The effect of BIS usage on anaesthetic agent consumption in high-risk patients for coronary artery bypass grafting off-pump surgery

Background: In patients undergoing coronary artery bypass grafting off-pump (CABG-OP) surgery with limited haemodynamic reserve, achieving the ideal anaesthesia depth is challenging. The risk of awareness during surgery increases with light anaesthesia, too deep anaesthesia can cause hypotension, delayed awakening, and increased morbidity and mortality. Aims and Objectives: In this study, we aimed to compare whether the use of the Bispectral Index (BIS) reduces the consumption of the anaesthetic drug and improves recovery time in CABG-OP surgery without awareness during surgery (ADS). Materials and Methods: This was a prospective, single-centre, randomised and double-blind comparative research performed on the American Society of Anaesthesiologists (PS) III patients booked for elective CABG-OP surgery under general anaesthesia. Patients received either propofol or isoflurane anaesthesia, and their consumption was calculated and compared. The conventional groups conventional propofol infusion group (CPG)-1 and conventional isoflurane group (CIG-3) received propofol and isoflurane, and haemodynamic parameters (±20% of initial values) were used to check the depth of anaesthesia. The groups BIS-guided propofol infusion group (BPG-2) and BIS-guided isoflurane group (BIG-4) received propofol and isoflurane, and BIS (value 50 ± 5) were used to check the depth of anaesthesia. In addition, haemodynamic parameters, awakening conditions, length of intubation, hospital stay and drug utilisation were recorded. To explicit ADS, patients were interviewed 24 h after extubation. Results: The quantity of propofol used was 178 ± 11 ml in CPG-1 and 117 ± 6 ml in BPG-2, with a 34.26% reduction with BIS. The isoflurane used was 39 ± 8 ml in CIG-3 and 25 ± 6 ml in BIG-4, with a 35.89% reduction in isoflurane requirement. This difference was statistically significantly low with BIS monitored anaesthesia compared to conventional anaesthesia. The length of intubation was 2.2 ± 1.27 and 2.3 ± 1.49 h in groups BPG-2 and BIG-4, respectively (P < 0.05). Conclusion: BIS monitoring aids CABG-OP surgeries by monitoring the depth of anaesthesia (BIS value 50 ± 5), preventing ADS (0%), reducing the anaesthetic agent requirement (propofol 34.26% and isoflurane 35.89%), reducing myocardial depression (mean arterial pressure maintained >74 mmHg) and aiding ultra-fast-track extubation (37% and 50% reduction in the duration of intubation in propofol and isoflurane with BIS).