A Randomized, Subject-Masked, Active-Controlled, Parallel-Arm Clinical Trial Comparing Erector Spinae and Paravertebral Nerve Blocks

This investigation will be a randomized, subject-masked, active-controlled parallel-arm, human subjects clinical trial. Of note, the investigators will be using standard-of-care local anesthetic under an FDA-approved purpose and do not plan to research a possible change of indication or use of these medications as part of this research project. The treatments in both groups are currently used at the study institution and there is true clinical equipoise at this time. The only difference in treatment between subjects who enroll versus those not enrolled in this study will be those who enroll will have the decision between which anatomic block location determined randomly, as opposed to the physician simply choosing him/herself.

Enrollment. Consenting adults undergoing breast surgery with a planned single-injection regional analgesic will be offered enrollment. Patients undergoing breast surgery with a planned perineural catheter regional analgesic will be excluded. 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 University of California San Diego (UCSD) Institutional Review Board (IRB)-approved Informed Consent Form (ICF). Selection for inclusion will not be based on gender, race, or socioeconomic status. The study population of interest includes men and women of all races and socioeconomic status. Inclusion and exclusion criteria are listed in another section.

Preoperative Procedures. Following written, informed consent, the investigators will collect baseline anthropomorphic information (e.g., age, sex, height, and weight). All subjects will have a peripheral intravenous (IV) catheter inserted, standard noninvasive monitors applied, supplemental oxygen administered via a nasal cannula or face mask, and placed in the sitting position. Midazolam and fentanyl (IV) will be titrated for patient comfort, while ensuring that patients remain responsive to verbal cues. Both possible block locations will be viewed with ultrasound. If one or both of the locations is unacceptable for block placement in the clinician's opinion, the subject will not be randomized and will not proceed further with the study.

Subjects will then be randomized using a computer-generated list and opaque, sealed envelopes to one of two treatment groups: (blocks of 4, stratified for unilateral vs. bilateral surgery): (1) erector spinae plane or (2) paravertebral block. All blocks will be placed by a regional anesthesia fellow or resident under the direct supervision and guidance of a regional anesthesia attending (or by the attending him/herself).

The area of needle insertion will be cleaned with chlorhexidine gluconate and isopropyl alcohol. All blocks will be placed using standard UCSD ultrasound-guided techniques.