Matthias Behrends

Purpose The pupil displays chaotic oscillations, also referred to as pupillary unrest in ambient light (PUAL). As pain has previously been shown to increase pupillary unrest, the quantitative assessment of PUAL has been considered a possible tool to identify and quantify pain. Nevertheless, PUAL is affected by various states, such as vigilance, cognitive load, or emotional arousal, independent of pain. Furthermore, systematically applied opioids are known to reduce PUAL, thus potentially limiting its usefulness to detect pain or changes in pain intensity. To test the hypothesis that PUAL can reliably identify changes in pain intensity in a clinical setting, we measured PUAL in patients experiencing substantial pain relief when regional anesthesia interventions were applied after surgery. Methods We conducted an observational study at an academic surgery centre following institutional review board approval. Eighteen patients with unsatisfactory pain control following surgery underwent regional anesthesia procedures to improve pain control. We used infrared pupillometry to assess pupillary unrest before and after the regional block. We then compared the changes in pupillary unrest with the changes in pain scores (numeric rating scale [NRS], range 0–10). Results Eighteen patients received epidural anesthesia (n = 14) or peripheral nerve blocks (n = 4), resulting in improvement of mean (standard deviation [SD]) NRS pain scores from 7.2 (1.7) to 1.9 (1.8) (difference in means, −2.2; 95% confidence interval [CI], −6.3 to −4.1; P < 0.001). Nevertheless, pupillary unrest did not change as pain decreased; the mean (SD) PUAL was 0.113 (0.062) before analgesia and 0.112 (0.068) after analgesia (difference in means, −0.001; 95% CI, −0.018 to 0.015; P = 0.88). Conclusion In this prospective observational study, pupillometric measurements of pupillary unrest did not identify changes in pain intensity in a postoperative, predominantly opioid-exposed patient population. While the sample size was small, the use of measurements of pupillary unrest to detect and quantify pain has to be questioned.

Hip arthroscopy continues to be one of the fastest‐growing orthopaedic procedures nationally, and pain control following these procedures can be challenging. As regional anesthesia techniques for this population have shown to have limited benefits, pain management for hip arthroscopy focused on multimodal analgesia and preventive analgesia, interventions that reduce postoperative hyperalgesia. The use of neuraxial anesthesia such as spinal and epidural anesthesia, established preventive analgesic anesthetic techniques, has demonstrated to improve postoperative pain in orthopaedic surgery when compared with general anesthesia. This promising finding highlights that despite potential disadvantages of neuraxial anesthesia, such as a small risk for complications or delayed resolution of the neuraxial block that could delay discharge, neuraxial anesthesia could be a suitable anesthetic technique for ambulatory orthopaedic surgery.