4.1. Limitations
This study had some limitations. First, the study was conducted on relatively young and healthy patients who underwent numerous types of lower extremity surgeries. However, since resting HR tends to be slow in young and healthy populations,Second, this study included a relatively small number of participants. We sought to control confounding factors by recruiting patients using strict exclusion criteria. However, there were no differences in the demographic data and postoperative outcomes between the 2 groups; therefore, randomization was effective. In addition, significant differences were observed in vital signs during the study drug administration, and the number of participants was not unreasonably small.Third, vital signs were observed for only 30 minutes during the study drug administration. However, considering the duration of the action of NCD, evaluating vital signs until 20 minutes after NCD administration may be reasonable.