Author: Michael Vlessides
Increased intraoperative opioid administration was associated with the occurrence of postoperative delirium in elderly patients undergoing outpatient surgery, according to a team of Rush University Medical Center researchers.
Of note, the study found that neither preoperative risk factors nor the use of intraoperative agents such as vasopressors, benzodiazepines, anticholinergics, dexamethasone or ketamine was associated with postoperative delirium in this often f ragile patient population.
“Despite that, there’s a surprising paucity of data looking at postoperative delirium in these patients in the outpatient setting,” Dr. Moges continued. “Other studies have discussed plans to minimize this occurrence, but no strategies have been evaluated in a prospective manner.”
Dr. Moges and his colleagues developed an avoid-delirium protocol that was aimed at minimizing or eliminating intraoperative drugs that have been associated with postoperative delirium. It was developed in accordance with the American Geriatric Society’s “Clinical Practice Guideline for Postoperative Delirium in Older Adults” (J Am Geriatr Soc 2015;63:142-150).
Subsequently, participants were randomly assigned to the delirium prevention group or a group given standard-of-care treatment. Patients were assessed preoperatively on a series of postoperative delirium risk factors; screening with the Confusion Assessment Method for the ICU tool was performed before surgery and one hour afterward. The researchers used medical records to determine intraoperative medication administration.
In presenting the findings at the 2019 annual meeting of the American Society of Anesthesiologists (abstract A1013), Dr. Moges noted that 146 patients have been analyzed to date in the ongoing study. Postoperative delirium was found in only six patients (4.1%; 95% CI, 1.5%-8.7%; P=0.92)—three in each group.
“Then we looked for factors that might be associated with delirium,” Dr. Moges explained. “We noticed that intraoperative morphine equivalents were both clinically and statistically different among patients who got delirium.”
Specifically, patients who did not experience delirium received a mean of 10 milligram morphine equivalents (MME; range, 10-30), compared with 40 MME (range, 14-50) for their counterparts who had postoperative delirium.
Surprisingly, ASA physical status of I or II also was associated with the incidence of postoperative delirium (P=0.004). “None of the patients who were ASA III or IV got delirium,” Dr. Moges added. “This seems very counterintuitive. But if we think about this, we can understand that we’re a lot more conservative when managing these patients, and they’re less likely to have extensive outpatient procedures.”
The mean duration of surgery was markedly longer among patients who experienced postoperative delirium (135 vs. 77 minutes), although the difference was not statistically significant (P=0.14). Nevertheless, recursive partitioning identified MME, ASA physical status and length of surgery as important factors for risk assessment.
“When we looked at patients who were ASA I or II, the driving force really seems to be the length of surgery which generally correlates with increased use of morphine equivalents in those patients,” Dr. Moges explained.
Perhaps not surprisingly, all six patients who experienced postoperative delirium received intraoperative opioids, compared with only 66% of their counterparts who did not have postoperative delirium (P=0.08).
No other patient- or procedure-related factors were found to be associated with the occurrence of postoperative delirium. This included female sex (P=0.68), race (P=0.29), history of dementia (P=0.83), history of postoperative delirium (P=0.77), and history of depression (P=0.91).
Similarly, type of primary anesthesia did not affect the incidence of postoperative delirium (P=0.17). Other procedure-related factors that did not play a role included use of intraoperative vasopressors (P=0.40), dexamethasone (P=0.20), ketamine (P=0.42) or midazolam (P=0.66). Finally, there was no association between intraoperative phenylephrine equivalents and postoperative delirium (P=0.46).
“We believe that the important finding from our study is that greater opioid administration was more associated with the risk of postoperative delirium than any of the other intraoperative drugs that we tried to avoid using in this elderly population,” Dr. Moges explained. “Therefore, future guidelines [that] try to minimize delirium should really focus [on] finding ways to control analgesia while … minimizing exposure to intraoperative opioids.”
The session co-moderator Rajeev Subramanyam, MBBS, MD, MS, asked, “In addition to reducing the amount of narcotics, is there anything else you can suggest to either reduce or stop the occurrence of postoperative delirium?” Dr. Subramanyam is the associate division chief for quality and safety in general anesthesiology at the Children’s Hospital of Philadelphia.
“I think that looking at the length of surgical time is very important,” Dr. Moges replied. “Length of surgery is also associated with increased use of opioids, so we need to be open to using more regional blocks and more adjuncts during these longer procedures.”