SPSS 16.0 will be used for data analysis. T-test would be used to assess the difference in sensory block level amongst the groups, The linear mixed model to analyze the continuous changes in systolic pressure and ScO2 over time. X2 test for trends would be used to test the association between adverse effects of anesthesia and the groups. In all cases, a P value less than 0.05 was considered statistically significant.