A Pain Study Comparing Two Commonly Used Medications to Treat Pain After Bowel Surgery

Overview

This research study is testing whether the local anesthetic lidocaine is as effective as ropivacaine for post-operative pain control in continuous thoracic paravertebral nerve blocks. Ropivacaine and Lidocaine are FDA-approved drugs that has been successfully used in this hospital for post-operative pain control for the past few years, thus has become the standard drugs used for this nerve block. Lidocaine has numerous potential advantages over ropivacaine, such as faster onset of action, better safety profile and greater anti-inflammatory action. Catheters placed near both sides of a patient's spine for postoperative pain control are called thoracic paravertebral nerve blocks and are a part of routine care. Through those catheters, a "numbing" medication, or local anesthetic, to block the transmission of pain from the surgical incision to the spinal cord, thus reducing pain. The research part of the study is whether subjects will receive either the local anesthetic lidocaine or ropivacaine. The goal of this study is to determine whether the lidocaine controls pain better and facilitates a faster recovery after abdominal surgery than ropivacaine. In this research study, the investigators will compare patient-reported pain scores, any additional pain medication requirements for adequate pain control, time it takes for bowel function to return to normal following surgery, as well as the incidence of any side effects, such as numbness and weakness, subjects may experience between those receiving lidocaine versus those receiving ropivacaine. The investigators will screen 100 patients and enroll 60 subjects into this study.

After determining eligibility, subjects will be enrolled in one of the two study groups on the day of surgery using a sealed envelope determined by a computer-generated list that made assignments randomly based on enrollment number. The study groups are defined as: Study group: Lidocaine 0.25%(L) 32 patients Control group: Ropivacaine 0.2%(R) 32 patients Paravertebral nerve block catheter placement and activation: After standard monitors and supplemental oxygen are applied, the patient will be placed in a sitting position. The two points of needle entry will be marked on the skin corresponding to each of the bilateral paravertebral catheter placements. The thoracic spine level will be at the anatomic level corresponding to the midpoint of the incision as determined by the surgeon preoperatively (range T7 to T11). The needle entry sites will be 2.5 cm lateral on each side of the midpoint of the spinous process of the corresponding thoracic vertebrae. The area will be prepared and draped in a sterile fashion, and 1% lidocaine infiltrated subcutaneously at each point of anticipated needle entry. For each of the two catheter placements, a sterile 18 gauge Tuohy needle (B. Braun Medical, Inc., Perifix Continuous Epidural Anesthesia Set, Product Code CE18T) will be introduced perpendicularly to the skin until the transverse process is encountered, and the depth to the skin will be noted. The needle will then be readjusted in a caudad direction and inserted inferior to the corresponding transverse process to a depth approximately 1 cm deep to the transverse process. After final needle placement, a hanging drop technique will be used to rule out intrapleural placement while the patient inhales and exhales deeply. Next 5 mL of 0.5% Ropivacaine will be injected incrementally through each needle after negative aspiration, followed by insertion of the nerve block catheter to a depth 5 cm beyond the tip of the needle. An additional 10 mL of 0.5% Ropivacaine will then be injected in 5 mL increments with negative aspiration in between, through each catheter yielding a total activation dose of 15 ml of 0.5% Ropivacaine on each side. The catheters will be secured with Steri-strips and a transparent occlusive dressing. Vital signs will be monitored by the nurse at regular intervals until the patient is taken to the operating room. Postoperative Management: Post Anesthesia Care Unit (PACU): Following routine intraoperative general anesthesia care, management in the post-anesthesia care unit will follow the standard of care for colorectal surgery. Bilateral paravertebral infusions of ropivacaine 0.2% or lidocaine 0.25% will be started at 7 mL/hr on each side for the patients depending which to group they were randomized. The patients in both groups will also be given access to PCA dilaudid (0.2 mg bolus, 8 min lockout, no basal infusion, no 1-hour limit) once verbal pain score is ≤4. Additional pain relief is available via nurse-administered 10 mL/hour boluses of ropivacaine 0.2% or lidocaine 0.25% via the catheter pumps (5 mL each side for paravertebral group).This will be continued until the patient is able to tolerate oral pain medication. A single IV bolus of ketorolac at 7.5 mg will be available for additional pain management. Patient reported pain scores and total analgesic requirements will be recorded. Once adequate analgesia is established without any signs of adverse effects from the nerve blocks, the patients will be transferred to a hospital floor bed. Floors: After discharge from the PACU, additional pain relief is available via nurse-administered 3 mL boluses of local anesthetic via the catheter pumps (3 mL each side for paravertebral group) given no more than hourly. In addition, nurse-administered intravenous boluses of dilaudid 0.3 mg every 30 minutes as needed up to 2 doses while the patient has PCA, and 0.8-1 mg every hour as needed up to 4 doses in 2 hours once the patient is taking oral pain therapy and is off the PCA. All patients will be assessed daily by members of the acute interventional perioperative pain service. Also, a member of the acute pain service will be on-call 24 hours if inadequate pain control or side effects arise. The infusion rates via the paravertebral catheters may be adjusted at the discretion of the pain service up to a rate of 10 mL/hr of either lidocaine 0.25% or ropivacaine 0.2% on each side (standard infusion rate used at UPMC). The PCA dose may be adjusted as deemed necessary by the acute pain team in order provide adequate analgesia. In addition 7.5mg IV of ketorolac may be administered every 6 hours for the first 48 hours. Once the patient is able to tolerate oral liquids as determined by the surgeon, the PCA will be discontinued and oxycodone 5 mg available to the patient every 4 hours as needed for mild-moderate pain or oxycodone 10 mg every 6 hours as needed for severe pain. These doses may be adjusted as necessary by the pain service. All paravertebral catheters will be stopped and removed on the day after the patient has his/her first bowel movement or post-operative day #4, whichever occurs first. Pain scores collected by the nurses and supplemental analgesic requirements will be the data points for this study. Also, return of flatus and first bowel movement as documented in the AIPPS and surgery team's daily round notes will be recorded during the length of the hospitalization respectively. For each patient, the investigators collected numerical rating scores (NRS) for pain at rest and during movement at baseline, at postanesthesia care unit discharge, at 24 hours and 48 hours after the end of surgery,