Statistical Analysis
The primary outcome of the study was total propofol consumption. The
power analysis was based on the results of the study conducted by
Luginbuhl et al. [12]. The authors found that total consumption of
propofol was 6.03±1.4 mg/kg and 6.64±0.9 mg/kg consecutively in groups
using BIS and not using BIS (p=0.023). With a power of 80% and an alpha
error of 5%, the sample size calculation determined that 60 patients
were required for each group, using the G ∗ Power (v3.1.7) program.
Considering the possibility of drop out and lack of data, the total
number of patients required for the study was determined to be 130 (65
patients for each group). We analyzed the data with SPSS version 16
(SPSS Inc., Chicago, Illinois, USA). Convenience of parameters to the
normal distribution was assessed with Shapiro Wilks test while assessing
the study data. Student t-test was used in comparing quantitative data
for comparing parameters that showed normal distribution between the two
groups, while Mann-Whitney U test was used in comparing data that did
not show a normal distribution between the two groups. Chi-square test
and Fisher’s exact tests were used in comparing qualitative parameters.
p ≤ 0.005 was considered statistically significant.