To the Editor:
The recent article titled “Delirium in Older Patients after Combined Epidural–General Anesthesia or General Anesthesia for Major Surgery: A Randomized Trial”1 explored whether combined epidural–general anesthesia reduces the incidence of postoperative delirium in elderly patients recovering from major noncardiac surgery. The authors suggested that delirium was significantly less common in the combined epidural–general anesthesia group than in the general anesthesia group. However, we have some commentary and questions for the authors on their conclusions.
Opioids are strongly associated with delirium2 ; the current study found that the combined epidural–general anesthesia reduced the incidence of delirium, supported by a decreased perioperative morphine equivalent consumption (mean difference, −32 mg; 95% CI, −41 to −23). But the occurrence of intraoperative hypotension events cannot be ignored. The authors reported that intraoperative hypotension (systolic blood pressure less than 80 mmHg) was more common in patients assigned to epidural anesthesia (421 [49%] vs. 288 [33%]), with more time with mean arterial pressure of less than 65 mmHg (17 min [interquartile range, 3 to 42] vs. 8 min [0 to 25]), and more epidural patients were given vasopressors (495 [58%] vs. 387 [45%]). The epidural anesthesia was associated with an increased risk of intraoperative hypotension, which is a well-known consequence of combining general and epidural anesthesia.2 Previous studies have demonstrated that intraoperative hypotension is associated with an increased risk of delirium.3,4 It is reasonable to take the intraoperative hypotension events into treatment-by-covariate interactions analysis. The benefit of combined epidural–general anesthesia thus needs to be balanced against potential risks of hypotension in individual patients (which strongly influences the number needed to treat). In the current study, the absolute risk reduction with combined epidural–general anesthesia was 3.2%, corresponding to the number-needed-to-treat to prevent a delirium event as close to 31.
In addition, we are wondering whether or not the patients had experienced multiple delirium and, if so, whether the subtype of delirium was evaluated each time and each event analyzed separately or as a composite. This point should be clarified for readers. Additionally, it would be useful if the authors could provide the durations of delirium.
The authors declare no competing interests.