Methods
This retrospective study consisted of 9,518 patients who underwent various types of cardiac surgery from July 2001 to June 2015 at three different US medical centers. The study was approved by the IRB committees from University of California Davis, Jefferson University and Christiana Care and consent was waived because this is a retrospective data analysis. All the methods were performed in accordance with the Declaration of Helsinki. After IRB approval, the patient's demographic information and perioperative data were reviewed from the institutional Society of Thoracic Surgeons (STS) database and there were no humans participated in this study directly. The perioperative period is the time the patient goes into the hospital, clinic, or doctor's office for surgery until the time the patient is discharged home. Inclusion criteria were patients who underwent CABG or CABG with other procedures. Exclusion criteria were patients who underwent cardiac surgery without CPB, any type of transplantation procedure, aortic procedure, minimally invasive surgery, non-CABG, and emergency surgery. The clinical follow-up was up to November 26, 2015. Patients with CABG surgery were identified and divided into two groups according to whether lipid-lowering medications were used before the surgery: the lipid-lowering treatment (LLT) group and non-lipid-lowering treatment (non-LLT) group. Postoperative complications, major adverse events, and mortality were evaluated. Postoperative lipid-lowering medication use was also recorded.
Statistical Analysis
Continuous variables were reported as mean ± standard deviation[18] and compared with a 2-sample t tests if normally distributed or as median (interquartile) and compared with Wilcoxon rank test if necessary. Categorical variables were reported as number and percentage, and compared with χ 2 test or fisher's exact test if necessary. Univariate and multivariate logistic regression were performed to assess associations between lipid-lowering use and demographic and clinical outcome variables. The inverse probability of treatment weighting (IPTW) method was used in logistic regression model to evaluate the lipid-lowering medication effect on the study patients for all patients and for patients undergoing CABG without other procedures. The propensity score with the nearest method was used in survival analysis to compare the results of time-event endpoints between groups based on lipid-lowering medication use. Data management and statistical analyses were conducted with R software (version 3.5.2). The Kaplan–Meier method was applied to study patient survival. The log-rank test was used to ascertain differences between groups. P value of equal or less than 0.05 was considered statistically significant.
BMC Anesthesiol. 2022;22(122) © 2022 BioMed Central, Ltd.
