Efficacy of the Presence of a Pulsatile Pressure Waveform to Confirm Correct Placement of the Epidural Needle and Catheter in Laboring Pregnant Patients: a Feasibility Study

Patients requesting epidural labor analgesia will be eligible for recruitment. After written informed consent is obtained, placement of monitors and aseptic technique, the 17G epidural needle will be placed using the loss of resistance (LOR) technique to air or saline at the lumbar level chosen by the anesthesiologist. When LOR occurs, the needle will then be filled with 2 mL NaCl 0.9% from that syringe and the pressure monitoring accessory will be connected to the needle. The second investigator will then connect the high pressure tubing to the acessory without touching it, and the pressure will be zeroed at level of the needle insertion. Pressure will then be transduced and the waveform, recorded. An epidural catheter (SIMS Portex) will then be passed through the needle and advanced 5 cm beyond the tip of the epidural needle. After securing the epidural catheter in place, the patient will be placed on the lateral position. The catheter will then be filled NaCl 0.9% from a syringe and a high-pressure tubing extension leveled at the spine level will be connected to the catheter and the pressure will be transduced and recorded. Data recorded will include 2 parameters: 1) The presence or absence of a pulsatile waveform, and 2) The actual pressure read at the epidural space, in mmHg. Those readings will be obtained in 2 distinct moments: at a " rest" state, meaning during an interval between contractions, and at an "active" state, during the first contraction after the epidural catheter is placed. A test dose of 3 mL of 2% lidocaine with epinephrine1:200.000 will then be given to exclude potential spinal or intravascular injection. After 3 minutes, a loading dose of 10mL of 0,125% bupivacaine will be given for labor analgesia and the presence or absence of a bilateral sensorial block at T10 or higher at 30 min will be assessed.