Sample size, with a reliability of 95%, a power of 80% and an expected rate of improvement in experimental group of 80% was calculated , for a total of 75 patients, and were randomly assigned to one of the three study groups, each group consisted of 25 patients. The investigators selected all patients who met the inclusion criteria such as age between 18 and 60 years , scheduled for elective surgery, have pre-anesthetic assessment, be classified according to their risk as ASA I or ASA II, having a body mass index between 18.5 and 29.99, not be pregnant, have a higher fasting 8 hours the day of the procedure, require regional anesthetic technique without contraindications to the procedure and can be performed with the patient in the lateral decubitus , have not known history of allergy, and haven't as an exclusion criteria malformations of the spine level that would prevent a spinal block without difficulty.