Anesthesiology
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Volatile anesthetic agents can activate the S channel, a baseline potassium (K+) channel, of the marine mollusk Aplysia. To investigate whether cloned ion channels with electrophysiologic properties similar to the S channel (potassium selectivity, outward rectification, and activation independent of voltage) also are modulated by volatile anesthetic agents, the authors expressed the cloned yeast ion channel TOK1 (tandem pore domain, outwardly rectifying K+ channel) in Xenopus oocytes and studied its sensitivity to volatile agents. ⋯ TOK1 is a potassium channel that is stimulated by volatile anesthetic agents. The concentrations over which potentiation occurred (EC50 values) were higher than those commonly used in clinical practice (approximately twice MAC).
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Randomized Controlled Trial Clinical Trial
Isoflurane alters shivering patterns and reduces maximum shivering intensity.
Shivering can be characterized by its threshold (triggering core temperature), gain (incremental intensity increase with further core hypothermia), and maximum response intensity. Isoflurane produces a clonic muscular activity that is not a component of normal shivering. To the extent that clonic activity is superimposed on normal thermoregulatory shivering, the gain of shivering might be increased during isoflurane anesthesia. Conversely, volatile anesthetics decrease systemic oxygen consumption and peripherally inhibit skeletal muscle strength, which might limit maximum intensity despite central activation. The purpose of the present study was, therefore, to evaluate the effect of isoflurane shivering patterns and the gain and maximum intensity of shivering. ⋯ These data indicate that isoflurane anesthesia markedly changes the overall pattern of shivering during progressive hypothermia from a linear increase to an unusual saw-tooth pattern. They further suggest that clonic muscular activity combines with shivering to increase the initial gain of shivering during isoflurane anesthesia, but that isoflurane peripherally inhibits the maximum expression of shivering.
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Comparative Study Clinical Trial Controlled Clinical Trial
Awakening propofol concentration with and without blood-effect site equilibration after short-term and long-term administration of propofol and fentanyl anesthesia.
The propofol awakening concentration can vary. However, the effect site awakening propofol concentration will be a fixed value. The purpose of this study was to determine the awakening propofol concentrations obtained from infusion Schede using abrupt discontinuation of propofol (half-maximal effective concentration [EC50]) or a descending decrease in concentration to allow blood-effect site equilibration (EC50eq). ⋯ The EC50eq was independent of propofol infusion length, compared with the EC50. Thus the potential for hysteresis during emergence from propofol anesthesia was confirmed.
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Comparative Study Clinical Trial
The pharmacokinetics and steady state pharmacodynamics of mivacurium in children.
The authors previously showed that children require larger infusion rates of mivacurium than adults to maintain target twitch depression. Here, they determined whether there are differences between children and adults in mivacurium's pharmacokinetic and pharmacodynamic properties. ⋯ Clearance of mivacurium's potent isomers is larger in younger patients, consistent with the larger mivacurium infusion requirement in children than in adults reported previously.
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Comparative Study Clinical Trial
The relation between the platelet-activated clotting test (HemoSTATUS) and blood loss after cardiopulmonary bypass.
Platelet dysfunction is one of several major causes of bleeding after cardiopulmonary bypass. A timely, simple, point-of-care determinant of platelet function recently became available for clinical use. Adding platelet-activating factor to conventional activated clotting time methods (platelet-activated clotting test [PACT]) produces rapid results (<15 min) and may yield a measure of platelet responsiveness and whole-blood procoagulant activity. ⋯ The PT correlated with blood loss and transfusion requirements and was superior to PACT, aPTT, and platelet count for predicting excessive blood loss after cardiopulmonary bypass.