Society for Pediatric Anesthesia Spring 2016 Meeting
Review of General Session I: Regional Anesthesia – “Comfortably Numb”
By Deepa Kattail, MD
The Johns Hopkins Hospital
The Society for Pediatric Anesthesia (SPA) 2016 spring meeting was in beautiful (but snowy!) Colorado Springs, Colorado. After an educational and informative SPPM meeting, the SPA meeting was in full force in the early morning of April 1. We were delighted that the first general session was devoted to pain management, specifically pediatric regional anesthesia.
The session was moderated by SPPM’S Yuan-Chi Lin, MD, MPH (Boston Children’s Hospital), an amazing feat considering Dr. Lin had just chaired the annual SPPM meeting one day earlier! The theme of the session was devoted to the mechanisms and clinical application of regional anesthesia. The main hall at The Broadmoor was completely filled in anticipation of the first general session. The first speaker was well known scientist, Tony L. Yaksh, PhD (University of California San Diego) who presented in his area of expertise, “Neuraxial anesthetic adjuvants”. His talk was focused on the mechanisms of neuraxial agents, specifically in the neonatal population. First, we were given a useful overview of the benefits of neuraxial analgesia for the neonate, such as minimizing exposure of general anesthetic to the developing brain (a hot topic!), reduction in hospital stay and improved surgical outcomes. We were reminded that neonates are a “different species”, a point further emphasized by the research conducted in Dr. Yaksh’s lab. From a mechanistic standpoint, differences in neonates are attributed to innervation patterns which are “in flux” and the delayed maturation of C and A fibers, which play key roles in pain transmission.
Next, Dr. Yaksh reviewed various medications currently used for neuraxial administration, including opioids, local anesthetics, and alpha-2 adrenergic agents. Despite the widespread and safe use of these agents for more than half a century, their use remains “off-label” due to a lack of systematic assessment that is required by the FDA. As pediatric anesthesiologists, most of us are quite familiar with this quandary, since the pediatric population is well known as “orphans” and excluded from FDA trials involving analgesics, due to ethical constraints. This controversy remains an issue and apparently major pain and anesthesia journals now have guidelines for accepting studies that involve the use of such "off-label" medications, including availability of systematic preclinical safety or specific FDA approval before a trial commences.
Parameters for preclinical intrathecal safety include defined injectate distribution (volume/age), defined nociceptive endpoints (measured using mechanically evoked withdrawal), and spinal histopathology. Examples provided were comparison of intrathecal (IT) administration of morphine and ketamine, including measurement of lowest therapeutic dose. Based on Dr. Yaksh’s studies, no significant apoptotic changes were observed at the spinal cord after various doses of IT morphine, whereas spinal histopathology performed after administration of IT ketamine demonstrated an increase in the number of degenerating and apoptotic neurons at 24 hours post-injection. The final message delivered to the audience was a succinct summary of the relationship between various neuraxial adjuvants. Based on ratio of minimum dose producing a pathological signal, and the dose required to produce an analgesic signal, morphine = clonidine = bupivacaine>>ketamine.
The session continued with a second speaker, Robert K. Williams, MD (Vermont Children's Hospital). Dr. Williams has become a well known spokesperson for the use of spinal anesthesia in young neonates, without concurrent use of general anesthesia. His talk started with a video of Dr. Christine Pedro (CA-1 resident physician) administering an awake spinal anesthetic to a young infant in preparation for ventral hernia repair. The video was remarkable! The procedure was completed within minutes, while the baby was fully awake and held in the sitting position. We then see the baby supine on the operating room table, pacifier in place, awake and ready to be prepared for surgery! This video was quite impressive and really set the mood for more details about this practice at Vermont Children’s Hospital.
In 2015, Dr. Williams’ unique clinical practice received mention in articles published in the New York Times and The Wall Street Journal, discussing the issue of anesthetic neurotoxicity in children. For this reason, Dr. Williams clarified that he is NOT advocating spinal anesthesia due to concerns for anesthetic neurotoxicity, an issue which has yet to be fully investigated with obvious implications of general anesthesia and neurotoxicity yet to clearly established and explained. We then heard of the advantages of awake spinal anesthesia, which were published in a 2006 paper by Dr. Williams and colleagues based on data collected in the Vermont Infant Spinal Registry. First, the relative cardiovascular stability in comparison to general anesthesia, allowing for the placement of an IV in the lower extremity AFTER the spinal anesthetic has been administered. The second advantage is overall decreased anesthesia time (51 minutes versus 66 minutes in control group) since intubation, emergence and extubation are avoided. In fact, his study found that end of case to departure from operating room was six minutes. To conclude his talk, Dr. Williams played a second video, another impressive demonstration of Dr. Williams’ famed technique.
The final speaker of the regional anesthesia session was Giovanni Cucchiaro, MD (Children’s Hospital Los Angeles) presenting on thoracic and abdominal blocks. Dr. Cucchiaro gave us a look at his own journey through medicine spanning from Europe to North America and the evolution of pediatric regional anesthesia over the past several decades. He provided a table which categorized what he considered to be old versus new blocks.
His first example was the rectus sheath block, which he categorized as a “new” block, but was quite forthcoming regarding the existing evidence, stating that of three randomized control trials, there was no difference in outcome when compared to local infiltration by the surgeon. He suggested that maybe outcomes would be more positive if the technique was used for specific surgeries, such as laparoscopic cases. He then moved on to the Transversus Abdominis Plane (TAP) block, which he described as the “darling of the fellows”. He described various technical aspects such as needle positioning, location and level of block to improve efficacy in relation to surgical incision. He mentioned that, once again, studies were few, with low participant numbers, although a 2010 meta-analysis did have positive findings, with overall decrease in opioid use and lower pain scores. Dr. Cucchiaro then went on to describe two more novel blocks, the serratus anterior block and quadratus lumborum block. He concluded his talk on a philosophical note, asking the audience, “Should we keep doing what we are doing every day?”. He went on to question whether we as anesthesiologists are performing regional nerve blocks for the benefit of patients or due to the novelty, and concluded that big data (such as NSQIP, Wake Up Safe, and PRAN) will eventually help provide answers to these apt questions.
Overall, the regional anesthesia session was extremely informative and thought provoking. The audience had a chance to learn of the mechanistic actions of regional techniques from Dr. Yaksh and also the real life experiences of well known anesthesiologists Drs. Cucchiaro and Williams. A great start to the SPA meeting for 2016!