Do neuraxial techniques affect perioperative outcomes? The story of vantage points and number games.

• Volume 119 • Number 3 www.anesthesia-analgesia.org 501 Copyright © 2014 International Anesthesia Research Society DOI: 10.1213/ANE.0000000000000276 A debate continues and has recently intensified among perioperative physicians on the question whether the technique used for anesthesia and/or analgesia can affect outcomes. Over the past decades, many attempts have been made to provide at least incremental evidence to support or refute the hypothesis that regional anesthesia and analgesia influences perioperative outcomes with definitive results still lacking. In a review of the literature published in this edition, Kooij et al.1 provide a critical assessment of a number of studies on the topic and conclude that neither neuraxial nor regional techniques improve perioperative outcomes in general surgical patients. While this interpretation of reviewed studies seems soundly founded on the presented scientific evidence, the article also highlights the complexity of the issue at hand. In this context, it is not surprising that in the presence of the same data sources, there are those who conclude that regional anesthetic and analgesic techniques can indeed improve outcomes after surgery. This phenomenon is intriguing because it suggests that the difference in opinion may be based more on the difference in vantage point rather than on an alternative scientific basis. What then may be the reasons for such a dichotomy in conclusion? In our opinion, a number of points need to be considered before drawing conclusions from the literature. First, a major problem and source of confusion that burdens the interpretation of results is the blurry line drawn between the use of regional techniques for anesthesia and/ or analgesia. Kooij et al.,1 recognizing the significance of this issue, have attempted to focus on the analgesic use, but this distinction is at best difficult to make, as evident by the inclusion of landmark publications such as that by Rodgers et al.2 After all, a regional technique used for intraoperative anesthesia may have a profound impact on subsequent analgesic needs, as suggested by the concept of preventive analgesia. Furthermore, neuraxial and regional anesthetics may suppress the stress response during the time of maximal injury and have long-term effects. Perhaps such a distinction is indeed artificial and not even possible. It is a fact that many of the most frequently quoted studies have difficulties differentiating between the two from a purely methodological perspective, that is, it is often not clear what the purpose of the neuraxial/regional technique was. In this context, the systematic review performed by Guay et al.,3 which also appears in this month’s Anesthesia & Analgesia, suggests that the use of neuraxial compared with that of general anesthesia can affect 30-day mortality and the risk of pneumonia while positively influencing the latter outcome when neuraxial is added to a general anesthetic. Similarly, recent population-based analyses, targeted to investigate the impact of neuraxial anesthesia on perioperative outcomes in joint arthroplasty patients, must be mentioned because they have found significant reductions in mortality, cardiopulmonary, and other complications.4–7 It is interesting to note that none of these studies could identify whether perhaps the use of these neuraxial techniques was pursued for postoperative “analgesia” in addition to their “anesthetic” purposes. Second, the number of patients included in most studies evaluating this subject is relatively small compared with the relatively low incidence of postoperative complications, thus limiting the power of even well-conducted meta-analyses, which are further burdened by inclusion of studies with high heterogeneity of populations and methodology. It is therefore not surprising that in the systematic review presented here by Guay et al.3 the authors conclude that larger sample sizes are needed to more definitively answer important questions on the topic. It must be pointed out, however, that in this3 as in most other studies on the topic, many effects that were found to not reach statistical significance did show a trend toward better outcome compared with that of control groups. The impact of the limited power of traditional studies and meta-analyses in this setting may have become more obvious in the era of large database research, which, despite many disadvantages, has the ability to employ much larger populations for analysis. However, the benefits associated with neuraxial techniques shown in these studies have Do Neuraxial Techniques Affect Perioperative Outcomes? The Story of Vantage Points and Number Games