Pain physician
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Patients with chronic whiplash associated disorders (WAD) demonstrate altered central pain processing and impaired endogenous analgesia. In addition, previous research reported disturbances in the autonomic nervous system and the presence of post-traumatic stress reaction in patients with chronic WAD. The autonomic nervous system, in particular the autonomic stress response, might modulate central pain processing in this population. ⋯ Results of this study refute autonomic dysfunction in response to pain in patients with chronic WAD. The autonomic nervous system activity or reactivity to acute pain appears unrelated to either pain thresholds or endogenous analgesia in patients with chronic WAD.
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Evidence for opioid-induced hyperalgesia (OIH) has been shown in animal and human studies, but the clinical implications of this phenomenon remain unclear. ⋯ The results of this study suggest that opioid medication is an important contributing factor to pain perception accompanying LA injection, and cancer patients using high-dose opioids may be highly susceptible to hyperalgesic responses to this clinical stimulus. We also suggest that the possible presence of OIH may be intensified among cancer patients with poor physical and psychosocial functional status.
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Case Reports
Using pulsed radiofrequency ablation to treat pain associated with a tumor involving the brachial plexus.
Pain associated with cancer is often difficult to treat, even more so when tumors involve peripheral nerves. Therapy is complex and often requires a multimodal approach that can include medications, radiation, and interventional techniques. These components are utilized with variable success, but are also limited by known complications or adverse effects. ⋯ Pulsed radiofrequency is a poorly understood technology that has increasing evidence for certain pain conditions; however, for cancer and peripheral nerves the evidence is slim to none. Our case presents a successful use for pain management of a brachial plexopathy due to a tumor. We propose that pulsed radiofrequency may present a non-neurodestructive pain management technique for tumors involving peripheral nerves, though more data is definitely needed.
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Meralgia paresthetica (MP) is a mononeuropathy of the lateral femoral cutaneous nerve (LFCN) characterized by pain, numbness or paresthesia on the anterolateral aspect of the thigh. Though several contributing factors have been identified, the cause of its idiopathic form still remains unclear. Anatomic and clinical studies have demonstrated a variable course for the LFCN and have suggested a contribution to the pathogenesis of MP. ⋯ The results of this study demonstrate a significantly different course of the LFCN, closer to the ASIS in patients with idiopathic MP.
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Postoperative pain management remains a challenge for clinicians due to unpredictable patient responses to opioid therapy. Some of this variability may result from single nucleotide polymorphisms (SNPs) of the human opioid mu-1 receptor (OPRM1) that modify receptor binding or signal transduction. The OPRM1 variant with the highest frequency is the A118G SNP. However, previous studies have produced inconsistent results regarding the clinical effects of A118G on opioid response. We hypothesized that measurement of serum opioid concentrations, in addition to determining total opioid consumption, may provide a more precise method of assessing the effects of A118G on analgesic response. The current study evaluated the relationship of analgesia, side effects, total hydrocodone consumption, quantitative serum hydrocodone and hydromorphone concentrations, and A118G SNP in postoperative patients following Cesarean section. ⋯ This study found a correlation between pain relief and total hydrocodone dose in patients homozygous for the 118A allele (AA) of the OPRM1 gene, but not in patients with the 118G allele (AG/GG). However, pain relief in 118A patients did not correlate with serum hydrocodone concentrations, but rather with serum hydromorphone levels, the active metabolite of hydrocodone. This suggests that pain relief with hydrocodone may be due primarily to hydromorphone. Although pain relief did not correlate with opioid dose in AG/GG patients, they had a higher incidence of opioid side effects. The correlations identified in this study may reflect the fact that serum opioid concentrations were measured directly, avoiding the inherent imprecision associated with relying solely on total opioid consumption as a determinant of opioid effectiveness. Thus, measurement of serum opioid concentrations is recommended when assessing the role of OPRM1 variants in pain relief. This study supports pharmacogenetic analysis of OPRM1 in conjunction with serum opioid concentrations when evaluating patient responses to opioid therapy.