Interventional approaches to pain management

Agents Used for Nerve Blocks and Neurolysis

The recognition of pain and the treatments used for it are vital for all practitioners. Many types of pain can be treated in a locoregional fashion, which has significant implications not just for any individual patient but for society as a whole. These treatments are most effective when performed in a minimally invasive, image-guided fashion. Interventional radiologists should play a central role in providing these lifestyle-limiting treatments. This article describes the medications most typically used for spinal and extra-axial treatments in the management of patients in pain.

Comparative evaluation of different volumes of 70% alcohol in celiac plexus block for upper abdominal malignsancies

Context:

Celiac plexus block (CPB) (is an effective way to reduce cancer-associated pain in upper abdominal malignancies.

Aims:

To evaluate the efficacy and safety of different volumes of 70% alcohol in CPB.

Settings and Design:

Prospective, randomized, controlled clinical study.

Subjects and Methods:

Thirty patients of carcinoma gall bladder were randomly divided into three groups (n = 10) to receive 20, 30, and 40 ml of 70% alcohol in CPB.

Statistical Analysis Used:

All the continuous data were assessed analysis of variance followed by post-hoc tests (Tukey's Honestly Significant Difference test). Ordinal data were compared using Kruskal–Wallis H-test followed by Mann–Whitney U-test. Categorical comparisons were performed using Chi-square test.

Results:

A significant difference in visual analog scale (VAS) score of Group I, Group I and Group III was observed from week 6 onward until the end of the study. At all these time intervals, VAS scores in Group I was higher than both Groups II and III during this time interval. VAS scores in Group III were significantly lower as compared to Group II from week 10 onward until the end of the study. As compared to baseline, at all the follow-up intervals, mean morphine requirement was significantly lower in Group II and Group III. A quality of life (QOL) score of Group III were higher as compared to Group I. Between Group II and Group III, significant difference was observed at week 16 only when Group III had a higher score as compared to Group II.

Conclusions:

VAS score, QOL, and reduction in morphine consumption were increased on increasing the volume of alcohol in CPB, 40 ml being most effective.

Use of Microfluidics to Fabricate Bioerodable Lipid Hybrid Nanoparticles Containing Hydromorphone or Ketamine for the Relief of Intractable Pain

PURPOSE

For patients with intractable cancer-related pain, administration of strong opioid analgesics and adjuvant agents by the intrathecal (i.t.) route in close proximity to the target receptors/ion channels, may restore pain relief. Hence, the aim of this study was to use bioerodable polymers to encapsulate an opioid analgesic (hydromorphone) and an adjuvant drug (ketamine) to produce prolonged-release formulations for i.t. injection.

METHODS

A two-stage microfluidic method was used to fabricate nanoparticles (NPs). The physical properties were characterised using dynamic light scattering and transmission electron microscopy. A pilot in vivo study was conducted in a rat model of peripheral neuropathic pain.

RESULTS

The in vitro release of encapsulated payload from NPs produced with a polymer mixture (CPP-SA/PLGA 50:50) was sustained for 28 days. In a pilot in vivo study, analgesia was maintained over a three day period following i.t. injection of hydromorphone-loaded NPs at 50 μg. Co-administration of ketamine-loaded NPs at 340 μg did not increase the duration of analgesia significantly.

CONCLUSIONS

The two-stage microfluidic method allowed efficient production of analgesic/adjuvant drug-loaded NPs. Our proof-of-principle in vivo study shows prolonged hydromorphone analgesic for 78 h after single i.t. injection. At the i.t. dose administered, ketamine released from NPs was insufficient to augment hydromorphone analgesia.

<p>A Case Report of an Ultrasound-Guided and Fluoroscopy-Assisted Posterior Approach for Celiac Plexus Neurolysis in a Patient with Pancreatic Cancer-Associated Abdominal Pain</p>

Background

Imaging-guided celiac plexus neurolysis using ultrasound (US) guidance via a transabdominal approach and endoscopic-ultrasound (EUS) has been increasingly applied for the treatment of pancreatic cancer-associated abdominal pain.

Objective

To investigate the application of ultrasound-guided and fluoroscopy-assisted celiac plexus neurolysis in a patient with advanced pancreatic cancer suffering from refractory abdominal pain for which oral opioid treatment was ineffective.

Case Report

We report a case of ultrasound-guided and fluoroscopy-assisted celiac plexus neurolysis in a patient with advanced pancreatic cancer with refractory abdominal pain. With the patient in the prone position, celiac plexus neurolysis was performed under real-time US guidance. The transducer was placed below the costal margin and a puncture needle with an ultrasound enhancement tip was inserted in-plane aiming for the lateral anterior end of the vertebral body. The correct needle tip position was confirmed by the C-arm with contrast material located anterior to the vertebral body and posterior to the diaphragm.

Conclusion

We highlight the use of an US-guided and fluoroscopy-assisted posterior approach for use in celiac plexus neurolysis procedures, particularly in patients suffering from contraindications from the US or EUS-guided anterior approaches.

Formulation of Bioerodible Ketamine Microparticles as an Analgesic Adjuvant Treatment Produced by Supercritical Fluid Polymer Encapsulation

Pain is inadequately relieved by escalating doses of a strong opioid analgesic such as morphine in up to 25% of patients with cancer-related severe pain complicated by a neuropathic (nerve damage) component. Hence, there is an unmet medical need for research on novel painkiller strategies. In the present work, we used supercritical fluid polymer encapsulation to develop sustained-release poly(lactic-co-glycolic acid) (PLGA) biodegradable microparticles containing the analgesic adjuvant drug ketamine, for injection by the intrathecal route. Using this approach with a range of PLGA co-polymers, drug loading was in the range 10⁻60%, with encapsulation efficiency (EE) of 60⁻100%. Particles were mainly in the size range 20⁻45 µm and were produced in the absence of organic solvents and surfactants/emulsifiers. Investigation of the ketamine release profiles from these PLGA-based microparticles in vitro showed that release took place over varying periods in the range 0.5⁻4.0 weeks. Of the polymers assessed, the ester end-capped PLGA5050DLG-1.5E gave the best-controlled release profile with drug loading at 10%.

Future Directions in Pain Management: Integrating Anatomically Selective Delivery Techniques With Novel Molecularly Selective Agents

Treatment for chronic, locoregional pain ranks among the most prevalent unmet medical needs. The failure of systemic analgesic drugs, such as opioids, is often due to their off-target toxicity, development of tolerance, and abuse potential. Interventional pain procedures provide target specificity but lack pharmacologically selective agents with long-term efficacy. Gene therapy vectors are a new tool for the development of molecularly selective pain therapies, which have already been proved to provide durable analgesia in preclinical models. Taken together, advances in image-guided delivery and gene therapy may lead to a new class of dual selective analgesic treatments integrating the molecular selectivity of analgesic genes with the anatomic selectivity of interventional delivery techniques.

Pain in cancer survivors

Pain is a common problem in cancer survivors, especially in the first few years after treatment. In the longer term, approximately 5% to 10% of survivors have chronic severe pain that interferes with functioning. The prevalence is much higher in certain subpopulations, such as breast cancer survivors. All cancer treatment modalities have the potential to cause pain. Currently, the approach to managing pain in cancer survivors is similar to that for chronic cancer-related pain, pharmacotherapy being the principal treatment modality. Although it may be appropriate to continue strong opioids in survivors with moderate to severe pain, most pain problems in cancer survivors will not require them. Moreover, because more than 40% of cancer survivors now live longer than 10 years, there is growing concern about the long-term adverse effects of opioids and the risks of misuse, abuse, and overdose in the nonpatient population. As with chronic nonmalignant pain, multimodal interventions that incorporate nonpharmacologic therapies should be part of the treatment strategy for pain in cancer survivors, prescribed with the aim of restoring functionality, not just providing comfort. For patients with complex pain issues, multidisciplinary programs should be used, if available. New or worsening pain in a cancer survivor must be evaluated to determine whether the cause is recurrent disease or a second malignancy. This article focuses on patients with a history of cancer who are beyond the acute diagnosis and treatment phase and on common treatment-related pain etiologies. The benefits and harms of the various pharmacologic and nonpharmacologic options for pain management in this setting are reviewed.

CT-guided celiac plexus neurolysis: a review of anatomy, indications, technique, and tips for successful treatment

The celiac plexus is the largest visceral plexus and is located deep in the retroperitoneum, over the anterolateral surface of the aorta and around the origin of the celiac trunk. It serves as a relay center for nociceptive impulses that originate from the upper abdominal viscera, from the stomach to the proximal transverse colon. Celiac plexus neurolysis, with agents such as ethanol, is an effective means of diminishing pain that arises from these structures. Percutaneous imaging-guided celiac plexus neurolysis has been established as an invaluable therapeutic option in the management of intractable abdominal pain in patients with upper abdominal malignancy. The use of multidetector computed tomography (CT) for imaging guidance has superseded other modalities and allows direct visualization of the spread of the neurolytic agent in the antecrural space. Accurate depiction of the retroperitoneal anatomy and the position of the needle tip helps avoid crucial anatomic structures such as the pancreas, aorta, celiac artery, and superior mesenteric artery. Proper patient education, meticulous preprocedure planning, use of optimal multidetector CT techniques, adjunctive CT maneuvers, and postprocedure care are integral to successful celiac plexus neurolysis. Celiac plexus neurolysis does not completely abolish pain; rather, it diminishes pain, helping to reduce opioid requirements and their related side effects and improving survival in patients with upper abdominal malignancy.

[Selected interventional methods for the treatment of chronic pain: Part 1: peripheral nerve block and sympathetic block]

Approximately 5-8 million people in Germany suffer from chronic pain. Some patients can obtain relief from specific interventional techniques. In detail these are blocks of the sympathetic chain and peripheral nerve blocks, regional anesthetic techniques close to the spinal cord and neuromodulation. Part 1 of this article presents peripheral nerve blocks using the example of intercostal blocks and blocks of the sympathetic chain. Peripheral nerve blocks are important for postoperative pain treatment. Only a few methods are used for chronic pain and this applies primarily to the intercostal block which is used for the treatment of pain occurring after thoracotomy, intercostal neuralgia and pain associated with infiltration of cancer. Blocks of the vegetative nervous system are accomplished on the ganglions of the head and the sympathetic chain and are therefore most commonly applied to treat headache, neuropathic and sympathetic pain in the area of abdomen and the extremities.

Maldynia: pathophysiology and management of neuropathic and maladaptive pain--a report of the AMA Council on Science and Public Health

BACKGROUND

Because of disparate taxonomic arrays for classification, the American Academy of Pain Medicine has proposed categorizing pain on a neurobiologic basis as eudynia (nociceptive pain), Greek for "good pain," or maldynia (maladaptive pain), Greek for "bad pain." The latter has been viewed as maladaptive because it may occur in the absence of ongoing noxious stimuli and does not promote healing and repair.

OBJECTIVE

To address recent findings on the pathogenesis of pain following neural injury and consider whether the development of maladaptive pain justifies its classification as a disease and to briefly discuss the scope of pharmacologic and non-pharmacologic approaches employed in patients with such pain.

METHODS

English language reports on studies using human subjects were selected from a PubMed search of the literature from 1995 to August 2010 and from the Cochrane Library. Further information was obtained from Internet sites of medical specialty and other societies devoted to pain management.

RESULTS

Neural damage to either the peripheral or central nervous system provokes multiple processes including peripheral and central sensitization, ectopic activity, neuronal cell death, disinhibition, altered gene expression, and abnormal sprouting and cellular connectivity. A series of neuro-immune interactions underlie many of these mechanisms. Imaging studies have shown that such damage is characterized by functional, structural, and chemical changes in the brain. Such pain is maladaptive in the sense that it occurs in the absence of ongoing noxious stimuli and does not promote healing and repair.

CONCLUSION

As defined, maldynia is a multidimensional process that may warrant consideration as a chronic disease not only affecting sensory and emotional processing but also producing an altered brain state based on both functional imaging and macroscopic measurements. However, the absolute clinical value of this definition is not established.

Interventional Management of Chronic Pain

Chronic non-cancer pain is a common clinical condition affecting a significant part of the population. This article aims to review the interventional options for non-cancer pain. Multiple searches using Medline were carried out and additional searches were made using reference lists of published papers and book chapters. The article discussed procedures ranging from selective nerve root or zygapophyseal (facet) joint block with local anaesthetics to irreversible neurodestruction with radiofrequency energy or neurolytic agents and neuromodulation with spinal cord stimulation. Other techniques include intraspinal delivery of analgesics. There is evidence that these interventional procedures are valuable both diagnostically and therapeutically. Key words: Intrathecal drug delivery, Neuropathic, Spine