Bispectral index monitoring during total intravenous anaesthesia: A comparative study between two dosage regimes of propofol

Introduction: The potential long-term complication of intraoperative awareness needs to be addressed. These complications range from mild auditory perceptions to being fully awake. Studies with prospective patient interviews that specifically inquire about awareness have noted an incidence of 0.1 to 0.2 percent in the general population and approximately 1 percent in high-risk populations. Aims and Objectives: Comparative evaluation of two dose regimens of propofol to assess the depth of anesthesia during total intravenou anesthesia using Bispectral index monitor. The objectives were to find the average Bispectral index during propofol anaesthesia, compare and determine, in two groups, the amount of additional bolus or reduction in the infusion rates of propofol in two dose regimens and to correlate the Bispectral indices with hemodynamic monitoring and to assess incidence of postoperative awareness in the two groups. Materials and Methods: This study was conducted as a prospective randomized double-blind study in a teaching hospital. After the approval from the Ethics committee of the institution, 50 ASA I-II patients were randomly divided into two groups (GI and GII). The patients were induced with a standard regimen of 2 mg kg-1 of propofol and 0.1 mg kg-1 of vecuronium and intubated using appropriate sized endotracheal tube. Following intubation, propofol was infused according to the group the patients was allotted. GI received propofol infusion maintenance dose of 10 mg kg-1 hour for the first 10 minutes following intubation, 8 mg. kg-1 hour for the next 10 minutes and thereafter 6 mg kg-1 hour for the entire length of the surgery. GII received propofol infusion maintenance dose of 8 mg kg -1hour for the first 10 minutes following intubation, 6 mg kg -1hour for the next 10 minutes and thereafter 4 mg kg-1 hour for the entire length of the surgery. The Bispectral index, blood pressure and heart rate were monitored during intubation and thereafter every five minutes for the entire length of the surgery. And the propofol dose was adjusted to maintain the Bispectral index between 40 and 60. Results: Additional doses of propofol were required in the GII 8/6/4 mg kg-1 hour regimen when compared to GI 10/8/6 mg kg-1 hour dose regimen. The average Bispectral index was comparable in the two groups. Conclusion: Patients were hemodynamically stable when the Bispectral index was maintained between 40 and 60. Intraoperative awareness was not detected during this study.