Although the spread of spinal anesthetic drug is unpredictable, patients factors (age, gender, height,weight, body-mass index), spinal anatomy, anesthetic drug dose, and lumbosacral cerebrospinal fluid volume are known to be the determinants of sensory block level. Among these determinants, the influence of body-mass index (BMI) on spinal anesthesia is controversial, and there is no specific guideline showing the relative priority of these determinants.~Therefore, in these prospective observational study, the investigators are trying to evaluate (1) the influence of body-mass index on spinal anesthetic outcome and (2) the relative influence of these determinants on spinal anesthetic outcome by logistic regression analysis.
In these prospective observational study, the investigators are trying to evaluate (1) the influence of body-mass index on spinal anesthetic outcome and (2) the determinants on spinal anesthetic outcome by logistic regression analysis.