Isoflurane regulates atypical type-A γ-aminobutyric acid receptors in alveolar type II epithelial cells.

BACKGROUND: Volatile anesthetics act primarily through upregulating the activity of γ-aminobutyric acid type A (GABAA) receptors. They also exhibit antiinflammatory actions in the lung. Rodent alveolar type II (ATII) epithelial cells express GABAA receptors and the inflammatory factor cyclooxygenase-2 (COX-2). The goal of this study was to determine whether human ATII cells also express GABAA receptors and whether volatile anesthetics upregulate GABAA receptor activity, thereby reducing the expression of COX-2 in ATII cells. METHODS: The expression of GABAA receptor subunits and COX-2 in ATII cells of human lung tissue and in the human ATII cell line A549 was studied with immunostaining and immunoblot analyses. Patch clamp recordings were used to study the functional and pharmacological properties of GABAA receptors in cultured A549 cells. RESULTS: ATII cells in human lungs and cultured A549 cells expressed GABAA receptor subunits and COX-2. GABA induced currents in A549 cells, with half-maximal effective concentration of 2.5 µM. Isoflurane (0.1-250 µM) enhanced the GABA currents, which were partially inhibited by bicuculline. Treating A549 cells with muscimol or with isoflurane (250 µM) reduced the expression of COX-2, an effect that was attenuated by cotreatment with bicuculline. CONCLUSIONS: GABAA receptors expressed by human ATII cells differ pharmacologically from those in neurons, exhibiting a higher affinity for GABA and lower sensitivity to bicuculline. Clinically relevant concentrations of isoflurane increased the activity of GABAA receptors and reduced the expression of COX-2 in ATII cells. These findings reveal a novel mechanism that could contribute to the antiinflammatory effect of isoflurane in the human lung.

Pulsed radiofrequency of suprascapular nerve for chronic shoulder pain: a randomized double-blind active placebo-controlled study.

BACKGROUND: The suprascapular nerve block is frequently implemented to treat chronic shoulder pain. Although effective the nerve blockade provides only a short-term relief, and more compelling apaproaches have been investigated. Pulsed radiofrequency (pRF) has been anecdotally reported as safe and reliable method. However, formal efficacy study has not been published. Ostensibly evidence-based validation of a new method is necessary for both scholastic and practical purposes. METHODS: This study was designed as a randomized active placebo-control double-blind trial. Because of encountered difficulties in recruitment and high rate of dropout, the study was redesigned as to allow a smaller sample size and statistical analyses were performed utilizing the last observation carry forward method. Lidocaine injections alone or with combination of the pRF were performed. Participants were followed up during 6 months, and multiple subjective and objective outcome variables were recorded. RESULTS: Thirteen of 22 participants completed 6 months follow-up. Dropout rate was higher in the lidocaine group. A significant linear trend (P < 0.05) for improvement on the numeric rating scale, Shoulder Pain and Disability Index and Constant-Murley score was observed in the pRF group, but not in the lidocaine group. Patients in the pRF group were on average more satisfied than the lidocaine group at 1 month (P = 0.041) and at 3 months (P = 0.035). DISCUSSION: Considering limitations of the study design and statistics, it seems plausible to attribute better results in the pRF group to unique properties of this physical modality.

Pulsed radiofrequency under ultrasound guidance for persistent stump-neuroma pain.

Limb amputation is a leading cause of pain and disability. Limb amputation can be associated with a myriad of symptoms, including phantom limb sensation, phantom limb pain, and stump pain. Treatment of phantom limb pain and stump pain, remains difficult, therefore optimal management must include a multidisciplinary approach. This case report describes the use of ultrasound for diagnosis and successful management, of persistent stump-neuroma pain, using pulsed radiofrequency ablation.

Regional anesthesia and co-existing chronic pain.

PURPOSE OF REVIEW: Investigate the rational for incorporation of regional anesthesia techniques into a multimodal approach toward patients with co-existing chronic pain as increasing numbers of chronic pain patients are presenting for surgery. RECENT FINDINGS: There is a growing body of evidence suggesting that regional anesthesia may be superior to opioids for improved pain control along with increased patient satisfaction and decreased perioperative morbidity and mortality comparing to general anesthesia in patients with significant medical disease(s) and may also carry several economic benefits. Despite the prevalence of chronic pain and data suggesting that patients with chronic pain are prone to exacerbation of their condition(s) following surgery, regional anesthesia techniques for these patients is only beginning to be developed. SUMMARY: The systemic condition of chronic pain has important practical and clinical implications for regional anesthesia implementation by anesthesiologists and pain management physicians. Comprehensive preadmission assessment together with a complete medication history and close follow-up management should always be employed in patients with pre-existing chronic pain throughout the perioperative setting. Despite successful implementation of neural blockade, and to avoid opioid withdrawal, at least half the chronic pain patient's daily pre-admission opioid dose should be continued daily throughout the perioperative period. Regional anesthesia is a preferable anesthetic option for perioperative management technique of patients with co-existing chronic pain, even if it requires supplementation with sedation or general anesthesia. The specifics of regional anesthesia performance and practical strategies for regional anesthesia application in chronic pain patients, including implanted pain management devices, are reviewed in this study.

Radiofrequency denervation of the lumbar zygapophysial joints--targeting the best practice.

OBJECTIVE: Radiofrequency denervation of the zygapophysial (facet) joint is a frequently performed procedure for chronic low back pain. Several studies have shown considerable efficacy of the procedure, but none of the randomized controlled trials performed to date has used anatomically correct placement of radiofrequency cannula parallel to the target nerve. Three main techniques have been utilized for many years: North American, European, and Australian. Each has conceptual and technical limitations. This review analyzes these techniques and proposes a standardized technique of radiofrequency denervation of lumbar zygapophysial joints. DESIGN: Current techniques of radiofrequency neurotomy were analyzed with respect to anatomic and technical accuracy. Step by step guidelines were developed using a combination of previously described techniques along with newly elaborated technical hints and details. CONCLUSION: We believe that the technique using "tunnel vision" with anatomically appropriate cannula placement and use of a large-bore, curved needle with a 10-mm active tip may improve the results of radiofrequency denervation of lumbar zygapophysial joints. Providing a detailed description of an anatomically accurate technique should be of value to those seeking to perform this procedure in a valid manner.

Radiofrequency denervation of the lumbar zygapophysial joints: 10-year prospective clinical audit.

BACKGROUND: Evidence for the efficacy of zygapophysial joint nerve radiofrequency neurotomy has remained controversial. Two randomized controlled trials showed positive results, but two others demonstrated no benefit. One carefully performed prospective trial confirmed high efficacy and lasting pain relief after the procedure; however, selection criteria for this study were superfluous, which resulted in a small number of patients available for follow up. OBJECTIVES: A large clinical audit with routine patient selection and use of appropriate technique was undertaken to determine the effect of radiofrequency neurotomy of the lumbar facet joints for relief of chronic low back pain. DESIGN: Prospective clinical audit for quality was conducted in the pain clinic affiliated with a tertiary care teaching hospital. SETTING: An interventional pain management setting in Canada. METHODS: All patients with low back pain of more than 6 months' duration, with or without non-radicular radiation to the buttock, hip, and leg were included. From January 1991 to December 2000, eligible patients underwent standardized diagnostic work-up, which included a self-reported pain questionnaire, physical examination, review of imaging studies, and diagnostic blockades. Those with an appropriate response to comparative double diagnostic blocks underwent standardized radiofrequency denervation of the lumbar zygapophysial joints. Patients were asked to estimate total perceived pain reduction (on a scale from 0% to 100%) at 6 weeks and at 6, 12, and 24 months after the procedure. RESULTS: Of the 209 patients, 174 completed the study, and 35 were lost to follow-up or did not provide complete data for assessment. Of the 174 patients with complete data, 55 (31.6%) experienced no benefit from the procedure. One hundred and nineteen patients (68.4%) had good (> 50%) to excellent (> 80%) pain relief lasting from 6 to 24 months. CONCLUSION: This large, prospective clinical audit indicates that proper patient selection and anatomically correct radiofrequency denervation of the lumbar zygapophysial joints provide long-term pain relief in a routine clinical setting.

Bilateral pain relief after unilateral thoracic percutaneous sympathectomy.

PURPOSE: To present a case of unexpected bilateral pain relief following unilateral thoracic percutaneous sympathectomy. CLINICAL FINDINGS: We present a case report where severe ischemic pain due to paraneoplastic Raynaud's syndrome with distal gangrene was successfully treated by means of percutaneous thoracic sympathectomy. A unilateral T2, T3 radiofrequency sympathectomy combined with small volume phenol injection resulted in unexpected bilateral pain relief. CONCLUSION: Our observations from this case report suggest a possible crossover of sympathetic innervation at the cervical and thoracic levels. Percutanenous thoracic radiofrequency sympathectomy is a feasible option for the treatment of refractory ischemic upper limb pain.