Pain management after robot-assisted thoracic surgery for mediastinal disease: a first step towards randomized control trials

Postoperative pain after robot-assisted thoracic surgery (RATS) for mediastinal disease alone has not been addressed to this day. Having investigated pain after RATS for both lung resection and mediastinal disease (1), Kusano et al. focused this time more specifically on mediastinal surgery (2). It is particularly helpful to be able to rely on the results of procedure-specific studies. Indeed, surgeries performed through the same approach but for a different type of pathology are not always comparable in terms of postoperative pain. The intensity and duration of the pain, as well as its somatic or visceral nature, can actually be very different depending on the surgery despite the same type of skin incision (3). Pathology-specific clinical studies are thus essential to establish recommendations for perioperative pain management tailored to each type of surgery.

In their retrospective study including 169 patients with mediastinal disease, Kusano et al. compared postoperative pain as well as adverse effects in the first 48 hours in three groups of patients: no block (NB), thoracic epidural analgesia (TEA), and ultrasound-guided thoracic paraspinal block (TB) (2).

The authors demonstrated a statically significant difference in pain scores at six and twelve hours after surgery between the NB and TEA groups, in favor of TEA (numerical rating scale 1.2±1.6 vs. 2.4±1.8 and 1.2±1.5 vs. 2.2±1.7). This finding is important but as highlighted by the authors, the clinical impact of this small difference may be questioned (2). Indeed, a statistical significance does not necessarily mean that the effect is clinically relevant. Authors and readers generally infer that a statistically significant difference in numerical rating scale for pain is related to a better analgesia, which is not automatically correct (4). Indeed, Myles et al. showed that a change of at least one out of ten points is required for a patient to consider that there is an improvement or worsening of pain. Therefore, an analgesic technique should only be considered superior to another if there is a statistically significant difference of more than 1/10 in the numerical rating scale (5). It is also important to notice that patients in Kusano’s study, regardless of the group, reported mean pain scores of less than 3/10, which is considered an acceptable level of pain for most patients (5).

Every time we need to evaluate the appropriateness of an analgesic technique, it is important to consider both the balance between its efficacy and its inherent adverse effects, and also between its invasiveness and the degree of pain associated with the surgical procedure. The question could be formulated this way: is it necessary to propose an additional locoregional analgesic technique if the average pain reported after surgery is low anyway? An argument for answering this question may also lie in potential differences in postoperative opioid consumption between groups: if the technique does not have a strong impact on pain scores, does it have an opioid-sparing effect allowing to reduce the adverse effects related to the morphine use?

The authors did not only compare a locoregional technique vs. no technique (NB group), but also two different locoregional techniques between them (TEA and TB). This is particularly interesting. Indeed, while it may sometimes be easy to demonstrate the superiority of a technique over “nothing” (e.g., TEA vs. NB), it is much more consistent to also compare two techniques, typically a new technique vs. a currently accepted reference technique.

Nevertheless, to demonstrate the advantages of a locoregional technique is rather easy when systematic analgesia with basic analgesics is not provided. And this is precisely one of the major limitations of this study. The particular combination of acetaminophen and non-steroidal anti-inflammatory drugs (NSAIDs) has been shown to be the most effective of the non-opioid analgesic combinations for decreasing postoperative opioid requirements (6-8) and is therefore recommended as a routine analgesic regimen by some scientific societies (3). In Kusano’s study, acetaminophen and NSAIDs were not systematically administered to every patient during and after surgery. However, before recommending an analgesic technique for a specific type of surgery, we need to know whether that technique allows an additional benefit to a basic analgesia. Again, it may be easy to demonstrate that a technique is effective without any other co-analgesic while it may not provide additional relief if a basic analgesia is ensured (9).

Thus, we need to remain cautious and to avoid drawing hasty inferences from the results of a single retrospective study lacking systematic baseline analgesia. These findings must be confirmed in future prospective studies to prevent us from falling into the trap of the “pigeon superstition”. The latter was described by the American psychologist BF Skinner after his famous experience: starving pigeons were placed in a cage equipped with an automatic device delivering food at regular intervals. He found that the pigeons associated the delivery of the food with incidental actions they performed at the time of delivery, and then continued to perform those same actions as if they were convinced that their behavior had a decisive effect on their environment (10). Of course, we have a more sophisticated decision process than birds, but the analogy is meaningful because the information on which we base our decisions is sometimes subject to misinterpretation, especially when a causal relationship is erroneously established between independent elements (11). In our medical field, this causal link can only be determined on the basis of well-conducted prospective randomized controlled trials (RCTs).

Precisely, this first retrospective study opens the door to conduct a RCT which will then allow to establish recommendations to manage postoperative pain after RATS for mediastinal disease. To conduct this future study, the approach that we advise is to evaluate the analgesic efficacy of different techniques by ensuring basic analgesia as a baseline in the different groups, in the philosophy of a multimodal approach with the ultimate goal of reducing postoperative opioid requirements.

Acknowledgments

Funding: None.

Footnote

Provenance and Peer Review: This article was commissioned by the editorial office, Annals of Translational Medicine. The article did not undergo external peer review.

Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at https://atm.amegroups.com/article/view/10.21037/atm-23-1095/coif). MM reports having received consulting fees as Advisor Board for Edwards Lifescience and CSLBehring. The other author has no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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