Negative results were obtained in all subjects that were analyzed (n=10)

Epidural analgesia is highly effective for labor pain relief and is widely chosen by pregnant patients. However, placement of the epidural needle can be challenging in pregnant patients due to lax tissue ligaments and edema so that the traditional loss of resistance method (LOR) used to find the space may be subtle leading to retries which may delay onset of analgesia as well as increase the risk of complications. The ability to transduce a pulsatile pressure waveform from epidural needles placed in non-laboring patients correlates highly with successful placement of the epidural needle. We wish to evaluate the efficacy of obtaining a pulsatile pressure waveform with correct epidural needle placement in laboring women.

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.

Inclusion Criteria:

• Female Patients
• ASA I-III
• Term Pregnancy (>37 weeks)
• 18 years or older
• Early Labour (<6 cm of cervical dilation)
• BMI<40

Exclusion Criteria:

• Any contraindication to epidural analgesia placement (coagulopathy, sepsis, infection at site, increased ICP, hypovolemia, unstable ischemic heart disease, unstable neurologic disease, severe aortic stenosis, prior spinal surgery, LA allergy)
• Serious concern for maternal or fetal wellfare.