Pain
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Although evidence shows that several dopamine neurotransmission pathway genes are associated with specific clinical pain syndromes, such as fibromyalgia, chronic headache, and postoperative pain, the exact role of dopamine in pain processing is not fully understood. The aim of this study was to explore the relationship between functional polymorphisms in dopaminergic candidate genes and sensitivity to pain in healthy subjects. Healthy subjects (n=192; 105 F, 87 M) were exposed to experimental tonic cold pain (1 degrees C) and phasic heat pain (47 degrees C) stimuli. ⋯ Significant associations between cold pain tolerance and DAT-1 (p=0.008) and MAO-A (p=0.024) polymorphisms were found. Specifically, tolerance was shorter for carriers of allele 10 and the rarer allele 11, as compared to homozygous for allele 9, and for carriers of allele 4 as compared to homozygous for allele 3, respectively. These results, together with the known function of the investigated candidate gene polymorphisms, suggest that low dopaminergic activity can be associated with high pain sensitivity and vice versa.
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Randomized Controlled Trial
Reliability and validity of observer ratings of pain using the visual analog scale (VAS) in infants undergoing immunization injections.
We tested the reliability and validity of observer-rated pain in infants undergoing immunization using the visual analog scale (VAS). Pain was assessed in real time and later, from videotapes, in 120 1-year-old infants participating in a double-blind randomized controlled trial of amethocaine vs. placebo. Altogether, 2 (1 physician, 1 non-physician) of 4 raters [2 physicians, 2 non-physicians (nurse and graduate student)] independently assessed baseline and vaccine injection pain using a 100mm unmarked VAS line. ⋯ Together, these results provide initial support for the VAS as an outcome measure for acute procedural pain in infants. However, different conclusions may be reached about the effectiveness of analgesic interventions depending on the rater. Sources of variability include use of multiple raters, rater focus (procedure vs. child) and experience level.
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Clinical Trial
Clinical and endocrinological changes after electro-acupuncture treatment in patients with osteoarthritis of the knee.
Neurobiological mechanisms invoking the release of endogenous opioids and depression of stress hormone release are believed to be the basis of acupuncture analgesia. This study compared plasma beta-endorphin and cortisol levels with self assessment scores of intensity of pain, before and after 10 days of electro-acupuncture treatment in patients suffering from chronic pain as a result of osteoarthritis knees. Forty patients of either sex over 40 years with primary osteoarthritis knee were recruited into a single-blinded, sham-controlled study. ⋯ Following electro-acupuncture treatment there was a significant improvement in WOMAC index and VAS (p=0.001), a significant rise in plasma beta-endorphin (p=0.001), and a significant fall in plasma cortisol (p=0.016). In conclusion electro-acupuncture resulted in an improvement in pain, stiffness and disability. Of clinical importance is that an improvement in objective measures of pain and stress/pain associated biomarkers was shown above that of a sham treatment; hence demonstrating acupuncture associated physiological changes beyond that of the placebo effects.
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Individual differences in sensitivity to fentanyl, a widely used opioid analgesic, can hamper effective pain treatment. Still controversial is whether the single nucleotide polymorphisms (SNPs) of the human OPRM1 gene encoding the mu-opioid receptor influence the analgesic effects of opioids. We examined associations between fentanyl sensitivity and the two SNPs, A118G and IVS3+A8449G, in the human OPRM1 gene in 280 Japanese patients undergoing painful orofacial cosmetic surgery, including bone dissection. ⋯ Furthermore, the IVS3+A8449G SNP in intron 3, which represents a complete linkage disequilibrium block with more than 30 SNPs from intron 3 to the 3' untranslated region, was associated with 24-h postoperative fentanyl requirements. Subjects carrying the minor G allele of the IVS3+A8449G SNP required significantly less fentanyl for 24-h postoperative pain control (median: 1.5microg/kg) compared with subjects not carrying this allele (median: 2.5microg/kg, p=0.010). Although further validation is needed, the present findings shed light on the involvement of OPRM1 3' untranslated region polymorphisms in fentanyl sensitivity in addition to the A118G SNP and open new avenues for personalized pain treatment with fentanyl.