2.7. Statistical analysis
blood coagulation
Continuous variables are tested by histogram and Shapiro-Wilk test, and those that conformed to normal distribution are expressed as mean and standard deviation (SD); those that did not conform to normal distribution are expressed as median and quartile spacing. By performing covariance adjustment on the four indexes of blood coagulation prior to locking, the least-squares mean difference (LSMD) and its corresponding 95% confidence interval (95%CI) were computed. When the proportion of missing values was below 20% and the assumption of random missingness was made, multiple imputation by chained equations (MICE) was utilized to handle the missing variables. Specifically, predictive mean matching was employed to impute the missing values of the four indexes of blood coagulation 7 d after the initial locking [Due to the uneven distribution of the catheter insertion location as baseline data, we performed a post hoc analysis to adjust this confounding factor: using the internal jugular vein and subclavian vein as subgroups, an analysis of covariance is performed in the four indexes of blood coagulation 10 minutes after locking, and a forest map is drawn. The α segmentation is used to control class I errors that come from multiple comparisons, and To get the following data, before the start of the experiment, a two-month pre-experiment is conducted. The results show that the mean APTT of the control group is 36.74±4.74 seconds, and the mean APTT of the experimental group is 32.84±7 seconds. Setting two-sided α = 0.05 and the power is 90%, the sample size of the experimental group N1 = 51 cases and the sample size of the control group N2 = 51 cases are calculated by PASS 15 software. Taking into account the 20% loss to follow-up and refusal to follow-up, at least 64 subjects in the experimental group and 64 subjects in the control group are finally required, and a total of at least 128 cases are included. This study includes 152 subjects totally. Sample size calculation was only conducted for the main outcome indicator, namely the APTT at 10 min after tube locking. The lack of sample size calculation for the remaining outcome measures may have led to inadequate statistical power and an increased risk of type II error, thereby potentially yielding false-negative results.All data are analyzed using the IBM SPSS Statistics for Windows (SPSS, ver. 25.0, USA) and R software (version 4.2.1, available at 