Peripheral Nerve Stimulation and Clinical Outcomes: A Retrospective Case Series.

PURPOSE: Peripheral nerve stimulation (PNS) is a rapidly expanding field within neuromodulation; however, there is limited data on therapeutic efficacy. This study describes the indications and clinical outcomes for patients undergoing PNS for chronic pain states. PATIENTS AND METHODS: This is a retrospective case series of adults undergoing PNS implantation from 2004 to 2017 at an academic medical center. The primary outcomes were changes in numeric rating scale (NRS) pain scores, opioid utilization in oral morphine milligram equivalent (MME), and self-reported patient functioning at 6 months postoperatively. Infectious and device-related complications were also assessed. RESULTS: A total of 72 patients underwent PNS implantation, including 59 patients that received a preceding PNS trial (59/78; 76% progression rate) and 13 that did not receive a PNS trial. The most common indication for stimulation was occipital neuralgia (47%) followed by lower-extremity neuropathies (17%). PNS implantation was associated with 6-month reductions in pain scores (7 [6, 8] baseline vs. 4 [2, 5] 6 months; P < 0.001) and opioid utilization (eg, median 60 [31, 104] vs. 18 [0, 52] MME among those with baseline opioid use; P < 0.001). Median functional improvement was 73% (50%, 88%). Seven patients (10%) suffered a postoperative surgical site infection at a median of 50 (30, 124) days, of which five devices were removed. CONCLUSION: Peripheral nerve stimulation was associated with reduced pain scores, lower opioid utilization, and improved patient function at 6 months. These data support PNS as a potentially effective nonopioid analgesic modality in chronic pain, though prospective multicenter evaluation is warranted to evaluate longer-term outcomes.

Simultaneous noninvasive recording of electrocardiogram and skin sympathetic nerve activity (neuECG).

neuECG, the simultaneous noninvasive recording of ECG and skin sympathetic nerve activity (SKNA), directly records sympathetic nerve activity over a long period of time. It can be used to measure sympathetic tone in healthy subjects and in subjects with non-cardiovascular diseases. The electrical activity that can be measured on the surface of the skin originates from the heart, the muscle or nerve structures. Because the frequency content of nerve activity falls in a higher frequency range than that of the ECG and myopotential, it is possible to use high-pass or band-pass filtering to specifically isolate the SKNA. neuECG is voltage calibrated and does not require invasive procedures to impale electrodes in nerves and thus has advantages over microneurography. Here, we present a protocol that takes <10 min to set up. The neuECG can be continuously recorded over a 24-h period or longer. We also describe methods to efficiently analyze neuECG from humans using commercially available hardware and software to facilitate adoption of this technology in clinical research.

Stellate ganglion block and cardiac sympathetic denervation in patients with inappropriate sinus tachycardia.

BACKGROUND: Inappropriate sinus tachycardia (IST) remains a clinical challenge because patients often are highly symptomatic and not responsive to medical therapy. OBJECTIVE: To study the safety and efficacy of stellate ganglion (SG) block and cardiac sympathetic denervation (CSD) in patients with IST. METHODS: Twelve consecutive patients who had drug-refractory IST (10 women) were studied. According to a prospectively initiated protocol, five patients underwent an electrophysiologic study before and after SG block (electrophysiology study group). The subsequent seven patients had ambulatory Holter monitoring before and after SG block (ambulatory group). All patients underwent SG block on the right side first, and then on the left side. Selected patients who had heart rate reduction ≥15 beats per minute (bpm) were recommended to consider CSD. RESULTS: The mean (SD) baseline heart rate (HR) was 106 (21) bpm. The HR significantly decreased to 93 (20) bpm (P = .02) at 10 minutes after right SG block and remained significantly slower at 97(19) bpm at 60 minutes. Left SG block reduced HR from 99 (21) to 87(16) bpm (P = .02) at 60 minutes. SG block had no significant effect on blood pressure or HR response to isoproterenol or exercise (all P > .05). Five patients underwent right (n = 4) or bilateral (n = 1) CSD. The clinical outcomes were heterogeneous: one patient had complete and two had partial symptomatic relief, and two did not have improvement. CONCLUSION: SG blockade modestly reduces resting HR but has no significant effect on HR during exercise. Permanent CSD may have a modest role in alleviating symptoms in selected patients with IST.

Electrophysiologic effects and outcomes of sympatholysis in patients with recurrent ventricular arrhythmia and structural heart disease.

INTRODUCTION: Autonomic modulation has been used as a therapy to control recurrent ventricular arrhythmia (VA). This study was to explore stellate ganglion block (SGB) effect on cardiac electrophysiologic properties and evaluate the long-term outcome of cardiac sympathetic denervation (CSD) for patients with recurrent VA and structural heart disease (SHD). MATERIALS AND METHODS: Patients who had recurrent VA due to SHD were enrolled prospectively. Electrophysiologic study and ventricular tachycardia (VT) induction were performed before and after left and right SGB. VA burden and long-term outcomes were assessed for a separate patient group who underwent left or bilateral CSD for drug-refractory VA due to SHD. RESULTS: Electrophysiologic study of nine patients showed that baseline mean (SD) corrected sinus node recovery time (cSNRT) increased from 320.4 (73.3) ms to 402.9 (114.2) ms after left and 482.4 (95.7) ms after bilateral SGB (P = .03). SGB did not significantly change P-R, QRS, and Q-T intervals and ventricular effective refractory period, nor did the inducibility of VA. Nineteen patients underwent left (n = 14) or bilateral (n = 5) CSD. CSD reduced VA burden and appropriate ICD therapies from a median (interquartile range) of 2.5 (0.4-11.6) episodes weekly to 0.1 (0.0-2.4) episodes weekly at 6-month follow-up (P = .002). Three-year freedom from orthotopic heart transplant (OHT) and death was 52.6%. New York Heart Association functional class III/IV and VT rate less than 160 beats per minute were predictors of recurrent VA, OHT, and death. CONCLUSION: SGB increased cSNRT without changing heart rate. CSD was more beneficial for patients with mild-to-moderate heart failure and faster VA.

Opioids: Clinical Practice, Monitoring, and Medicolegal Considerations.

BACKGROUND: In the past decade, opioid use in the general population of the US has increased dramatically. Concomitantly, opioid-related morbidity and mortality have also risen steeply. The causes of opioid over-prescribing are multifactorial, with pressure from medical agencies, patients, aggressive patient-directed marketing, and use of patient surveys as an evaluation tool to unduly influence medical providers' decision-making. Providers also have significant concerns regarding scrutiny from their medical board and exposure to medicolegal liability. CONTENT: To provide the basis for best practice recommendations, several aspects of modern opioid prescribing practice require review. The practicing clinician should be aware of: (a) the pervasiveness of current opioid prescribing within the US; (b) the availability and applicability of clinical tools used to assess patient risk; (c) the new guidelines designed to facilitate appropriate and safe medical use of opioids; (d) the incorporation of clinical tools and best documentation practices to reduce medicolegal exposure. SUMMARY: On completion of this review, the reader should be able to recognize the magnitude of the problem of opioid over-prescribing in the US and identify several patient risk factors for opioid misuse, abuse, and/or diversion. Specifically, better familiarity with the recently published CDC guidelines for opioid prescribing will help ensure the adoption of best-use practices that maximize therapeutic efficacy while attenuating the possibility of harm to patients. A thorough review of the legal principles and risk-mitigation strategies relevant to opioid prescribing will also lessen the clinician's exposure to medicolegal liability.

Utilization of Leads After Permanent Implant in Spinal Cord Stimulator Systems.

OBJECTIVE: The goal of this study was to determine the frequency and clinical indications associated with implantation of single vs. dual percutaneous lead spinal cord stimulator (SCS) systems and to look further into how these leads are utilized for treatment. MATERIALS AND METHODS: A retrospective cohort analysis of all patients undergoing SCS implantation between January 2001 and December 2013 with a minimum of 2 years of clinical follow-up was performed. Number of trial leads and implanted leads was recorded. For patients with dual-lead systems, it was noted if and when the second lead was used, along with the clinical indication for lead activation. RESULTS: In the 259-patient cohort, 15.8% (n = 41) patients underwent placement of a single-lead system, 83.0% (n = 215) underwent placement of a dual-lead system, and 1.2% (n = 3) underwent placement of 3-lead systems. Placement of dual-lead systems was similar among all indication groups. Of those patients with a dual-lead system in place, 88.1% utilized both leads and average time to programming of the second lead was 2.3 months. The most common reason to activate the second lead was inadequate stimulation coverage. Five of the 41 patients with single-lead systems underwent an additional surgery to implant a second lead due to inadequate stimulation with 1 lead. CONCLUSIONS: To our knowledge this is the first descriptive analysis of the frequency of single- and dual-lead SCS systems. This report indicates that dual-lead systems are most often placed and both leads are required for optimal patient therapy.

Misrepresentation in multidisciplinary pain medicine fellowship applications to a single academic program.

BACKGROUND AND OBJECTIVES: Publication misrepresentation by residency applicants has been well documented, but fewer studies have investigated it in fellowship applicants, specifically in pain medicine. We therefore sought to evaluate the demographics of pain medicine fellowship applicants and the type, number, and accuracy of referenced publications they reported. METHODS: Applications to the Multidisciplinary Pain Medicine fellowship program in the Mayo School of Graduate Medical Education, Rochester, Minnesota were reviewed for three consecutive academic years (2009-2012). Demographic information and publications claimed by applicants were compiled, and publications were scrutinized by a medical librarian for accuracy. RESULTS: Over a 3-year period, 179 fellowship applications were received. Of the 179 applicants, more than half (106 [59%]) listed at least one publication. Of 324 listed publications, 263 were verifiable; of these, 14 (5.3%) were deemed fraudulent, and six (2.3%) contained an inaccuracy possibly conferring a competitive advantage. In our small sample size, we found no difference in the rate of publications or in the accuracy of listed publications across subspecialties, or between US medical graduates and international medical graduates. CONCLUSIONS: The lack of national data, specifically on applicant misrepresentation, due to the heretofore absence of a universal application process or match, impedes assessment of the extent to which these findings are representative of the national applicant pool. We observed notable trends (few female applicants; numerous international medical graduate applicants) different from those reported by other specialties. Despite the low rate (5.3%) of fraudulent publications, fellowship program directors and selection committees should be aware of this possibility to ensure selection of fellows with the highest degree of professional and ethical integrity.

Incidence of clinically significant percutaneous spinal cord stimulator lead migration.

OBJECTIVE: To examine the incidence of percutaneous spinal cord stimulator lead migration, given current hardware and surgical technique. MATERIALS AND METHODS: We retrospectively reviewed records of patients who underwent spinal cord stimulator implantation with percutaneous leads at our institution from 2008 through 2011. We determined the number of patients who required surgical revision for clinically significant lead migration. RESULTS: Clinically significant lead migration requiring surgical revision occurred in three of 143 patients (2.1%) with primary SCS system implants utilizing percutaneous-type leads. CONCLUSIONS: The rate of lead migration observed in our practice was considerably lower than previously published estimates of clinically significant lead migration or revision for lead migration (13%-22%). However, our study did not determine the reason for the decreased rate, which may be influenced by current hardware and implant techniques.

Interventional modalities to treat cancer-related pain.

Cancer-related pain is a significant cause of morbidity in those affected by both primary and metastatic disease. Although oral, transdermal, and parenteral opioid medications are an integral part of the World Health Organization's analgesic ladder, their use may be limited by side effects. Fortunately, there are advanced interventional pain management strategies effective in reducing pain in the cancer patient while mitigating the aforementioned side effects. Celiac plexus blocks and neurolysis have been proven effective in treating cancers of the abdominal viscera (ie, pancreas). Transversus abdominis plane blocks, neurolysis, and catheter placement can be used to treat cancer pain associated with the abdominal wall. Peripheral nerve blocks and catheter placement at the brachial and lumbosacral plexus or peripheral nerves treat cancer pain associated with the upper and lower limbs, whereas paravertebral and intercostal blocks treat cancer pain associated with the chest wall and ribs. Finally, alternate drug delivery methods such as intrathecal drug delivery systems concentrate medication at central opioid receptors without affecting the peripheral receptors implicated in unwanted side effects. This article provides an overview of these interventions, including indications, contraindications, and potential complications of advanced interventional pain management options available for the treatment of intractable cancer-related pain.

Incidence of neuropathic pain after radiofrequency denervation of the third occipital nerve.

The purpose of this study was to identify the incidence of neuropathic pain occurring after radiofrequency neurotomy of the third occipital nerve (TON). This study was conducted at a teaching hospital from January 1, 2008, to March 31, 2010. With institutional review board approval, Current Procedural Terminology codes were used to identify patients who received radiofrequency ablation (RFA) of the nerves supplying the C2-3 facet joint and the TON. The C3 dorsal ramus provides innervation to the C2-3 facet joint and the suboccipital cutaneous region, and procedures that included ablation to this region were reviewed for complications. Postprocedural data were collected by reviewing follow-up appointment notes and telephone calls. Included were patients who had new neuropathic pain in the distribution of the TON after RFA. They described what they were feeling as burning, tingling, or numbness. All patients who presented with complaints had normal neurologic findings and no secondary cause for their symptoms. The included patient medical records were then reviewed for severity and duration of symptoms and the need for treatment with pain medication. Sixty-four patients underwent C2-3 RFA or TON RFA, and 12 patients were identified as experiencing ablation-induced third occipital neuralgia, an incidence rate of 19%. This finding suggests that patients undergoing RFA of the nerves supplying the C2-3 joint or TON are at risk for postprocedural third occipital neuralgia. This possibility may affect providing informed consent as well as anticipating and managing postprocedural pain.

Ultrasound-guided transversus abdominis plane injection with computed tomography correlation: a cadaveric study.

BACKGROUND: Ultrasound-guided transversus abdominis plane (TAP) injections are increasingly being used as an alternative to traditional perioperative analgesia in the abdominal region. With the use of a "blind" TAP block technique, these procedures have had variable success in cadaver and in vivo studies. For more accurate injection with the intended medication, ultrasound guidance allows visualization of the correct layer of the abdominal wall planes in which the thoracolumbar nerves reside. OBJECTIVE: To assess the spread of various volumes of contrast placed under live ultrasound guidance into the TAP using computed tomography (CT). METHODS: Four TAP blocks were performed on 2 fresh frozen cadaver torsos with predetermined contrast volumes of 5, 10, 15, or 20 mL. A CT scan of the cadaver was then performed and interpreted by a musculoskeletal radiologist. This cadaver study was carried out at a tertiary care academic medical center. RESULTS: Cranial-caudal spread of injected contrast correlated with increasing injectate volume and was roughly 1 vertebral level (end plate to end plate) for the 5 mL injection and 2 vertebral levels for the 10, 15, and 20 mL injections. However, the degree of injectate spread may be different for live patients than for cadavers. CONCLUSION: This study helps further the understanding of injectate spread following ultrasound-guided TAP injections. Specifically, it suggests that 15 mL provides additional cranial-caudal spread and may be an optimal volume of anesthesia.

Topical amitriptyline combined with ketamine for the treatment of erythromelalgia: a retrospective study of 36 patients at Mayo Clinic.

BACKGROUND: Erythromelalgia is an uncommon neurovascular disorder characterized by redness, increased skin temperature, and pain that usually occurs in the extremities. Treatment remains challenging because of its varying response to medical therapy. The objective of this study was to assess the response of erythromelalgia to compounded topical amitriptyline-ketamine. METHODS: We retrospectively evaluated 36 patients with erythromelalgia who were treated with compounded topical amitriptyline-ketamine from January 1, 2004, through January 31, 2011. RESULTS: Thirty-two patients (89%) were female. Mean (standard deviation) age was 44.7 (15.8) years (range, 5-74 years). Patients applied the medication 1 to 6 times per day (median, 5 times). One patient (3%) had complete relief from symptoms, 14 (39%) had substantial relief, 12 (33%) had some relief, 7 (19%) had no relief, and 2 (6%) had local worsening of symptoms. No patients had systemic adverse effects. CONCLUSIONS: A majority of patients with erythromelalgia (75%) reported improvement in pain with topical application of a compounded amitriptyline-ketamine formulation. The medication was well tolerated.

Topical amitriptyline-ketamine for treatment of rectal, genital, and perineal pain and discomfort.

BACKGROUND: Pain in the rectal, genital, and perineal area is a common condition treated by pain physicians. These chronic pain syndromes are therapeutically challenging because both interventional and drug therapies often are ineffective. OBJECTIVES: To determine if pelvic pain can be treated effectively with compounded topical amitriptyline-ketamine. STUDY DESIGN: A retrospective review of medical records. SETTING: A single academic medical center in the United States. METHODS: We identified all patients treated with topical amitriptyline-ketamine from January 1, 2004, through November 28, 2011. Medical records were evaluated to determine the diagnosis for which the medication was prescribed. Treatment efficacy and any adverse effects were recorded. RESULTS: Of the 1,068 patients who received amitriptyline-ketamine, 13 had the medication prescribed for genital, rectal, or perineal pain and had medication efficacy recorded. Of these 13 patients, one (8%) had complete relief, 6 (46%) had substantial relief, 4 (31%) had some relief, and 2 (15%) had no response. One patient reported occasional irritation while using topical amitriptyline-ketamine with lidocaine; no other patients reported local or systemic adverse effects. LIMITATIONS: Retrospective review; lack of uniform system for pain grading; concurrent use of other medications. CONCLUSIONS: Topical amitriptyline-ketamine provided a high rate of pain relief with a low adverse-effect burden in patients with pelvic pain. This topical medication could offer an effective, noninvasive, nonopioid therapy for pain in the rectum, perineum, and genitals.

Preoperative gabapentin for acute post-thoracotomy analgesia: a randomized, double-blinded, active placebo-controlled study.

BACKGROUND: The role of preoperative gabapentin in postoperative pain management is not clear, particularly in patients receiving regional blockade. Patients undergoing thoracotomy benefit from epidural analgesia but still may experience significant postoperative pain. We examined the effect of preoperative gabapentin in thoracotomy patients. METHODS: Adults undergoing elective thoracotomy were enrolled in this prospective, randomized, double-blinded, placebo-controlled study, and randomly assigned to receive 600 mg gabapentin or active placebo (12.5 mg diphenhydramine) orally within 2 hours preoperatively. Standardized management included thoracic epidural infusion, intravenous patient-controlled opioid analgesia, acetaminophen and ketorolac. Pain scores, opioid use and side effects were recorded for 48 hours. Pain was also assessed at 3 months. RESULTS: One hundred twenty patients (63 placebo and 57 gabapentin) were studied. Pain scores did not significantly differ at any time point (P = 0.53). Parenteral and oral opioid consumption was not significantly different between groups on postoperative day 1 or 2 (P > 0.05 in both cases). The frequency of side effects such as nausea and vomiting or respiratory depression was not significantly different between groups, but gabapentin was associated with decreased frequency of pruritus requiring nalbuphine (14% gabapentin vs. 43% control group, P < 0.001). The frequency of patients experiencing pain at 3 months post-thoracotomy was also comparable between groups (70% gabapentin vs. 66% placebo group, P = 0.72). CONCLUSIONS: A single preoperative oral dose of gabapentin (600 mg) did not reduce pain scores or opioid consumption following elective thoracotomy, and did not confer any analgesic benefit in the setting of effective multimodal analgesia that included thoracic epidural infusion.

An exploratory pilot study of palliative medicine compared to anesthesia-pain consultation for pain in patients with cancer.

Oncologists often manage cancer-associated symptoms including pain. When symptoms are severe, anesthesia-pain medicine (APM) and/or palliative medicine (PM) can effectively treat symptoms. Nevertheless, symptom management may be suboptimal, leading to diminished quality of life (QOL). We assessed the value of PM vs. APM consultation in cancer patients referred for pain management alone. Patients referred to an APM-based Cancer Pain Clinic (CPC) over an 8-month period were evaluated by PM or APM based on the first available appointment. Symptoms and QOL were assessed by the MD Anderson Symptom Inventory and Linear Analog Self-Assessment at baseline and 4-6 weeks after initial encounter. Data were analyzed on an available-case basis. Sixty-two patients (37 PM, 25 APM) completed the initial survey, with 48 patients (31 PM, 17 APM) completing followup. Mean pain score improved from 7.97 to 5.47 in the PM group (P < 0.0001) and from 7.1 to 4.5 (P = 0.29) in the APM group. The PM group demonstrated a clinically significant improvement in 8/19 symptoms vs. 3/19 in the APM group and in 3/5 QOL parameters in the PM group vs. 1/5 in the APM group. Our small sample size weakens our power and ability to detect significant differences between the groups. Only one follow-up symptom-assessment point was obtained. PM consultation is as effective as APM in improving cancer pain but may be more effective with symptom management and improving QOL.

Management of cerebral spinal fluid leak complicating spinal cord stimulator implantation.

Accidental puncture of the dura mater with resultant leakage of cerebral spinal fluid (CSF) and development of postdural puncture headache (PDPH) is a known potential complication of percutaneous placement of spinal cord stimulator (SCS) leads. However, the implications and management strategies for this complication have not been thoroughly reported. We report two cases of SCS lead placement complicated by CSF leak and PDPH.

The history of subcutaneous oxygen therapy.

Soon after the discovery of oxygen, experiments began on the use of oxygen for therapeutic purposes, including subcutaneous administration of oxygen, on humans and animals. The history of subcutaneous oxygen therapy (SQOT) is examined in the context of the growing understanding of the use and methods of oxygen administration. Little was written about this therapy until the 19th century, despite an advocacy for its use in some circles. There was resurgence in the use of SQOT in the early 20th century. Investigators in the field of anesthesia, including such notable figures as Paul M. Wood, Ralph M. Waters, and John Henry Evans, contributed to the growth in popularity of the therapy and to the literature on the subject. Although SQOT has been supplanted by other means of administration, it may have a role in management of some inflammatory or pain conditions.