Bilateral Continuous Erector Spinae Blocks for Post-Sternotomy Pain Management: A Pilot Study

Regional anesthesia-and pediatric regional anesthesia in particular-is a rapidly evolving subfield of anesthesia practice driven with considerable urgency by the growing recognition that even appropriate perioperative narcotic administration can have significant derogatory long-term effects.

Regional anesthetics can provide targeted, continuous analgesia to select dermatomes with minimal additional patient risk and as such have become routine components of opioid-sparing intraoperative and postoperative pain management plans for surgical patients at BCH. In addition to the postulated benefit of reducing overall opioid exposure and potentially reducing the risk for long term physiologic and behavioral dependence upon opioids, regional anesthetics may allow for earlier extubation after selected surgeries, shorter ICU, PACU and inpatient admissions, earlier mobilization, fewer gastrointestinal complications, and improved patient satisfaction scores.

Despite a robust literature supporting the safety and efficacy of regional anesthesia for postoperative pain control across a broad range or surgery types, patient demographics and underlying comorbidities, there are certain classes of surgeries that have (to date) not benefitted from the advantages that regional anesthetics may provide, most notably spine surgery and cardiac surgery.

Concerns have been expressed with regard to regional anesthetics for cardiac surgeries in particular (this being the primary surgical type associated with sternotomies in a pediatric populations), given that most patients are pharmacologically anticoagulated to some extent during their procedures and are thus at increased risk for bleeding. This is further complicated in the pediatric cardiac surgical population as many of these children are intubated for an extended period of time and therefore may not have particularly reliable neurological exams in the setting of neuraxial regional anesthetics-potentially resulting in unrecognized acquired neurological defecits. While there is emerging evidence of improved outcomes with neuraxial regional anesthetics in adult cardiac surgery patients, this has not trickled down to the pediatric population, likely for some of these reasons.

The investigators at BCH are fortunate to have one of the largest concentrated pediatric cardiac surgical populations in the US along with an active, and well organized regional anesthesia service. Because of this, the investigators are in a unique position to more thoroughly evaluate the effectiveness and safety of regional anesthetics in children following cardiac surgery. Furthermore it is thought to be critical that institutions such as BCH take a leading role in documenting the effects of regional anesthesia on the most important outcome measures when considering perioperative medicine. These include: overall pain management, surgical healing, functional recovery, long term pain symptoms, and emotional/behavioral outcomes after surgery.

Recently, the erector spinae block (ESB) has become popular for providing analgesia after a number of anterior chest and abdominal procedures. This is a simple interfascial plane block that can reliably provide unilateral chest and/or abdominal wall analgesia. It has been described in numerous case reports and one case series as an effective block for management of unilateral thoracotomies, unilateral rib fractures, unilateral abdominal incisions and most notably, when used bilaterally, for management of post-sternotomy pain. New case reports and series involving the ESB are being published almost weekly at this point with a growing literature specific to cardiac surgical applications. Indeed a randomized controlled trial to investigate the analgesic efficacy of bilateral erector spinae plane (BESP) blocks compared with conventional treatment for pain after cardiac surgery in adult patients was published recently (2018) with promising results.

As an interfascial plane block in a compressible anatomical space, the ESB is thought to be safe in anticoagulated (or recently anticoagulated) patients. It is fast becoming a preferred anesthetic option for these pharmacologically or otherwise coagulopathic patients as opposed to neuraxial (e.g. epidural) and paraneuraxial blocks (i.e. paravertebral) nerve blocks, which are largely contraindicated in this setting.

Given the ESB's potentially favorable risk profile versus the other blocks that would subserve the same dermatomes (i.e. it is technically less challenging, more distant from critical structures, and thought to be safe in anticoagulated patients) it could provide both a safer and easier to perform regional anesthesia option for many patients. In particular, it offers a new option for a subset of anticoagulated patients for whom other regional techniques (epidural, paravertebral) are contraindicated. This is particularly true for the populations of pediatric cardiac surgical patients at BCH if used bilaterally.

Indeed, given the current information available related to the ESB, the regional anesthesia service at BCH has begun employing it when possible in circumstances when a neuraxial or paravertebral block(s) would commonly be used but is/are relatively or absolutely contraindicated. Patients undergoing thoracotomies while anticoagulated for cardiopulmonary bypass, aortic clamping, etc. have been successfully managed with unilateral continuous ESBs. In addition, thoracotomies in patients with acquired (e.g. dilutional) and other pathologic coagulopathies have been managed with ESBs. As such, the ESB has been adopted for routine use in specific patient populations at BCH and has even occasionally been utilized in lieu of the more longstanding routine PVBs or epidural blocks for patients without contraindication for such.

Retrospective review of BCH outcomes data for 67 ESBs done for a variety of surgeries and populations has not revealed any significant differences between PVBs and ESBs in terms of adverse events, postoperative opiate use, median pain scores, or other standard outcomes measures. As this data is observational in nature, it is difficult to draw firm conclusions as to the efficacy of the two blocks. However, since there are distinct known and described advantages associated with regional anesthetics for postoperative pain management, it would be prudent to evaluate these blocks in a controlled, randomized, trial. Prior to such a trial, a pilot study to evaluate the feasibility of such a trial is warranted.

As such, the investigators propose to evaluate the feasibility of investigating bilateral continuous erector spinae blocks (BESB) for patients undergoing surgical sternotomy by means of a pilot study. For this study, 'feasibility' will be defined primarily as a successful intervention completion rate of 75% or greater of all subjects with no major adverse outcomes. Secondary measures of feasibility will include aggregate 'data integrity' as defined by successful collection of 75% or greater of all possible data points for successfully completed subjects as well as 'efficient intervention duration' as evaluated by intervention completion time being less than 40 minutes.