Surgical Pleth Index and Analgesia Nociception Index for intraoperative analgesia in patients undergoing neurosurgical spinal procedures, a comparative study
Dostalova V, Schreiberova J, Dopitova P, Dostal P
Dept. of Anaesthesiology and Intensive Care, Charles University Prague, Faculty of Medicine Hradec Kralove, University Hospital Hradec Kralove

Background and Goal of the study: The Surgical Pleth Index (SPI) and the Analgesia Nociception Index (ANI) have been recently suggested for the non-invasive intraoperative monitoring of nociception/anti-nociception balance. The goal of this study was to compare intraoperative use of opioids guided either by ANI, SPI or anaesthesiologist's judgment during desflurane-sufentanil anaesthesia respectively. 
Material and Methods: 72 adult ASA I – III patients scheduled for elective neurosurgical spinal procedures were randomized into the ANI group, SPI group and control group. Exclusion criteria included presence of non-sinus rhythm, pacemaker, planned postoperative ventilation, procedures with planned awake intervals, chronic pain with opioid medication, opioid addiction, epidural administration of local anaesthetic in combination with opioid, hormonal contraceptives. Anaesthesia and intraoperative use of opioids (sufentanil boluses based on body weight) were managed according to a strict protocol. The use of sufentanil was targeted to keep ANI value within the range of 50 – 70 in the ANI group and SPI value below individual postinduction baseline SPI value plus 10 points in the SPI group. In the control group, the use of opioids was left at anaesthesiologist's discretion. Results are expressed as mean ± SD. Intergroup differences were tested using ANOVA with Student-Newman-Keuls test for all pairwise comparisons.
Results and Discussion: There were no differences in patient´s baseline characteristics, duration and type of surgery, duration of anaesthesia, used concentrations of desflurane and total sufentanil dose. Additional sufentanil boluses were administered earlier the ANI and SPI groups in comparison the control group (3rd dose after 51.8 ± 22.1 vs 52.7 ± 14.8 vs 84.5 ± 24.8 min respectively, p = 0.001; 4th dose after 61.3 ± 30.1 vs 57.2 ± 14.1 vs 120.0 ± 26.2 min, p = 0.003, and 5th dose after 78.8 ± 33.7 vs 74.0 ± 11.6 vs 146.7 ± 23.2 min respectively, p = 0.009). There were no differences in time to spontaneous breathing at the end of anaesthesia (6.2 ± 5.4 vs 4.4 ± 3.2 vs 4.3 ± 2.6 min respectively, p = 0,207), postoperative pain scores and complication rates between groups.   
Conclusion: Both SPI and ANI monitoring provided clinically usable intraoperative sufentanil use guidance and significantly modified timing of sufentanil boluses in comparison with anesthesiologist's guided intraoperative analgesia.

Surgical Pleth Index and Analgesia Nociception Index for intraoperative analgesia in patients undergoing neurosurgical spinal procedures, a comparative study