To the Editor:
We read with great interest the large, retrospective database review of perioperative epidural use for abdominal surgery by Ladha et al.1 We agree that studying anesthetic techniques that might have an impact on the incidence of persistent postsurgical pain is an important area, and is one in which large, well-controlled studies are lacking. Indeed, the large sample population was a strength of the study. However, we have serious concerns about the design of the study. First, and perhaps most importantly, the study’s premise that a single intervention alone, regardless of how it was administered and in what context, would lead to decreased long-term opioid consumption is flawed. In the meta-analysis cited by the authors that examined the effects of regional anesthesia on chronic postsurgical pain,2 that study’s authors could find only a single prospective trial that reported positive results comparing epidural analgesia to placebo after abdominal surgery. That single study3 used preventive epidural analgesia in a multimodal regimen to decrease chronic postsurgical pain, while equivocal results were found in another that did not use multimodal analgesia.4 It is not surprising, then, that Ladha et al. found no benefit. They did not report on the presence or absence of multimodal analgesia, which would impact their results.
Second, virtually nothing is known about the details of the epidural placement, location, medication choice, and timing and duration of therapy. As de Leon-Casasola5 described over a decade ago, knowledge of these and other procedural details is critical in assessing the effectiveness of epidural analgesia for any postoperative outcome. Unfortunately, the authors used Current Procedural Terminology codes to identify patients who received epidurals, leaving the timing of epidural placement (pre-, intra-, or postoperative), as well as all other technical details, unclear. Preoperative initiation of epidural analgesia may be more effective than intraoperative initiation at preventing hyperalgesia,6 and the duration of the infusion likely plays a role as well,4 but combining all epidurals into one category would likely dilute any effect seen in any patient subset.
Finally, the use of a 30-day period free of opioid prescription fills after hospital discharge is an unusual endpoint and may not accurately reflect postsurgical pain and opioid use. Pain medication adherence is often poor in patients with chronic pain,7 so the use of filled opioid prescriptions as a marker of chronic pain is questionable at best.
It would have been more interesting to test the hypothesis that epidural analgesia decreases chronic pain when standardized and used in a multimodal protocol. Unfortunately, this may not be possible retrospectively.
Dr. Viscusi has received consultancy fees from AcelRx (Redwood City, California), Medicines Company (Parsippany, New Jersey), Mallinckrodt (St. Louis, Missouri), Trevena (King of Prussia, Pennsylvania), Cara Pharmaceuticals (Shelton, Connecticut), and AstraZeneca (Wilmington, Delaware). He has received lecturing fees from AcelRx, Merck (Kenilworth, New Jersey), Salix (Raleigh, North Carolina), and Mallinckrodt. His institution has received grant money from AcelRx and Pacira (Parsippany, New Jersey). The other authors declare no competing interests.