Data analysis: Quantitative variables and proportions will be compared with the student t-test and chi-square test respectively. Normality was tested by using the Kolmogorov-Smirnov test. Receiver operating characteristic (ROC) curve analysis will be performed to evaluate the diagnostic performance of clinical/Doppler parameters in identifying patients who experienced spinal-induced hypotension. The area under the curve (AUC) and the respective 95% confidence interval (95% CI) are estimated according to Hanley and McNeil. 1 The AUC curves are compared using the method described by DeLong et al. 2. The results are expressed as percentage (%) or mean ± SD; a p value of <0.05 is considered statistically significant. Statistical analysis will be done with statistical analysis software (SPSS, 17.0, Chicago, IL; MedCalc Software, Mariakerke, Belgium).