Pain physician
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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
Transversus abdominis plane neurolysis with phenol in abdominal wall cancer pain palliation.
Pain is commonly perceived by patients during cancer and its treatment. Although most patients respond to conservative management implemented according to the World Health Organization guidelines, a subset of patients with advanced disease develop intractable pain that may require additional interventions such as regional blocks and intrathecal therapy. Patients with terminal abdominal or pelvic cancer who have high tumor burdens are often offered a diagnostic visceral nerve block followed by neurolysis for pain palliation. ⋯ The patient tolerated the procedure well and demonstrated sustained analgesia for 45 days before dying of the disease. We also demonstrated that TAP block significantly reduces the total opioid requirement as demonstrated by the morphine equivalent daily dose score after the neurolytic procedure. This result supports our belief that TAP block with TAP neurolysis is an effective and inexpensive modality that can be used to palliate intractable abdominal wall pain in patients with terminal abdominal cancer.
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Several studies have described pain prevalence, risk factors, pain and medical variables in spinal cord injury (SCI) populations. In this study on traumatic SCI in Turkey, we surveyed the neuropathic pain experiences during in-patient rehabilitation and defined the relationships between neuropathic pain and demographic and SCI characteristics of patients. ⋯ We found the neuropathic pain due to SCI to be mostly below the lesion level with a burning or aching character and we did not find a significant relationship between the demographic and SCI-related characteristics of the patient and the pain characteristics.