Evaluation of analgesia nociception index monitoring inintracranial surgical anesthesia

In this study, we aimed to compare perioperative opioid consumption, postoperative pain, and recovery from anesthesia in patients undergoing intracranial surgery who were managed with general anesthesia and analgesia based on entropy monitoring or a combination of entropy and ANI monitoring during the intraoperative period. A total of 75 patients aged between 18 and 80 years, classified as ASA I-II, who underwent intracranial surgery at Trakya University Medical Faculty Hospital between January 1, 2021, and January 1, 2024, were included in the study. Patients were divided into two groups based on the intraoperative monitoring techniques used: the ANI group (n=38) and the Control group (n=37). All patients underwent entropy monitoring during the operation. In the ANI group, ANI monitoring was additionally used for pain management. The study recorded intraoperative data such as mean arterial pressure, heart rate, SpO2, end-tidal CO2, ANI, RE, SE values at baseline, induction, intubation, pin placement, skin incision, craniotomy, dura opening, bleeding control, pin removal, skin closure, and postoperatively. These values were measured at intervals of 5 minutes for the first 20 minutes, then every 10 minutes until 60 minutes, and every 30 minutes up to 180 minutes. Surgical type, anesthesia duration, the amount of erythrocyte suspension and fresh frozen plasma used based on intraoperative requirements, and anesthetic drugs (propofol, rocuronium, fentanyl) were recorded. The total remifentanil consumption was documented via the infusion pump. Postoperative recovery in the recovery unit was evaluated using the Glasgow Coma Scale (GCS), the Ramsey Sedation Scale, and the duration with a Modified Aldrete Score (MAS) greater than 9. Pain was assessed using the Visual Analog Scale (VAS). VAS values were recorded at 1, 2, 4, 6, 12, and 24 hours. If VAS scores exceeded 4, intravenous paracetamol, tramadol, and meperidine were administered in stepwise treatment. The time to first analgesic use, postoperative analgesic consumption in the first 24 hours, and any postoperative complications were recorded. Categorical variables were expressed as frequency distributions (number, percentage), and numerical variables were analyzed with descriptive statistics (mean, standard deviation). Differences between the two groups for categorical variables were examined using the independent samples t-test, Pearson correlation analysis was used to assess relationships between two numerical variables, and the Chi-square test was used to analyze relationships between two categorical variables. A p-value of <0.05 was considered statistically significant. In patients divided into two groups based on the use of ANI monitoring, it was found that significantly more fentanyl was used in the Control group compared to the ANI group. Additionally, both the number of patients using remifentanil and the total amount used were higher in the Control group compared to the ANI group. The duration of MAS >9 was also significantly longer in the Control group. Postoperative VAS scores at 1 hour were lower in the ANI group compared to the Control group. Our study shows that the use of ANI monitoring reduced intraoperative opioid consumption, which led to lower postoperative pain scores and higher postoperative recovery. However, we also found that entropy monitoring alone was insufficient for pain assessment, and its combination with ANI monitoring is more appropriate for patient safety. Key words: Analgesia Nociception Index, Intracranial Surgery, Entropy