Anesthesiology
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Randomized Controlled Trial Clinical Trial
Naloxone, meperidine, and shivering.
Meperidine, which binds both mu and kappa opioid receptors, is reportedly more effective in treating shivering than are equianalgesic doses of morphine (a nearly pure mu-receptor agonist). Furthermore, butorphanol, a kappa-receptor agonist/antagonist, treats shivering better than does fentanyl, which mostly binds mu receptors. These data indicate that much of meperidine's special antishivering activity may be mediated by its kappa activity. Accordingly, the authors tested the hypothesis that the antishivering activity of meperidine will be minimally impaired by low-dose naloxone (blocking most mu-receptors), but largely prevented by high-dose naloxone (blocking all mu and most kappa receptors). ⋯ These data indicate that the antishivering property of meperidine is not fully mediated by mu-receptors. Although meperidine has well-known nonopioid actions, stimulation of kappa receptors seems a likely alternative explanation for much of the drug's antishivering action.
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Large studies reporting anesthetic outcome for morbidly obese parturients are lacking. This study compares the anesthetic and obstetric outcome in morbidly obese parturients and matched control parturients. ⋯ The high incidences of antepartum medical disease and emergency cesarean section complicate anesthetic care in the morbidly obese parturients. Epidural anesthesia is feasible; however, the high initial failure rate necessitates early catheter placement, critical block assessment and catheter replacement when indicated, and provision for alternative airway management.
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Etomidate exerts a mild, positive inotropic effect in rat ventricular myocardium, yet has a negative inotropic effect in isolated rabbit ventricular myocardium. The aim of this study was to investigate the mechanisms of etomidate's inotropic effect and its underlying mechanism in isolated ferret ventricular myocardium (which shows similar physiologic characteristics as human ventricular myocardium) and in frog ventricular myocardium, in which Ca++ ions for myofibrillar activation are derived almost entirely from transsarcolemmal influx. ⋯ These findings indicate that the direct negative inotropic effect of etomidate results from a decrease in intracellular Ca++ availability with no changes in myofibrillar Ca++ sensitivity. At least part of etomidate's action is caused by inhibition of transsarcolemmal Ca++ influx. Yet, these effects become apparent only at concentrations that are at least one order of magnitude larger than those encountered in clinical practice.
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Randomized Controlled Trial Clinical Trial
The interactions of midazolam and flumazenil on human memory and cognition.
Previous research has been unable to show unequivocally whether flumazenil can reverse completely, partially, or not at all the memory effects of benzodiazepines. The effects of midazolam on implicit memory are also unknown. The behavioral effects of flumazenil by itself, and the acute reversal of benzodiazepine effects, are also controversial. The current study was designed to investigate these questions. ⋯ Midazolam impairs explicit and implicit memory. Flumazenil reverses both the sedative and memory effects of the drug. Flumazenil, in the doses used, has no intrinsic actions.