Sample size
PONV
The sample size calculation was based on our preliminary data, which indicated that 55% of the patients experienced PONV within the first 48 h postoperatively. Thus, we considered a 35% reduction in the incidence of PONV as clinically significant. The required sample size was estimated using Power Analysis and Sample Size software (PASS, version 15.0. NCSS, LLC. Kaysville, Utah, USA). The result suggested that 104 patients in the Control group and 207 in the PHC group would be necessary to achieve a power of 90% (