associated with increased postoperative delirium and epidural along with acetaminophen use reduced opioid utilization. Future study should examine the impact of opioid reduction strategies on outcomes after major vascular surgery.