Analgesic Efficacy of Single-shot Erector Spinae Block for Thoracic Surgery

Purpose To investigate the postoperative analgesic effectiveness of the ultrasound-guided ESP block compared to a placebo injection for patients undergoing thoracoscopic wedge resection of the lung.

Hypothesis Thoracoscopic surgery patients who receive an ESP block in addition to current standard of care, consisting of parenteral and enteral opioids and surgical wound infiltration, will have a clinically significant improvement in their QoR-40 at POD 1 and lower pain levels, as measured by VAS in the PACU on arrival and one hour after, and on POD 1, and OME opioid consumption in the PACU and at 24 hours post-operatively, in comparison to those patients who receive the current standard of care along with a placebo injection.

Justification The ESP block is a novel regional anesthetic technique that has shown efficacy in the management of thoracic pain as published in numerous case reports and observational case series. To date, no randomized control trials exist of its efficacy in comparison to conventional parental opioid analgesic management. Thoracoscopic wedge resections of the lung are procedures not usually treated with regional analgesia techniques, but given the moderate pain experienced by many patients, this surgical population will serve as a proof-of-concept for the potential of improved post-operative analgesic and recovery profiles. Proof of analgesic efficacy in this setting may allow a future head-to-head comparison with more invasive analgesic techniques currently used for thoracic surgery such as epidural and paravertebral catheterizations.

In undertaking this aim, we will measure a number of different metrics. The 40-item Quality of Recovery Score (QoR-40) will be our primary objective as it provides a patient-centered global measure of overall health in the postoperative period. It has been tested for validity and reliability, and has undergone quantification for the minimal clinically important difference. Other traditional metrics of analgesic performance including the VAS and 24-hour post-op OME opioid consumption will also be monitored as secondary objectives.

Objectives

Primary Objective:

• Quality-of-Recovery 40 scale at POD 1.

Secondary Objectives:

• Cumulative OME opioid consumption intra-operatively and through PACU, and at 24 hours post operatively.
• Visual analog pain scale assessments post-operatively in PACU on arrival, after 1 hour, and at POD 1.

Research Design The study will be a prospective, single center, randomized, placebo-controlled pilot study requiring 2 patient visits for assessment in the PACU and on POD 1. One interim analysis for safety monitoring will be undertaken.

Sample Size Calculation and Statistical Methods No prior studies have been conducted to calculate an exact sample size calculation. Based on similar work, we will power this study on an expected difference of at least 10 points on the QoR-40 and a SD of 15 when comparing the block to placebo. This is a clinically meaningful difference. Assuming an alpha level of 0.05 and a power of 0.80, our sample size is 74. With a 10% dropout rate we will require recruitment of 82 patients. All outcomes will be analysed with the independent student t-test.

Inclusion criteria

• 18-75 years of age
• Presenting for elective thoracoscopic wedge resection
• Proficient in the use of the English language
• Able to provide informed consent
• Expected stay > 24 hrs in hospital

Exclusion criteria

• ASA greater than, or equal to 4
• Expected post-operative endotracheal intubation
• High likelihood of conversion to open thoracotomy
• A diagnosis of a chronic pain condition
• Depression or other psychiatric diagnosis
• Dementia
• Pregnancy
• Preoperative opioid use >30mg of oral morphine equivalents per day
• Known alcohol or recreational drug abuse
• Contraindication to local anesthetic use including allergy or sensitivity to ropivacaine or other amide-type local anesthetics
• Contraindication to the ESP block or regional anesthetic technique including: allergy or sensitivity to ultrasound gel; previous spine instrumentation; previous rib surgery; injured, diseased, or infected skin overlying the area to be blocked
• Perioperative use, or planned use, of alternative regional anesthetic technique (not including surgical local anesthetic infiltration)
• Perioperative ketamine and lidocaine infusion use