 The sample size calculation was based on the ability to detect a difference in incidence of postoperative nausea in between the two groups of 40 i.e. 50 in the ondansetron arm, and 30 in the ramosetron arm, consistent with a previous study. Using a power of 80 β0.2 and a two sided significance levelalpha of 0.05, 45 patients in each group were required. 