Sampling
hypotensive
HYPOTENSIVE
Because our study was the first study to compare the effect of deliberate hypotensive anesthesia using nitroglycerine versus phentolamine on P300, we calculated the sample size based on the results of a pilot study we performed before starting our study. The sample size calculation was done using G*Power version 3.1.9.7 Software. The probability of type I error (α) was 5%, effect size = 0.821, df = 78, critical t = 1.99, noncentrality parameter λ = 3.673, A total sample size of 40 patients in each group was required to achieve a statistical power (1–β) 95%.