Clinical utility of implantable neurostimulation devices in the treatment of chronic migraine

John A Freeman, Terrance L Trentman Department of Anesthesiology, Division of Pain Medicine, Mayo Clinic Arizona, Phoenix, AZ, USA Abstract: Chronic migraine is a disabling disorder that is costly to individuals and society. Occipital nerve stimulation has been used to treat refractory cases of primary headache disorders including drug-resistant chronic cluster headaches and chronic migraine. The Food and Drug Administration (FDA) off-labeled application of equipment used for peripheral nerve (occipital) stimulation is borrowed from FDA-labeled spinal cord stimulation. Manufacturer-sponsored randomized trials include a feasibility study (ONSTIM-Medtronic) and a safety and efficacy study (St Jude). A non-industry sponsored prospective, randomized crossover study by Serra and Marchiotretto suggests improved quality of life and a significant reduction in medication use. Though preliminary studies suggest occipital nerve stimulation is safe and efficacious in treating chronic migraine headache, complication rates, including lead migration, lead fracture, and surgical site infections remain high. Further studies are needed to demonstrate long-term outcomes, while improved surgical techniques and site-specific equipment are needed to minimize complications. Keywords: headache, occipital nerve stimulation, peripheral nerve stimulation, neuromodulation, electrical stimulation therap

Peroral endoscopic myotomy: procedural complications and pain management for the perioperative clinician

Lopa Misra,1 Norio Fukami,2 Katarina Nikolic,1 Terrence L Trentman1 1Department of Anesthesiology, 2Division of Gastroenterology and Hepatology, Mayo Clinic Arizona, Phoenix, AZ, USA Abstract: Achalasia refers to the lack of smooth muscle relaxation of the distal esophagus. Although nonsurgical treatments such as pneumatic dilatation of the distal esophagus and botulinum toxin injections have been performed, these procedures have limited duration. Similarly, surgical treatment with Heller myotomy is associated with complications. At our institution, we perform the peroral endoscopic myotomy (POEM) in qualified patients. Briefly, POEM involves endoscopic creation of a mid-esophageal submucosal bleb, creation of a submucosal tunnel with the endoscope, and then a distal myotomy, resulting in relaxation of the distal esophagus. The aim of our study is to document perioperative pain and associated pain management for our initial patients undergoing POEM and to review the literature for perioperative complications of this procedure. Therefore, anesthetic and pain management for our initial eleven patients undergoing POEM were reviewed. Patient demographics, pre-POEM pain medication history, perioperative pain medication requirements, and post-POEM pain scores were examined. We found post-POEM pain was usually in the mild–moderate range; a combination of medications was effective (opioids, nonsteroidal anti-inflammatory drugs, acetaminophen). Our literature search revealed a wide frequency range of complications such as pneumoperitoneum and subcutaneous emphysema, with rare serious events such as capnopericardium leading to cardiac arrest. In conclusion, our experience with POEM suggests pain and can be managed adequately with a combination of medications; the procedure appears to be safe and reasonable to perform in an outpatient endoscopy unit. Keywords: pain management, retrospective study, combination of medicines, perioperative, endoscop

Survey of pain specialists regarding conversion of high-dose intravenous to neuraxial opioids

Andrew W Gorlin, David M Rosenfeld, Jillian Maloney, Christopher S Wie, Johnathan McGarvey, Terrence L Trentman Department of Anesthesiology, Mayo Clinic Arizona, Phoenix, AZ, USA Abstract: The conversion of high-dose intravenous (IV) opioids to an equianalgesic epidural (EP) or intrathecal (IT) dose is a common clinical dilemma for which there is little evidence to guide practice. Expert opinion varies, though a 100 IV:10:EP:1 IT conversion ratio is commonly cited in the literature, especially for morphine. In this study, the authors surveyed 724 pain specialists to elucidate the ratios that respondents apply to convert high-dose IV morphine, hydromorphone, and fentanyl to both EP and IT routes. Eighty-three respondents completed the survey. Conversion ratios were calculated and entered into graphical scatter plots. The data suggest that there is wide variation in how pain specialists convert high-dose IV opioids to EP and IT routes. The 100 IV:10 EP:1 IT ratio was the most common answer of survey respondent, especially for morphine, though also for hydromorphone and fentanyl. Furthermore, more respondents applied a more aggressive conversion strategy for hydromorphone and fentanyl, likely reflecting less spinal selectivity of those opioids compared with morphine. The authors conclude that there is little consensus on this issue and suggest that in the absence of better data, a conservative approach to opioid conversion between IV and neuraxial routes is warranted. Keywords: intrathecal pump, epidural, cancer pai