Consensus Guidelines on the Use of Intravenous Ketamine Infusions for Chronic Pain From the American Society of Regional Anesthesia and Pain Medicine, the American Academy of Pain Medicine, and the American Society of Anesthesiologists

Chronic Neuropathic Pain and Comorbid Depression Syndrome: From Neural Circuit Mechanisms to Treatment

Chronic neuropathic pain and comorbid depression syndrome (CDS) is a major worldwide health problem that affects the quality of life of patients and imposes a tremendous socioeconomic burden. More than half of patients with chronic neuropathic pain also suffer from moderate or severe depression. Due to the complex pathogenesis of CDS, there are no effective therapeutic drugs available. The lack of research on the neural circuit mechanisms of CDS limits the development of treatments. The purpose of this article is to provide an overview of the various circuits involved in CDS. Notably, activating some neural circuits can alleviate pain and/or depression, while activating other circuits can exacerbate these conditions. Moreover, we discuss current and emerging pharmacotherapies for CDS, such as ketamine. Understanding the circuit mechanisms of CDS may provide clues for the development of novel drug treatments for improved CDS management.

Narcotic Consumption Analysis among Severely Injured and Advanced Aged Trauma Patients

BACKGROUND

Multimodal pain management has been shown to be effective in treating pain in acutely injured trauma patients. Our community-based, level 1 trauma center previously published in 2022 the efficacy of implementing multimodal pain control (MMPC) protocol in our inpatient trauma population which decreased the use of opioids while maintaining similar pain control. The MMPC group had a trend toward higher age and was significantly less injured. We hypothesize MMPC will reduce opioid consumption in both the advanced aged and more severely injured trauma populations while still providing adequate pain control.

METHODS

Defined by the year of admission, MMPC and physician managed pain control (PMPC) were compared in both advanced age groups and between the severely injured groups. The advanced age group included patients ≥55 years old. The severely injured group included ≥18 years old with ≥15 ISS. Primary outcomes were total opioid utilization per day, calculated in morphine milliequivalents (MME), and median daily pain scores.

RESULTS

For the severely injured population, the MMPC group showed a 3-fold decrease in opioid use (30 MME/d vs 90.3 MME/d, P < .001) and lower pain scores (5/10 vs 6/10, P < .001) than the PMPC group. In the advance age group, there was no significant difference between MMPC and PMPC groups in opioid use (P = .974) or pain scores (P = .553).

CONCLUSION

MMPC effectively reduces opioid consumption in a severely injured patient population while simultaneously improving pain control. Advanced age trauma patients can require complex pain management solutions and future research to determine their needs is recommended.

Multidisciplinary strategies to treat painful mononeuropathies in the upper extremity: from lab to bedside

Neuropathic pain in the upper extremity is a serious problem, commonly involving relatively young patients. The pain causes loss of function and productivity, changes a patient's lifestyle and can progress into a chronic pain syndrome with secondary psychosocial co-morbidities. Treating patients with a painful mononeuropathy remains challenging, with a monodisciplinary approach often having limited treatment efficacy. This narrative review discusses how to deal with this challenge in the treatment of patients with peripheral nerve injury pain, addressing the four important pillars: (1) diagnosing a painful mononeuropathy; (2) clinical pain phenotyping; (3) personalized pain treatment; and (4) using a multidisciplinary team approach.

Psychotherapy for Ketamine's Enhanced Durability in Chronic Neuropathic Pain: Protocol for a Pilot Randomized Controlled Trial

BACKGROUND

Chronic pain affects approximately 8 million Canadians (~20%), impacting their physical and mental health while burdening the health care system with costs of upwards of US $60 billion a year. Indeed, patients are often trialed on numerous medications over several years without reductions to their symptoms. Therefore, there is an urgent need to identify new therapies for chronic pain to improve patients' quality of life, increase the availability of treatment options, and reduce the burden on the health care system.

OBJECTIVE

The primary objective of this study is to examine the feasibility of a parallel 3-arm pilot randomized controlled trial whereby patients are randomized to either intravenous ketamine alone, cognitive behavioral therapy (CBT) and mindfulness meditation (MM) training (CBT/MM), or the combination of intravenous ketamine and CBT/MM. The secondary outcome is to assess the durability and efficacy of combination intravenous ketamine and CBT/MM for treatment of chronic pain as compared to CBT/MM or intravenous ketamine alone (assessed at week 20 of the study).

METHODS

This is a single-center, 16-week, 3-arm pilot study that will take place at the Chronic Pain Clinic at St. Michael's Hospital, Toronto, Ontario, which receives 1000 referrals per year. Patients will be enrolled in the study for a total of 20 weeks. Participants who are allocated CBT/MM therapy will receive remote weekly psychotherapy from week 1 to week 16, inclusive of health coaching administered through the NexJ Health Inc (NexJ Health) platform. Patients who are allocated ketamine-infusion therapy will receive monthly ketamine infusion treatments on weeks 2, 7, and 12. Patients who are allocated ketamine+CBT/MM will receive weekly psychotherapy from weeks 1 to 16, inclusive, as well as ketamine infusion treatments on weeks 2, 7, and 12. We will be assessing recruitment rates, consent rates, withdrawal rates, adherence, missing data, and adverse events as pilot outcome measures. Secondary clinical outcomes include changes relative to baseline in pain intensity and pain interference.

RESULTS

As of November 1, 2023, the recruitment process has not been initiated. Given the recruitment, consent, and intervention target of 30 participants for this feasibility study, with each patient undergoing monitoring and treatments for a course of 20 weeks, we expect to complete the study by December 2025.

CONCLUSIONS

This study assesses the feasibility of conducting a 3-arm randomized controlled trial to examine the effects of ketamine administration with the concurrent use of CBT/MM in a population with chronic neuropathic pain. The results of this pilot randomized controlled trial will inform the development of a larger-scale randomized controlled trial. Future studies will be aimed at including a sufficiently powered sample that will inform decisions about optimal treatment calibration and treatment effect duration.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05639322; https://classic.clinicaltrials.gov/ct2/show/NCT05639322.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

PRR1-10.2196/54406.

Ketamine Use for Palliative Care in the Austere Environment: Is Ketamine the Path Forward for Palliative Care

The goal of palliative care is to focus on the holistic needs of the patient and their family versus the pathology of the patient's diagnosis to reduce the stress of illness. U.S. servicemembers deployed to austere environments worldwide have significantly less access to palliative care than in military treatment facilities in the U.S. Preparation for future conflicts introduces the concept of prolonged medical management for an environment where urgent casualty evacuation is impossible. Ketamine is currently widely used for analgesia and anesthesia in the care of military service members and its use has increased in combat zones of Iraq and Afghanistan due to the favorable preservation of respiratory function, minimal changes in hemodynamics, and lower pain scores compared to opioids. Ketamine acts as a non-competitive antagonist on N-methyl-D aspartate (NMDA) receptors. Its anesthesia and analgesic effects are complex and include both presynaptic and postsynaptic neurons in brain and spinal cord. The use of palliative care to minimize suffering should not be withheld due to the logistical boundaries of austere military environments or lack of guidelines for recommended use. The use of ketamine for palliative care is a new clinical management strategy to provide both sedation and pain management for an acute pain crisis or comfort measures for the terminally ill. This makes ketamine an attractive consideration for palliative care when managing critically wounded patients for an extended time.

The Use of Ketamine for Malignant and Nonmalignant Chronic Pain in Children: A Review of Current Evidence

Chronic pain in children continues to pose significant challenges. The pharmacological approach most often revolves around trials and errors, expert opinions, and extrapolation of adult study findings. Ketamine is one of the agents used for chronic pain, especially with a neuropathic component. This article aims to provide an overview of its properties and highlight the current evidence for its use in malignant and nonmalignant chronic pain management. A search on the use of ketamine for chronic pain in children up to 18 years of age covering the period from January 1, 2000, to December 14, 2022, was performed through PubMed, Cochrane Library, EBSCO, EBM Review, Wiley, BMJ, Web of Science, Google Scholar, and the Saudi Digital Library. 218 articles were found and 42 underwent full review. Currently, the evidence about ketamine efficacity and safety for chronic pain management is at best of moderate to low quality. The heterogeinity of ketamine infusion protocols and frequent concomitant use of other analgesics make it difficult to draw robust conclusions. The long-term effect of prolonged usage also remains a concern. Nevertheless, with careful monitoring, the drug may be a reasonable choice for malignant and nonmalignant pain management in selected cases, especially for refractory pain not responding to conventional approaches.

Observational study of the effect of ketamine infusions on sedation depth, inflammation, and clinical outcomes in mechanically ventilated patients with SARS-CoV-2

Severely ill patients with COVID-19 are challenging to sedate and often require high-dose sedation and analgesic regimens. Ketamine can be an effective adjunct to facilitate sedation of critically ill patients but its effects on sedation level and inflammation in COVID-19 patients have not been studied. This retrospective, observational cohort study evaluated the effect of ketamine infusions on inflammatory biomarkers and clinical outcomes in mechanically ventilated patients with SARS-CoV-2 infection. A total of 186 patients were identified (47 received ketamine, 139 did not). Patients who received ketamine were significantly younger than those who did not (mean (standard deviation) 59.2 (14.2) years versus 66.3 (14.4) years; P = 0.004), but there was no statistically significant difference in body mass index (P = 0.25) or sex distribution (P = 0.91) between groups. Mechanically ventilated patients who received ketamine infusions had a statistically significant reduction in Richmond Agitation-Sedation Scale score (-3.0 versus -2.0, P < 0.001). Regarding inflammatory biomarkers, ketamine was associated with a reduction in ferritin (P = 0.02) and lactate (P = 0.01), but no such association was observed for C-reactive protein (P = 0.27), lactate dehydrogenase (P = 0.64) or interleukin-6 (P = 0.87). No significant association was observed between ketamine administration and mortality (odds ratio 0.971; 95% confidence interval 0.501 to 1.882; P = 0.93). Ketamine infusion was associated with improved sedation depth in mechanically ventilated COVID-19 patients and provided a modest anti-inflammatory benefit but did not confer benefit with respect to mortality or intensive care unit length of stay.

Ketamine restriction correlates with reduced cholestatic liver injury and improved outcomes in critically ill patients with burn injury

Background & Aims

Ketamine-associated cholestatic liver injury is reported in patients with severe burn injury, but its association with patient outcome is unclear. We investigated the relationship between ketamine exposure, cholestatic liver injury, and outcome of critically ill patients with burn injury.

Methods

In a retrospective study, patients with severe burn injury were analysed across two periods: unrestricted ketamine prescription (ketamine-liberal) and capped ketamine dosage (ketamine-restricted). The primary endpoint was cholestatic liver injury, and the secondary endpoint was 3-month mortality. Binary logistic regression models and the revised electronic causality assessment method were used to measure the strength of associations and causality assessment, respectively.

Results

Of 279 patients (median age 51 [IQR 31-67] years; 63.1% men; burned surface area 28.5%, IQR 20-45%), 155 (56%) were in the ketamine-liberal group, and 124 (44%) were in the ketamine-restricted group, with comparable clinical characteristics, except for ketamine exposure (median doses 265.0 [IQR 0-8,021] mg and 20 [IQR 0-105] mg, respectively; p <0.001). A dose- and time-dependent relationship was observed between ketamine exposure and cholestatic liver injury. Ketamine restriction was associated with a reduced risk of cholestatic liver injury (adjusted odds ratio 0.16, 95% CI 0.04-0.50; p = 0.003) and with a higher probability of 3-month survival (p = 0.035). The revised electronic causality assessment method indicated that ketamine was probably and possibly the cause of cholestatic liver injury for 14 and 10 patients, respectively. Cholangitis was not observed in the ketamine-restricted group. In propensity-matched patients, the risk of 3-month mortality was higher (adjusted odds ratio 9.92, 95% CI 2.76-39.05; p = 0.001) in patients with cholestatic liver injury and ketamine exposure ≥10,000 mg. Other sedative drugs were not associated with liver and patient outcome.

Conclusions

In this cohort, ketamine restriction was associated with less cholestatic liver injury and reduced 3-month mortality.

Impact and implications

In a cohort of 279 critically ill patients with burn injury, ketamine was associated with a risk of liver bile duct toxicity. The risk was found to be dependent on both the dosage and duration of ketamine use. A restriction policy of ketamine prescription was associated with a risk reduction of liver injury and 3-month mortality. These findings have implications for the analgesia and sedation of critically ill patients with ketamine, with higher doses raising safety concerns.

Emergency Department Management of Low Back Pain: A Comparative Review of Guidelines and Practices

This narrative review examines the current best practices and guidelines for integrating pharmacologic interventions, imaging, and physiotherapy in the management of low back pain. The review also explores how patient factors such as age, sex, comorbidities, and prevalent pathologies/diagnoses influence the choice and effectiveness of these treatment approaches.

A systematic review and network meta-analysis of pharmaceutical interventions used to manage chronic pain

It is estimated 1.5 billion of the global population suffer from chronic pain with prevalence increasing with demographics including age. It is suggested long-term exposure to chronic could cause further health challenges reducing people's quality of life. Therefore, it is imperative to use effective treatment options. We explored the current pharmaceutical treatments available for chronic pain management to better understand drug efficacy and pain reduction. A systematic methodology was developed and published in PROSPERO (CRD42021235384). Keywords of opioids, acute pain, pain management, chronic pain, opiods, NSAIDs, and analgesics were used across PubMed, Science direct, ProQuest, Web of science, Ovid Psych INFO, PROSPERO, EBSCOhost, MEDLINE, ClinicalTrials.gov and EMBASE. All randomised controlled clinical trials (RCTs), epidemiology and mixed-methods studies published in English between the 1st of January 1990 and 30th of April 2022 were included. A total of 119 studies were included. The data was synthesised using a tri-partied statistical methodology of a meta-analysis (24), pairwise meta-analysis (24) and network meta-analysis (34). Mean, median, standard deviation and confidence intervals for various pain assessments were used as the main outcomes for pre-treatment pain scores at baseline, post-treatment pain scores and pain score changes of each group. Our meta-analysis revealed the significant reduction in chronic pain scores of patients taking NSAID versus non-steroidal opioid drugs was comparative to patients given placebo under a random effects model. Pooled evidence also indicated significant drug efficiency with Botulinum Toxin Type-A (BTX-A) and Ketamine. Chronic pain is a public health problem that requires far more effective pharmaceutical interventions with minimal better side-effect profiles which will aid to develop better clinical guidelines. The importance of understanding ubiquity of pain by clinicians, policy makers, researchers and academic scholars is vital to prevent social determinant which aggravates issue.

Patient experiences with requests for medical assistance in dying: Perspectives of those with complex chronic conditions

OBJECTIVE

To explore experiences of patients who have complex chronic conditions (CCCs), such as fibromyalgia and chronic fatigue syndrome, when they request medical assistance in dying (MAID) in Canada.

DESIGN

Qualitative study using semistructured interviews.

SETTING

Canada.

PARTICIPANTS

Individuals with CCCs who had contacted any 1 of 4 advocacy organizations between January 21, 2021, and December 20, 2022, about requesting MAID for suffering related to CCCs or who had applied and been assessed for MAID.

METHODS

Interviews were conducted virtually (by video or audio) and recordings were transcribed. Thematic analysis was conducted in an iterative manner with abductive analysis. As interviews were completed, transcripts were reviewed and emerging themes were discussed at regular intervals.

MAIN FINDINGS

Sixteen individuals were interviewed. All spoke of long-lasting suffering that was unresponsive to an array of medical treatments. Although some participants had hoped to receive MAID immediately following the 90-day assessment period, many mentioned that approval would provide or had provided validation of their illness and a sense of control, especially should their illness become unbearable. Participants sharply distinguished between MAID and suicide, saying they preferred MAID because it offered greater certainty and caused less emotional pain to others. Many said that participating in this research was beneficial because they believed the interviewers truly listened to them.

CONCLUSION

Participants described experiences with CCCs and requests for MAID. This information may provide family doctors with new insight to inform interactions with patients with CCCs.

Maintenance IV Ketamine Therapy in the Fibromyalgia Patient: A Case Report

Introduction

Fibromyalgia is a complex disorder characterized by distributed and persistent pain often associated with fatigue and depression. The underlying causal agents of this dysfunction are not clear. Ketamine has been used to treat chronic pain in a variety of pain syndromes, including fibromyalgia, but the dosing protocols used are neither standardized nor consistent across cases. The current case presents an opportunity to contribute to a progression towards a consensus on ketamine dosing for fibromyalgia.

Case Presentation

A 60-year-old female presented with indications of fibromyalgia and was administered a 9-session IV ketamine treatment for pain. The initial dosing was 50 mg, with a concentration of 1.0 mg/ml at an infusion rate of 0.8 mg/kg/hr. This was increased to 200 mg and eventually to 240 mg, maintaining a ketamine concentration 4.0-4.8 mg/ml at an infusion rate of 1.5 mg/kg/hr.

Management and Outcomes

Following the first 9-session therapy, the patient reported >50% pain relief from pre-infusion levels and was placed on a maintenance regimen in perpetuity. This regimen involves two monthly IV ketamine infusions, one day apart for two hours at a maintenance rate of 4.8 mg/kg/hr.

Conclusion

Ketamine by IV is an effective option for pain management in patients with fibromyalgia. Compared to previous case studies, it is recommended that increased total dose, frequent administration, and longer duration of infusions all may be necessary for ketamine to maximize its beneficial effects.

Comparison of the effects of ketamine via nebulization versus different pharmacological approaches in pediatric sedation: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Nebulized drug delivery is commonly used in pediatric clinical practice. The growing number of literatures have reported the application of nebulized ketamine in pediatric sedation in recent years. This meta-analysis of randomized controlled trials comparing the efficacy and safety of nebulized ketamine versus different pharmacological approaches was conducted to estimate the effects of this technique in pediatric sedation.

METHODS

We searched PubMed, Embase, and Cochrane Library from inception to Feb 2023. All randomized controlled trials used nebulized ketamine as presurgical and pre-procedural sedatives in children were included. Sedative effects and various adverse events were considered as the outcomes.

RESULTS

Ten studies with 727 pediatric patients were enrolled. Compared to nebulized dexmedetomidine, using of ketamine via nebulization showed similar sedation satisfaction (54.79% vs. 60.69%, RR = 0.88, with 95%CI [0.61, 1.27]), success rate of parental separation (57.27% vs. 73.64%, RR = 0.81, with 95%CI [0.61, 1.08]), and mask acceptability (37.27% vs. 52.73%, RR = 0.71, with 95%CI [0.45, 1.10]). However, the using of combination of two medications (nebulized ketamine plus nebulized dexmedetomidine) was associated with better sedative satisfaction (33.82% vs. 68.11%, RR = 0.50, with 95%CI [0.27, 0.92]) and more satisfactory mask acceptance (45.59% vs. 71.01%, RR = 0.69, with 95%CI [0.56, 0.86]). Compared with nebulized ketamine, using of nebulized dexmedetomidine was associated with less incidence of emergence agitation (18.18% vs. 3.33%, RR = 4.98, with 95%CI [1.88, 13.16]).

CONCLUSIONS

Based on current evidences, compared to nebulized dexmedetomidine, nebulized ketamine provides inconspicuous advantages in pediatric sedation, and it has a relatively high incidence of emergence agitation. Combination of nebulized ketamine and dexmedetomidine might be considered as one preferred option in pediatric sedation as it can provide more satisfactory sedative effects. However, there is insufficient evidence regarding nebulized ketamine versus ketamine administered through other routes and nebulized ketamine versus other sedatives. The overall low or moderate quality of evidence evaluated by the GRADE system also calls for more high-quality studies with larger sample sizes in future.

RESEARCH REGISTRATION

The protocol of present study was registered with PROSPERO (CRD42023403226).

The use of ketamine infusion to dramatically reduce opioid requirements in a patient whose high-dose intrathecal opioid pump was inadvertently cut during surgery

BACKGROUND

Chronic opioid therapy may lead to high level tolerance development, hyperalgesia, and central sensitization, which further complicates long-term therapeutic management of chronic pain patients. In this case, we encounter a patient who was receiving over 15,000 morphine milligram equivalents through their intrathecal pain pump. Unfortunately, the intrathecal pump was inadvertently cut during a spinal surgery. It was deemed unsafe to delivery IV equivalent opioid therapy in this case; instead, the patient was admitted to the ICU and given a four-day ketamine infusion.

METHOD

The patient was started on a ketamine infusion at a rate of 0.5mg/kg/h, which was continued for three days. On the fourth day, the infusion rate was tapered over 12 h before being completely stopped. No coinciding opioid therapy was given during this time, which was only restarted in the outpatient setting.

RESULTS

Despite chronic high levels of opioid therapy immediately prior to the ketamine infusion, the patient did not experience florid withdrawals during the infusion period. Additionally, the patient experienced remarkable improvement in their subjective pain rating, which decreased from 9 to 3-4 on an 11-point Number Rating Scale, while simultaneously being managed on an MME <100. These results were sustained through a 6-month follow-up period.

CONCLUSION

Ketamine may play an important role in attenuating not only tolerance but also acute withdrawal in a setting where rapid or instant weaning from high dose chronic opioid therapy is needed.

Effects of S-ketamine on Postoperative Recovery Quality and Inflammatory Response in Patients Undergoing Modified Radical Mastectomy

INTRODUCTION

S-ketamine plays an important role in reducing postoperative pain, but its impact on the quality of recovery in breast cancer has not been clarified. We designed this trial to explore the effects of s-ketamine on the quality of postoperative recovery and inflammatory response in modified radical mastectomy.

METHODS

A total of 138 patients were randomly assigned to group C (group control), group K1 (group of s-ketamine dose 1) and group K2 (group of s-ketamine dose 2). Groups K1 and K2 were given 0.1 mg/kg, 0.2 mg/kg s-ketamine intravenous (IV) after induction, followed by 0.1 mg/kg/h or 0.2 mg/kg/h continuous intravenous infusion, respectively. Group C received the same volume of saline. A 40-item Quality of Recovery Questionnaire (QoR-40) was used to assess the quality of recovery at 24 h postoperatively. Changes in inflammatory markers, nociceptive thresholds, and the occurrence of adverse events were recorded at 24 h postoperatively.

RESULTS

The QoR-40 scores at 24 h postoperatively were higher in group K2 [182.00 (179.00-185.00)] compared to group K1 [174.00 (169.50-180.50)] and group C [169.00 (163.75-174.25)] (group K2 vs. group K1, P < 0.001; group K2 vs. group C, P < 0.001). At 24 h postoperatively, the neutrophil count, NLR (neutrophil-lymphocyte ratio), and CRP (C-creative protein) were all significantly lower in group K2 than group C(P < 0.05), no differences were observed between group K1 and C(P > 0.05), group K1 and K2(P > 0.05), respectively. There was no significant difference in the incidence of adverse effects among the three groups (P > 0.05).

CONCLUSIONS

A high dose of s-ketamine improved the quality of recovery at 24 h after surgery, as well as alleviated the inflammatory response without increasing the incidence of adverse effects.

Low-dose ketamine infusions for chronic pain management: Does this qualify as evidence-based practice?

Chronic pain is becoming increasingly prevalent and burdensome both worldwide and in the United Kingdom. Due to the complexity of chronic pain and the therapeutic challenge associated, management is often difficult and requires multidisciplinary care encompassing a combination of pharmacological and non-pharmacological strategies. Conventional analgesic treatments, such as opioids and anticonvulsants, are effective in less than half of chronic pain sufferers and are typically limited to short-term use to prevent complications associated with long-term use such as tolerance and dependence. Consequently, research and clinical interest in alternative management options for chronic pain have increased in recent years, with ketamine being one example under investigation. However, since ketamine has been licensed as an anaesthetic for decades, it has bypassed the traditional scrutinous drug development sequence that is typically seen for therapeutics marketed for pain. As such, data supporting the unlicensed administration of ketamine for chronic pain management is lacking and is being outpaced by the rates of off-label use in pain clinics. Recent limited evidence suggests that ketamine, when given as an intravenous infusion in subanaesthetic doses for refractory pain patients, may provide modest analgesic effects in nearly all aetiologies of chronic pain, with side effects common but typically mild. However, there are concerns over the safety of this practice due to the paucity of robust supportive evidence and the accompanying lack of clinical guidelines or standardised protocols. This review shall summarise the literature examining the use of subanaesthetic-dose ketamine infusions for chronic pain to comment on the current level of evidence, with limitations of existing research and future recommendations discussed.

Ketamine for Chronic Pain and Mental Health: Regulations, Legalities, and the Growth of Infusion Clinics

PURPOSE OF REVIEW

In this article, we will review evidence for ketamine's role in chronic pain and mental health conditions, its current legal status and abuse potential, and the regulations related to its administration in stand-alone infusion clinics, as well as future considerations.

RECENT FINDINGS

In the management of chronic pain, ketamine has shown potential to manage neuropathic pain and complex regional pain syndrome and has been used as a treatment for chronic pain management by clinics across the USA. Analogous to the historic rise of lidocaine clinics, ketamine clinics are demonstrating a similar pattern of unregulated growth. Ketamine is an anesthetic and analgesic agent commonly used in the perioperative setting and emergency department for sedation and pain management (Mo et al in West J Emerg Med 21(2):272-281, 2020). It was approved for use by the Federal Drug Administration in the USA in the 1970s as the sole anesthetic agent for short diagnostic and surgical procedures (Coppel et al. in Anaesthesia 28(3):293-296, 1973; Schwenk et al. in Reg Anesth Pain Med 43(5):456-466, 2018). Regarding its rising popularity as a treatment option in mental health, ketamine holds promise as a rapidly acting treatment for suicidal ideation and refractory depression.

Ketamine Infusions for Treatment-Resistant Neuropathic Pruritus

This case report describes a patient in her 50s with a 4-year history of brachioradial pruritus with bilateral pruritus on her upper arms and forearms.

Outpatient Ketamine Infusions for the Treatment of Fibromyalgia and Chronic Pain Syndrome: A Case Report

Intravenous (IV) ketamine has demonstrable efficacy for chronic pain management. Its use in an outpatient setting has provided relief from myriad pain syndromes and additionally may reduce dependence on opioids. Nevertheless, its long-term ability to provide these benefits is understudied. Here, we present the case of a 68-year-old female who presented to our clinic with persistent fibromyalgia, accompanied by other pain symptoms that had been recalcitrant to traditional pain management therapy including nerve blocks, ablations, spinal cord stimulation, and morphine medication. We administered seven increasing IV ketamine doses over two weeks. The patient reported significant, widespread pain relief. The patient continued to receive IV ketamine twice weekly for over a year and remains on this schedule. Pain relief has persisted under this regimen, along with a demonstrable improvement in quality of life, a reduced use of morphine, and the cessation of anti-depressant medication. This case indicates that long-term ketamine infusions show promise for chronic pain management and that more longitudinal studies on this treatment are warranted.

Hallucinogenic potential: a review of psychoplastogens for the treatment of opioid use disorder

The United States is entering its fourth decade of the opioid epidemic with no clear end in sight. At the center of the epidemic is an increase in opioid use disorder (OUD), a complex condition encompassing physical addiction, psychological comorbidities, and socioeconomic and legal travails associated with the misuse and abuse of opioids. Existing behavioral and medication-assisted therapies show limited efficacy as they are hampered by lack of access, strict regimens, and failure to fully address the non-pharmacological aspects of the disease. A growing body of research has indicated the potential of hallucinogens to efficaciously and expeditiously treat addictions, including OUD, by a novel combination of pharmacology, neuroplasticity, and psychological mechanisms. Nonetheless, research into these compounds has been hindered due to legal, social, and safety concerns. This review will examine the preclinical and clinical evidence that psychoplastogens, such as ibogaine, ketamine, and classic psychedelics, may offer a unique, holistic alternative for the treatment of OUD while acknowledging that further research is needed to establish long-term efficacy along with proper safety and ethical guidelines.

A systematic review of the efficacy of ketamine for craniofacial pain

Background

Craniofacial pain (CFP) poses a burden on patients and health care systems. It is hypothesized that ketamine, an N-methyl-d-aspartate (NMDA) receptor antagonist, can reverse central sensitization associated with causation and propagation of CFP. This systematic review aims to assess the role of ketamine for CFP.

Methods

Databases were searched for studies published up to September 26, 2022, investigating the efficacy of ketamine for adults with CFP. Primary outcome was the change in pain intensity at 60 min postintervention. Two reviewers screened and extracted data. Registration with PROSPERO was performed (CRD42020178649).

Results

Twenty papers (six randomized controlled trials [RCTs], 14 observational studies) including 670 patients were identified. Substantial heterogeneity in terms of study design, population, dose, route of administration, treatment duration, and follow-up was noted. Bolus dose ranged from 0.2-0.3 mg/kg (intravenous) to 0.4 mg/kg (intramuscular) to 0.25-0.75 mg/kg (intranasal). Ketamine infusions (0.1-1 mg/kg/h) were given over various durations. Follow-up was short in RCTs (from 60 min to 72 h) but longer in observational studies (up to 18 months). Ketamine by bolus treatment failed to reduce migraine intensity but had an effect by reducing intensity of aura, cluster headache (CH), and trigeminal neuralgia. Prolonged ketamine infusions showed sustainable reduction of migraine intensity and frequency of CH attacks, but the quality of the evidence is low.

Conclusion

Current evidence remains conflicting on the efficacy of ketamine for CFP owing to low quality and heterogeneity across studies. Ketamine infusions are suggested to provide sustained improvement, possibly because of prolonged duration and higher dosage of administration. RCTs should focus on the dose-response relationship of prolonged ketamine infusions on CFP.

Perioperative Administration of Pregabalin and Esketamine to Prevent Chronic Pain After Breast Cancer Surgery: A Randomized Controlled Trial

Background

Perioperative multimodal analgesia can prevent chronic pain after breast cancer surgery. This study aimed to investigate the efficacy of combined perioperative oral pregabalin and postoperative esketamine in preventing chronic pain after breast cancer surgery.

Methods

Ninety patients undergoing elective breast cancer surgery were randomized into the combined pregabalin and esketamine group (EP group) and the general anesthesia alone group (Control group). The EP group received 150 mg of oral pregabalin 1 h before surgery and twice daily for seven days postoperatively, and a patient-controlled analgesia pump after surgery that delivered 100 μg sufentanil + 1.25 mg/kg esketamine + 4 mg tropisetron in 100 mL saline solution intravenously. The Control group received placebo capsules before and after the surgery and routine postoperative analgesia (100 μg sufentanil + 4 mg tropisetron in 100 mL saline solution). The primary outcome was the incidence of chronic pain three and six months after surgery. Secondary outcomes included acute postoperative pain, postoperative opioid consumption, and incidence of adverse events.

Results

The incidence of chronic pain in the EP group was significantly lower than in the Control group three (14.3% vs 46.3%, P = 0.005) and six (7.1% vs 31.7%, P = 0.009) months postoperatively. The rest numerical rating scale (NRS) pain scores 1-3 days postoperatively and coughing NRS pain scores 1-7 days postoperatively in the EP group were significantly lower than in the Control group (all P ˂ 0.05). The cumulative sufentanil consumption in the EP group during postoperative 0-12, 12-24, and 24-48, 0-24, and 0-48 hours were significantly lower than in the Control group (all P ˂ 0.05).

Conclusion

Combined perioperative oral pregabalin and postoperative esketamine effectively prevented chronic pain after breast cancer surgery, improved acute postoperative pain, and reduced postoperative opioid consumption.

Explainable drug side effect prediction via biologically informed graph neural network

Early detection of potential side effects (SE) is a critical and challenging task for drug discovery and patient care. In-vitro or in-vivo approach to detect potential SEs is not scalable for many drug candidates during the preclinical stage. Recent advances in explainable machine learning may facilitate detecting potential SEs of new drugs before market release and elucidating the critical mechanism of biological actions. Here, we leverage multi-modal interactions among molecules to develop a biologically informed graph-based SE prediction model, called HHAN-DSI. HHAN-DSI predicted frequent and even uncommon SEs of the unseen drug with higher or comparable accuracy against benchmark methods. When applying HHAN-DSI to the central nervous system, the organs with the largest number of SEs, the model revealed diverse psychiatric medications' previously unknown but probable SEs, together with the potential mechanisms of actions through a network of genes, biological functions, drugs, and SEs.

Effect of subanesthetic dose of esketamine on postoperative rehabilitation in elderly patients undergoing hip arthroplasty

OBJECTIVE

The majority of individuals with femoral neck fractures opt for total hip replacement to enhance their quality of life. However, this group frequently exhibits perioperative symptoms of pain, anxiety, and sadness, which extends recovery time to some extent. Esketamine, the right-handed monomer of ketamine, is more popular these days due to its sedative, analgesic, and antidepressant properties. There are currently few domestic and international research on the use of esketamine in elderly individuals who have undergone surgery for a femoral neck fracture. In order to further cut the length of the hospital stay and hasten postoperative recovery, this study investigates whether esketamine postoperative analgesia can lessen postoperative pain, anxiety, and depression in older patients having hip replacement.

METHODS

150 patients, ASA physical status I-II, aged ≥ 60 years, no limitation in gender, BMI 18-25 kg/cm², who underwent selective total hip arthroplasty, according to random number table method, esketamine group (group A) and sufentanil group (group B) were randomized, 75 patients in each group. The two groups received general anesthesia method. At the end of the operation, PCIA was connected for analgesia. In group A, esketamine 2.5 mg/kg was mixed with normal saline to 100 ml. In group B, sufentanil 2.5 ug/kg was mixed with normal saline to 100 ml. Record the VAS scores after operation. Record the first ambulation time, ambulation distance and Patient-controlled Analgesia compression times after operation. The incidence of postoperative adverse reactions such as drowsiness, dizziness, nausea and vomiting, multilingual were recorded. ELISA was used to detect IL-6 and CRP in the morning, 24 h and 72 h after operation. The Hospital Anxiety and Depression Scale (HAD) score and Harris score at 3 days, 1 week and 1 month after operation were followed up.

RESULTS

There was no significant difference in VAS score and PCA compression times (P > 0.05), but the incidence of nausea, vomiting and dizziness in group B was higher than that in group A (P < 0.05). Compared with group B, the levels of IL-6 and CRP in group A at 24 h and 72 h after operation were significantly decreased (P < 0.05). Postoperative ambulation time and ambulation distance in group A were better than those in group B (P < 0.05). The HAD score of group A was lower than that of group B at 3 days and 1 week after operation (P < 0.05). However, there was no significant difference between the two groups at 1 month after operation (P > 0.05). The Harris score of group A was higher than that of group B at 3 days, 1 week and 1 month after operation (P < 0.05).

CONCLUSIONS

Esketamine can reduce short-term postoperative anxiety and depression, relieve postoperative pain and stress response, shorten bed rest time after total hip replacement, and accelerate postoperative recovery.

Intermittent versus continuous esketamine infusions for long-term pain modulation in complex regional pain syndrome: protocol of a randomized controlled non-inferiority study (KetCRPS-2)

BACKGROUND

Complex regional pain syndrome (CRPS) is a chronic pain condition of an extremity. While achieving pain relief in CRPS is challenging, esketamine infusions can accomplish pain relief for several weeks post-infusion in a subgroup of CRPS patients. Unfortunately, CRPS esketamine protocols are very heterogeneous in advice on dosage, administration and treatment setting. Currently, no trials are available that study differences between intermittent and continuous esketamine infusions for CRPS. With the current situation of bed shortages, it is difficult to admit patients for several consecutive days for inpatient esketamine treatments. In this study, we investigate whether 6 intermittent outpatient esketamine treatments are not inferior to a continuous 6-day inpatient esketamine treatment in establishing pain relief. In addition, several secondary study parameters will be assessed in order to investigate mechanisms responsible for pain relief by esketamine infusions. Furthermore, the cost-effectiveness will be analyzed.

METHODS

In this RCT, the primary objective is to demonstrate that an intermittent esketamine dosing regimen is non-inferior to a continuous esketamine dosing regimen at 3 months follow-up. We will include 60 adult CRPS patients. The inpatient treatment group receives a continuous intravenous esketamine infusion for 6 consecutive days. The outpatient treatment group receives a 6-hour intravenous esketamine infusion every 2 weeks for 3 months. Esketamine dose will be individually tailored and is started at 0.05 mg/kg/h and can be increased to a maximum of 0.2 mg/kg/h. Each patient will be followed for 6 months. The primary study parameter is perceived pain intensity, measured by an 11-point Numerical Rating Scale. Secondary study parameters are conditioned pain modulation, quantitative sensory testing, adverse events, thermography, blood inflammatory parameter, questionnaires about functionality, quality of life and mood and costs per patient.

DISCUSSION

If our study reveals non-inferiority between intermittent and continuous esketamine infusions, these findings can be beneficial to increase the availability and flexibility of esketamine infusions through outpatient treatments. Furthermore, the costs of outpatient esketamine infusions could be lower than inpatient esketamine infusions. In addition, secondary parameters may predict response to esketamine treatment.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier NCT05212571 , date of registration 01-28-2022.

PROTOCOL VERSION

Version 3, February 2022.

Comparison of the Effect of Adding Low-dose Ketamine to Dexmedetomidine and Propofol on the Quality of Sedation and Hemodynamic Response in Children During Upper Gastrointestinal Endoscopy: A Double-blind Randomized Clinical Trial

Background: As endoscopy is an invasive and painful procedure, it is necessary to use a suitable sedative with a minimum dose, especially in children. Objectives: This study aimed to compare the effect of adding low-dose ketamine to dexmedetomidine and propofol on the quality of sedation and hemodynamic response in children during upper gastrointestinal endoscopy. Methods: This double-blind, randomized clinical trial was conducted on 52 children who were candidates for endoscopy in 2 groups, each consisting of 26 patients. In the first group (Ketadex group), infusion of dexmedetomidine (0.7 - 1 μg/kg) for 10 minutes and ketamine bolus (0.4 mg/kg) for anesthesia induction was prescribed. In the second group (Ketofol group), infusion of propofol (50 - 100 μg/kg) for 10 minutes and ketamine bolus (0.4 mg/kg) for anesthesia induction was prescribed. Results: The mean blood pressure of children decreased slightly during and after the endoscopic procedure in the Ketadex group than in the Ketofol group (P < 0.05). The recovery time was significantly less in the Ketofol group (41.85 ± 7.03 minutes) than in the Ketadex group (55.12 ± 7.55 minutes; P < 0.001). Conclusions: The addition of the low-dose ketamine to propofol and dexmedetomidine did not result in any significant changes in the level of sedation, the incidence of adverse effects, and the endoscopist’s satisfaction; however, the recovery time was shorter in the propofol-ketamine combination than in the dexmedetomidine-ketamine combination.

Trial protocol for a multicenter randomized controlled trial to assess the efficacy and safety of intravenous ketamine for chronic daily headaches: the "KetHead" trial

BACKGROUND

Chronic daily headaches (CDH) are common and associated with significant morbidity, poor quality of life, and substantial burden on the healthcare system. CDH tends to be refractory to conventional medical management and/or patients cannot afford expensive treatments. It is stipulated that CDH share a mechanism of central sensitization in the trigeminocervical complex, mediated by activation of the N-methyl-D-aspartate (NMDA) receptors. Ketamine, a non-competitive NMDA antagonist, has been used in the treatment of chronic pain, but its role in CDH has not been completely established. This trial aims to evaluate the effect of high-dose IV ketamine infusions (compared to placebo) on the number of headache days at 28 days post-infusion.

METHODS

A multicenter, placebo-controlled, randomized controlled trial will be conducted with two parallel groups and blinding of participants and outcome assessors. The study will include 56 adults with a CDH diagnosis as per ICHD-3 criteria. Participants will be randomized (1:1) to either ketamine (1 mg. kg^-1 bolus followed by infusion of 1 mg. kg^-1. h^-1 for 6 h) or placebo (0.9% saline in the same volume and infusion rate as the trial medication) bolus and infusion for 6 h. The impact on the number of monthly headache days, headache intensity, physical activity, mood, sleep, quality of life, analgesic consumption, and adverse effects will be recorded at baseline, immediately post-infusion, and from 1 to 28 days, 29 to 56 days, and 57 to 84 days after the infusion DISCUSSION: Despite advancements in treatment, many patients continue to suffer from CDH. This trial investigates whether high-dose IV ketamine infusions can effectively and safely improve the CDH burden as compared to a placebo infusion. This treatment could become a safe, affordable, and widely available option for patients living with refractory headache.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05306899. Registered on April 1, 2022.

Continuous Ketamine Infusion as a Treatment for Refractory Facial Pain

Complex orofacial pain disorders, such as trigeminal neuralgia (TN) and atypical facial pain (AFP), can be excruciating and debilitating during attacks. Ketamine, an N-methyl-D-aspartate (NMDA) antagonist, is a powerful analgesic that has been used to treat various chronic pain conditions, but its role in treating complex facial pain has only been recently explored. In this retrospective case series, we reviewed the efficacy of continuous ketamine infusion for 12 patients with facial pain refractory to medical treatment. Patients who presented with a diagnosis of TN were more likely to have significant and sustained pain relief after receiving ketamine infusion. By contrast, those who did not respond to the treatment were more likely to have a diagnosis of AFP. The current report suggests a fundamental difference between these two facial pain disorders in their respective underlying pathophysiology and supports the use of continuous ketamine infusion for refractory TN, but not AFP.

Integrating mechanistic-based and classification-based concepts into perioperative pain management: an educational guide for acute pain physicians

Chronic pain begins with acute pain. Physicians tend to classify pain by duration (acute vs chronic) and mechanism (nociceptive, neuropathic and nociplastic). Although this taxonomy may facilitate diagnosis and documentation, such categories are to some degree arbitrary constructs, with significant overlap in terms of mechanisms and treatments. In clinical practice, there are myriad different definitions for chronic pain and a substantial portion of chronic pain involves mixed phenotypes. Classification of pain based on acuity and mechanisms informs management at all levels and constitutes a critical part of guidelines and treatment for chronic pain care. Yet specialty care is often siloed, with advances in understanding lagging years behind in some areas in which these developments should be at the forefront of clinical practice. For example, in perioperative pain management, enhanced recovery protocols are not standardized and tend to drive treatment without consideration of mechanisms, which in many cases may be incongruent with personalized medicine and mechanism-based treatment. In this educational document, we discuss mechanisms and classification of pain as it pertains to commonly performed surgical procedures. Our goal is to provide a clinical reference for the acute pain physician to facilitate pain management decision-making (both diagnosis and therapy) in the perioperative period.

Mechanism-Based Pharmacological Treatment for Chronic Non-cancer Pain in Adolescents: Current Approaches and Future Directions

Chronic non-cancer pain in pediatrics is a widespread phenomenon that affects about 20% of adolescents (10-19 years old). Although interdisciplinary pain treatment programs, which often include pharmacological treatment, have emerged as the standard of care in management of this patient population, evidence regarding an optimal treatment is lacking. The efficacy and safety profiles of pharmacological treatments used to help adolescents suffering from chronic non-cancer pain remain understudied. This lack of evidence may increase polypharmacy and the risk of drug interactions and adverse events. This review examines evidence for the use of pharmacological treatments prescribed to treat chronic pain in adolescents (10-19 years old), with a focus on mechanism-based pharmacology. The objectives of this review are to: (a) review the evidence for mechanism-based pharmacological treatments for chronic non-cancer pain in adolescents and (b) describe the pharmacological agents that are commonly prescribed to manage chronic pain in adolescents, including dosage information, mechanism, and potential adverse effects. Pharmacological treatments should be used carefully with adolescents, ideally within an interdisciplinary treatment program that will incorporate physical rehabilitation, integrative medicine/active mind-body techniques, psychology, and global efforts to normalize daily activities.

Adverse Effects Associated with Patient-Controlled Analgesia with Ketamine Combined with Opioids and Ketamine Infusion with PCA Bolus in Postoperative Spine Patients: A Retrospective Review

Objective

There has been increasing use of ketamine at subanesthetic doses as an adjunct to opioids in perioperative pain management. There are several known adverse drug effects (ADEs) associated with ketamine. However, the incidence of ADEs with ketamine infusions with patient-controlled analgesia (PCA) boluses compared with combined opioid and ketamine PCAs is not well described. The objectives of this study were to compare the incidence and type of ADEs in postoperative spine surgery patients on ketamine infusions with as-needed PCA boluses to patients on combined opioid and ketamine PCAs.

Methods

The medical records of patients who underwent spine surgery between March 2016 and March 2020 who were postoperatively treated with a ketamine infusion and as-needed PCA boluses and parenteral opioids or treated with a combined opioid and ketamine PCA were reviewed. Perioperative information including patient characteristics and preoperative morphine equivalent daily dose (MEDD) were collected. Patient charts were reviewed for ADEs including psychological and neurological side effects, nausea, and new-onset tachycardia.

Results

A total of 315 patients met the inclusion criteria and were included in the final analysis. Of these patients, 121 experienced at least one ADE (38%). Sixteen of the 68 ketamine infusion with PCA bolus patients (24%), 77 of the 203 hydromorphone and ketamine patients (38%), and 28 of the 44 morphine and ketamine patients (64%) experienced an ADE [p<0.01]. In patients with preoperative MEDD ≤ 90, nausea was the only ADE that differed significantly among the three groups.

Conclusion

This retrospective analysis suggests that postoperative spine patients treated with a ketamine infusion with as-needed PCA boluses and parenteral opioids were associated with fewer ADEs when compared to an intravenous combined opioid and ketamine PCA. In patients with preoperative MEDD ≤ 90, nausea with and without emesis was the only ADE that showed statistically significant difference amongst the three groups.

Subanesthetic ketamine: the way forward for pain management in sickle cell disease patients?

INTRODUCTION

Patients with sickle cell disease (SCD) present recurrent episodes of acute pain, the hallmark of the disease, and some will also develop chronic pain. Currently, the treatment of SCD acute pain only targets its symptoms, rather than underlying mechanisms, and is directed by expert and consensus guidelines.

AREAS COVERED

While opioids remain the mainstay of therapy for acute pain and are also used to treat SCD-related chronic pain, in some patients, opioids are ineffective or are associated with severe undesirable side effects. In those instances, clinicians caring for patients with SCD face an unmet need for effective non-opioid analgesics. Recently, the use of subanesthetic ketamine has been explored as a strategy to meet this need. While definitive evidence of its efficacy is lacking, some information exists suggesting that subanesthetic ketamine improves pain control and may have opioid-sparing effects in SCD-related acute pain. However, ketamine can also yield undesirable psychotomimetic and cardiovascular effects.

EXPERT OPINION

After weighing potential risks and benefits, in the absence of better alternatives and in settings where it can be administered safely, ketamine may be a reasonable option for patients with SCD-related acute refractory pain.

Novel Therapies for Centralized Pain: a Brief Review

PURPOSE OF REVIEW

Centralized pain presents a complex pathology that many classic pharmacological agents for pain have not been able to sufficiently treat. To date, there are no clear guidelines for preferred treatment methods or comprehensive protocol that addresses confounding factors in this population. We sought to summarize the current field of knowledge around centrally mediated pain and to understand promising novel therapies.

RECENT FINDINGS

Many treatments currently used address not only the centralized pain phenotypem but the impact of central sensitization and the common comorbidities that reside within this population. Some novel therapies with promising evidence include the following: low-dose naltrexone, IV ketamine, acupuncture, aerobic activity, and laser therapy. Non-interventional treatment options include aerobic exercise, cognitive-behavioral therapy, mind-body therapies, virtual reality, and patient education on disease expectations. Much of the literature further emphasizes the importance of patient-level predictors, including factors like pain catastrophizing and social history, on treatment compliance and reported pain relief. We found that there are many potential treatment options for patients with centralized pain, particularly those that can be used as adjunct or combination therapies. The introduction of new approaches should occur in a carefully controlled, titrated manner to avoid exacerbation of pain symptoms. This is successfully conducted through patient-physician communication as this is a highly complex and personalized pain category. Our examination shows that while physicians have many options with proven success, there is a need for studies with longitudinal and larger patient populations to better articulate treatment guidelines.

Antinociceptive and Analgesic Effects of (2R,6R)-Hydroxynorketamine

Commonly used pain therapeutics, such as opioid medications, exert dangerous side effects and lack effectiveness in treating some types of pain. Ketamine is also used to treat pain, but side effects limit its widespread use. (2R,6R)-hydroxynorketamine (HNK) is a ketamine metabolite that potentially shares some beneficial behavioral effects of its parent drug without causing significant side effects. This study compared the profile and potential mechanisms mediating the antinociception activity of ketamine and (2R,6R)-HNK in C57BL/6J mice. Additionally, this study compared the reversal of mechanical allodynia by (2R,6R)-HNK with gabapentin in a model of neuropathic pain. Unlike the near-immediate and short-lived antinociception caused by ketamine, (2R,6R)-HNK produced late-developing antinociception 24 hours following administration. Pharmacological blockade of α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors with 2,3-dioxo-6-nitro-7-sulfamoyl-benzo[f]quinoxaline (NBQX) prevented the initiation and expressionof (2R,6R)-HNK antinociception, suggesting the involvement of α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor-dependent glutamatergic mechanisms in the pain reduction-like responses. Blockade of opioid receptors with naltrexone partially prevented the antinociceptive effect of ketamine but was ineffective against (2R,6R)-HNK. Furthermore, (2R,6R)-HNK did not produce dystaxia, even when tested at doses five times greater than those needed to produce antinociception, indicating a superior safety profile for (2R,6R)-HNK over ketamine. Additionally, (2R,6R)-HNK reversed mechanical allodynia in a spared nerve injury model of neuropathic pain with similar short-term efficacy to gabapentin (within 4 hours) while outperforming gabapentin 24 hours after administration. These findings support the further study of (2R,6R)-HNK as a potentially valuable agent for treating different types of pain and establish certain advantages of (2R,6R)-HNK treatment over ketamine and gabapentin in corresponding assays for pain. SIGNIFICANCE STATEMENT: The ketamine metabolite (2R,6R)-HNK produced antinociception in male and female mice 24 hours after administration via activation of AMPA receptors. The effects of (2R,6R)-HNK differed in time course and mechanism and presented a better safety profile than ketamine. (2R,6R)-HNK also reversed allodynia in SNI-operated animals within 4 hours of treatment onset, with a duration of effect lasting longer than gabapentin. Taken together, (2R,6R)-HNK demonstrates the potential for development as a non-opioid analgesic drug.

Targeting Affective Mood Disorders With Ketamine to Prevent Chronic Postsurgical Pain

The phencyclidine-derivative ketamine [2-(2-chlorophenyl)-2-(methylamino)cyclohexan-1-one] was added to the World Health Organization's Model List of Essential Medicines in 1985 and is also on the Model List of Essential Medicines for Children due to its efficacy and safety as an intravenous anesthetic. In sub-anesthetic doses, ketamine is an effective analgesic for the treatment of acute pain (such as may occur in the perioperative setting). Additionally, ketamine may have efficacy in relieving some forms of chronic pain. In 2019, Janssen Pharmaceuticals received regulatory-approval in both the United States and Europe for use of the S-enantiomer of ketamine in adults living with treatment-resistant major depressive disorder. Pre-existing anxiety/depression and the severity of postoperative pain are risk factors for development of chronic postsurgical pain. An important question is whether short-term administration of ketamine can prevent the conversion of acute postsurgical pain to chronic postsurgical pain. Here, we have reviewed ketamine's effects on the biopsychological processes underlying pain perception and affective mood disorders, focusing on non-NMDA receptor-mediated effects, with an emphasis on results from human trials where available.

Management of Postoperative Pain in Patients Following Spine Surgery: A Narrative Review

Perioperative pain management is a unique challenge in patients undergoing spine surgery due to the increased incidence of both pre-existing chronic pain conditions and chronic postsurgical pain. Peri-operative planning and counseling in spine surgery should involve an interdisciplinary approach that includes consideration of patient-level risk factors, as well as pharmacologic and non-pharmacologic pain management techniques. Consideration of psychological factors and patient focused education as an adjunct to these measures is paramount in developing a personalized perioperative pain management plan. Understanding the currently available body of knowledge surrounding perioperative opioid management, management of opioid use disorder, regional/neuraxial anesthetic techniques, ketamine/lidocaine infusions, non-opioid oral analgesics, and behavioral interventions can be useful in developing a comprehensive, multi-modal treatment plan among patients undergoing spine surgery. Although many of these techniques have proved efficacious in the immediate postoperative period, long-term follow-up is needed to define the impact of such approaches on persistent pain and opioid use. Future techniques involving the use of precision medicine may help identify phenotypic and physiologic characteristics that can identify patients that are most at risk of developing persistent postoperative pain after spine surgery.

Ketamine use in critically ill patients: a narrative review

Ketamine is unique among anesthetics and analgesics. The drug is a rapid-acting general anesthetic that produces an anesthetic state characterized by profound analgesia, preserved pharyngeal-laryngeal reflexes, normal or slightly enhanced skeletal muscle tone, cardiovascular and respiratory stimulation, and occasionally a transient and minimal respiratory depression. Research has demonstrated the efficacy of its use on anesthesia, pain, palliative care, and intensive care. Recently, it has been used for postoperative and chronic pain, as an adjunct in psychotherapy, as a treatment for depression and posttraumatic stress disorder, as a procedural sedative, and as a treatment for respiratory and/or neurologic clinical conditions. Despite being a safe and widely used drug, many physicians, such as intensivists and those practicing in emergency care, are not aware of the current clinical applications of ketamine. The objective of this narrative literature review is to present the theoretical and practical aspects of clinical applications of ketamine in intensive care unit and emergency department settings.

Acquired Methemoglobinemia in a Ketamine-induced Ulcerative Cystitis Patient: A Case Report

Introduction

As ketamine gains traction as an alternative to opiates in the treatment of chronic pain, ketamine-induced ulcerative cystitis is now being recognized as a complication of its use. The first-line treatment is phenazopyridine, an over-the-counter medication for dysuria that historically has been known to cause methemoglobinemia. This report details the case of a patient presenting to the emergency department (ED) with methemoglobinemia.

Case Report

A 66-year-old woman with a complicated medical history presented to the ED with anemia and hypoxia after extended use of phenazopyridine for treatment of ketamine-induced ulcerative cystitis. She was found to have methemoglobinemia secondary to phenazopyridine used to treat her ketamine-induced ulcerative cystitis, a previously undocumented sequelae of chronic ketamine use. She was admitted to the hospital for three days and made a full recovery.

Conclusion

This case highlights the need to suspect ketamine-induced ulcerative cystitis in patients who use ketamine chronically and be judicious in the use of phenazopyridine for symptom management to prevent life-threatening complications.

From a Symptom-Based to a Mechanism-Based Pharmacotherapeutic Treatment in Complex Regional Pain Syndrome

Complex regional pain syndrome (CRPS) is a debilitating painful condition of a distal extremity that can develop after tissue damage. CRPS is thought to be a multimechanism syndrome and ideally the most prominent mechanism(s) should be targeted by drugs in an individually tailored manner. This review gives an overview of the action and evidence of current and future pharmacotherapeutic options for CRPS. The available options are grouped in four categories by their therapeutic actions on the CRPS mechanisms, i.e. inflammation, central sensitisation, vasomotor disturbances and motor disturbances. More knowledge about the underlying mechanisms of CRPS helps to specifically target important CRPS mechanisms. In the future, objective biomarkers could potentially aid in selecting appropriate mechanism-based drugs in order to increase the effectiveness of CRPS treatment. Using this approach, current and future pharmacotherapeutic options for CRPS should be studied in multicentre trials to prove their efficacy. The ultimate goal is to shift the symptom-based selection of therapy into a mechanism-based selection of therapy in CRPS.

Three Birds, One Excipient: Development of an Improved pH, Isotonic, and Buffered Ketamine Formulation for Subcutaneous Injection

Subcutaneous (SC) ketamine has been found to be effective in pain management, though reports of injection site irritation and sterile abscesses exist with currently available ketamine HCl formulations. Such adverse SC reactions are commonly associated with low pH, high osmolality and/or high injection volumes. An optimal SC formulation of ketamine would thus have a pH and osmolality close to physiological levels, without compromising on concentration and, thus, injection volume. Such a formulation should also be buffered to maintain the pH at the acceptable level for extended time periods. As many of these physicochemical properties are interrelated, achieving these aims represented a significant challenge in formulation development. We describe the development of a novel Captisol^®-based formulation strategy to achieve an elevated pH, isosmotic and buffered formulation of ketamine (hence, three birds, one excipient) without compromising on concentration. This strategy has the potential to be readily adapted to other amine-based APIs.

Opioid-free anesthesia in oncologic surgery: the rules of the game

BACKGROUND

Opioids are frequently used in the postoperative period due to their analgesic properties. While these drugs reduce nociceptive somatic, visceral, and neuropathic pain, they may also lead to undesirable effects such as respiratory depression, urinary retention, nausea and vomiting, constipation, itching, opioid-induced hyperalgesia, tolerance, addiction, and immune system disorders. Anesthesiologists are in the critical position of finding balance between using opioids when they are necessary and implementing opioid-sparing strategies to avoid the known harmful effects. This article aims to give an overview of opioid-free anesthesia.

MAIN BODY

This paper presents an overview of opioid-free anesthesia and opioid-sparing anesthetic techniques. Pharmacological and non-pharmacological strategies are discussed, highlighting the possible advantages and drawbacks of each approach.

CONCLUSIONS

Choosing the best anesthetic protocol for a patient undergoing cancer surgery is not an easy task and the available literature provides no definitive answers. In our opinion, opioid-sparing strategies should always be implemented in routine practice and opioid-free anesthesia should be considered whenever possible. Non-pharmacological strategies such as patient education, while generally underrepresented in scientific literature, may warrant consideration in clinical practice.

Evaluation of anesthesia quality with three methods: "propofol + fentanyl" vs. "propofol + fentanyl + lidocaine" vs. "propofol + fentanyl + lidocaine + ketamine" in patients referred to the scoping ward

Introduction:

Toleration of the complexity and pain of interventions such as endoscopy and colonoscopy is highly difficult for patients. Considering the disagreement on the method of injection of propofol, this study was performed to evaluate the quality of anesthesia using the three methods of propofol + fentanyl, propofol + fentanyl + lidocaine, and propofol + fentanyl + lidocaine + ketamine.

Methods:

This one-way blind clinical trial study included 99 patients who were admitted in three groups by block randomization method. In a group of patients that were sedated with propofol + fentanyl + lidocaine + ketamine, the dose of all drugs is reduced by half the amount of the other groups. Variables included age, sex, frequency of cough, apnea, need for jaw thrust maneuver, O₂ saturation, duration of recovery, and procedural satisfaction. Data were analyzed using SPSS version 20.0. P value of < 0.05 was considered to be significant.

Results:

The three groups were similar in terms of demographic characteristics. The effects of the three sedation protocols on the variables showed that patient’s apnea, cough, O₂ saturation, and also proceduralist satisfaction in the group of the patient that sedated with four drugs was significantly higher (P < 0.05) than other groups. But there was no significant difference between the three groups when comparing the recovery time and need for jaw thrust during the procedure.

Conclusion:

The findings of the present study showed that the use of combination of “propofol + fentanyl + lidocaine + ketamine” with lower doses, significantly results in higher quality sedation compared with higher doses of “propofol + fentanyl + lidocaine” or “propofol + fentanyl” for scoping procedures.

Ketamine therapy for chronic pain in The Netherlands: a nationwide survey

OBJECTIVES

Ketamine is used to treat chronic refractory pain. However, there are no scientific guidelines for ketamine use in the Netherlands. The aim of this survey was to provide an overview of the use of ketamine for chronic pain in the Netherlands.

METHODS

All pain clinics in the Netherlands were contacted. A digital survey, available from June 2019 to January 2020, was sent to 68 pain clinics. The survey was completed by one pain physician as a representative of the entire pain department. The survey included questions about ketamine treatment indications, administration, dose, duration, treatment repetition and the inpatient or outpatient setting.

RESULTS

The survey was completed by 51 pain clinics (75.0%). Thirty-one clinics used ketamine for chronic pain treatment. The most common indication was Complex Regional Pain Syndrome (83.9%). Pain clinics administered ketamine via intravenous infusions (96.8%), iontophoresis (61.3%), subcutaneous (3.2%) or oral administration (3.2%). Intravenous ketamine treatment was offered in an inpatient setting in 14 pain clinics, in both an inpatient and outpatient setting in 11 pain clinics and in six pain clinics in an outpatient setting. In the outpatient setting, the median starting dose was 5 mg/h (IQR=17.5-5). The median maximum dose was 27.5 mg/h (IQR=100-11.9). The median infusion duration was 6 h (IQR=8-4). In the inpatient setting, the median starting dose was 5 mg/h (IQR=5-1.5) and the median maximum dose was 25 mg/h (IQR=25-14). Patients were admitted to hospital for a median of 4 days (IQR=5-1).

CONCLUSIONS

The results of this Dutch nationwide survey study show that there are heterogeneous treatment protocols with different indications, treatment setting and dosing regimen for the treatment of chronic pain with ketamine. This study encourages the formulation of a broader consensus and the development of evidence based guidelines for ketamine treatment.

Systematic Review of the Use of Intravenous Ketamine for Fibromyalgia

Background: Fibromyalgia, a complex disorder that affects 1% to 5% of the population, presents as widespread chronic musculoskeletal pain without physical or laboratory signs of any specific pathologic process. The mechanism, while still being explored, suggests central sensitization and disordered pain regulation at the spinal cord and supraspinal levels, with a resulting imbalance between excitation and inhibition that may alter central nervous system nociceptive processing. Nociceptive hypersensitivity results from activity of the N-methyl-D-aspartate receptor (NMDAR)-mediated glutamatergic synaptic transmission in the spinal cord and brain. Because ketamine, an NMDAR antagonist, may reduce induction of synaptic plasticity and maintenance of chronic pain states, the study of its use in intravenous form to treat fibromyalgia has increased. Methods: We conducted a literature search with the objectives of examining the effect of intravenous ketamine administration on pain relief, identifying side effects, and highlighting the need for clinical studies to evaluate ketamine infusion treatment protocols for patients with fibromyalgia. We used the keywords "fibromyalgia," "chronic pain," "ketamine," "intravenous," and "infusion" and found 7 publications that included 118 patients with fibromyalgia who met inclusion criteria. Results: Clinical studies revealed a short-term reduction-only for a few hours after the infusions-in self-reported pain intensity with single, low-dose, intravenous ketamine infusions, likely attributable to nociception-dependent central sensitization in fibromyalgia via NMDAR blockade. Case studies suggest that increases in the total dose of ketamine and longer, more frequent infusions may be associated with more effective pain relief and longer-lasting analgesia. Another neurotransmitter release may be contributing to this outcome. Conclusion: This systematic review suggests a dose response, indicating potential efficacy of intravenous ketamine in the treatment of fibromyalgia.

Non-parenteral Ketamine for Depression: A Practical Discussion on Addiction Potential and Recommendations for Judicious Prescribing

Intravenous (IV) ketamine is increasingly used off-label at subanesthetic doses for its rapid antidepressant effect, and intranasal (IN) esketamine has been recently approved in several countries for treating depression. The clinical utility of these treatments is limited by a paucity of publicly funded IV ketamine and IN esketamine programs and cost barriers to private treatment programs, as well as the drug cost for IN esketamine itself, which makes generic ketamine alternatives an attractive option. Though evidence is limited, use of non-parenteral racemic ketamine formulations (oral, sublingual, and IN) may offer more realistic access in less rigidly supervised settings, both for acute and maintenance treatment in select cases. However, the psychiatric literature has repeatedly cautioned on the addictive potential of ketamine and raised caution for both less supervised and longer-term use of ketamine. To date, these concerns have not been discussed in view of available evidence, nor have they been discussed within a broader clinical context. This paper examines the available relevant literature and suggests that ketamine misuse risks appear not dissimilar to those of other well-established and commonly prescribed agents with abuse potential, such as stimulants or benzodiazepines. As such, ketamine prescribing should be considered in a similar risk/benefit context to balance patient access and need for treatment with concern for potential substance misuse. Our consortium of mood disorder specialists with significant ketamine prescribing experience considers prescribing of non-parenteral ketamine a reasonable clinical treatment option in select cases of treatment-resistant depression. This paper outlines where this may be appropriate and makes practical recommendations for clinicians in judicious prescribing of non-parenteral ketamine.

Beyond the Raskin Protocol: Ketamine, Lidocaine, and Other Therapies for Refractory Chronic Migraine

PURPOSE OF REVIEW

The purpose of this review is to discuss the available evidence and therapeutic considerations for intravenous drug therapy for refractory chronic migraine.

RECENT FINDINGS

In carefully monitored settings, the inpatient administration of intravenous lidocaine and ketamine can be successful in treating refractory chronic migraine. Many patients with refractory chronic migraine have experienced treatment failure with the Raskin protocol. The use of aggressive inpatient infusion therapy consisting of intravenous lidocaine or ketamine, along with other adjunctive medications, has become increasingly common for these patients when all other treatments have failed. There is a clear need for prospective studies in this population comprised of patients who have largely been excluded from other studies.

The place of S-ketamine in fibromyalgia treatment (ESKEFIB): study protocol for a prospective, single-center, double-blind, randomized, parallel-group, dose-escalation controlled trial

Background

Fibromyalgia is a chronic multidimensional pain disease with no curative treatment currently available. Its management relies on a multimodal approach involving pharmacologic and non-pharmacologic elements. Because a suggested factor in its etiology is a central sensitization phenomenon involving the N-methyl-D-aspartate receptor (NMDAR), NMDAR antagonists have been proposed as a treatment target. Ketamine and its levogyre form, S-ketamine, have been used to treat chronic pain for many years without consensus about their therapeutic efficiency. We aim to assess the efficacy of S-ketamine as a co-treatment for fibromyalgia.

Methods

This prospective, randomized, single-center, double-blind, parallel-group, dose-escalation trial will compare a co-treatment with S-ketamine (intervention) to a control treatment without S-ketamine (control). It will consist of two successive cohorts with 2:1 randomization ratio (S-ketamine at two different doses: control) with 105 participants in each cohort. The protocol follow-up time will be 12 weeks, including 3 visits for the treatment (week 0, week 2, and week 4) and 3 visits for follow-up (week 6, week 9, and week 12). Our primary outcome, pain relief and/or better patient function, will be assessed with the Brief Pain Inventory questionnaire. The statistical analysis will be performed on an intention-to-treat basis. If the primary outcome is reached at the end of follow-up in the first cohort with low-dose S-ketamine (0.2 mg/kg), the trial will end. If not, the trial will continue with the second cohort and high-dose S-ketamine (0.4 mg/kg).

Discussion

The challenge of our trial is the inclusion of a large number of participants in comparison to other trials involving ketamine or S-ketamine infusions for chronic pain management. The originality of our protocol is to include functionality in addition to pain relief as a primary outcome because these two endpoints are not linked in a linear way. For some patients, functional status is more important than pain relief.

Trial registration

EudraCT reference: 2020-000473-25, ClinicalTrials.gov: NCT04436250, first posted June 18, 2020; last updated July 21, 2020. Protocol version 2.2 issued on September 30, 2020, after a revision by the ethics committee. https://clinicaltrials.gov/ct2/show/NCT04436250

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-021-05814-4.

Use of Ketamine Infusions for Treatment of Complex Regional Pain Syndrome: A Systematic Review

This systematic review aims to review clinical studies on the use of ketamine infusion for patients with treatment-resistant complex regional pain syndrome (CRPS).

The following systematic review was registered on the International Prospective Register of Systematic Reviews (PROSPERO) (CRD42021228470). Studies for the systematic review were identified through three databases: PubMed, Cumulative Index of Nursing and Allied Health Literature (CINAHL), and Cochrane Reviews. Inclusion criteria for studies consisted of randomized clinical trials or cohort studies that conducted trials on the use of ketamine infusion for pain relief in patients with CRPS. Exclusion criteria for studies included any studies that were systematic reviews, meta-analyses, case reports, literature reviews, or animal studies. In the included studies, the primary outcome of interest was the post-drug administration pain score.

In this systematic review, 14 studies met the inclusion criteria and were reviewed. In these studies, the dosage of ketamine infusion used ranged from 0.15 mg/kg to 7 mg/kg with the primary indication being the treatment of CRPS. In 13 of the studies, ketamine infusion resulted in a decrease in pain scores and relief of symptoms.

Patients who received ketamine infusion for treatment-resistant CRPS self-reported adequate pain relief with treatment. This suggests that ketamine infusion may be a useful form of treatment for patients with no significant pain relief with other conservative measures. Future large-scale studies, including randomized double-blind placebo-controlled trials on the use of ketamine infusion for CRPS, must be conducted in a large-scale population to further assess the effectiveness of ketamine infusion in these populations.