2.2. Anesthesia and operating procedures
ALTERNATION
All patients received CSEA for open hysterectomy. L3-4 interspace was the first puncture attempt for CSEA, and the L2-3 interspace was chosen as the alternation when the L3-4 interspace puncture was failed. Unless for special reasons, each patient was placed in the right-side position with the back arched and the arms embracing the knees, which facilitated the use of ultrasound by right-handed operators. In group A, the needle puncture location was marked by ultrasound guidance that was administered using a Sonosite Edge portable system. The puncture interspace was confirmed through twice ultrasound scans. At the first confirmation (Fig. Ultrasound-assisted positioning. (A) The sacrum and L5-S1 interspace were positioned using sliding and tilting scanning techniques in paramedian sagittal oblique orientation with a curved array transducer and the L4-5, L3-4, and L2-3 interspace was successively located by moving the transducer cephalad. Arrowhead indicated sacrum. (B) The T12 vertebra was identified at its joint with the 12th rib and the transducer was moved caudad to identify each consecutive interspace.After positioning the puncture interspace, disinfection and drape were performed. Local anesthesia was administrated with 1% lidocaine and CSEA operation was conducted aseptically throughout the process. Negative pressure method was used to confirm that a 16G puncture needle had entered the epidural space, and then the 25G spinal anesthesia trocar was inserted. A successful dural puncture was verified by the outflow of cerebrospinal fluid (CSF), 0.6% ropivacaine (1.5 ml 1% ropivacaine plus 1 ml 10% glucose) was injected. Then, spinal anesthesia trocar was pulled out, and an epidural catheter was inserted, and the catheter was placed cephalad to a depth of 3 cm. Additional anesthesia needed for epidural was determined according to the length of operation and the block plane of spinal anesthesia. CSEA was performed until it failed up to 5 times, and then it was replaced by general anesthesia.