DPE Technique in Labor Epidural for Morbidly Obese Women

The primary purpose of this study is to determine differences in block quality between the "dural-puncture epidural" (DPE) and standard epidural (EPL) techniques for labor analgesia in the morbidly obese patient. The investigators hypothesize that when compared to the standard EPL, the DPE technique will improve block quality . Study participants will be randomized by computer-generated sequence to EPL or DPE arms, stratified by class of obesity (BMI 35-39.9 kg/m2, 40\< 50 kg/m2 and ≥ 50 kg/m2) and by parity (nulliparous versus multiparous). All patients will receive a neuraxial technique in the sitting position at L3/4 or L4/5 using loss of resistance to saline. In the DPE group, a 25-g Whitacre needle will be used to puncture the dura. In both groups, the epidural catheter will be threaded 5 cm in the epidural space with an initiation dose of 15 ml of ropivacaine 0.1% with fentanyl (2 mcg/ml) over 6 minutes as per standard practice. After the initial loading dose and epidural pump is started, the blinded investigator will enter the patient's room to start data collection (time 0). Data will be collected for the first 30 minutes of epidural placement at 3,6,9,12,15,18 21, and 30 minutes to detect the time to achieve target pain ≤ 1/10, then assessed at standardized times (ever 2 hour) until delivery. Breakthrough pain will be managed by a standardized protocol. Other data to be collected will include: catheter adjustments and replacements, physician top-ups, asymmetrical block, pain score, motor block, sensory level to ice, hypotension, total anesthetic dose required, and PCEA use. The primary outcome of this study is block quality defined by a composite of five components: (1) asymmetric block after 30 minutes of initiation, (2) top-up interventions, (3) catheter adjustments (4) failed catheter requiring replacement, and (5) failed epidural requiring general anesthesia or replacement neuraxial anesthesia for emergency cesarean section. Secondary outcomes include