Anesthesia, Spinal (MeSH: D000775)

This study compares two methods of identifying the correct intervertebral level before performing spinal anesthesia in women undergoing elective cesarean delivery. In current practice, anesthesiologists locate the puncture site by feeling anatomical landmarks on the lower back (palpation of Tuffier's line). Ultrasound imaging offers an alternative in which the spine is scanned and the intended level is marked on the skin before the needle is inserted. It is not yet clear whether this additional step improves the success of the procedure or affects the mother's blood pressure and heart rate after the block. Sixty pregnant women scheduled for elective cesarean section will be randomly assigned to one of two groups. In one group, the puncture level will be determined by preprocedural ultrasound marking; in the other, by conventional landmark palpation. All other aspects of anesthetic care, including drug doses, will be identical in both groups. The main outcome is the proportion of patients in whom the subarachnoid space is entered successfully at the first attempt with a single skin puncture, producing a block adequate for surgery. Additional outcomes include the number of needle passes, procedure duration, changes in maternal blood pressure and heart rate, vasopressor requirement, sensory block level, and complications such as headache or back pain within 24 hours after surgery.