Continuous Erector Spinae Plane Blocks to Treat Postoperative Pain After Open Gynecologic Procedures Via a Low Transverse (Pfannenstiel) Incision: A Randomized, Triple-masked, Placebo-controlled, Split-body Clinical Trial

Open gynecologic surgery can be significantly painful. With the goal of minimizing the use of opioids (with undesired side effects and potential for abuse), the investigators frequently administer bilateral single-injection erector spinae plane (ESP) blocks which help to numb the surgical area and decrease postoperative pain. However, the numbing medication typically lasts for only 8-18 hours. For other peripheral nerve blocks, this duration can be increased with the insertion of a percutaneous catheter-a tiny tube smaller than a piece of spaghetti-followed by an infusion of additional local anesthetic. However, the effects of the various peripheral nerve blocks are determined by the anatomy and physiology of the specific peripheral nerve, with an infusion resulting in dramatic benefits for one nerve yet having no effect for another. The potential benefits and risks of adding a catheter and subsequent local anesthetic infusion to a single-injection ESP block remain unknown.

The investigators therefore propose a randomized, triple-masked, placebo-controlled, split-body clinical trial to determine the potential benefits and risks of adding the infusion to single-injection ESP blocks. Patients undergoing gynecologic surgery via a low transverse (Pfannenstiel) incision who already have bilateral ESP blocks as part of their analgesic plan will be offered enrollment. Participants will have bilateral catheters inserted through the same block needles used for their single-injections, followed by perineural administration of bupivacaine on one side and normal saline on the other (determined randomly and in a triple-masked fashion).

This will be a single-center, randomized, triple-masked, placebo-controlled, split-body human subjects clinical trial.

Enrollment. Participants will be consenting adults undergoing open gynecologic surgery via a low transverse incision. Study inclusion will be proposed to eligible patients prior to surgery. If a patient desires study participation, written, informed consent will be obtained using a current Institutional Review Board-approved informed consent form. The study population of interest includes women of all races and socioeconomic status. Inclusion and exclusion criteria are listed in section #10 below. Of note, the investigators will be using local anesthetic, perineural catheters, and infusion pumps as approved/cleared by the Food and Drug Administration and do not plan to research a possible change of indication or use of these medications/devices as part of this research project.

Preoperative Procedures. Following written, informed consent, the investigators will record baseline anthropometric information (age, sex, height, and weight) that is already provided by all patients having surgery. Participants will have a peripheral intravenous catheter inserted, standard noninvasive monitors applied, supplemental oxygen administered via a nasal cannula or face mask, and positioned sitting. Intravenous midazolam and fentanyl will be titrated for patient comfort, while ensuring that patients remain responsive to verbal cues. The area of insertion will be sterily prepared and a clear, sterile, fenestrated drape applied. In the sitting position and with ultrasound guidance, after subcutaneous local infiltration with lidocaine- a 17g Tuohy and 5-10 ml of saline with 1:200,000 epinephrine will be used to identify the correct plane, as defined by a hyperechoic shadow of the 10th transverse process and erector spine muscle immediately superficial. Once appropriate needle tip location is confirmed, a perineural catheter will be inserted under ultrasound guidance. This procedure will be repeated on the contralateral side.