Bispectral index analysis in general anesthesia: An observational study

Bispectral index monitoring (BIS) is one of the major techniques used in monitoring depth of anesthesia. The present study was carried out to observe the changes in BIS values vis-a-vis the changes in hemodynamic parameters during the standard general anaesthesia practices in our institute.

This prospective observational study was carried out in 50 ASA I/II elective surgeries in adults under general anesthesia. Conditions and drugs likely to interfere with BIS values were excluded. Anesthesia protocol was kept uniform. Patients were induced with IV propofol 2mg/kg, IV pentazocine 0.5mg/kg and IV vecuronium 0.1mg/kg. Patients were intubated with appropopriate size endotracheal tube and oxygen, nitrous oxide, halothane and vecuronium were used for maintanence of anesthesia. Patients were reversed with IV neostigmine 0.05mg/kg and I V Atropine 20mcg/kg. The BIS values, hemodymanic changes, recovery characteristics (including awareness) were noted. Correlation between BIS scores and hemodynamic parameters was assessed.

There were predictable changes in BIS scores with the standard anesthesia technique followed in the present study. Similarly, hemodynamic changes were also on the expected lines during the course of anesthesia. However, the correlation between BIS score and hemodynamics could not be established.

Bispectral Index Monitor is a useful tool to assess the depth of anesthesia in standard anesthetic management. Alterations in anesthetic management and drug dosages can be guided by BIS scores. Cost factor and the need to use updated and refined versions of the software are the possible limitations.