This prospective, randomized comparative study was conducted using the bispectral index, a dimensionless number from 0 (isoelectric) to 100 (awake) where 80 reflects some sedation and 40 to 60 adequate depth of anesthesia with reasonable rapid recovery (Arya et al., 2013).

Awareness under anesthesia is an unintended intraoperative distressing complication during general anesthesia and can occur due to various reasons. This awareness has the potential for long-term psychological consequences; hence, every effort of utilizing modern technology has been put into clinical practice with a titrated dosage of drugs to prevent it (Samuelsson et al., 2007).

BIS monitoring system is the depth of anesthesia-monitoring device that was introduced in 1992. It works on the principle of providing continuous single variable data on display by integrating processed several EEG discrepancies at various stages of anesthesia by applying QUADRO SENSOR on the patient’s forehead (Parikh, 2012).

Nowadays, BIS has been used in routine clinical practices to achieve adequate depth of anesthesia, and thus, its preference is increasing to obtain remarkable recovery by using a required titrated dosage of drugs.

This leads to reduced propofol consumption, prompt smooth recovery with an adequate depth of anesthesia, and smooth outcome for patients.

In our study, in both groups BIS and non-BIS, there was no significant difference with respect to demographic variables such as age, height, weight, gender, ASA physical status, and duration of surgery (Table 1).

In the group of BIS patients where propofol was titrated as per the BIS target, the induction dose of propofol was 1.75 ± 0.15 mg/kg and the maintenance dose was 5.50 ± 1.5 mg/kg/h. While the propofol dosage in the non-BIS group was according to the standard propofol dose of 2.15 ± 0.15 mg/kg and the maintenance infusion dosage was 9.0 ± 1.8mg/kg/h. The p value is <0.0001 for both loading dose and maintenance dose. This reflected a highly significant difference among them.

Thus, the total propofol consumption in the BIS group was reduced to 8.25 ± 1.7 as compared to the non-BIS group value where the total propofol required was 11.15 ± 2.5mg/kg with a p value <0.0001, a highly statistically significant (Table 2).

Parikh and Mehta’s study entitled “Utility of BIS index for titration of propofol dosage and recovery from anesthesia” revealed observations similar to ours where they observed a total propofol consumption in the BIS group of 7.28 ± 1.38 versus 10.86 ± 2.03 mg/kg in the non-BIS group which is reduced with an early recovery in the group of BIS patients (Parikh, 2012).

Their observations had similar results to the study of Masula et al. research entitled “BIS monitoring is useful to reduce the total amount of propofol and to obtain immediate recovery after propofol anesthesia” who studied 46 pts and concluded that propofol required was decreased significantly in the BIS group of 709 ± 210 mg compared to the control group of 914 ± 326 mg with a p< 0.05 (Masuda et al., 2002).

Other eminent researchers ELerkMarnRk and Myus also had similar observations and henceforth strengthen our results (Ellerkmann et al., 2006; Myles et al., 2004)

Thus, it is stated that clinical utility trials showed that the BIS has the potential to be used as an index to measure the pharmacodynamic effect of propofol and facilitate its titration of dosage which allows improved recovery from anesthesia.

In our study, we monitored hemodynamic parameters; the mean heart rate (HR) and mean arterial pressure (MAP) at various time intervals were observed and variations were seen. The patients of both groups remained hemodynamically stable throughout.

However, the HR and MAP of patients in the BIS group showed fewer fluctuations as compared to the non-BIS groups (Figs 2 and 3).

The HR and BP increased immediately after intubation in both groups, and this increase was more evident in the non-BIS group. The reason for fewer fluctuations in hemodynamic variables in BIS could be due to the titrated dosage of drugs given according to BIS values during the perioperative period.

These results suggest that BIS monitoring aids to stabilize hemodynamic parameters during induction of anesthesia with titrated propofol dosage as compared to a routine dosage regimen.

Biswal in his study “Evaluation of the effect of BIS monitoring in patients undergoing Renal Transplant” included 30 adults and concluded that the hemodynamic parameter variability was lesser in the BIS group compared to the control group. These results were in accordance with our study results (Biswal et al., 2017).

In our study, we found that 98% of patients in the BIS group and 92% of patients in the non-BIS group showed no awareness while 2% of patients in the BIS group and 8% of patients in the non-BIS group reported awareness postoperatively when interviewed by a modified form of BRICE questionnaire at various time intervals (Fig. 4).

Ambulkar in her study among the Indian population revealed the incidence of awareness to be <0.33% and mentioned that the reason for such decreased incidence of awareness would be that the patients received inhalation-based balanced anesthesia and respiratory gas monitoring with ETAC (end-tidal anesthetic agent concentration) measurement that led to dose accuracy for adequate depth of anesthesia (Ambulkar et al., 2016).

Norton et al. in their research on “Intra-operative awareness detected using BRICE interview in European Journal Of anaesthesia” included 118 patients and interviewed them with a BRICE questionnaire post-anesthesia; a total of 8 patients answers proved awareness and dreams during general anesthesia. This would account near to 9% on approximation, remarkably similar to ours (Norton et al., 2013).

Avidan et al. conducted a randomized control trial and implemented the modified BRICE questionnaire in 967 BIS-monitored patients, and 6 patients among them reported awareness (Avidan et al., 2008).

On the other hand, Myles et al. in 2004 included 1225 patients in the BIS group and only 2 patients had a recall of events (Myles & Cairo, 2004).