Pain physician
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Intrathecal drug delivery (IDD) and spinal cord stimulator (SCS) systems are implantable devices for the management of both chronic and cancer pain. Although these therapies have favorable long-term outcomes, they are associated with occasional complications including infection. The incidence of infectious complications varies from 2 - 8% and frequently requires prolonged antibiotics and device revision or removal. Cancer patients are particularly susceptible to infectious complications because they are immunocompromised, malnourished, and receiving cytotoxic cancer-related therapies. ⋯ The experience of this tertiary cancer pain center demonstrates that infectious complications following implantation of IDD and SCS systems are relatively rare events in cancer patients. Contrary to our initial hypothesis, no difference was found in the infection rate between cancer and non-cancer patients. The main factor associated with increased risk of infectious complications was increased surgical time, indicating a need to minimize patient time in the operating room. The low infectious complication rate seen in this series compared to previous reports in non-cancer patients is likely multifactorial in nature.
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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.
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For more than 3 decades, spinal cord stimulation (SCS) has successfully been employed to treat neuropathic pain. Psychological factors are assumed to be important for the efficacy of SCS. However, the impact of psychological factors on the outcome of SCS has only rarely been studied. ⋯ The outcome of SCS therapy could not be predicted on the basis of tested psychological factors anxiety/depression and pain-related disability. FESS correlated inversely with HADS-D, BDI-II, and PDI scores and showed a tendency towards correlation with the percentage of pain reduction. Further research is needed to define the impact of psychological factors on SCS outcomes.
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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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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.