 There are two possible outcomes in our study: a satisfactory outcome is defined if the sensory block reaches at least at T6 and the patient does not complain of any pain or discomfort that requires intraoperative supplemental drugs; an unsatisfactory outcome is defined if the sensory block reaches a level lower than T6 or the patient complains of pain or discomfort that requires intraoperative supplemental drugs. The decision whether or not the supplementation is required will be made exclusively by the patient, and not by the physician in charge. 