The effect of epidural analgesia combined with general anaesthesia on burst suppression in electroencephalography based anesthesia management

Burst supression occurs at cerebral hypoperfusion, hypotermia and deep anesthesia situtations. This study aims to examine the effect of epidural analgesia on burst suppression and delirium caused by general anesthesia. Our study, planned as a randomized controlled double-blinded study, included 64 ASA I-III patients aged 60 and over who underwent total knee and hip surgery at Bezmialem Vakıf University Orthopedics and Traumatology clinic between 02/09/2022-25/05/2023. All patients were informed about the study and written consent was obtained. The cases were divided into two equal groups using the sealed envelope method. Group 1 (Group A) received 20ml 2mcg/ml fentanyl + 0.125% bupivacaine through the epidural catheter and 5ml/h 2mcg/ml fentanyl + 0.125% bupivacaine infusion after intubation, Group 2 (Group K) received 20ml 0.9% saline through the epidural catheter and, 5ml/h 0.9% saline infusion after intubation was administered. Last 15 minutes of surgery both groups were started on 2mcg/ml fentanyl + 0.125% bupivacaine for postoperative analgesia. 4-channel electroencephalogram (EEG) recordings were noted in 4 different time periods: before the epidural catheter for 5 minutes, between epidural drug application and induction for 30 minutes, postoperative 5 minutes and intraoperative. During these time periods, mean arterial pressure (MAP), heart rate (HR), and patient safety index (PSI) values were recorded at 5-minute intervals. For anesthesia maintenance, total intravenous anesthesia (TIVA) (propofol: 0.05-0.2mcg/kg/min, remifentanil: 0.2 mcg/kg/min) infusion was applied to the patient, keeping PSI value at 25-50. Intraoperative propofol, remifentanil, IV fluid consumption and, inotropic agent and antihypertensive drug consumption (if needed) was recorded. Confusion Assessment Scale (CAM), mini mental test (MMSE) and Montreal Cognitive Assessment Scale (MOCA) were applied to all cases on preoperative day 1, postoperative day 1 and day 2. Telephone MOCA and quality of recovery-15(QoR-15) survey were administered at postoperative 3rd month. The recorded EEG data were evaluated in terms of waveform and burst suppression duration with the Mathlab program. There was no statistically significant difference in burst suppression rate and duration between the two groups. The incidence of postoperative delirium was similar. There was no statistically significant difference in MMSE, MOCA and QoR-15 scores between the two groups. After epidural drug administration, a statistically significant difference was observed in the power of the beta waveform between the groups (p = 0.036). There was no statistically significant difference in SPI values recorded between the groups. Propofol (p=0.028) and remifentanil (p<0.001) consumption was statistically significantly low in Group A compared to Group K. We think that epidural analgesia provides a similar depth of anesthesia despite the reduced anesthetic agent consumption, but the reduced anesthetic consumption has no effect on burst suppression.