Stellate ganglion block for non-pain indications: a scoping review.

INTRODUCTION: Stellate ganglion block (SGB) is performed to relieve head, face, neck, or upper limb pain, and several non-pain indications for performing this block have emerged over the years. To date, there has been no attempt to synthesize evidence on SGB for treating non-pain indications. This scoping review presents a summary of the efficacy and adverse effects of SGB when performed for 6 non-pain indications. METHODS: This scoping review was accomplished through the use of Arksey and O'Malley framework. A literature search was conducted for relevant articles in medical databases to identify publications on SGB and specified study types. Two reviewers independently assessed the risk of bias for randomized controlled trials, nonrandomized comparative studies, and case series. Results were summarized and recommendations were made on the basis of the strength of the available evidence according to the US Preventative Services Task Force grading system. RESULTS: Twenty-four studies (19 randomized controlled trials and 5 nonrandomized studies) were included in this review. On the basis of the evidence, SGB is recommended for obtunding cardiovascular sympathetic stimulation, improving perfusion in limbs, and alleviating menopausal symptoms with a Grade B or C recommendation and a moderate-to-low level of certainty. There was insufficient evidence to recommend SGB for the other indications. CONCLUSIONS: SGB can be considered for obtunding cardiovascular sympathetic stimulation and stress response, reducing vascular tone to improve vascular insufficiency in the limbs and perioperative hemodynamic stability, and alleviating hot flashes in menopause, in conditions refractory to conventional medical management.

North American Neuromodulation Society Educational Curriculum for Intrathecal Drug Delivery Systems Implantation and Management.

OBJECTIVES: Intrathecal drug delivery systems (IDDSs) are used for the treatment of pain and spasticity. A wide range of educational criteria exist for these devices. The North American Neuromodulation Society (NANS) Education Committee developed a comprehensive IDDS curriculum to function as a standard for physician graduate education and assessment through training and into practice. MATERIAL AND METHODS: A multidisciplinary and diverse task force gathered by the NANS Education Committee met in person and virtually over several sessions and developed an IDDS curriculum modeling their previous work on spinal cord stimulation and following the Accreditation Council for Graduate Medical Education (ACGME) Milestones. There were iterative revisions and adaptations to the curriculum, and the final version was approved by the NANS Board of Directors. RESULTS: The curriculum was developed with distinction between implanting physicians and managing physician and physicians who perform both tasks. There is a lateral temporal progression from early learner to practitioner, with advanced learner in the middle. In addition, there is a modular vertical organization that divides the curriculum into the six educational competencies outlined by the ACGME. CONCLUSION: A comprehensive, modular, graduated, and segmented educational curriculum for IDDSs was developed by NANS. We propose the curriculum to be the standard for guidance and assessment of trainees and physicians pursuing training in implanting or managing IDDSs.

No Benefits of Adding Dexmedetomidine, Ketamine, Dexamethasone, and Nerve Blocks to an Established Multimodal Analgesic Regimen after Total Knee Arthroplasty.

BACKGROUND: An optimal opioid-sparing multimodal analgesic regimen to treat severe pain can enhance recovery after total knee arthroplasty. The hypothesis was that adding five recently described intravenous and regional interventions to multimodal analgesic regimen can further reduce opioid consumption. METHODS: In a double-blinded fashion, 78 patients undergoing elective total knee arthroplasty were randomized to either (1) a control group (n = 39) that received spinal anesthesia with intrathecal morphine, periarticular local anesthesia infiltration, intravenous dexamethasone, and a single injection adductor canal block or (2) a study group (n = 39) that received the same set of analgesic treatments plus five additional interventions: local anesthetic infiltration between the popliteal artery and capsule of the posterior knee, intraoperative intravenous dexmedetomidine and ketamine, and postoperatively, one additional intravenous dexamethasone bolus and two additional adductor canal block injections. The primary outcome measure was 24-h cumulative opioid consumption after surgery and secondary outcomes were other analgesics, patient recovery, functional outcomes, and adverse events. RESULTS: Opioid consumption was not different between groups at 24 h (oral morphine equivalents, mean ± SD; study: 23.7 ± 18.0 mg vs. control: 29.3 ± 18.7 mg; mean difference [95% CI], -5.6 mg [-2.7 to 13.9]; P = 0.189) and all other time points after surgery. There were no major differences in pain scores, quality of recovery, or time to reach rehabilitation milestones. Hypotensive episodes occurred more frequently in the study group (25 of 39 [64.1%] vs. 13 of 39 [33.3%]; P = 0.010). CONCLUSIONS: In the presence of periarticular local anesthesia infiltration, intrathecal morphine, single-shot adductor canal block and dexamethasone, the addition of five analgesic interventions-local anesthetic infiltration between the popliteal artery and capsule of the posterior knee, intravenous dexmedetomidine, intravenous ketamine, an additional intravenous dexamethasone dose, and repeated adductor canal block injections-failed to further reduce opioid consumption or pain scores or to improve functional outcomes after total knee arthroplasty.

A Scoping Review of the Diurnal Variation in the Intensity of Neuropathic Pain.

BACKGROUND: Recent studies have suggested that neuropathic pain exhibits a daily diurnal pattern, with peak levels usually occurring in the late afternoon to evening and the trough in the morning hours, although literature on this topic has been sparse. This scoping review examines current evidence on the chronobiology of neuropathic pain both in animal models and in humans with neuropathic pain. METHODS: A literature search was conducted in major medical databases for relevant articles on the chronobiology of neuropathic pain both in animal models and in humans with neuropathic pain. Data extracted included details of specific animal models or specific neuropathic pain conditions in humans, methods and timing of assessing pain severity, and specific findings of diurnal variation in pain intensity or its surrogate markers. RESULTS: Thirteen animal and eight human studies published between 1976 and 2020 were included in the analysis. Seven of the 13 animal studies reported specific diurnal variation in pain intensity, with five of the seven studies reporting a trend toward increased sensitivity to mechanical allodynia or thermal hyperalgesia in the late light to dark phase. All eight studies in human subjects reported a diurnal variation in the intensity of neuropathic pain, where there was an increase in pain intensity through the day with peaks in the late evening and early night hours. CONCLUSIONS: Studies included in this review demonstrated a diurnal variation in the pattern of neuropathic pain that is distinct from the pattern for nociceptive pain. These findings have implications for potential therapeutic strategies for neuropathic pain.

Consensus practice guidelines on interventions for cervical spine (facet) joint pain from a multispecialty international working group.

BACKGROUND: The past two decades have witnessed a surge in the use of cervical spine joint procedures including joint injections, nerve blocks and radiofrequency ablation to treat chronic neck pain, yet many aspects of the procedures remain controversial. METHODS: In August 2020, the American Society of Regional Anesthesia and Pain Medicine and the American Academy of Pain Medicine approved and charged the Cervical Joint Working Group to develop neck pain guidelines. Eighteen stakeholder societies were identified, and formal request-for-participation and member nomination letters were sent to those organizations. Participating entities selected panel members and an ad hoc steering committee selected preliminary questions, which were then revised by the full committee. Each question was assigned to a module composed of 4-5 members, who worked with the Subcommittee Lead and the Committee Chairs on preliminary versions, which were sent to the full committee after revisions. We used a modified Delphi method whereby the questions were sent to the committee en bloc and comments were returned in a non-blinded fashion to the Chairs, who incorporated the comments and sent out revised versions until consensus was reached. Before commencing, it was agreed that a recommendation would be noted with >50% agreement among committee members, but a consensus recommendation would require ≥75% agreement. RESULTS: Twenty questions were selected, with 100% consensus achieved in committee on 17 topics. Among participating organizations, 14 of 15 that voted approved or supported the guidelines en bloc, with 14 questions being approved with no dissensions or abstentions. Specific questions addressed included the value of clinical presentation and imaging in selecting patients for procedures, whether conservative treatment should be used before injections, whether imaging is necessary for blocks, diagnostic and prognostic value of medial branch blocks and intra-articular joint injections, the effects of sedation and injectate volume on validity, whether facet blocks have therapeutic value, what the ideal cut-off value is for designating a block as positive, how many blocks should be performed before radiofrequency ablation, the orientation of electrodes, whether larger lesions translate into higher success rates, whether stimulation should be used before radiofrequency ablation, how best to mitigate complication risks, if different standards should be applied to clinical practice and trials, and the indications for repeating radiofrequency ablation. CONCLUSIONS: Cervical medial branch radiofrequency ablation may provide benefit to well-selected individuals, with medial branch blocks being more predictive than intra-articular injections. More stringent selection criteria are likely to improve denervation outcomes, but at the expense of false-negatives (ie, lower overall success rate). Clinical trials should be tailored based on objectives, and selection criteria for some may be more stringent than what is ideal in clinical practice.

The Use of Contrast Agents in Interventional Pain Procedures: A Multispecialty and Multisociety Practice Advisory on Nephrogenic Systemic Fibrosis, Gadolinium Deposition in the Brain, Encephalopathy After Unintentional Intrathecal Gadolinium Injection, and Hypersensitivity Reactions.

This Practice Advisory presents a comprehensive and evidence-based set of position statements and recommendations for the use of contrast media in interventional pain procedures. The advisory was established by an international panel of experts under the auspices of 11 multinational and multispecialty organizations based on a comprehensive review of the literature up to December 31, 2019. The advisory discusses the risks of using gadolinium-based contrast agents. These include nephrogenic systemic fibrosis, gadolinium brain deposition/retention, and encephalopathy and death after an unintentional intrathecal gadolinium injection. The advisory provides recommendations on the selection of a specific gadolinium-based contrast agent in patients with renal insufficiency, those who had multiple gadolinium-enhanced magnetic resonance imaging examinations, and in cases of paraspinal injections. Additionally, recommendations are made for patients who have a history of mild, moderate, or severe hypersensitivity reactions to contrast medium.

Factors associated with success and failure of patient-controlled oral analgesia after total hip and knee arthroplasty: a historical comparative cohort study.

PURPOSE: Patient-controlled oral analgesia (PCOA) is a novel method of oral opioid administration using set doses of short-acting oral opioids self-administered by patients with a "lockout" period as part of a multimodal regimen. Failure of PCOA can result in severe postoperative pain necessitating use of intravenous patient-controlled analgesia (IV-PCA) with its potential complications. This study evaluated factors related to success or failure of PCOA following total hip arthroplasty (THA) and total knee arthroplasty (TKA). METHODS: We conducted a retrospective cohort study of all adults who underwent THA and TKA at our institution by extracting data from the proprietary database of our acute pain service. Patient, anesthetic, and surgical variables associated with PCOA failure defined as inadequate analgesia requiring conversion to IV-PCA within 24 hr following THA and TKA were evaluated. Univariable and multivariable logistic regression analyses were performed to identify predictors of PCOA failure. RESULTS: Of the 926 patients who underwent THA or TKA (n = 411 and 515, respectively), 147 (15.9%) patients (67 THA and 80 TKA patients) had PCOA failure with moderate-to-severe pain. Multivariable regression analysis showed that PCOA failure occurred in those with younger age (adjusted odds ratio [aOR] per year of age, 0.97; 99% CI, 0.95 to 0.99; P < 0.001), preoperative chronic use of controlled-release opioids (aOR, 3.45; 99% CI, 1.60 to 7.35; P < 0.001), and with the use of general anesthesia vs spinal anesthesia (aOR, 2.86; 99% CI, 1.20 to 6.84; P = 0.002). CONCLUSION: The use of PCOA provides adequate analgesia to a majority of patients undergoing THA and TKA. Factors predictive for PCOA failure should be considered when choosing the primary breakthrough analgesic modality following THA/TKA.

RéSUMé: OBJECTIF: L'analgésie orale contrôlée par le patient (AOCP) est une méthode novatrice d'administration d'opioïdes oraux qui utilise des doses pré-établies d'opioïdes oraux à courte action auto-administrées par les patients avec un intervalle minimal entre les doses dans le cadre d'un régime multimodal. Le non-fonctionnement d'une AOCP peut entraîner une douleur postopératoire grave nécessitant le recours à une analgésie intraveineuse contrôlée par le patient (ACP-IV), ce qui s'accompagne de complications potentielles. Cette étude a évalué les facteurs liés à la réussite ou à l'échec de l'AOCP à la suite d'une arthroplastie totale de la hanche (ATH) ou du genou (ATG). MéTHODE: Nous avons réalisé une étude de cohorte rétrospective de tous les adultes ayant subi une ATH ou une ATG dans notre établissement en extrayant les données de la base de données de notre service de douleur aiguë. Les variables liées au patient, à l'anesthésie, et à la chirurgie et associées à un échec de l'AOCP, défini comme une analgésie inadéquate exigeant la conversion en ACP-IV dans les 24 heures suivant l'ATH ou l'ATG, ont été évaluées. Des analyses de régression logistique univariée et multivariée ont été effectuées pour identifier les prédicteurs d'un échec de l'AOCP. RéSULTATS: Sur les 926 patients ayant subi une ATH ou une ATG (n = 411 et 515, respectivement), l'AOCP n'a pas fonctionné chez 147 (15,9 %) patients (67 patients d'ATH et 80 d'ATG), entraînant une douleur modérée à grave. L'analyse de régression multivariée a montré que les échecs de l'AOCP sont survenus chez les personnes plus jeunes (rapport de cotes ajusté [RCA] par année d'âge, 0,97; IC 99 %, 0,95 à 0,99; P < 0,001), lors d'une utilisation préopératoire chronique d'opioïdes à libération contrôlée (RCA, 3,45; IC 99 %, 1,60 à 7,35; P < 0,001), et lors d'une anesthésie générale vs une rachianesthésie (RCA, 2,86; IC 99 %, 1,20 à 6,84; P = 0,002). CONCLUSION: L'utilisation de l'AOCP procure une analgésie adéquate à la majorité des patients subissant une ATH ou une ATG. Les facteurs prédictifs d'un échec de l'AOCP devraient être pris en considération lors du choix de la principale modalité analgésique après une ATH/ATG.

Intrathecal Morphine and Pulmonary Complications after Arthroplasty in Patients with Obstructive Sleep Apnea: A Retrospective Cohort Study.

BACKGROUND: Intrathecal morphine is commonly and effectively used for analgesia after joint arthroplasty, but has been associated with delayed respiratory depression. Patients with obstructive sleep apnea may be at higher risk of postoperative pulmonary complications. However, data is limited regarding the safety of intrathecal morphine in this population undergoing arthroplasty. METHODS: This retrospective cohort study aimed to determine the safety of intrathecal morphine in 1,326 patients with documented or suspected obstructive sleep apnea undergoing hip or knee arthroplasty. Chart review was performed to determine clinical characteristics, perioperative events, and postoperative outcomes. All patients received neuraxial anesthesia with low-dose (100 µg) intrathecal morphine (exposure) or without opioids (control). The primary outcome was any postoperative pulmonary complication including: (1) respiratory depression requiring naloxone; (2) pneumonia; (3) acute respiratory event requiring consultation with the critical care response team; (4) respiratory failure requiring intubation/mechanical ventilation; (5) unplanned admission to the intensive care unit for respiratory support; and (6) death from a respiratory cause. The authors hypothesized that intrathecal morphine would be associated with increased postoperative complications. RESULTS: In 1,326 patients, 1,042 (78.6%) received intrathecal morphine. The mean age of patients was 65 ± 9 yr and body mass index was 34.7 ± 7.0 kg/m. Of 1,326 patients, 622 (46.9%) had suspected obstructive sleep apnea (Snoring, Tired, Observed, Pressure, Body Mass Index, Age, Neck size, Gender [STOP-Bang] score greater than 3), while 704 of 1,326 (53.1%) had documented polysomnographic diagnosis. Postoperatively, 20 of 1,322 (1.5%) patients experienced pulmonary complications, including 14 of 1,039 (1.3%) in the exposed and 6 of 283 (2.1%) in the control group (P = 0.345). Overall, there were 6 of 1 322 (0.5%) cases of respiratory depression, 18 of 1,322 (1.4%) respiratory events requiring critical care team consultation, and 4 of 1,322 (0.3%) unplanned intensive care unit admissions; these rates were similar between both groups. After adjustment for confounding, intrathecal morphine was not significantly associated with postoperative pulmonary complication (adjusted odds ratio, 0.60 [95% CI, 0.24 to 1.67]; P = 0.308). CONCLUSIONS: Low-dose intrathecal morphine, in conjunction with multimodal analgesia, was not reliably associated with postoperative pulmonary complications in patients with obstructive sleep apnea undergoing joint arthroplasty.

Radiofrequency Procedures for the Treatment of Symptomatic Knee Osteoarthritis: A Systematic Review.

OBJECTIVE: To evaluate the effectiveness and safety of radiofrequency (RF) ablation and neuromodulation modalities for knee osteoarthritis (OA). METHODS: The Pubmed, Medline, Embase, and Cochrane Library databases were searched from inception to August 2018. All comparative and noncomparative studies that reported clinical outcome measures and adverse events related to RF modalities for knee OA were included. Pain scores, physical function measures, quality of life (QOL), patient satisfaction, and adverse events for three months and beyond of postprocedure follow-up were analyzed qualitatively. RESULTS: Thirty-three studies, including 13 randomized controlled trials (RCTs), two nonrandomized comparative studies, and 18 noncomparative cohort studies, were identified, with 1,512 patients (mean age = 64.3 years, 32.5% males). All 33 studies were considered to be of moderate or high methodological quality. All 33/33 (100%) studies reported alleviation of OA-related knee pain from baseline until three to 12 months with RF modalities, with six comparative studies reporting 194/296 (65.5%) and 29/150 (19.3%) RF and control patients achieving >50% pain relief, respectively. Three of the 33 studies reported QOL, with three of three studies (100%) achieving improvements in disease-specific QOL from baseline until three to 12 months. Twenty-eight of the 33 studies reported functional outcomes, with 27/28 (96%) studies obtaining enhanced functionality from baseline up until three to 12 months. Ten of the 33 studies reported patient satisfaction, with eight of 10 studies (80%) indicating that patients were significantly satisfied after RF procedures, and from these eight studies, four were comparative studies that indicated that 86/154 (56%) and 33/104 (32%) RF and control patients were extremely satisfied or satisfied, respectively. Regarding adverse events (AEs), 29 of the 33 studies reported AEs, with 20/29 (69%) studies indicating no AEs related to the RF modalities and the remaining nine studies only indicating minor localized AEs. Twenty-nine of the 33 studies indicated no serious knee-related AEs pertaining to RF modalities. CONCLUSIONS: Current evidence substantiates that RF modalities for knee OA potentially improve pain, functionality, and disease-specific QOL for up to three to 12 months with minimal localized complications. This suggests that RF modalities are perhaps an effective adjunct therapy for patients with knee OA who are unresponsive to conservative therapies. Further RCTs with larger sample sizes and long-term follow-up that directly compare the three primary RF modalities are warranted to confirm the clinical efficaciousness and superiority of these RF modalities for knee OA.

Interventional pain management for chronic pain: a survey of physicians in Canada.

PURPOSE: The use of interventional pain management (IPM) modalities to alleviate chronic pain is increasing despite the lack of high-quality evidence. We undertook this survey to explore patterns, training, and attributes of IPM practice. METHODS: We administered a 32-item survey via seven Canadian physician member organizations, whose members were engaged in the management of chronic pain. RESULTS: Of 777 physicians contacted, 256 (33%) responded: 45 (6%) declined to participate and 211 (27%) agreed to participate; the number of participants answering any given question varied. One hundred and sixty-nine of 194 (87%) practiced IPM and 103 of 194 (53%) managed only non-cancer pain. Pain management training of ≥ six months was associated with higher odds of IPM training (odds ratio [OR], 2.98; 95% confidence interval [CI], 1.32 to 6.7), but not necessarily ongoing IPM practice (OR, 1.97; 95% CI, 0.74 to 5.3). A substantial percentage of physicians (108 of 168 [64%]) practiced IPM based only on training received during either their base residency program or courses. Only 48 of 186 (26%) felt that there were adequate opportunities for IPM training, and 69 of 186 (37%) believed that their colleagues practiced IPM in accordance with the best current evidence. CONCLUSIONS: Our survey indicates that IPM practice and training were not uniform, and that interventional therapies for chronic pain may not be performed in accordance with the best available evidence. Our survey highlights a lack of IPM training opportunities, which may result in substandard training. Concerted efforts involving physician organizations and regulators are needed to standardize IPM training and develop clinical guidelines to optimize evidence-based practice.

Percutaneous Ozone Treatment for Herniated Lumbar Discs: 1-Year Follow-up of a Multicenter Pilot Study of a Handheld Disposable Ozone-Generating Device.

PURPOSE: To evaluate the safety and efficacy of oxygen-ozone treatment delivered via a novel, handheld ozone-generating device for improving pain and function in herniated disc patients. MATERIALS AND METHODS: A total of 39 patients with contained herniated lumbar discs received oxygen-ozone treatment at 1 of 3 centers. Treatment consisted of injection of 2% ozone (10 mL): 3 mL delivered into the nucleus pulposus and 7 mL delivered into the adjacent paravertebral tissues. The first 8 patients received only ozone injections, whereas subsequent patients also received periganglionic methylprednisolone (40 mg) and 0.5% bupivacaine (1 mL) injections. Patients were evaluated at baseline and at 1 month, 6 months, and 12 months after treatment using the Oswestry Disability Index (ODI) and the Visual Analogue Scale (VAS) for leg pain and for back pain. Analgesic medication use was also assessed at each timepoint. RESULTS: Overall, 91% (32/35) of the per-protocol patients (those who completed follow-up and did not have significant protocol deviations) showed detectable improvement in ODI at 1-month follow-up; this increased to 93% (26/28) of patients at 12-months follow-up. At 1 month after treatment, 60% (21/35) of patients showed significant improvement in ODI scores (P = .01); 54% (19/35) showed significant improvement in VAS scores for leg pain (P = .05); and 49% (17/35) showed significant improvement in VAS scores for back pain (P = .12). At 6 months after treatment, 67% (22/33) of patients showed significant improvement in ODI scores (P = .02); 64% (21/33) showed significant improvement in VAS scores for leg pain (P = .01); and 52% (17/33) showed significant improvement in VAS scores for back pain (P = .12). At 12 months after treatment, 68% (19/28) of patients showed significant improvement in ODI scores (P < .01); 64% (18/28) showed significant improvement in VAS scores for leg pain (P < .01); and 61% (17/28) showed significant improvement in VAS scores for back pain (P = .09). Leg pain typically subsided more quickly than back pain. Use of analgesic medications also significantly decreased at all follow-up timepoints compared to baseline (P < .01). There were no adverse events or device-related issues. CONCLUSIONS: At 1, 6, and 12 months after treatment, patients experienced significant improvements in pain and function as well as significantly decreased use of analgesic medication. Taken together with the absence of adverse events at 1-year follow-up, these data suggest that oxygen-ozone treatment is a safe and effective therapy for contained herniated discs.

Ketamine Infusions for Chronic Pain: A Systematic Review and Meta-analysis of Randomized Controlled Trials.

BACKGROUND: IV ketamine is widely used to treat patients with chronic pain, yet the long-term impact remains uncertain. We synthesized evidence from randomized control trials to investigate the effectiveness of IV ketamine infusions for pain relief in chronic conditions and to determine whether any pain classifications or treatment regimens are associated with greater benefit. METHODS: We searched Medline, Embase, and Google Scholar, as well as the clinicaltrials.gov website from inception through December 16, 2017 for randomized control trials comparing IV ketamine to placebo infusions for chronic pain that reported outcomes for ≥48 hours after the intervention. Three authors independently screened the studies, pooled the data, and appraised risk of bias. Random-effects model was used to calculate weighted mean differences for pain scores and secondary outcomes. Our primary outcome was the lowest recorded pain score ≥48 hours after cessation of treatment. Secondary outcomes included responder rate and adverse effects. RESULTS: Among 696 studies assessed for eligibility, 7 met inclusion criteria. All studies except one were at high risk of bias. These studies randomly assigned 211 patients with neuropathic (n = 2), mixed (n = 2), and nonneuropathic (nociplastic or nociceptive) (n = 3) pain. Three studies reported significant analgesic benefit favoring ketamine, with the meta-analysis revealing a small effect up to 2 weeks after the infusion (mean difference in pain scores, -1.83 points on a 0-10 numerical rating scale; 95% CI, -2.35 to -1.31 points; P < .0001). In the 3 studies that reported responder rates, the proportion with a positive outcome was greater in the ketamine than in the placebo group (51.3% vs 19.4%; relative risk, 2.43; 95% CI, 1.10-5.40; P = .029; I = 0.0%). No differences were noted based on pain classification or condition. Compared to low-dose ketamine studies and investigations that evaluated non-complex regional pain syndrome conditions, a small but nonsignificant greater reduction in pain scores was found among studies that either utilized high-dose ketamine therapy (P = .213) or enrolled complex regional pain syndrome patients (P = .079). CONCLUSIONS: Evidence suggests that IV ketamine provides significant short-term analgesic benefit in patients with refractory chronic pain, with some evidence of a dose-response relationship. Larger, multicenter studies with longer follow-ups are needed to better select patients and determine the optimal treatment protocol.

Weeding Out the Problem: The Impact of Preoperative Cannabinoid Use on Pain in the Perioperative Period.

BACKGROUND: The recreational and medical use of cannabinoids has been increasing. While most studies and reviews have focused on the role of cannabinoids in the management of acute pain, no study has examined the postoperative outcomes of surgical candidates who are on cannabinoids preoperatively. This retrospective cohort study examined the impact of preoperative cannabinoid use on postoperative pain scores and pain-related outcomes in patients undergoing major orthopedic surgery. METHODS: Outcomes of patients who had major orthopedic surgery at our hospital between April 1, 2015 and June 30, 2017 were reviewed. Data were obtained from Networked Online Processing of Acute Pain Information, a locally developed database for our Acute Pain Service. Propensity score matching was used to balance baselines variables including age, sex, type of surgery, history of depression or anxiety, and perioperative use of regional anesthesia between patients who reported use of cannabinoids and those not on this substance. Intensity of pain with movement in the early postoperative period (defined as up to 36 hours after surgery) was the primary outcome of this study. The secondary outcomes (all in early postoperative period) were pain at rest, opioid consumption, incidence of pruritus, nausea and vomiting, sedation, delirium, constipation, impairment of sleep and physical activity, patient satisfaction with analgesia, and the length of Acute Pain Service follow-up. RESULTS: A total of 3793 patients were included in the study. Of these, 155 patients were identified as being on cannabinoids for recreational or medical indications in the preoperative period. After propensity score matching, we compared data from 155 patients who were on cannabinoids and 155 patients who were not on cannabinoids. Patients who were on preoperative cannabinoids had higher pain numerical rating score (median [25th, 75th percentiles]) at rest (5.0 [3.0, 6.1] vs 3.0 [2.0, 5.5], P = .010) and with movement (8.0 [6.0, 9.0] vs 7.0 [3.5, 8.5], P = .003), and a higher incidence of moderate-to-severe pain at rest (62.3% vs 45.5%, respectively, P = .004; odds ratio, 1.98; 95% CI, 1.25-3.14) and with movement (85.7% vs 75.2% respectively, P = .021; odds ratio, 1.98; 95% CI, 1.10-3.57) in the early postoperative period compared to patients who were not on cannabinoids. There was also a higher incidence of sleep interruption in the early postoperative period for patients who used cannabinoids. CONCLUSIONS: This retrospective study with propensity-matched cohorts showed that cannabinoid use was associated with higher pain scores and a poorer quality of sleep in the early postoperative period in patients undergoing major orthopedic surgery.

A Review of Current Denervation Techniques for Chronic Hip Pain: Anatomical and Technical Considerations.

PURPOSE OF REVIEW: Percutaneous radiofrequency (RF) denervation of articular sensory nerves of the hip joint is a minimally invasive neurotomy technique that can provide pain relief in patients with chronic hip pain. There has been an increase in the number of publications on RF denervation of the hip over the last few years although many questions remain regarding anatomical targets, technical aspects, selection criteria, and evidence for effectiveness. RECENT FINDINGS: For this updated review, publications were identified by searching MEDLINE and other medical literature databases from inception through November 30, 2018. Existing knowledge of hip joint innervation was reviewed and data on patient selection, prognostication of analgesic benefit from ablation by using local anesthetic blocks, current techniques of performing hip joint ablation, analgesic success, functional outcomes, and adverse effects were critically reviewed and analyzed. Sensory denervation of the anterior hip joint using RF current is a viable treatment option for management of chronic hip pain after conservative methods fails to do so. We have synthesized knowledge from papers on techniques of ablation and from recently elaborated anatomical details. We also provide suggestions regarding anticipated outcomes of the procedure. Our review of existing literature indicates evidence for analgesic benefits, improvement in function, and a low incidence of adverse effects of RF ablation of sensory innervation to the hip joint. Future research should focus on refining the technique of ablation and monitoring of long-term outcomes.

Correction to: A Review of Current Denervation Techniques for Chronic Hip Pain: Anatomical and Technical Considerations.

In the original publication, the legend in the Figure 1 caption were missing and Table 2 was not presented correctly.

Brain Dynamics and Temporal Summation of Pain Predicts Neuropathic Pain Relief from Ketamine Infusion.

WHAT WE ALREADY KNOW ABOUT THIS TOPIC: WHAT THIS ARTICLE TELLS US THAT IS NEW: BACKGROUND:: Ketamine is an N-methyl-D-aspartate receptor antagonist that reduces temporal summation of pain and modulates antinociception. Ketamine infusions can produce significant relief of neuropathic pain, but the treatment is resource intensive and can be associated with adverse effects. Thus, it is crucial to select patients who might benefit from this treatment. The authors tested the hypothesis that patients with enhanced temporal summation of pain and the capacity to modulate pain via the descending antinociceptive brain pathway are predisposed to obtain pain relief from ketamine. METHODS: Patients with refractory neuropathic pain (n = 30) and healthy controls underwent quantitative sensory testing and resting-state functional magnetic resonance imaging and then completed validated questionnaires. Patients then received outpatient intravenous ketamine (0.5 to 2 mg · kg · h; mean dose 1.1 mg · kg · h) for 6 h/day for 5 consecutive days. Pain was assessed 1 month later. Treatment response was defined as greater than or equal to 30% pain relief (i.e., reduction in pain scores). We determined the relationship between our primary outcome measure of pain relief with pretreatment temporal summation of pain and with brain imaging measures of dynamic functional connectivity between the default mode network and the descending antinociceptive brain pathway. RESULTS: Approximately 50% of patients achieved pain relief (mean ± SD; Responders, 61 ± 35%; Nonresponders, 7 ± 14%). Pretreatment temporal summation was associated with the effect of ketamine (ρ = -0.52, P = 0.003) and was significantly higher in Responders (median [25th, 75th] = 200 [100, 345]) compared with Nonresponders (44 [9, 92]; P = 0.001). Pretreatment dynamic connectivity was also associated with the clinical effect of ketamine (ρ = 0.51, P = 0.004) and was significantly higher in Responders (mean ± SD, 0.55 ± 0.05) compared with Nonresponders (0.51 ± 0.03; P = 0.006). Finally, the dynamic engagement of the descending antinociceptive system significantly mediated the relationship between pretreatment pain facilitation and pain relief (95% CI, 0.005 to 0.065). CONCLUSIONS: These findings suggest that brain and behavioral measures have the potential to prognosticate and develop ketamine-based personalized pain therapy.

Treatment of Chronic Pain With Various Buprenorphine Formulations: A Systematic Review of Clinical Studies.

Clinical studies demonstrate that buprenorphine is a pharmacologic agent that can be used for the treatment of various types of painful conditions. This study investigated the efficacy of 5 different types of buprenorphine formulations in the chronic pain population. The literature was reviewed on PubMed/MEDLINE, EMBASE, Cochrane Database, clinicaltrials.gov, and PROSPERO that dated from inception until June 30, 2017. Using the population, intervention, comparator, and outcomes method, 25 randomized controlled trials were reviewed involving 5 buprenorphine formulations in patients with chronic pain: intravenous buprenorphine, sublingual buprenorphine, sublingual buprenorphine/naloxone, buccal buprenorphine, and transdermal buprenorphine, with comparators consisting of opioid analgesics or placebo. Of the 25 studies reviewed, a total of 14 studies demonstrated clinically significant benefit with buprenorphine in the management of chronic pain: 1 study out of 6 sublingual and intravenous buprenorphine, the only sublingual buprenorphine/naloxone study, 2 out of 3 studies of buccal buprenorphine, and 10 out of 15 studies for transdermal buprenorphine showed significant reduction in pain against a comparator. No serious adverse effects were reported in any of the studies. We conclude that a transdermal buprenorphine formulation is an effective analgesic in patients with chronic pain, while buccal buprenorphine is also a promising formulation based on the limited number of studies.

Selective Cannabinoids for Chronic Neuropathic Pain: A Systematic Review and Meta-analysis.

BACKGROUND: There is a lack of consensus on the role of selective cannabinoids for the treatment of neuropathic pain (NP). Guidelines from national and international pain societies have provided contradictory recommendations. The primary objective of this systematic review and meta-analysis (SR-MA) was to determine the analgesic efficacy and safety of selective cannabinoids compared to conventional management or placebo for chronic NP. METHODS: We reviewed randomized controlled trials that compared selective cannabinoids (dronabinol, nabilone, nabiximols) with conventional treatments (eg, pharmacotherapy, physical therapy, or a combination of these) or placebo in patients with chronic NP because patients with NP may be on any of these therapies or none if all standard treatments have failed to provide analgesia and or if these treatments have been associated with adverse effects. MEDLINE, EMBASE, and other major databases up to March 11, 2016, were searched. Data on scores of numerical rating scale for NP and its subtypes, central and peripheral, were meta-analyzed. The certainty of evidence was classified using the Grade of Recommendations Assessment, Development, and Evaluation approach. RESULTS: Eleven randomized controlled trials including 1219 patients (614 in selective cannabinoid and 605 in comparator groups) were included in this SR-MA. There was variability in the studies in quality of reporting, etiology of NP, type and dose of selective cannabinoids. Patients who received selective cannabinoids reported a significant, but clinically small, reduction in mean numerical rating scale pain scores (0-10 scale) compared with comparator groups (-0.65 points; 95% confidence interval, -1.06 to -0.23 points; P = .002, I = 60%; Grade of Recommendations Assessment, Development, and Evaluation: weak recommendation and moderate-quality evidence). Use of selective cannabinoids was also associated with improvements in quality of life and sleep with no major adverse effects. CONCLUSIONS: Selective cannabinoids provide a small analgesic benefit in patients with chronic NP. There was a high degree of heterogeneity among publications included in this SR-MA. Well-designed, large, randomized studies are required to better evaluate specific dosage, duration of intervention, and the effect of this intervention on physical and psychologic function.

Pectoralis and Serratus Fascial Plane Blocks Each Provide Early Analgesic Benefits Following Ambulatory Breast Cancer Surgery: A Retrospective Propensity-Matched Cohort Study.

BACKGROUND: Pectoralis and serratus blocks have been described recently for use in breast surgery, but evidence supporting their analgesic benefits is limited. This cohort study evaluates the benefits of adding a pectoralis or serratus block to conventional opioid-based analgesia (control) in patients who underwent ambulatory breast cancer surgery at Women's College Hospital between July 2013 and May 2015. We tested the joint hypothesis that adding a pectoralis or serratus block reduced postoperative in-hospital (predischarge) opioid consumption and nausea and vomiting (PONV). We also examined the 2 block types for noninferiority. METHODS: A total of 225 patients were propensity matched on 5 potential confounders among 3 study groups (75 per group): (1) pectoralis; (2) serratus; and (3) control. The propensity-matched cohort was used to evaluate the effect of the study group on postoperative in-hospital oral morphine equivalent consumption and PONV. We considered pectoralis noninferior to serratus block if it was noninferior for both outcomes, within 10 mg morphine and 17.5% in PONV incidence margins. Other outcomes included intraoperative fentanyl requirements, pain scores, time to first analgesic request, and duration of recovery room stay. RESULTS: Both pectoralis and serratus blocks were each associated with reduced postoperative in-hospital opioid consumption and PONV compared with control. Pectoralis was noninferior to serratus block for these 2 outcomes. Pectoralis and serratus blocks were each associated with reduced intraoperative fentanyl requirements, prolonged time to first analgesic request, and expedited recovery room discharge compared with control; there were no differences for the remaining outcomes. CONCLUSIONS: Pectoralis and serratus blocks were each associated with a reduction in postoperative in-hospital opioid consumption and PONV compared with conventional opioid-based analgesia after ambulatory breast cancer surgery.