1.5 Statistical analysis
Statistical analysis was performed using SPSS22 for windows.
Quantitative variables are presented as mean ± standard deviation when
normally distributed, or as median (interquartile range, IQR) if
non-normally distributed. Independent t-test and chi-square test were
used to compare baseline characteristics between groups. We used
univariate analysis and multivariable logistic regression to evaluate
the risk factors with non-survivors. P < 0.05 were considered
statistically significant.