Dural Puncture Epidural Versus Epidural Anesthesia for Cesarean Delivery

The aim of this study is to compare the onset time of anesthesia between standard epidural and Dural Puncture Epidural (DPE) for cesarean delivery. The study will hypothesize that a DPE technique with a 25-gauge spinal needle will have a faster onset and improved quality of surgical anesthesia when compared to a standard epidural. Participants will be blinded to which group they are being assigned. An unblinded anesthesiologist will insert the epidural or DPE based on randomization. After insertion of the epidural or DPE, a low dose local anesthetic infusion will be infused into the epidural catheter up until the time of surgery. This is the standard infusion used to provide pain relief in laboring women (bupivacaine 0.0625% with 2 mcg/ml fentanyl). In this way participants enrolled in the study would mimic anesthetic the conditions of a "labor epidural".

Participants will then move on to the next phase of the study. In this phase, the epidural pump will be discontinued, and anesthesia care will be conducted in the same manner as all cesarean deliveries under epidural extension anesthesia (this refers to the process of providing anesthesia using a pre-existing epidural/DPE that was inserted for the purpose of providing labor analgesia). Anesthesia will be induced in a standardized manner with 20 ml of 3% chloroprocaine. Motor and sensory block will be tested at the end of the epidural loading dose. Loss of sharp sensation will be measured using a blunt plastic neurotip® (Owen Mumford, USA) until a sensory bilateral block to the T6 dermatomal level has been reached. The T6 level measured at the xiphoid process will be marked bilaterally with a washable marker pen to guarantee the precision of the primary endpoint (which will be assumed when sensory block goes above T6). Sensory testing will be performed from caudad to cephalad (i.e. from blocked to unblocked dermatomes) to identify the first unblocked dermatome. To identify the level where the sensation of touch is first appreciated, the investigator will ask the question: "Tell me when you feel the sensation of something sharp touching your skin." Both the motor and sensory block evaluations are part of the standard clinical care of patients receiving neuraxial anesthesia. The main difference for participants enrolled in the study is that the frequency of sensory assessments will be increased so that the onset of surgical anesthesia can be accurately documented (approximately every minute and then more frequently as the sensory block approaches the primary endpoints). A second anesthesiologist, blind to the type of block will manage the clinical care of the patient from the beginning of the study (after epidural catheter placement) and will administer the induction drug (prepared by that anesthesiologist as per SOC). There will be no difference in this clinician's care of the subject than if she were not enrolled in the study. This will assess the onset of anesthesia and manage all aspects of the subject's clinical care including the documentation of the local anesthetic (LA) solution administration timing and its clinical effects. The speed of onset will be assessed from the end of epidural test dose. This will be defined as time zero and the start of anesthesia. If required, intra-operative analgesia will be offered in the form of further epidural top-up, intravenous fentanyl, ketamine, nitrous oxide or replacement of neuraxial anesthesia/conversion into general anesthesia as the standard of care (SOC).