Pain
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What’s the relevance?
Remifentanil’s ultrashort-acting kinetics have driven its growth as a reliable technique for maintaining intraoperative analgesia. It is now one of the most widely used synthetic opioids in anesthesia.
However these unique pharmacological characteristics are associated with both Opioid Induced Hyperalgesia and Acute Opioid Tolerance, and possibly increase the risk of chronic pain after surgery.
Details:
Niedermayer and team performed a large, multicenter, propensity-matched observational study of remifentanil use during intra-abdominal surgery, and its association with postoperative pain in the PACU. Importantly the patients receiving epidural analgesia in addition to TIVA GA were also included. Volatile GA was excluded.
Among 16,420 patients meeting inclusion criteria, 3,652 GA/TIVA patients received remifentanil and were matched to 3,318 controls, and 829 GA/epi received remifentanil, being matched to 631 controls. Mean remifentanil infusions rates were 0.11 and 0.13 mcg/kg/min for non-EA and EA groups respectively.
They showed:
Among GA-only patients, remifentanil was associated with higher PACU pain scores (both on arrival and discharge), greater analgesic requirements and more PONV – however there was no decrease of either time-to-extubation or PACU discharge.
Interestingly, the epidural analgesia cohort also showed higher PACU pain scores when receiving remifentanil.
The rapid nociceptive changes due to remifentil are well known, however real clincial consequences remain unclear. This large observational study highlights the detrimental analgesic effects of remifentanil in the most immediate post-op period, reminding anesthetists and anesthesiologists that gold-standard intraoperative analgesia may come at a cost.
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Explore collected articles answering: Is remifentanil associated with Opioid Induced Hyperalgesia and Acute Opioid Tolerance?
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Native Americans (NAs) have a higher prevalence of chronic pain than other U. S. racial/ethnic groups, but there have been few attempts to understand the mechanisms of this pain disparity. This study used a comprehensive battery of laboratory tasks to assess peripheral fiber function (cool/warm detection thresholds), pain sensitivity (eg, thresholds/tolerances), central sensitization (eg, temporal summation), and pain inhibition (conditioned pain modulation) in healthy, pain-free adults (N = 155 NAs, N = 150 non-Hispanic Whites [NHWs]). ⋯ There were no group differences on any measure, except that NAs had lower cold-pressor pain thresholds and tolerances, indicating greater pain sensitivity than NHWs. These findings suggest that there are no group differences between healthy NAs and NHWs on peripheral fiber function, central sensitization, or central pain inhibition, but NAs may have greater sensitivity to cold pain. Future studies are needed to examine potential within-group factors that might contribute to NA pain risk.
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Localizing pain is crucial because it allows for detecting which part of the body is being hurt and identifying in its surrounding which stimulus is producing the damage. Nociceptive inputs should therefore be mapped according to somatotopic ("which limb is stimulated?") and spatiotopic representations ("where is the stimulated limb?"). Because the body posture constantly changes, the brain has to realign the different spatial representations, for instance when the arms are crossed with the left hand in the right space and vice versa, to adequately guide actions towards the threatening object. ⋯ Relative to the uncrossed posture, sighted participants' performances were decreased when the hands were crossed, whatever the instruction be. Early blind participants' performances were affected by crossing the hands during spatial instruction, but not during anatomical instruction. These results indicate that nociceptive stimuli are automatically coded according to both somatotopic and spatiotopic representations, but the integration of the different spatial reference frames depends on early visual experience and ongoing cognitive goals, illustrating the plasticity and the flexibility of the nociceptive system.
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Meta Analysis
Intraoperative methadone administration and postoperative pain control: a systematic review and meta-analysis.
Postoperative pain is not adequately managed in greater than 40% of surgical patients and is a high priority for perioperative research. In this meta-analysis, we examined studies comparing postoperative opioid consumption and pain scores in surgical patients who received methadone by any route vs those who received another opioid by any route. Studies were identified from PubMed, Cochrane, Web of Science, EMBASE, and Scopus from January 1966 to November 2018. ⋯ The results demonstrate that surgical patients who received intraoperative methadone had lower postoperative opioid consumption, generally reported lower pain scores and experienced better satisfaction with analgesia. However, these advantages need to be weighed carefully against dangerous risks with perioperative methadone, specifically respiratory depression and arrhythmia. Future studies should explore logistics, safety, and cost effectiveness.
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Observational Study
Vitamin D insufficiency increases risk of chronic pain among African Americans experiencing motor vehicle collision.
African Americans experience an increased burden of motor vehicle collision (MVC), post-MVC musculoskeletal pain, and vitamin D insufficiency. In this prospective multicenter study, we tested the hypothesis that African Americans (n = 133) presenting to the emergency department after MVC with low peritraumatic vitamin D levels would have worse chronic musculoskeletal pain outcomes compared to individuals with sufficient vitamin D. Vitamin D levels were assessed in the early aftermath of MVC through enzyme-linked immunosorbent assay, and pain severity was assessed using the 0 to 10 numeric rating scale at 6 weeks, 6 months, and 1 year. ⋯ Secondary analyses suggest that the effect of vitamin D on post-MVC pain outcomes may be influenced by genetic variation in IL-10 and NLRP3. Further studies are needed to assess the impact of vitamin D insufficiency on pain outcomes in African Americans experiencing MVC and other common trauma exposures, to assess factors affecting this relationship, and to assess the efficacy of administering vitamin D in the immediate aftermath of MVC to prevent chronic pain. Such low-cost, nonopioid interventions are urgently needed to address chronic pain development after MVC.