Analgesic Benefit of PECS Blocks for Biceps Tenodesis Shoulder Surgery

Overview

The standard practice for arthroscopic shoulder surgery at our institution is a general anesthetic with a long-acting interscalene block for post-operative pain control, which can reduce the amount of opiates needed after surgery. The interscalene block is effective in providing analgesia to the majority of the shoulder joint and has been shown to reduce post-operative pain scores after arthroscopic shoulder surgeries. However, there is a subset of arthroscopic shoulder surgery patients who have pain in the axilla even in the setting of a functioning interscalene brachial plexus nerve block. One of our surgeons has reported a high incidence of axillary pain in patients who undergo a sub-pectoral biceps tenodesis as part of their arthroscopic procedure. A newly described nerve block approach to the nerves that supply sensation to the axillary region called the PECS "Pectoralis" 1 \& 2 block may provide additional analgesia to these patients. The purpose of this prospective, randomized, observer and patient blinded, single-center, sham block trial is to determine if the addition of PECS blocks to an interscalene block will reduce the severity of axillary pain following arthroscopic shoulder surgery that involves a sub-pectoral biceps tenodesis. Secondarily, the study will assess the duration of PECS 1 \& 2 and whether the block reduces post-operative opioid usage. We hypothesize that the addition of the PECS 1 \& 2 block will reduce the severity of axillary pain at 6hrs and reduce postoperative narcotic usage for the first 24 hours.

Subjects that meet the inclusion criteria will be assigned a group by using a random numbers generator. All subjects will receive the standard practice at our institution of an interscalene brachial plexus block along with a general anesthetic. The intervention arm will get an additional local anesthetic block targeting nerves that we presume cover the axillary region (PECS "Pectoralis" 1 \& 2). These nerves in the upper chest are the lateral branches of the 2nd to 5th intercostal nerves, which includes the intercostobrachial nerve. The anesthesiologist placing the nerve blocks will be un-blinded to perform the procedures. Both the surgeon and the Acute Pain Service anesthesiologist will be blinded as to whether or not the intervention was provided to any given subject. The Acute Pain Service team will remain blinded and collect the data outcomes. Initially, pilot data was collected in a total of ten patients with five patients randomized to each arm. Primary endpoint was NRS "Numerical Rating Scale" of 0-10 at 6hrs after block placement. Our pilot data indicate that the mean NRS is about 5 for the control group, with a standard deviation of 1.4. Using a two-sided two-sample t test (an alpha of 0.05 and power of 0.95), we conservatively estimate that 14 subjects per arm will be needed to detect a clinically meaningful difference of 2 in NRS between the arms. We decided to plan enrollment of 20 subjects per arm for potential loss during this randomized, double-blinded, single-center, sham block trial. * Potential subjects undergoing arthroscopy will have their electronic medical record reviewed by the study team to look for exclusion criteria. If the subject is excluded, then they will be added to the Screening Log with date and reason for their exclusion. If all inclusion criteria are met, then the subject will be approached in the Regional Anesthesia area for their consent. A copy of the consent will be given to the study subject. The other informed consent document will be maintained by the study team in the research files. * Patients will be asked to provide baseline pain scores both, at rest and with movement, on a scale of 0-10 (0 being no pain and 10 being the worst pain). Preoperative opioid use including drug(s), dosage and frequency will be recorded. Randomization of patients will then occur through the use of sequentially numbered envelopes with only those directly involved in the care of the patient during block placement being aware of which arm of the study the patient has been randomized. Those members of the study team who will be collecting post-operative data will be blinded to the randomization. Standard American Society of Anesthesiology monitors and oxygen will be applied. Unless there is a contraindication, each patient will receive 650mg "milligrams" of oral acetaminophen. To standardize the effect on postoperative pain, ketamine will not be given as a preoperative sedation medication or intraoperative medication. No long acting opioids will be given in the operating room or post-anesthesia care unit. Intraoperative fentanyl will be limited to 5 micrograms per kg "kilogram". Intraoperative dexamethasone will not be given for post-operative nausea/vomiting prophylaxis. Subjects will be sedated as per usual practice and will also be blinded to their randomization. All peripheral nerve blocks will be performed by a resident or fellow under supervision by an attending anesthesiologist. The attending anesthesiologist may perform the procedures alone. All volumes and concentrations of nerve block mixtures administered will be identical to assist in the blinding process. All 40 subjects will receive an ultrasound guided interscalene nerve block using 20mL "milliliters" of 0.25% bupivacaine with 1:400,000 epinephrine and 1:600,000 clonidine dosed at the upper trunk location near the 6th cervical vertebral level, per standard clinical practice. The intervention arm, consisting of 20 patients, will additionally receive the following: 10mL of 0.25% bupivacaine with 1:400,000 epinephrine and 1:600,000 clonidine at the PECS1 location and 20mL of 0.25% bupivacaine with 1:400,000 epinephrine and 1:600,000 clonidine at the PECS2 location as described by Blanco, et al.3,4 All procedures will be performed under a sterile technique including the use of chlorhexidine prep of the skin, sterile gloves, sterile ultrasound probe covers with sterile ultrasound gel, a cap and a mask. For the interscalene block, a 21 gauge 90mm "millimeter" stimulating block needle will be directed, under real-time ultrasound guidance, into the interscalene muscle space at the level of the 5th and 6th cervical nerve roots. Twenty mL of the above local anesthetic mixture will be dosed incrementally, aspirating every 5 mL, to surround the upper trunk of the brachial plexus. For the PECS 1 \& 2 block, a 21 gauge 90mm stimulating block needle will be placed under real-time ultrasound guidance at approximately the level of the 4th and 5th ribs near the mid-axillary line. The needle will be advanced into a tissue plane between the serratus anterior muscle and the pectoralis minor muscle. Twenty mL of the same local anesthetic mixture will be dosed incrementally, every 5 mL, to spread within this PEC2 space. The needle will be withdrawn, following the first injection, to a tissue plane between the pectoralis minor and pectoralis major muscles. Ten mL of the same local anesthetic mixture will be dosed incrementally, every 5 mL, to spread within this PEC1 space. Fifteen and 30 minutes (if no change at 15min) following block placement, success will be assessed by absence/decrease of pin-prick sensation to a 25 gauge Whitacre needle in the following manner: Cutaneous sensation will be tested over the deltoid region to assess for successful interscalene block. Cutaneous sensation will be tested over the lateral aspect of the pectoralis muscles at the level of the nipple. Scoring of sensation will be the following: 0= full sensation, 1= partial sensation, 2= no sensation (complete block) Following block placements, the subjects will be transported to the OR and general anesthesia will be induced. Following intubation, surgical procedure, emergence and extubation, the subject will be transported to the recovery room. In the recovery room or via phone post-discharge, at the 6 hour mark post-block placement, we will ask the subject if they are having any axillary pain. The severity of pain will be determined using the Numerical Rating Scale of 0-10. Zero is no pain and 10 is the most pain possible. Total opiate and benzodiazepine doses will be charted for the preoperative, intraoperative and PACU time frames.