Pain physician
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Constriction of the sciatic nerve by loose ligation produces an inflammatory neuropathic injury. This represents an animal model for peripheral mononeuropathy. Oxygen-derived free radicals are suspected to play an important role in the pathogenesis of ischemia/reperfusion injury, leading to neurogenic inflammation. Hyperbaric oxygen (HBO) has been used anecdotally to treat clinically similar conditions in humans, but specific effects on the animal model have not been well studied. ⋯ This study evaluated tissue changes after nerve injury caused by loose ligation of the sciatic nerve in rats. Hyperbaric oxygen treatment following sciatic nerve injury reduced tissue edema, improved skin blood flow, and preserved muscle and neuronal ultrastructural integrity.
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Complex regional pain syndrome (CRPS) is characterized by pain that is out of proportion to the injury and is regional in distribution. A large body of literature supports a dynamic change in the physiology and structure of central pain projecting neurons mediated through the N-methyl-D-aspartate (NMDA) receptor. A critical factor in central sensitization seems to be the release of the magnesium block on the NMDA receptor with influx of calcium and initiation of intracellular cascades. Current literature supports the effectiveness of ketamine in blocking central sensitization through its effects on the NMDA receptor. Recent treatment with anesthetic doses of ketamine in severely ill patients with generalized CRPS prompted our interest in a lower dose therapy. ⋯ A four-hour ketamine infusion escalated from 40-80 mg over a 10-day period can result in a significant reduction of pain with increased mobility and a tendency to decreased autonomic dysregulation.
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Chronic refractory spinal pain poses a peculiar diagnostic challenge because of multiple putative pain sources, overlapping clinical features, and nonspecific radiologic findings. Diagnostic injection techniques are employed to isolate the source(s) of pain. Facet or zygapophysial joint pain is an example of spinal pain diagnosed by local anesthetic injections of the facet joint or its nerve supply. Diagnostic facet joint injections are expected to meet the cardinal features of a diagnostic test (i.e., accuracy, safety and reproducibility). Accuracy must be compared with a "gold" or criterion standard that can confirm presence or absence of a disease. There is, however, no available gold standard, such as biopsy, to measure presence or absence of pain. Hence, there is a degree of uncertainty concerning the accuracy of diagnostic facet joint injections. ⋯ The evidence obtained from literature review suggests that controlled comparative local anesthetic blocks of facet joint nerves (medial branch or dorsal ramus) are reproducible, reasonably accurate, and safe. The sensitivity, specificity, false-positive rates, and predictive values of these diagnostic tests for neck and low back pain have been validated and reproduced in multiple studies.
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Enthesopathies are a common cause of axial pain that is amenable to "minimally invasive" therapy. ⋯ Injection therapy of painful enthesopathies can provide significant relief of axial pain and tenderness combined with functional improvement, even in "failed back syndrome" patients. Phenol-glycerol prolotherapy provides better and longer lasting relief than injection with anesthetics alone. Prolotherapy provides over six months of relief for some patients but generally provides relief for only a few months. However, most patients described good to excellent relief, felt that the injections had been beneficial, and requested additional injections for recurrent or residual focal pain.
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Transforaminal epidural injections, or selective nerve root blocks, are used for a myriad of different spinal disorders. A clear consensus on the use of selective nerve root injections as a diagnostic tool does not currently exist. Additionally, the effectiveness of this procedure as a diagnostic tool is not clear. ⋯ Selective nerve root injections may be helpful as a diagnostic addition in evaluating spinal disorders with radicular features, but the role of this diagnostic test needs to be further clarified by additional research and consensus on technique.