Anesthesiology
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Epidural anesthesia has an unpredictable extent and duration. Differences in the surface area of the lumbosacral dura, epidural fat volume, and epidural venous plexus velocity might explain the variability in the extent and duration of epidural anesthesia with ropivacaine. ⋯ These findings indicate that dural surface area influences the spread of epidural anesthesia with ropivacaine and posterior fat volume influences the duration of epidural anesthesia in healthy patients within a narrow age range. Epidural venous plexus velocity might also influence the duration of epidural anesthesia with ropivacaine.
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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.
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Randomized Controlled Trial Clinical Trial
Effect of clonidine on cardiovascular morbidity and mortality after noncardiac surgery.
Perioperative myocardial ischemia occurs in 20-40% of patients at risk for cardiac morbidity and is associated with a ninefold increase in risk of cardiac morbidity. ⋯ Perioperative administration of clonidine for 4 days to patients at risk for coronary artery disease significantly reduces the incidence of perioperative myocardial ischemia and postoperative death.