A Prospective, Randomized, Double-Blind, Active-Comparator, Pilot Study to Observe Relative Efficacy of Ultrasound-Guided Erector Spinae Plane Block (ESP) vs. Combination of Ultrasound - Guided Erector Spinae Plane Block With Serratus Anterior Plane Block in Managing Post-operative Pain Following Thoracic Surgery.

Once consented, the patient will be randomized by computer generated random number to one of the two treatment groups.

Blinding Plan: At the acute pain management office, one member of the research team will be responsible for providing the anesthesiologist in charge of performing the block with a sealed envelope. Each envelope will be labeled with a number corresponding to a matching number labeled on each patient binder. This envelope will contain the randomized block to be administered - ESP with SAP or ESP with SAP normal saline. Once the anesthesiologist knows which block combination to administer, he/she will reseal the envelope and return it to the research team member. This process allows only the anesthesiologist performing the block to have knowledge of the block being administered, keeping both the patients and research team members blinded. The envelopes and binders will be kept by the principle investigator in a safe place and only reopened to be analyzed at the end of the study.

All study procedures will take place in the preoperative patient room in DAS prior to surgery, as is standard practice in this institution. The consent process will take place prior to performing any research procedures.

If randomized to the ESP block with SAP normal saline, an anesthesiologist on the Acute Interventional Perioperative Pain Service (AIPPS) will administer the block with this approach: Prior to initiating the block procedure and receiving any sedative medications, patient will be asked to give 3 maximum efforts using the incentive spirometer by first taking a maximum breath in and blowing out forcefully and completely into the incentive spirometer device. Average of these three efforts will be recorded as the patient's incentive spirometer effort baseline. Patient will be positioned in seated position with side to be blocked marked. T5 spinous process will be identified by palpating starting with C7 and continuing caudad. C7 is the most prominent spinous process anatomically. T5 spinous process will be marked with a marking pen. Block area will be cleaned using 2% Chlorhexidine solution. Entire block procedure is performed under strict aseptic technique. Ultrasound probe covered in sterile probe cover will be placed at the T5 spinous process in a cephalad to caudad orientation and moved lateral until the T5 transverse process is identified. 1-2ml of 1% lidocaine will be administered just above the ultrasound probe for local skin infiltration. An 18 gauge Touhy needle will then be inserted in plane in a cephalad to caudad direction under ultrasound visualization until the tip of the needle touches the T5 transverse process. The T5 transverse process is the anatomical target for this block. 20ml of 0.375% bupivacaine will then be injected using slow fractionated injection, aspirating every 5ml to ensure needle tip is not intravascular. Local anesthetic spread in the appropriate plane will be confirmed with ultrasound. Once injection is complete, a 20 gauge non-stimulating catheter will be inserted through the Touhy needle. Catheter tip placement will be confirmed with ultrasound.

SAP Approach with normal saline - Patient will be placed in a lateral position with the side to be blocked facing up. After disinfecting the block area with 2% Chlorhexidine solution and under strict aseptic technique the ultrasound probe will be placed over the midclavicular region of the thorax in a sagittal plane. Ribs will be counted inferiorly and laterally starting with the 2nd rib, until 5th rib is identified in midaxillary line. At this level the 3 appropriate muscle layers overlying the 5th rib are easily identifiable. Latissimus dorsi M. is superficial and posterior, teres major m. is superior, and serratus m. is deep and inferior. Skin at the block site will be infiltrated with 1-2ml of 1% lidocaine, and a 20 gauge Touhy needle will be introduced in plane under ultrasound visualization in a superoanterior to posteroinferior direction just above the Serratus m. At this point 20ml Normal Saline will be injected using slow fractionated injection, aspirating every 5ml to ensure needle tip is not intravascular. Injectate spread in the appropriate plane will be confirmed with ultrasound. Total procedure time for both injections is expected to take 30 minutes from start to finish.