4. Discussion
postoperative pain, ESPB, pain
COLD
This post hoc analysis proves that the ESPB group achieved an early and durable control of nociception within a NOL index-directed anesthetic protocol. In contrast, the control patients achieved a late control of nociception at the extra cost of more fentanyl consumption, as demonstrated in the original trial.Several considerations must be addressed before extracting conclusions. First, a gold standard nociception or pain monitor has yet to be determined. However, multiple NAN surrogates have been introduced in the last decade, including electroencephalography and electromyography, photoplethysmography, heart rate variability, skin conductance, and pupillometry [Second, the extent to which nociception monitors can improve clinical practice and outcomes has yet to be determined. A consistent finding among studies comparing nociception-guided anesthesia to standard protocols was an improvement in postoperative pain scores, likely as a result of a better-timed and more personalized intraoperative opioid administration [Third, our analysis confirms that nociception monitors lend themselves well to combined regional and general anesthesia. Pinprick and cold stimulation are classically used to assess the extent of sensory block in awake patients, yet this is poorly correlated with intraoperative antinociception [Lastly, our study adds to the growing evidence upholding the efficacity of bilateral ESPB in cardiac surgery with midline sternotomy [There are several limitations to our study. First, the post hoc design is inherently biased. Second, given the pragmatic scope of our original trial, we could only retrieve and analyze NOL index data collected at five different time points instead of continuous trends. Indeed, the complete trend analysis may have increased the robustness of data interpretation. Third, the NOL index monitor was applied only until CPB initiation, precluding any objectivity regarding the post-CPB period. Additionally, the NOL index monitor is not a gold standard in itself. Therefore, a second independent loop of nociception control, such as the perioperative levels of stress hormones, could have further endorsed our findings. Finally, the generalizability is limited since the original study was single-centered and had an open-label design. Although sham blocks could have secured a double-blinding design, this practice has remained controversial in several institutions [