Anesthesiology
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Butorphanol is an opioid analgesic with partial agonist actions at micro- and kappa-opioid receptors (MOR and KOR). Previous studies have demonstrated that both MOR antagonists and KOR agonists are effective in alleviating intrathecal morphine-induced itch in primates. The aim of the study was to investigate the effectiveness of butorphanol as an antipruritic and to elucidate the receptor mechanisms underlying butorphanol's antipruritic effect in primates. ⋯ Butorphanol is effective in attenuating systemic or spinal morphine-induced itch without reducing morphine analgesia. This study provides functional evidence that both partial MOR and KOR agonist actions contribute to the effectiveness of butorphanol as an antipruritic in primates.
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Randomized Controlled Trial
Influence of administration rate on propofol plasma-effect site equilibration.
The authors hypothesized a difference in plasma-effect site equilibration, depicted by a first-order constant k(e0), depending on the injection rate of propofol. ⋯ Propofol plasma-effect site equilibration occurs more rapidly after a bolus than after rapid infusion, based on the electroencephalogram as a drug effect measure, mostly because of misspecification of the pharmacokinetic model in the first minutes after bolus.
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Whether patients who subsequently develop early postoperative delirium have a genetic predisposition that renders them at risk for postoperative delirium has not been determined. ⋯ Apolipoprotein e4 carrier status was associated with an increased risk for early postoperative delirium after controlling for known demographic and clinical risk factors. These results suggest that genetic predisposition plays a role and may interact with anesthetic/surgical factors contributing to the development of early postoperative delirium.
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Clinical Trial
Differential contribution of sodium channel subtypes to action potential generation in unmyelinated human C-type nerve fibers.
Multiple voltage-dependent sodium channels (Na(v)) contribute to action potentials and excitability of primary nociceptive neurons. The aim of the current study was to characterize subtypes of Na(v) that contribute to action potential generation in peripheral unmyelinated human C-type nerve fibers. ⋯ These data indicate that more than one type of Na(v) contributes to the generation of action potentials in unmyelinated human C-type nerve fibers. The peak height of an action potential produced by a short electrical impulse is dependent on the activation of tetrodotoxin-resistant ion channels. In contrast, membrane threshold and action potential peak height at the end of a slow membrane depolarization are regulated by a subtype of Na(v) with high sensitivity to low concentrations of tetrodotoxin, lidocaine, and mexiletine. The electrophysiologic and pharmacologic characteristics may indicate the functional activity of the Na(v) 1.7 subtype of voltage-dependent sodium channels.
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Chronic pain models are commonly defined as either nerve-injury or inflammation models, but recent work suggests inflammatory processes are important in nerve injury-induced pain. ⋯ Several components of the spinal nerve injury model are responsive to corticosteroid, suggesting inflammatory processes are important in the development of neuropathic pain. The observation that TA was effective when given starting at the time of injury suggests that steroid treatment might alter the development of chronic pain after surgical procedures that involve nerve injury, such as amputation or hernia repair.