Nociception Index Level (NOL) Perioperative Monitoring During Regional Anesthesia

Introduction: Intraoperative pain assessment is difficult and based on indirect parameters of sympathetic-parasympathetic system stimulation. Recently, the Nociception Level index (NOL™) providing a value from combination of multiple physiological parameters to measure pain has been developed to enable intraoperative pain monitoring during general anesthesia. While this monitoring has also been used postoperatively in awake patients, data are scarce to assess pain under locoregional anesthesia. This study was conducted to assess pain using NOL index under locoregional anesthesia for orthopedic surgery of the upper limb.

Method: 50 consecutive patients scheduled for orthopedic surgery of the upper limb under locoregional anesthesia were included. Exclusion criteria were emergencies, request for general anesthesia, and patients under 18 years of age. All patients were informed and consented to the technique of locoregional anesthesia and pain monitoring without change of practice. After premedication with oral hydroxyzine, locoregional anesthesia was performed under ultrasound, with or without neurostimulation. Monitoring began as soon as the venous infusion was started, and parameters were recorded at the time of locoregional anesthesia, tourniquet inflation, surgical incision, skin closure and dressing.

Pain is also assessed using the ALGISCORE by the nurse and the numerical scale (0 to 5) and satisfaction score at the end of the procedure. The need to administer midazolam or propofol at the anesthetist's discretion is noted, as is the effectiveness of locoregional anesthesia (conversion to general anesthesia). Data were analyzed using Friedman and Mann-Whitney tests.