Forty pregnant women (36 to 41 weeks gestation) will randomly allocate to two groups. Groups will be defined based on the method used to identify the epidural space for epidural anesthesia: the loss of resistance group (n=20) and the epidural electric stimulation group (n=20). Pain during the cesarean section will be assessed using a numerical visual analog scale and maternal satisfaction by a post-partum interview. The success rate of epidural anesthesia, maternal satisfaction, and neonatal Apgar scores will be compared between groups.

Investigators will place epidural catheter in the epidural space using loss of resistance technique, and will confirm correct placement of the epidural catheter using electric stimulation.

Epidural catheter placement, electric stimulation, and confirmation of response is followed:

Patients will be placed in the left lateral decubitus position. The site will be aseptically prepared and 1% lidocaine will be infiltrated to the skin. An 18-gauge Tuohy needle will be inserted midline of L4/5 interspinous space.

For the LOR group, after identification of the epidural space, the Tuohy needle will be stopped, and a 20-gauge epidural catheter will be advanced through the Touhy needle.

The same process will be followed for the EES group. In addition, the epidural space will be confirmed by epidural electric stimulation using a 20-gauge epidural catheter (RegionalStimTm, Sewoon Medical Co., Ltd, Seoul, Korea, 800 mm) with a conductive guidewire (conductive guidewire, Nitinol, 1100 mm).

After confirming there is no reverse flow of cerebrospinal fluid or blood with aspiration, 3 mL of 1% lidocaine, with 15 mcg of epinephrine (1:200000), will be injected through the epidural catheter as test dose. If there is no response to the test dose, patients will be moved to the operating room. In operating room, 20 mL of 2% lidocaine, 2 mL of bicarbonate (total volume 22 mL) will be administered in divided doses.

Blood pressure (BP), heart rate (HR), oxygen saturation (SpO2), and neurologic assessment findings will be monitored.

Pain relief in cesarean section is assessed in the visual analogue scale (VAS) score. A 10 point VAS, where 0 is no pain and 10 is unbearable pain, is used to assess pain during labor. The scale is assessed after epidural anesthesia. Differences in the VAS we used to assess the efficacy of the epidural anesthesia in decreasing labor pain. Comparison of the change in VAS between groups is used to compare pain control of the two methods. The success of epidural anesthesia is defined by sensory block, without motor block, and a decrease in pain score after adequate dosing of epidural medication. Failure of epidural anesthesia is defined in several ways. Objective outcome include conversion to general anesthesia, conversion to any different form of anesthesia, or pain during surgery.

Patient satisfaction will be evaluated by a postpartum interview. Satisfaction is graded between a score of 1-5, where 1 represent very unsatisfied and 5 represent very satisfied. Patients will indicate a score of 1 to 5.

One- and 5-minute Apgar scores will be compared to assess the effect of epidural electric stimulation on the neonate. Additional time required for epidural electric stimulation will be determined by the difference (in seconds) from LOR to identification of the epidural space through electric stimulation.

Inclusion Criteria:

• Patients who were at 36 to 41 weeks' gestation and admitted in labor to the university clinic for cesarean section were included. Patients were American Society of Anesthesiologists (ASA) physical status of I or II, and were scheduled to receive epidural anesthesia.

Exclusion Criteria:

• Skin infection at the injection site
• Difficult catheter placement owing to previous lumbar spinal surgery or deformity
• Presence of a hemostatic disorder or use of antiplatelet therapy
• Presence of a cardiac pacemaker.
• Removal of patient

Maternal

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