Multimodal sedation guided by processed electroencephalography and autonomic nervous system monitoring for spinal cord stimulator implantation: retrospective identification of anesthetic drug doses.

Background: Spinal cord stimulation is a validated approach for managing chronic pain syndromes. The stimulator placement typically requires sedation, and an awake phase is needed to ensure optimal lead positioning. We describe a novel multimodal sedation approach using target-controlled infusions of propofol, remifentanil, and dexmedetomidine, combined with boluses of ketamine, guided by electroencephalography and nociception-antinociception balance monitoring.

Methods: This retrospective, single-center cohort study reviewed all spinal cord stimulator procedures, including both trials and permanent implants. A standardized anesthetic protocol, administered by a single anesthesiologist, included target controlled infusions of propofol, remifentanil, and dexmedetomidine, with additional boluses of ketamine. Processed electroencephalogram guided sedation depth, and antinociception was assessed using the Analgesia Nociception Index. Data collected included drug doses, time to intraoperative awakening, hemodynamic stability, and airway management.

Results: A total of 25 procedures (11 trials, 14 permanent implants) were analyzed in 21 patients, with 4 patients undergoing both procedures. All patients received the same four-drug regimen. The median (interquartile range) minimum and maximum effect-site concentrations of propofol required to achieve an adequate level sedation (level - 4 of the Richmond Agitation-Sedation Scale) were 1 (0.5) µg/mL and 1.5 (0.8) µg/mL, respectively. The median (interquartile range) minimum and maximum effect-site remifentanil concentrations needed to achieve sufficient antinociception (Analgesia Nociception Index between 50 and 70) were 0.5 (0.3) ng/mL and 1.2 (0.4) ng/mL, respectively. The median (interquartile range) minimum and maximum effect-site concentrations of dexmedetomidine required to achieve adequate antinociception were 0.3 (0.1) ng/mL and 0.5 (0.1) ng/mL, respectively. The median (interquartile range) dose of ketamine was 25 (20) mg. The ketamine dose used during the implant was significantly higher than during the trial procedure (30 (30) vs. 20 (10) mg), p = 0.006. The average time to intraoperative awakening was 114 ± 56 s, and there was no significant difference between the trial and implant groups.

Conclusions: This study demonstrates the feasibility and safety of a multimodal sedation protocol for the placement of a spinal cord stimulator, combining propofol, remifentanil, dexmedetomidine, and ketamine, guided by electroencephalogram and nociception-antinociception monitoring.