Anesthesiology
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Comparative Study Clinical Trial Controlled Clinical Trial
A comparison of baroreflex sensitivity during isoflurane and desflurane anesthesia in humans.
Desflurane anesthesia has been associated with heart rate (HR) and sympathetic nerve activity (SNA) responses that differ from those during isoflurane anesthesia. Whether these differences might be due to better preservation by desflurane of the baroreceptor reflex control of HR or SNA in humans was examined. ⋯ Increasing MAC of desflurane and isoflurane anesthesia results in similar and progressive decreases in BP but dissimilar SNA and HR responses. These differences are not explained by disparate effects of these anesthetics on the baroreceptor reflex control of SNA or HR.
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Clinical Trial
The maximum depth of an atracurium neuromuscular block antagonized by edrophonium to effect adequate recovery.
The inability of edrophonium to rapidly reverse a deep nondepolarizing neuromuscular block may be due to inadequate dosage or a ceiling effect to antagonism of neuromuscular block by edrophonium. A ceiling effect means that only a certain level of neuromuscular block could be antagonized by edrophonium. Neuromuscular block greater than this could not be completely antagonized irrespective of the dose of edrophonium administered. The purpose of this study was to determine whether a ceiling effect occurred for antagonism of an atracurium-induced neuromuscular block by edrophonium and, if so, the maximum level of block that could be antagonized by edrophonium. ⋯ There is a maximum level of neuromuscular block that can be antagonized by edrophonium to effect adequate recovery. The level corresponds approximately to the reappearance of the fourth response to TOF stimulation. It is probably safest to wait until this level of block occurs before edrophonium is given for reversal. Earlier administration will not hasten recovery.
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Comparative Study
pH-stat management reduces the cerebral metabolic rate for oxygen during profound hypothermia (17 degrees C). A study during cardiopulmonary bypass in rabbits.
Greater cerebral metabolic suppression may increase the brain's tolerance to ischemia. Previous studies examining the magnitude of metabolic suppression afforded by profound hypothermia suggest that the greater arterial carbon dioxide tension of pH-stat management may increase metabolic suppression when compared with alpha-stat management. ⋯ At 17 degrees C, CMRO2 with pH-stat management is 35-40% less than that with alpha-stat management and is independent of CBF or arterial pressure differences between the techniques.
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Comparative Study
Myocyte contractile responsiveness after hypothermic, hyperkalemic cardioplegic arrest. Disparity between exogenous calcium and beta-adrenergic stimulation.
Acute left ventricular dysfunction is commonly encountered after hypothermic, hyperkalemic cardioplegic arrest (HHCA) and often requires inotropic intervention for successful separation from cardiopulmonary bypass. However, the basic mechanisms involved in depressed left ventricular function and the cellular basis for the differential effects of inotropic drugs after HHCA are unknown. Accordingly, the goal of this study was to determine the effects of calcium (Ca2+) and beta-adrenergic receptor agonists (beta AR) stimulation on isolated myocyte contractile function after HHCA. ⋯ The minimal improvement in myocyte contractile function after HHCA with increased extracellular Ca2+ suggests that Ca2+ depletion is not the primary mechanism for depressed myocyte contractility after HHCA. On the other hand, because beta AR administration improved myocyte contractile function after HHCA, the cellular basis for the effects of beta AR stimulation after HHCA is probably not increased myocyte Ca2+ but rather alternative mechanisms, such as changes in myofilament sensitivity to Ca2+. These results also suggest that the abnormalities in left ventricular function after HHCA result from the direct effects of hyperkalemic induced electromechanical uncoupling as well as relative hypoxic conditions.
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Clinical Trial
Effects of propofol sedation on seizures and intracranially recorded epileptiform activity in patients with partial epilepsy.
Case reports suggesting both pro- and anticonvulsant effect(s) of propofol have been published in recent years. The effects of sedative doses of propofol on epileptiform activities in patients suffering from intractable partial epilepsy were systematically investigated. ⋯ We were unable to demonstrate a significant change in epileptiform activity with sedative doses of propofol in patients suffering from complex partial epilepsy.