The effect of bis monitorization during coronary artery bypass grafting surgery on intraoperative anesthetic and analgesic requirement and postoperative outcome

Investigations for evaluation of the depth of anesthesia effectively, induced development of recent techniques for central nerve system monitorization. Bispectral index (BIS) is one of the most reliable monitoring systems of brain and BIS monitoring is the most frequently used processed electroencephalography monitor in cardiac anesthesia practice. Titrating desflurane and sevoflurane with the use of BIS monitoring decreased utilisation of drugs and contributed to faster emergence from anesthesia. The primary end-point of this study is to investigate the effect of BIS monitorization during coronary artery bypass grafting (CABG) surgery to intraoperative anesthetic and analgesic requirement; secondary end-point is to assess the effect of anesthetic and analgesic consumption determined by BIS monitorization, on postoperative time to extubation, 28 day mortality and morbidity. This study was approved by Baskent University Institutional Review Board and Ethics Committee (Project No: KA13/294) and supported by Baskent University Research Fund. After approval and written informed consents were obtained, 50 patients undergoing elective on-pump CABG surgery were enrolled into the study. The study was conducted as a prospective-clinical trial. Patients were randomly divided into two groups and desflurane was titrated in one group using BIS monitorization (Group BIS, n=25), in other group according to a minimum alveolar concentration (MAC) within 0.7 to 1.3 (Group MAC, n=25) . The amount of desflurane administered from the start of the anesthesia to the end of surgical procedure was calculated and recorded. Intraoperative and postoperative hemodynamic parameters and drug requirements of patients, amounts of fluid and blood administered, central venous pressure (CVP), urine output, features of the surgery, duration of intubation and mechanical ventilation, lengths of ICU and hospital stay were recorded. Also postoperative opioid requirement, postoperative complications, revision requirement and mortality within 28 days were recorded. Demographic features were similar in both groups. Surgical times, intraoperative maximum positive inotropic and vasodilator drug requirements, defibrillation and pacemaker requirements, amounts of intraoperative fluids, blood and blood products used and urine outputs at the end of surgery, intraoperative arterial blood gas results and CVP values were similar between the groups (p>0.05 for all). Hourly desflurane consumption was significantly less for Group BIS as compared with Group MAC (Grup BIS:12 ± 1.66 mL, Grup MAC: 13.4 ± 3.20 mL, p=0.031). When groups were compared regarding hemodynamic parameters, there was no significant difference between the groups except significantly higher diastolic blood pressure 30, 45 and 60 minutes after cardiopulmonary bypass in the BIS group (p=0.047, p=0.017, p=0.005 respectively). Intraoperative hourly and total amounts of remifentanil, muscle relaxant and fentanyl used were similar between the groups (p>0.05 for all). There were no significant differences between the groups regarding systolic, diastolic and mean blood pressure, heart rate, oxygen saturation measurements during the first 24 hours in the ICU (p > 0.05 for all). There were no significant differences between the groups regarding the amounts of blood and blood products administered, chest tube drainage and urine output during the first 24 hours, postoperative mean CVP values, postoperative analgesic, maximum positive inotrop and vasodilator drug requirements, postoperative creatinin levels (p>0.05 for all). There were no significant differences between groups regarding durations of intubation, mechanical ventilation, lengths of ICU and hospital stay (p>0.05 for all). Groups were similar regarding 28 days mortality and postoperative complications. In conclusion, BIS monitorization during CABG surgery decreases hourly desfluran consumption compared with the MAC group but does not effect postoperative time to extubation. When the cost benefit achieved by reducing desflurane consumption is calculated, the cost return due to especially usage of electrodes during BIS should be considered. However, larger studies are needed to better understand the eligibility for routine usage of BIS monitorization during cardiac surgery.