Statistical analysis
The sample size was calculated assuming that the first-needle-puncture success rate was 0.75 in the single-plane group based on previous studies, which reported success rates of 52–85.5% when using single-plane US-guided technique in IJVC and FVC [Data are expressed as median, interquartile range (IQR), range, count number, or percentage, as indicated. The Kolmogorov–Smirnov test was used to evaluate the normal distribution of continuous variables. Unpaired Student’s 