Raman Microscopy Investigation of GLP-1 Peptide Association with Supported Phospholipid Bilayers.

A wide range of important biological processes occur at phospholipid membranes including cell signaling, where a peptide or small molecule targets a membrane-localized receptor protein. In this work, we report the adaptation of confocal Raman microscopy to quantify populations of unlabeled glucagon-like peptide-1 (GLP-1), a membrane-active 30-residue incretin peptide, in supported phospholipid bilayers deposited on the interior surfaces of wide-pore porous silica particles. Quantification of lipid bilayer-associated peptide is achieved by measuring the Raman scattering intensity of the peptide relative to that of the supported lipid bilayer, which serves as an internal standard. The dependence of the bilayer-associated GLP-1 population on the solution concentration of GLP-1 produces an isotherm used to determine the equilibrium constant for peptide-bilayer association and the maximum peptide surface coverage. The maximum coverage of GLP-1 in the lipid bilayer was found to be only 1/5th of a full monolayer based on its hydrodynamic radius. The saturation coverage, therefore, is not limited by the size of GLP-1 but by the ability of the bilayer to accommodate the peptide at high concentrations within the bilayer. Raman spectra show that GLP-1 association with the supported bilayer is accompanied by structural changes consistent with the intercalation of the peptide into the bilayer, where the observed increase in acyl-chain order would increase the lipid density and provide free volume needed to accommodate the peptide. These results were compared with previous measurements of the association of fluorescently labeled GLP-1 with a planar-supported bilayer; the unlabeled peptide exhibits a 3-fold greater affinity for the lipid bilayer on the porous silica support, suggesting that the fluorescent label alters the GLP-1 lipid bilayer association.

Confocal Raman Microscopy Investigation of Phospholipid Monolayers Deposited on Nitrile-Modified Surfaces in Porous Silica Particles.

Phospholipid bilayers deposited on a variety of surfaces provide models for investigation of the lipid membrane structure and supports for biocompatible sensors. Hybrid-supported phospholipid bilayers (HSLBs) are stable membrane models for these investigations, typically prepared by self-assembly of a lipid monolayer over an n-alkane-modified surface. HSLBs have been prepared on n-alkyl chain-modified silica and used for lipophilicity-based chromatographic separations. The structure of these hybrid bilayers differs from vesicle membranes where the lipid head group spacing is greater due to interdigitation of the lipid acyl chains with the underlying n-alkyl chains bound to the silica surface. This interdigitated structure exhibits a broader melting transition at a higher temperature due to strong interactions between the lipid acyl chains and the immobile n-alkyl chains bound to silica. In the present work, we seek to reduce the interactions between a lipid monolayer and its supporting substrate by self-assembly of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) on porous silica functionalized with nitrile-terminated surface ligands. The frequency of Raman scattering of the surface -C≡N stretching mode at the lipid-nitrile interface is consistent with an n-alkane-like environment and insensitive to lipid head group charge, indicating that the lipid acyl chains are in contact with the surface nitrile groups. The head group area of this lipid monolayer was determined from the within-particle phospholipid concentration and silica specific surface area and found to be 54 ± 2 Å2, equivalent to the head group area of a DMPC vesicle bilayer. The structure of these nitrile-supported phospholipid monolayers was characterized below and above their melting transition by confocal Raman microscopy and found to be nearly identical to DMPC vesicle bilayers. Their narrow gel-to-fluid-phase melting transition is equivalent to dispersed DMPC vesicles, suggesting that the acyl chain structure on the nitrile support mimics the outer leaflet structure of a vesicle membrane.

Confocal Raman Microscopy Investigation of Self-Assembly of Hybrid Phospholipid Bilayers within Individual Porous Silica Chromatographic Particles.

Hybrid-supported phospholipid bilayers are a model structure utilized for measurement of molecular interactions that typically occur at cell membranes. These membrane models are prepared by adsorption of a lipid monolayer onto a stable n-alkyl chain layer that is covalently bound to a support surface. Hybrid bilayers have been adapted to chromatographic retention measurements of lipophilicity through the assembly of a phospholipid monolayer onto n-alkane-modified silica surfaces in reversed-phase chromatographic particles. Recent Raman microscopy studies of these particles have shown that the acyl chains of the phospholipid interact with the C18-alkyl chains immobilized on the silica surface, where both lipid and C18 alkyl chains become ordered because of chain interdigitation. Confocal Raman microscopy has also been used to investigate the association of small molecules with hybrid-lipid bilayers in C18 chromatographic silica particles; the partitioning of model solutes compares favorably to that in lipid vesicle membranes with similar changes in acyl-chain structure (disordering) with solute partitioning. The present study seeks information about how these membrane-mimetic bilayers assemble onto the C18-derivatized silica surfaces of reversed-phase chromatographic silica particles. Confocal Raman microscopy is capable of interrogating the time-dependent internal composition and structure within individual silica particles. The Raman scattering data can be resolved into component Raman spectra and corresponding composition vectors that describe the time-dependent changes in intensity of the component spectra. This analysis provides insight into how the structures of both the lipid and C18 alkyl chains of hybrid lipid bilayers evolve during deposition and organization on the internal surfaces of reversed-phase chromatographic silica particles.

Confocal-Raman Microscopy Characterization of Supported Phospholipid Bilayers Deposited on the Interior Surfaces of Chromatographic Silica.

A common approach to exploring the structure and dynamics of biological membranes is through the deposition of model lipid bilayers on planar supports by Langmuir-trough or vesicle-fusion methods. Planar-supported lipid bilayers have been shown to exhibit structure and properties similar to those of lipid-vesicle membranes and are suitable for biosensing applications. Investigations using these planar-membrane models are limited to high-sensitivity methods capable of detecting a small population of molecules at the interface between a planar support and aqueous solution. In this work, we present evidence that supported-lipid bilayers can be deposited by vesicle fusion onto the interior surfaces throughout the wide-pore network of chromatographic silica particles. The thickness of a 1,2-dimyristoyl- sn-glycero-3-phosphocholine (DMPC) film and headgroup spacing are consistent with a single bilayer of DMPC deposited onto the pore surfaces. The high specific surface area of these materials generates phospholipid concentrations easily detected by confocal-Raman microscopy within an individual particle, which allows the structure of these supported bilayers to be investigated. Raman spectra of porous-silica-supported DMPC bilayers are equivalent to spectra of DMPC vesicle membranes, both above and below their melting phase transitions, suggesting comparable phospholipid organization and bilayer structure. These porous-silica-supported model membranes could share benefits that planar-supported lipid bilayers bring to biosensing applications, but in a material that overcomes the limited surface area of a planar support. To test this concept, the potential of these porous-silica-supported lipid bilayers as high-surface-area platforms for label-free Raman-scattering-based protein biosensing is demonstrated with detection of concanavalin A selectively binding to a lipid-immobilized mannose target.

Confocal Raman Microscopy for Label-Free Detection of Protein-Ligand Binding at Nanopore-Supported Phospholipid Bilayers.

Interactions of lectins, proteins that selectively bind carbohydrates, play an important role in many biological processes including cell adhesion, immune response, and cell signaling. Given the range of lectin functions and their potential for application in disease detection, there is a need for methods to investigate lectin-carbohydrate interactions that are rapid, structurally specific, and sensitive to binding from low-concentration samples. In this work, we describe the preparation and application of supported phospholipid bilayers deposited in wide-pore chromatographic silica particles for confocal Raman-microscopy-based detection of specific binding of concanavalin-A to mannose-functionalized phospholipids. The high surface area of porous-silica supports provides an ample concentration of phospholipid and protein for rapid, label-free detection of lectin binding to be carried out in an individual lipid-bilayer-functionalized particle. The Raman spectrum provides structural information on the bound protein as well as the phospholipid bilayer. Using scattering from the supported-lipid bilayer as an internal standard, Raman scattering from accumulated protein can be interpreted quantitatively to determine its absolute surface coverage on the lipid bilayer. At low glycolipid fraction (<1 mol %) in the prepared bilayer, the surface coverage by protein increases linearly with mannose-lipid densities, where the lectin population corresponds to ∼96% occupancy of the mannose ligands. At increasing glycolipid site densities in excess of 1 mol %, the surface-associated protein population saturates at a coverage that is equivalent to a full monolayer of mannose-bound lectin proteins. The results suggest that Raman microscopy of supported phospholipid bilayers in high-surface-area support particles is a promising approach for in situ, label-free, and quantitative investigation of bilayer-localized protein-ligand interactions.

Confocal Raman Microscopy for in Situ Measurement of Phospholipid-Water Partitioning into Model Phospholipid Bilayers within Individual Chromatographic Particles.

The phospholipid-water partition coefficient is a commonly measured parameter that correlates with drug efficacy, small-molecule toxicity, and accumulation of molecules in biological systems in the environment. Despite the utility of this parameter, methods for measuring phospholipid-water partition coefficients are limited. This is due to the difficulty of making quantitative measurements in vesicle membranes or supported phospholipid bilayers, both of which are small-volume phases that challenge the sensitivity of many analytical techniques. In this work, we employ in situ confocal Raman microscopy to probe the partitioning of a model membrane-active compound, 2-(4-isobutylphenyl) propionic acid or ibuprofen, into both hybrid- and supported-phospholipid bilayers deposited on the pore walls of individual chromatographic particles. The large surface-area-to-volume ratio of chromatographic silica allows interrogation of a significant lipid bilayer area within a very small volume. The local phospholipid concentration within a confocal probe volume inside the particle can be as high as 0.5 M, which overcomes the sensitivity limitations of making measurements in the limited membrane areas of single vesicles or planar supported bilayers. Quantitative determination of ibuprofen partitioning is achieved by using the phospholipid acyl-chains of the within-particle bilayer as an internal standard. This approach is tested for measurements of pH-dependent partitioning of ibuprofen into both hybrid-lipid and supported-lipid bilayers within silica particles, and the results are compared with octanol-water partitioning and with partitioning into individual optically trapped phospholipid vesicle membranes. Additionally, the impact of ibuprofen partitioning on bilayer structure is evaluated for both within-particle model membranes and compared with the structural impacts of partitioning into vesicle lipid bilayers.

Raman Spectroscopy Reveals Selective Interactions of Cytochrome c with Cardiolipin That Correlate with Membrane Permeability.

Permeabilization of the outer mitochondrial membrane is an integral step in apoptosis. The resulting release of pro-apoptotic signaling proteins leads to cell destruction through activation of the cysteine-aspartic protease (caspase) cascade. However, the mechanism of outer mitochondrial membrane (OMM) permeabilization remains unclear. It was recently shown that cytochrome c can induce pore formation in cardiolipin-containing phospholipid membranes, leading to large dextran and protein permeability. In this work, the interaction of cytochrome c with cardiolipin-containing phospholipid vesicles, serving as models of the OMM, is investigated to probe cytochrome c-induced permeability. Lipid vesicles having either a 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) or mixed-DPPC/cardiolipin membrane and containing a membrane-impermeable Raman tracer 3-nitrobenzenesulfonate (3-NBS) were optically trapped, translated into a solution containing cytochrome c, and monitored for 3-NBS leakage. Cytochrome-correlated leakage was observed only in cardiolipin-containing vesicles. Structural changes observed in the Raman spectra during permeabilization indicated acyl chain disordering along with decreased intensity of the cardiolipin cis-double-bond stretching modes. When the vesicle-associated cytochrome c Raman spectrum is compared with a spectrum in buffer, heme-resonance bands are absent, indicating loss of Met-80 coordination. To verify selective interactions of cytochrome c with cardiolipin, these experiments were repeated where the DPPC acyl chains were deuterated (D62-DPPC), allowing spectral resolution of the DPPC acyl chain response from that of cardiolipin. Interestingly, D62-DPPC acyl chains were unaffected by cytochrome c accumulation, while cardiolipin showed major changes in acyl chain structure. These results suggest that cytochrome-induced permeabilization proceeds through selective interaction of cytochrome c with cardiolipin, resulting in protein unfolding, where the unfolded form interacts with cardiolipin acyl chains within the bilayer to induce permeability.

Confocal Raman Microscopy Investigation of Molecular Transport into Individual Chromatographic Silica Particles.

Porous silica is used as a support in a variety of separation processes, including chromatographic separation and solid-phase extraction. The resolution and efficiency of these applications is significantly impacted by the kinetics of partitioning and molecular transport into the interior of the porous particles. Molecular transport in porous silica has been explored previously by measuring chromatographic elution profiles, but such measurements are limited to relatively low retention conditions, where within-particle molecular transport must be inferred from elution profiles of solutes emerging from a packed column. In this work, a measurement of within-particle molecular transport is carried out using confocal Raman microscopy to probe the time-dependent accumulation of pyrene from an aqueous mobile phase into the center of individual C18-chromatographic particles. The measured time constants for pyrene accumulation were much slower than diffusion-limited transport of solute in solution to the particle surface. Furthermore, the accumulation into the center of the particle did not show a time-lag characteristic of slow-transport into the particle interior. The exponential rise of pyrene concentration is, however, consistent with first-order Langmuir adsorption kinetics at low surface coverages. The linear dependence of the time-constant on particle radius indicates an adsorption barrier near the outer boundary of the particle, where the accumulation rate depends on flux across the boundary (proportional to the particle area) to satisfy the within-particle capacity at equilibrium (proportional to the particle volume). The pyrene accumulation kinetics into the porous particle, expressed as a heterogeneous rate constant, were nearly 50-times faster than the pyrene adsorption rate at a planar C18-functionalized silica surface, which demonstrates the impact of multiple surface encounters within the porous structure leading to much greater capture efficiency compared to a planar surface. Monte Carlo simulations of within-particle pyrene diffusion, with the adsorption efficiency estimated from the planar-surface adsorption rate, predict a diffusion-to-capture distance within the porous particle that is within 40% of that observed in the radial dependence of the pyrene within-particle accumulation results.

Implementing Population Medicine in a Pain Management Practice.

PURPOSE: To document and improve the quality of our chronic pain management using population management methods. METHODS: An analytic registry was developed, and all new patients were enrolled for 12 months. Patient demographics, standardized pain and function measures, and treatments were recorded. Usual care was provided. The registry was used to organize care and analyze management and outcomes. RESULTS: Of 454 total patients, only 154 (34%) completed a 6-month cycle of care. High no-show rates were documented for follow-up appointments for several reasons. The majority of 6-month completers showed improved pain levels. DISCUSSION: This quality improvement project identified assessment and care gaps and led to improvements. An ongoing need to improve measures of pain and function was documented.

Determination of Organic Partitioning Coefficients in Water-Supercritical CO2 Systems by Simultaneous in Situ UV and Near-Infrared Spectroscopies.

CO2 injected into depleted oil or gas reservoirs for long-term storage has the potential to mobilize organic compounds and distribute them between sediments and reservoir brines. Understanding this process is important when considering health and environmental risks, but little quantitative data currently exists on the partitioning of organics between supercritical CO2 and water. In this work, a high-pressure, in situ measurement capability was developed to assess the distribution of organics between CO2 and water at conditions relevant to deep underground storage of CO2. The apparatus consists of a titanium reactor with quartz windows, near-infrared and UV spectroscopic detectors, and switching valves that facilitate quantitative injection of organic reagents into the pressurized reactor. To demonstrate the utility of the system, partitioning coefficients were determined for benzene in water/supercritical CO2 over the range 35-65 °C and approximately 25-150 bar. Density changes in the CO2 phase with increasing pressure were shown to have dramatic impacts on benzene's partitioning behavior. Our partitioning coefficients were approximately 5-15 times lower than values previously determined by ex situ techniques that are prone to sampling losses. The in situ methodology reported here could be applied to quantify the distribution behavior of a wide range of organic compounds that may be present in geologic CO2 storage scenarios.

Epidural Interventions in the Management of Chronic Spinal Pain: American Society of Interventional Pain Physicians (ASIPP) Comprehensive Evidence-Based Guidelines.

BACKGROUND: Chronic spinal pain is the most prevalent chronic disease with employment of multiple modes of interventional techniques including epidural interventions. Multiple randomized controlled trials (RCTs), observational studies, systematic reviews, and guidelines have been published. The recent review of the utilization patterns and expenditures show that there has been a decline in utilization of epidural injections with decrease in inflation adjusted costs from 2009 to 2018. The American Society of Interventional Pain Physicians (ASIPP) published guidelines for interventional techniques in 2013, and guidelines for facet joint interventions in 2020. Consequently, these guidelines have been prepared to update previously existing guidelines. OBJECTIVE: To provide evidence-based guidance in performing therapeutic epidural procedures, including caudal, interlaminar in lumbar, cervical, and thoracic spinal regions, transforaminal in lumbar spine, and percutaneous adhesiolysis in the lumbar spine. METHODS: The methodology utilized included the development of objective and key questions with utilization of trustworthy standards. The literature pertaining to all aspects of epidural interventions was viewed with best evidence synthesis of available literature and  recommendations were provided. RESULTS: In preparation of the guidelines, extensive literature review was performed. In addition to review of multiple manuscripts in reference to utilization, expenditures, anatomical and pathophysiological considerations, pharmacological and harmful effects of drugs and procedures, for evidence synthesis we have included 47 systematic reviews and 43 RCTs covering all epidural interventions to meet the objectives.The evidence recommendations are as follows: Disc herniation: Based on relevant, high-quality fluoroscopically guided epidural injections, with or without steroids, and results of previous systematic reviews, the evidence is Level I for caudal epidural injections, lumbar interlaminar epidural injections, lumbar transforaminal epidural injections, and cervical interlaminar epidural injections with strong recommendation for long-term effectiveness.The evidence for percutaneous adhesiolysis in managing disc herniation based on one high-quality, placebo-controlled RCT is Level II with moderate to strong recommendation for long-term improvement in patients nonresponsive to conservative management and fluoroscopically guided epidural injections. For thoracic disc herniation, based on one relevant, high-quality RCT of thoracic epidural with fluoroscopic guidance, with or without steroids, the evidence is Level II with moderate to strong recommendation for long-term effectiveness.Spinal stenosis: The evidence based on one high-quality RCT in each category the evidence is Level III to II for fluoroscopically guided caudal epidural injections with moderate to strong recommendation and Level II for fluoroscopically guided lumbar and cervical interlaminar epidural injections with moderate to strong recommendation for long-term effectiveness.The evidence for lumbar transforaminal epidural injections is Level IV to III with moderate recommendation with fluoroscopically guided lumbar transforaminal epidural injections for long-term improvement. The evidence for percutaneous adhesiolysis in lumbar stenosis based on relevant, moderate to high quality RCTs, observational studies, and systematic reviews is Level II with moderate to strong recommendation for long-term improvement after failure of conservative management and fluoroscopically guided epidural injections. Axial discogenic pain: The evidence for axial discogenic pain without facet joint pain or sacroiliac joint pain in the lumbar and cervical spine with fluoroscopically guided caudal, lumbar and cervical interlaminar epidural injections, based on one relevant high quality RCT in each category is Level II with moderate to strong recommendation for long-term improvement, with or without steroids. Post-surgery syndrome: The evidence for lumbar and cervical post-surgery syndrome based on one relevant, high-quality RCT with fluoroscopic guidance for caudal and cervical interlaminar epidural injections, with or without steroids, is Level II with moderate to strong recommendation for long-term improvement. For percutaneous adhesiolysis, based on multiple moderate to high-quality RCTs and systematic reviews, the evidence is Level I with strong recommendation for long-term improvement after failure of conservative management and fluoroscopically guided epidural injections. LIMITATIONS: The limitations of these guidelines include a continued paucity of high-quality studies for some techniques and various conditions including spinal stenosis, post-surgery syndrome, and discogenic pain. CONCLUSIONS: These epidural intervention guidelines including percutaneous adhesiolysis were prepared with a comprehensive review of the literature with methodologic quality assessment and determination of level of evidence with strength of recommendations.

Systematic assessment of diagnostic accuracy and therapeutic utility of lumbar facet joint interventions.

BACKGROUND: Lumbar facet joints are a well recognized source of low back pain and referred pain in the lower extremity in patients with chronic low back pain. Conventional clinical features and other non-invasive diagnostic modalities are unreliable in diagnosing lumbar zygapophysial joint pain. Controlled diagnostic studies have shown the prevalence of lumbar facet joint pain in 27% to 40% of the patients with chronic low back pain without disc displacement or radiculitis, with a false-positive rate of 27% to 47% with a single diagnostic block. STUDY DESIGN: A systematic review of diagnostic and therapeutic lumbar facet joint interventions. OBJECTIVE: To determine the clinical utility of diagnostic and therapeutic lumbar facet joint interventions in managing chronic low back pain of facet joint origin. METHODS: Review of the literature for clinical studies on efficacy and utility of facet joint interventions in diagnosing and managing facet joint pain was performed according to the Agency for Healthcare Research and Quality (AHRQ) criteria for diagnostic studies and observational studies and the Cochrane Musculoskeletal Review Group criteria as utilized for interventional techniques for randomized trials. Data sources included relevant literature of the English language identified through searches of Medline and EMBASE from 1966 to December 2008 and manual searches of bibliographies of known primary and review articles. Analysis results were performed for diagnostic and therapeutic interventions separately. LEVEL OF EVIDENCE: The level of evidence was defined as Level I, II, or III with 3 subcategories in Level II based on the quality of evidence developed by the U.S. Preventive Services Task Force (USPSTF) for therapeutic interventions. OUTCOME MEASURES: For diagnostic interventions, studies must have been performed utilizing controlled local anesthetic blocks. Pain relief was categorized as at least 80% pain relief from baseline pain and ability to perform previously painful movements. For therapeutic interventions, the primary outcome measure was pain relief with secondary outcome measures of improvement in functional status, psychological status, return to work, and reduction in opioid intake. For therapeutic interventions, short-term pain relief was defined as relief lasting 6 months or less and long-term relief as longer than 6 months. RESULTS: Based on USPSTF criteria, evidence showed Level I or II-1 for diagnostic facet joint nerve blocks. Based on the review of included therapeutic studies, Level II-1 to II-2 evidence was indicated for lumbar facet joint nerve blocks with indicated level of evidence of Level II-2 to II-3 for lumbar radiofrequency neurotomy. LIMITATIONS: The shortcoming of this systematic review of lumbar facet joint interventions is the paucity of published literature. CONCLUSION: The evidence for diagnosis of lumbar facet joint pain with controlled local anesthetic blocks is Level I or II-1. The indicated level of evidence for therapeutic lumbar facet joint interventions is Level II-1 or II-2 for lumbar facet joint nerve blocks, Level II-2 or II-3 evidence for radiofrequency neurotomy, and Level III (limited) evidence for intraarticular injections.

Systematic review of diagnostic utility and therapeutic effectiveness of cervical facet joint interventions.

BACKGROUND: Chronic, recurrent neck pain is common and is associated with high pain intensity and disability, which is seen in 14% of the adult general population. Controlled studies have supported the existence of cervical facet or zygapophysial joint pain in 36% to 67% of these patients. However, these studies also have shown false-positive results in 27% to 63% of the patients with a single diagnostic block. There is also a paucity of literature investigating therapeutic interventions of cervical facet joint pain. STUDY DESIGN: A systematic review of cervical facet joint interventions. OBJECTIVE: To evaluate the accuracy of diagnostic facet joint nerve blocks and the effectiveness of cervical facet joint interventions. METHODS: Medical databases and journals were searched to locate all relevant literature from 1966 through December 2008 in the English language. A review of the literature of the utility of facet joint interventions in diagnosing and managing facet joint pain was performed according to the Agency for Healthcare Research and Quality (AHRQ) criteria for diagnostic studies and observational studies and the Cochrane Musculoskeletal Review Group criteria as utilized for interventional techniques for randomized trials. LEVEL OF EVIDENCE: The level of evidence was defined as Level I, II, or III based on the quality of evidence developed by the U.S. Preventive Services Task Force (USPSTF). OUTCOME MEASURES: For diagnostic interventions, studies must have been performed utilizing controlled local anesthetic blocks which achieve at minimum 80% relief of pain and the ability to perform previously painful movements. For therapeutic interventions, the primary outcome measure was pain relief (short-term relief up to 6 months and long-term relief greater than 6 months) with secondary outcome measures of improvement in functional status, psychological status, return to work, and reduction in opioid intake. RESULTS: Based on the utilization of controlled comparative local anesthetic blocks, the evidence for the diagnosis of cervical facet joint pain is Level I or II-1. The indicated evidence for therapeutic cervical medial branch blocks is Level II-1. The indicated evidence for radiofrequency neurotomy in the cervical spine is Level II-1 or II-2, whereas the evidence is lacking for intraarticular injections. LIMITATIONS: A systematic review of cervical facet joint interventions is hindered by the paucity of published literature and lack of literature for intraarticular cervical facet joint injections. CONCLUSIONS: The evidence for diagnosis of cervical facet joint pain with controlled comparative local anesthetic blocks is Level I or II-1. The indicated evidence for therapeutic facet joint interventions is Level II-1 for medial branch blocks, and Level II-1 or II-2 for radiofrequency neurotomy.

Effectiveness of spinal endoscopic adhesiolysis in post lumbar surgery syndrome: a systematic review.

BACKGROUND: Post lumbar surgery syndrome with persistent chronic low back and lower extremity pain is common in the United States. Epidural fibrosis may account for as much as 20% to 36% of all cases of failed back surgery syndrome (FBSS). Percutaneous adhesiolysis with a catheter or direct visualization of the spinal canal and the contents with an endoscope are techniques employed in resistant cases when patients fail to respond to conservative modalities of treatment, including fluoroscopically directed epidural injections. Some patients failing to respond to percutaneous adhesiolysis are candidates for spinal endoscopic adhesiolysis. However, literature evaluating the effectiveness of spinal endoscopic adhesiolysis is sparse and discussions continue about its effectiveness, utility, and complications. STUDY DESIGN: A systematic review of the available literature. OBJECTIVE: To evaluate the effectiveness and safety of spinal endoscopic adhesiolysis in the management of chronic low back and lower extremity pain in post surgical patients with chronic recalcitrant pain, non-responsive to conservative modalities of management and fluoroscopically directed epidural injections. METHODS: A search of relevant resources (PubMed, EMBASE, and the Cochrane database) was accomplished and the resulting publications were examined based on the inclusion/exclusion criteria set forth. Randomized controlled trials and observational studies were included in the search. Two reviewers assessed the studies' methodologies and outcomes. Randomized clinical trials were assessed and scored based on the criteria established by the Cochrane methodological assessment criteria of randomized clinical trials and the observational studies were assessed and scored based on the Agency for Healthcare Research and Quality (AHRQ) criteria. Clinical relevance was evaluated utilizing Cochrane review criteria. Analysis was conducted using 5 levels of evidence, ranging from Level I to III, with 3 subcategories in Level II. OUTCOME MEASURES: The primary outcome measure was pain relief (> or = 50%) in follow-up for at least 6 months. Pain relief for longer than 6 months was considered long-term and 6 months or less was considered short-term. The secondary outcome measures were functional and psychological status, return to work, patient satisfaction, and opioid intake. RESULTS: Of the 13 studies considered for inclusion, one randomized trial and 5 observational studies met inclusion criteria for evidence synthesis based on the inclusion criteria and methodologic quality scores of 50 or more. The indicated level of evidence for endoscopic adhesiolysis is Level II-1 or II-2 evidence for short- and long-term relief based on the U.S. Preventive Services Task Force (USPSTF) criteria. LIMITATIONS: There was a paucity of literature for randomized trials. CONCLUSION: Spinal endoscopic adhesiolysis may be used as an effective treatment modality for chronic refractory low back pain and radiculopathy that is related to epidural adhesions.

Calorimetry-Derived Composition Vectors to Resolve Component Raman Spectra in Phospholipid Phase Transitions.

Multidimensional least squares analysis is a well-established technique for resolving component vibrational spectra from mixed samples or systems. Component resolution of temperature-dependent vibrational spectra is challenging, however, due to the lack of a suitable model for the variation in sample composition with temperature. In this work, analysis of temperature-dependent Raman spectra of lipid membranes is accomplished by using "concentration" vectors independently derived from enthalpy changes determined by differential scanning calorimetry. Specifically, the lipid-bilayer phase transitions of DMPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) are investigated through Raman spectra acquired from individual, optically trapped vesicles in suspension as a function of temperature. Heat capacity profiles of the same vesicle suspension are measured using differential scanning calorimetry and numerically integrated to generate enthalpy change curves of each phase transition, which are in turn used to construct composition vectors. Multidimensional least squares analysis optimized for a fit to these composition vectors allows resolution of the component spectra corresponding to gel, ripple, and liquid-crystalline phases of the DMPC. The quality of fit of the calorimetry-derived results is confirmed by unstructured residual differences between the data and the model, and a composition variation predicted by the resolved spectra that matches the calorimetry results. This approach to analysis of temperature-dependent spectral data could be readily applied in other areas of materials characterization, where one is seeking to learn about structural changes that occur through temperature-dependent phase transitions.

Randomized clinical trial of an implantable drug delivery system compared with comprehensive medical management for refractory cancer pain: impact on pain, drug-related toxicity, and survival.

PURPOSE: Implantable intrathecal drug delivery systems (IDDSs) have been used to manage refractory cancer pain, but there are no randomized clinical trial (RCT) data comparing them with comprehensive medical management (CMM). PATIENTS AND METHODS: We enrolled 202 patients on an RCT of CMM versus IDDS plus CMM. Entry criteria included unrelieved pain (visual analog scale [VAS] pain scores >/= 5 on a 0 to 10 scale). Clinical success was defined as >/= 20% reduction in VAS scores, or equal scores with >/= 20% reduction in toxicity. The main outcome measure was pain control combined with change of toxicity, as measured by the National Cancer Institute Common Toxicity Criteria, 4 weeks after randomization. RESULTS: Sixty of 71 IDDS patients (84.5%) achieved clinical success compared with 51 of 72 CMM patients (70.8%, P =.05). IDDS patients more often achieved >/= 20% reduction in both pain VAS and toxicity (57.7% [41 of 71] v 37.5% [27 of 72], P =.02). The mean CMM VAS score fell from 7.81 to 4.76 (39% reduction); for the IDDS group, the scores fell from 7.57 to 3.67 (52% reduction, P =.055). The mean CMM toxicity scores fell from 6.36 to 5.27 (17% reduction); for the IDDS group, the toxicity scores fell from 7.22 to 3.59 (50% reduction, P =.004). The IDDS group had significant reductions in fatigue and depressed level of consciousness (P <.05). IDDS patients had improved survival, with 53.9% alive at 6 months compared with 37.2% of the CMM group (P =.06). CONCLUSION: IDDSs improved clinical success in pain control, reduced pain, significantly relieved common drug toxicities, and improved survival in patients with refractory cancer pain.

Intradiscal electrothermal annuloplasty therapy: a case series study leading to new considerations.

OBJECTIVE: To evaluate outcomes of intradiscal electrothermal annuloplasty (IDEA) therapy in the treatment of chronic discogenic low back pain in consecutive IDEA patients treated at a rural pain management clinic. STUDY DESIGN: An observational case series study design was applied to consecutive IDEA patients qualifying under the inclusion and exclusion criteria. Patient assessment of pain and disability were performed at baseline and 6 weeks, 3, 6, 12, and 24 months post-IDEA. METHODS: Selected patients underwent IDEA for an average of 15 minutes at a temperature of 90 degrees C. Analyses of outcomes included Visual Analog Scale (VAS) assessments of levels of pain, and Roland Morris Disability Questionnaire (RMDQ) assessments of functional capacity at pretreatment, and 6 weeks, 3, 6, 12, and 18 months post-treatment time points. RESULTS: At 6 months post-IDEA treatment, patients (n=51) demonstrated statistically significant improvement (P < 0.001) as measured by a mean change of over 20 points from the pretreatment score on the RMDQ. At 1 year, post data remained significant in the 33 patients who had achieved this time point. VAS pain data were also statistically significant at 6 months (P = 0.023). Analysis of patient profiles revealed that statistically significant improvement of pain and functional capacity was strongly associated with female gender and age (range of 18-45 years), and that statistically significant improvement was not sustained in males beyond the 3-6 month point. These data support the outcomes reported in the few existing observational studies to date. Of 86 patients receiving IDEA therapy, 73 provided RMDQ data at baseline and at 3 months or later and were included in the analyses. Some patients were lost to follow-up at later time points. CONCLUSIONS: These data show favorable outcomes after IDEA therapy, and suggest that women may experience more improvement than men, particularly with regard to perceived disability improvements. Data suggest that greater improvement in IDEA outcomes may be achieved by profiling the characteristics of patients who achieve the optimal long-term outcomes following treatment and should be considered during evaluation of patient eligibility for IDEA.

Spatial filtering of a diode laser beam for confocal Raman microscopy.

With the development of single-longitudinal mode diode lasers, there has been an increase in using these sources for Raman spectroscopy. This is largely due to the cost-effectiveness of diode lasers, which offer savings not only in initial capital cost, but also electrical, cooling, and replacement costs over time, when compared with ion lasers. The use of diode-lasers in confocal Raman microscopy has remained a challenge, however, due to poor transverse beam quality. In this work, we present the design and implementation of a simple spatial filter capable of adapting a single-mode diode laser source to confocal Raman microscopy, yielding comparable spatial resolution as a gas-ion laser beam for profiling and optical-trapping applications. For profiling applications, spatial filtering improved x,y resolution of the beam by a factor 10, which in turn increased optical-trapping forces by ~90 times and yielded sevenfold greater Raman scattering signal intensity from an optically trapped phospholipid vesicle.

Intrathecal ziconotide in the treatment of refractory pain in patients with cancer or AIDS: a randomized controlled trial.

CONTEXT: Ziconotide (formerly SNX-111) selectively blocks N-type voltage-sensitive calcium channels and may be effective in patients with pain that is refractory to opioid therapy or those with intolerable opioid-related adverse effects. OBJECTIVE: To assess the safety and efficacy of intrathecal ziconotide in patients with pain that is refractory to conventional treatment. DESIGN, SETTING, AND PATIENTS: Double-blind, placebo-controlled, randomized trial conducted from March 12, 1996, to July 11, 1998, at 32 study centers in the United States, Australia, and the Netherlands. Patients were 111 individuals ages 24 to 85 years with cancer or AIDS and a mean Visual Analog Scale of Pain Intensity (VASPI) score of 50 mm or greater. Patients were randomly assigned in a 2:1 ratio to receive ziconotide or placebo treatment. INTERVENTIONS: Intrathecal ziconotide was titrated over 5 to 6 days, followed by a 5-day maintenance phase for responders and crossover of nonresponders to the opposite treatment group. MAIN OUTCOME MEASURE: Mean percentage change in VASPI score from baseline to the end of the initial titration period. RESULTS: Of the evaluable population, 67 (98.5%) of 68 patients receiving ziconotide and 38 (95%) of 40 patients receiving placebo were taking opioids at baseline (median morphine equivalent dosage of 300 mg/d for the ziconotide group and 600 mg/d for the placebo group; P =.63, based on mean values), and 36 had used intrathecal morphine. Mean (SD) VASPI scores were 73.6 (1.8) mm in the ziconotide group and 77.9 (2.3) mm in the placebo group (P =.18). Mean VASPI scores improved 53.1% (95% confidence interval [CI], 44.0%-62.2%) in the ziconotide group and 18.1% (95% CI, 4.8%-31.4%) in the placebo group (P<.001), with no loss of efficacy of ziconotide in the maintenance phase. Pain relief was moderate to complete in 52.9% of patients in the ziconotide group compared with 17.5% in the placebo group (P<.001). Five patients receiving ziconotide achieved complete pain relief, and 50.0% of patients receiving ziconotide responded to therapy compared with 17.5% of those receiving placebo (P =.001). CONCLUSION: Intrathecal ziconotide provided clinically and statistically significant analgesia in patients with pain from cancer or AIDS.

An update of comprehensive evidence-based guidelines for interventional techniques in chronic spinal pain. Part II: guidance and recommendations.

OBJECTIVE: To develop evidence-based clinical practice guidelines for interventional techniques in the diagnosis and treatment of chronic spinal pain. METHODOLOGY: Systematic assessment of the literature. EVIDENCE: I. Lumbar Spine • The evidence for accuracy of diagnostic selective nerve root blocks is limited; whereas for lumbar provocation discography, it is fair. • The evidence for diagnostic lumbar facet joint nerve blocks and diagnostic sacroiliac intraarticular injections is good with 75% to 100% pain relief as criterion standard with controlled local anesthetic or placebo blocks. • The evidence is good in managing disc herniation or radiculitis for caudal, interlaminar, and transforaminal epidural injections; fair for axial or discogenic pain without disc herniation, radiculitis or facet joint pain with caudal, and interlaminar epidural injections, and limited for transforaminal epidural injections; fair for spinal stenosis with caudal, interlaminar, and transforaminal epidural injections; and fair for post surgery syndrome with caudal epidural injections and limited with transforaminal epidural injections. • The evidence for therapeutic facet joint interventions is good for conventional radiofrequency, limited for pulsed radiofrequency, fair to good for lumbar facet joint nerve blocks, and limited for intraarticular injections. • For sacroiliac joint interventions, the evidence for cooled radiofrequency neurotomy is fair; limited for intraarticular injections and periarticular injections; and limited for both pulsed radiofrequency and conventional radiofrequency neurotomy. • For lumbar percutaneous adhesiolysis, the evidence is fair in managing chronic low back and lower extremity pain secondary to post surgery syndrome and spinal stenosis. • For intradiscal procedures, the evidence for intradiscal electrothermal therapy (IDET) and biaculoplasty is limited to fair and is limited for discTRODE. • For percutaneous disc decompression, the evidence is limited for automated percutaneous lumbar discectomy (APLD), percutaneous lumbar laser disc decompression, and Dekompressor; and limited to fair for nucleoplasty for which the Centers for Medicare and Medicaid Services (CMS) has issued a noncoverage decision. II. Cervical Spine • The evidence for cervical provocation discography is limited; whereas the evidence for diagnostic cervical facet joint nerve blocks is good with a criterion standard of 75% or greater relief with controlled diagnostic blocks. • The evidence is good for cervical interlaminar epidural injections for cervical disc herniation or radiculitis; fair for axial or discogenic pain, spinal stenosis, and post cervical surgery syndrome. • The evidence for therapeutic cervical facet joint interventions is fair for conventional cervical radiofrequency neurotomy and cervical medial branch blocks, and limited for cervical intraarticular injections. III. Thoracic Spine • The evidence is limited for thoracic provocation discography and is good for diagnostic accuracy of thoracic facet joint nerve blocks with a criterion standard of at least 75% pain relief with controlled diagnostic blocks. • The evidence is fair for thoracic epidural injections in managing thoracic pain. • The evidence for therapeutic thoracic facet joint nerve blocks is fair, limited for radiofrequency neurotomy, and not available for thoracic intraarticular injections. IV. Implantables • The evidence is fair for spinal cord stimulation (SCS) in managing patients with failed back surgery syndrome (FBSS) and limited for implantable intrathecal drug administration systems. V. ANTICOAGULATION • There is good evidence for risk of thromboembolic phenomenon in patients with antithrombotic therapy if discontinued, spontaneous epidural hematomas with or without traumatic injury in patients with or without anticoagulant therapy to discontinue or normalize INR with warfarin therapy, and the lack of necessity of discontinuation of nonsteroidal anti-inflammatory drugs (NSAIDs), including low dose aspirin prior to performing interventional techniques. • There is fair evidence with excessive bleeding, including epidural hematoma formation with interventional techniques when antithrombotic therapy is continued, the risk of higher thromboembolic phenomenon than epidural hematomas with discontinuation of antiplatelet therapy prior to interventional techniques and to continue phosphodiesterase inhibitors (dipyridamole, cilostazol, and Aggrenox). • There is limited evidence to discontinue antiplatelet therapy with platelet aggregation inhibitors to avoid bleeding and epidural hematomas and/or to continue antiplatelet therapy (clopidogrel, ticlopidine, prasugrel) during interventional techniques to avoid cerebrovascular and cardiovascular thromboembolic fatalities. • There is limited evidence in reference to newer antithrombotic agents dabigatran (Pradaxa) and rivaroxan (Xarelto) to discontinue to avoid bleeding and epidural hematomas and are continued during interventional techniques to avoid cerebrovascular and cardiovascular thromboembolic events. CONCLUSIONS: Evidence is fair to good for 62% of diagnostic and 52% of therapeutic interventions assessed. DISCLAIMER: The authors are solely responsible for the content of this article. No statement on this article should be construed as an official position of ASIPP. The guidelines do not represent "standard of care."