Anesthesiology
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Incisional pain is a common form of acute pain. Previously, the authors studied persistent pain behaviors caused by incisions, using animal models for postoperative pain. In this study, the authors measured tissue pH and hind paw temperature before and after incision to understand factors that may activate and sensitize nociceptors in the incision. ⋯ A decrease in pH occurs immediately after incision and is sustained for at least 4 days. During the period of decreased tissue pH, pain behaviors are evident. When the tissue pH returns to normal, pain behaviors are diminished. The decreased pH is localized at the incision site and not to areas surrounding the incision. Decreased pH likely contributes to nociceptor sensitization and pain related behaviors after incision. The magnitude of the pH change varies among tissues. An increase in hind paw skin temperature does not play a role in these pain-related behaviors.
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Clinical Trial
Lumbar plexus in children. A sonographic study and its relevance to pediatric regional anesthesia.
Pediatric regional anesthesia has gained increasing interest over the past decades. The current study was conducted to investigate the lumbar paravertebral region and the lumbar plexus at L3-L4 and L4-L5 by means of sonography to obtain fundamentals for the performance of ultrasound-guided posterior lumbar plexus blocks. ⋯ Sonography of the lumbar plexus in children proved to be feasible. Skin-plexus distances correlated with the children's weight rather than with their age. The sonographic findings were fundamental for the performance of successful ultrasound-guided posterior approaches in a small group of pediatric patients.
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Although clonidine is commonly combined with local anesthetics to extend duration of peripheral nerve block, the mechanism by which clonidine potentiates local anesthetic action in vivo is unclear. ⋯ The findings indicate that prolongation of duration of in vivo lidocaine nerve blockade by clonidine is not mediated by an alpha-adrenergic mechanism but likely involves the Ih current.
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Doses of volatile anesthetics around 0.3 minimum alveolar concentration (MAC) inhibit learning. However, threshold amnesic doses and relative potencies between agents are not well established. The authors determined amnesic potency in rats for four common volatiles and nitrous oxide. ⋯ Amnesic potency differs between agents; nitrous oxide is most potent and halothane is least potent relative to MAC. The amnesic threshold ranges from 0.06 to 0.3 MAC. The correlation between potency and oil:gas partition coefficients suggests a fundamental role for hydrophobicity in mediating amnesia, similar to its association with MAC. Some agents (e.g., halothane) may enhance aversive memory retention at doses typically encountered during emergence.