Sample size

The sample size is calculated based on the incidence of intraoperative hypotension. Due to intraoperative hypotension lacking a clear definition, some previous studies reported the incidence of hypotension between 5% and 99%.²⁷ In a secondary analysis of VISION trial data, even brief periods of systolic blood pressure (SBP)<100 mm Hg in patients undergoing non-cardiac surgery were associated with myocardial injury and increased mortality.²⁸ Thus, we chose this threshold (SBP<100 mm Hg) to define hypotension. To our knowledge, there have been no studies reporting the incidence of intraoperative hypotension for patients undergoing elective thoracoscopic lobectomy. We conducted a pilot study according to the collected data from 1 September 2021 to 30 September 2021 in our institution. Based on our pilot study, the incidence of intraoperative hypotension is about 36.8% (109 of 296 patients) in the control cohort and 48% (43 of 89 patients) in the exposure cohort. Assuming 95% power with a two-sided α of 0.05, this would require 504 patients per group, with an overall sample of n=1008. An estimated 2300 patients will be included, which represents all patients between 1 September 2021 and 1 March 2022 who meet the inclusion criteria. Therefore, we estimate that the sample size in this study will ensure sufficient statistical power.