Shihab U. Ahmed

Patient selection and trial methods for intraspinal drug delivery for chronic pain: a national survey.

Objectives  Intraspinal drug delivery via indwelling pump is an effective means of treating refractory pain. Before a patient is selected for pump implantation, an intraspinal drug delivery trial must be performed to establish side‐effects and efficacy profiles. No consensus protocol currently exists for such trials. As a preliminary step in this process, we surveyed a group of interventional pain physicians to explore attitudes on patient selection criteria, drug choice, trial techniques, and efficacy assessment.

Seizures after a Bier block with clonidine and lidocaine.

A 47-yr-old man with history of complex regional pain syndrome type 1 underwent an IV Bier block with a mixture of lidocaine and clonidine. The tourniquet was deflated after 60 min, and approximately 10 min later he presented with complex partial seizures. The possible mechanisms for this are discussed, and the effects of clonidine, lidocaine, and the mixture of both are reviewed, as are four additional published cases reporting seizures after the administration of clonidine.

Diagnosis and Treatment of Posterior Sacroiliac Complex Pain: A Systematic Review with Comprehensive Analysis of the Published Data

OBJECTIVE To assess the evidence on the validity of sacral lateral branch blocks and the effectiveness of sacral lateral branch thermal radiofrequency neurotomy in managing sacroiliac complex pain. DESIGN Systematic review with comprehensive analysis of all published data. INTERVENTIONS Six reviewers searched the literature on sacral lateral branch interventions. Each assessed the methodologies of studies found and the quality of the evidence presented. OUTCOME MEASURES The outcomes assessed were diagnostic validity and effectiveness of treatment for sacroiliac complex pain. The evidence found was appraised in accordance with the Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) system of evaluating scientific evidence. RESULTS The searches yielded two primary publications on sacral lateral branch blocks and 15 studies of the effectiveness of sacral lateral branch thermal radiofrequency neurotomy. One study showed multisite, multidepth sacral lateral branch blocks can anesthetize the posterior sacroiliac ligaments. Therapeutic studies show sacral lateral branch thermal radiofrequency neurotomy can relieve sacroiliac complex pain to some extent. The evidence of the validity of these blocks and the effectiveness of this treatment were rated as moderate in accordance with the GRADE system. CONCLUSIONS The literature on sacral lateral branch interventions is sparse. One study demonstrates the face validity of multisite, multidepth sacral lateral branch blocks for diagnosis of posterior sacroiliac complex pain. Some evidence of moderate quality exists on therapeutic procedures, but it is insufficient to determine the indications and effectiveness of sacral lateral branch thermal radiofrequency neurotomy, and more research is required.

Increased Pain Sensitivity in Chronic Pain Subjects on Opioid Therapy: A Cross-Sectional Study Using Quantitative Sensory Testing

OBJECTIVE The aim of this study was to compare the sensitivity to experimental pain of chronic pain patients on opioid therapy vs chronic pain patients on non-opioid therapy and healthy subjects by quantitative sensory testing (QST). SETTING There is a growing body of evidence demonstrating that chronic use of opioid drugs may alter pain sensitivity. Identifying the characteristic changes in thermal pain sensitivity in chronic opioid users will be helpful in diagnosing pain sensitivity alterations associated with chronic opioid use. METHODS Utilizing an office-based QST technique, we examined thermal pain threshold, tolerance, and temporal summation in 172 chronic pain subjects receiving opioid therapy, 121 chronic pain subjects receiving non-opioid therapy, and 129 healthy subjects. RESULTS In chronic pain subjects receiving opioid therapy, there were detectable differences in QST characteristics compared with both chronic pain subjects receiving non-opioid therapy and healthy subjects. Specifically, in chronic pain subjects receiving opioid therapy, 1) sensitivity to heat pain was increased; threshold to heat pain was significantly lower; 2) tolerance to supra-threshold heat pain was significantly decreased; and 3) temporal pain summation was exacerbated, as compared with chronic pain subjects receiving non-opioid therapy. In a subgroup of chronic pain subjects receiving opioid therapy with increased heat pain sensitivity, their average opioid medication dosage was significantly higher than those who had an above-average heat pain threshold. Moreover, a subset of chronic pain subjects on opioid therapy exhibited a significant decrease in diffuse noxious inhibitory control (DNIC) compared with chronic pain subjects on non-opioid therapy. CONCLUSION These findings suggest that a subset of QST parameters can reflect opioid-associated thermal pain sensitivity alteration, including decreased heat pain threshold, decreased cold and heat pain tolerance, diminished DNIC, and/or exacerbated temporal summation.

Complex Regional Pain Syndrome Type I After Myocardial Infarction Treated With Spinal Cord Stimulation

Objective A rare case of Complex Regional Pain Syndrome (CRPS) type I after myocardial infarction (MI) and significant comorbid illness with few treatment options for pain control was successfully managed with the placement of a spinal cord stimulator (SCS). Case Report A 44-year old man presented with left upper extremity burning pain after MI. His past medical history included insulin-dependent diabetes mellitus, oxygen-dependent idiopathic pulmonary fibrosis, and recent coronary revascularization surgery. His pain was presumed to be related to his MI and a clinical diagnosis of CRPS type I (or reflex sympathetic dystrophy) was made. Facing limited medical and less invasive options for his pain relief, he underwent a spinal cord stimulation trial with excellent response. He had more than 70% pain relief from the spinal cord stimulation at the last follow-up, 2 years later. Conclusion CRPS type I after MI can be difficult to treat because of other comorbid illnesses. SCS can be a safe and effective mode of therapy for patients facing limited treatment options.

Influence of jet direction on pulmonary vein flow patterns in severe mitral regurgitation

Pulmonary vein flow patterns measured with transesophageal echocardiography have been used recently to assess the severity of mitral valve regurgitation.This study was designed to determine whether regurgitant jet direction selectively influences the pattern of flow in right and left pulmonary veins. Thirty-seven patients undergoing mitral valve repair or replacement for severe valvular regurgitation were studied intraoperatively with biplane transesophageal echocardiography. Regurgitant jets were classified by color flow mapping as central or wall, with the latter further classified as septal, lateral, anterior, or posterior in the two orthogonal scan planes. Pulmonary vein flow patterns were measured with pulsed wave Doppler ultrasonography and categorized as showing normal, blunted, or reversed systolic flow. Right and left pulmonary vein flow patterns were identical in the majority of patients studied (78%). Eight patients had discordant flow patterns. In seven of eight patients, the more abnormal pattern was seen in the right pulmonary vein, despite the fact that the regurgitant jets were directed centrally in four of these seven patients. Since discordant pulmonary vein flow patterns occurred in 5 of 15 patients (33%) with central jets, but in only 3 of 22 patients (14%) with eccentric wall jets, it is unlikely that mitral regurgitation jet direction per se causes predictable and selective unilateral alteration in pulmonary vein flow patterns. (Anesth Analg 1995;80:486-91)

High-Frequency Spinal Cord Stimulation for Chronic Pain: Pre-Clinical Overview and Systematic Review of Controlled Trials.

OBJECTIVE To assess the evidence base for high-frequency spinal cord stimulation (HFSCS). HFSCS has the potential to provide paresthesia-free pain relief for patients with chronic pain, in contrast to conventional spinal cord stimulation, which produces distracting and potentially unpleasant paresthesias. DESIGN A systematic review following standard methodological guidelines (Prospero #CRD42015029215). METHODS We searched PubMed to March 14, 2016 without language restriction and hand-checked reference lists. Two authors independently performed study selection, bias evaluations, and data extraction. The pre-clinical review selected studies focusing on the mechanism and non-human experience with HFSCS. Clinically, any prospective study of adults using HFSCS (≥ 1000 Hz) was included. RESULTS Pre-clinical studies have characterized many aspects underlying the mechanism of HFSCS. For the clinical systematic review, eight trials (236 participants randomized or 160 followed prospectively) met inclusion criteria. All trials of HFSCS focused on patients with chronic low back pain with one exception, which included patients with chronic migraine. All but one trial documented funding by industry. Performance bias due to unmasked participants, physicians, and outcome assessors limited the quality of all but one study. CONCLUSIONS Significant growth in the preclinical and clinical evidence base for HFSCS suggests that HFSCS may differ from conventional SCS in mechanism of action and efficacy of treatment, respectively. Addressing current knowledge gaps in clinical evidence will require standardization in trial reporting and leveraging the paresthesia-free characteristic of HFSCS to enable masking in high-quality randomized controlled trials.

Effect of 1.5% Topical Diclofenac on Clinical Neuropathic Pain

Background:Neuropathic pain is a condition resulting from injury to the peripheral and/or central nervous system. Despite extensive research over the last several decades, neuropathic pain remains difficult to manage. Methods:The authors conducted a randomized, placebo-controlled, double-blinded, and crossover clinical trial to examine the effect of 1.5% topical diclofenac (TD) on neuropathic pain. The authors hypothesized that 1.5% TD would reduce the visual pain score and improve both quantitative sensory testing and functional status in subjects with neuropathic pain. The authors recruited subjects with postherpetic neuralgia and complex regional pain syndrome. The primary outcome was subject’s visual pain score. Results:Twenty-eight subjects completed the study (12 male and 16 female) with the mean age of 48.8 yr. After 2 weeks of topical application, subjects in 1.5% TD group showed lower overall visual pain score compared with placebo group (4.9 [1.9] vs. 5.6 [2.1], difference: 0.8; 95% CI, 0.1 to 1.3; P = 0.04) as well as decreased burning pain (2.9 [2.6] vs. 4.3 [2.8], difference, 1.4; 95% CI, 0.2 to 2.6; P = 0.01). There were no statistical differences in constant pain, shooting pain, or hypersensitivity over the painful area between the groups. This self-reported improvement of pain was corroborated by the decreased pain summation detected by quantitative sensory testing. There were no statistically significant changes in functional status in these subjects. There were no complications in both groups. Conclusion:The findings indicate that 1.5% TD may serve as an effective treatment option for patients with neuropathic pain from postherpetic neuralgia and complex regional pain syndrome.

Spontaneous intracranial hypotension: presentation, diagnosis, and treatment.

1327 December 2014 B ecause of cerebrospinal fluid (csF) leak, orthostatic headaches sometimes follow neuraxial blockade or diagnostic lumbar puncture. etiology and treatment are straightforward in those settings, since a site of dural disruption is known.1,2 With patient consent, we present a case in which intracranial hypotension resulted from dural puncture by a vertebral osteophytic spur. This case scenario illustrates the diagnostic dilemma of spontaneous intracranial hypotension (sIH), the role of imaging studies, and the value of empiric lumbar epidural blood patch (LeBP).

Effects of Spinal Cord Stimulation on Pain Thresholds and Sensory Perceptions in Chronic Pain Patients

Spinal cord stimulation (SCS) has been in clinical use for nearly four decades. In earliest observations, researchers found a significant increase in pain threshold during SCS therapy without changes associated with touch, position, and vibration sensation. Subsequent studies yielded diverse results regarding how SCS impacts pain and other sensory thresholds. This pilot study uses quantitative sensory testing (QST) to objectively quantify the impact of SCS on warm sensation, heat pain threshold, and heat pain tolerance.