Support of Acute Pain Therapy by Analgesia Nociception Index in Post Anesthesia Care Unit: A Randomized Controlled Trial

Abstract

Objective: Postoperative pain management requires a well-directed pain therapy. Generally, the assessment of pain intensity depends on a self-evaluated numeric rating scale (NRS, 0 to 10). Recently, a pain monitor using a socalled “ANI” (analgesia nociception index; 100 to 0) was introduced. The higher the ANI, the lower the pain intensity is considered. The aim of this study was to investigate if the use of ANI improves acute pain therapy in the post anesthesia care unit (PACU) by means of the experienced pain intensity (mean NRS) as the primary outcome parameter.Methods: After admission to PACU, patients were randomly assigned to the “supported by technique” (TC) or the control group (CO). In both groups, self-assessment of pain intensity was requested every 15 minutes and pain therapy was provided according to internal clinical standards when the self-reported NRS by the patient exceeded 4. In the TC group, NRS pain score was additionally assessed when ANI fell below 50.Results: Out of 91 collectively included patients, 46 were assigned to the TC group. The mean NRS did not differ between the groups (p=0.192) at discharge. However, suitability of the ANI monitor was strongly dependent from the individual patient. In some patients, a strong negative correlation was obtained, in other patients no correlation or, curiously, a strong positive correlation was observed.Conclusion: Although objective pain intensity assessment would be beneficial for postoperative care, its measurement remains challenging.