Anesthesiology
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Randomized Controlled Trial Clinical Trial
Oral clonidine premedication does not alter the efficacy of simulated intravenous test dose containing low dose epinephrine in awake volunteers.
Clonidine premedication modifies the hemodynamic responses to sympathomimetics. The present study was designed to test whether clonidine altered the response to a small intravenous dose of epinephrine, such as that which might be used in an epidural test dose. ⋯ Oral clonidine does not alter the efficacy of epinephrine-containing test doses used for detecting intravascular injection.
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The authors tested the hypothesis that isoflurane directly preconditions myocardium against infarction via activation of K(ATP) channels and that the protection afforded by isoflurane is associated with an acute memory phase similar to that of ischemic preconditioning. ⋯ Isoflurane directly preconditions myocardium against infarction via activation of K(ATP) channels in the absence of hemodynamic effects and exhibits acute memory of preconditioning in vivo.
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A knowledge of the distribution of different fluids given by intravenous infusion is basic to the understanding of the effects of fluid therapy. Therefore, a mathematical model was tested to analyze the volume kinetics of three types of fluids. ⋯ The distribution of intravenous fluids can be analyzed by a kinetic model adapted for fluid spaces, but slightly different results are obtained, depending on the marker used to indicate dilution of the primary fluid space. Analysis and simulation of plasma volume expansion by this model is a tool that can help the anesthetist to better plan fluid therapy.
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The intrathecal alpha2-adrenergic agonist, clonidine, has been shown to have considerable antinociceptive effect, although clonidine causes hypotension and bradycardia. The combination of intrathecal clonidine and local anesthetics enhances analgesic effects, whereas the combination may cause marked hypotension and motor blockade, which may limit the clinical application of the combination. Tizanidine, another alpha2-adrenergic agonist, has also provided antinociception without producing pronounced hemodynamic changes. This study was designed to evaluate the antinociceptive and hemodynamic interactions of tizanidine and clonidine with lidocaine. ⋯ The authors' results show that intrathecal tizanidine and clonidine synergistically interact with lidocaine so that the degree of antinociception to somatic noxious stimuli are enhanced. The antinociceptive synergistic interaction between tizanidine and lidocaine may be useful in clinical practice without affecting blood pressure, heart rate, or motor function.