Effect of Opioid Versus Non-Opioid Analgesia on Surgical Pleth Index and Biomarkers of Surgical Stress During Neurosurgery for Brain Tumors: Preliminary Findings

Background: Stress response to surgery is mediated by the sympathetic nervous system and manifests as changes in hemodynamic and neuroendocrine parameters. Recently, the surgical pleth index (SPI) is employed for objective and continuous monitoring of nociceptive response during surgery. Opioids are the mainstay of managing stress response to nociception during the perioperative period. However, due to the well-known adverse effects of opioids, alpha 2 agonists are increasingly used to ablate stress response and reduce opioid usage. Objectives: This study compared SPI and biomarkers of surgical stress between opioid (fentanyl) and non-opioid (dexmedetomidine) analgesia during craniotomy. Methods: Patients aged 18 to 60 years undergoing elective craniotomies for brain tumor resection under general anesthesia were randomized to receive fentanyl 1 mu g/kg/h or dexmedetomidine 0.5 mu/kg/h infusion as the primary intraoperative analgesic. Our objective was to compare SPI and biomarkers of surgical stress-serum cortisol, blood glucose, arterial pH, and leucocyte count between the two groups. Results: Data of all 24 patients recruited into the study were analyzed. There was no difference in the demographic parameters between the groups. The SPI remained similar with both the drugs over various time points during the study period. There was no difference between the groups in the biomarkers of surgical stress-cortisol, blood glucose, and pH while leucocyte count was higher in the fentanyl group. Conclusions: The stress response to surgery during craniotomy for brain tumors is similar with opioid (fentanyl) and non-opioid (dexmedetomidine) analgesia as assessed by SPI and blood markers such as cortisol, glucose, and pH.