Anesthesiology
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Cardioplegia is used to protect the myocardium from ischemic injury during open-heart surgery. However, the delivery of cardioplegic solutions may be impaired by anatomic and/or functional conditions, such as the development of transient aortic regurgitation during antegrade administration of cardioplegia or shunting through a foramen ovale during retrograde administration. In this study, the authors used a new method of cardioplegia administration, based on intraoperative contrast echocardiography, to detect on-line causes of inadequate cardioplegia delivery. ⋯ This study shows that incomplete myocardial distribution of cardioplegia, secondary to transient aortic valve incompetence or shunting through the foramen ovale, is not uncommon in patients undergoing coronary surgery.
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There has been little systematic examination concerning the comparative effects of the anesthetized versus the awake state on outcome from cerebral ischemia. This experiment evaluated infarct volume and neurologic function in rats subjected to temporary focal ischemia while anesthetized with either sevoflurane or halothane. Outcome in these animals was compared to that observed in rats maintained unanesthetized during a similar ischemic insult. ⋯ Both halothane and sevoflurane substantially reduced damage in this focal ischemia model when compared to outcome resulting from the same insult induced in awake rats. The reduction in intraischemic mean arterial pressure caused by the anesthetics did not seem contributory to outcome. Brain temperature differences among the groups were not defined. Because small differences in pericranial temperature were shown to have major effects on outcome, further work is required to determine if differences in brain temperature explain the observed protective effects of these anesthetics.
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It generally is assumed that the potency of inhalational anesthetics remains unchanged during the course of the administration of an anesthetic. Only one study has indicated a decrease of minimum alveolar concentration with time. In this study, an effect of the duration of anesthesia administration and surgery on the potency of isoflurane was investigated by determining MACtetanus (the minimum alveolar concentration that prevents movement in response to electrical tetanic stimulation in 50% of patients) before and after surgery. ⋯ The authors conclude that MACtetanus decreases during the administration of anesthesia and the performance of surgery.
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Respiratory distress syndrome carries a high morbidity and mortality when treated with mechanical ventilation with positive end-expiratory pressure. Perfluorocarbon liquids are employed in liquid ventilation due to low surface tension and high gas solubility. To assess whether intratracheal administration of the perfluorocarbon, perflubron, in combination with conventional mechanical ventilation could be of therapeutic benefit in respiratory distress syndrome, the authors tested the effects of different doses of intratracheal perflubron administration on gas exchange and lung mechanics in adult animals with respiratory failure during a 6-h observation period. ⋯ The results of this study imply that there is no association between the lung mechanics and gas exchange parameters for mechanical ventilation in combination with intratracheal perfluorocarbon administration. The data suggest that this type of perfluorocarbon administration with conventional mechanical ventilation offers a simple, alternative treatment of respiratory distress syndrome. With this technique, adequate pulmonary gas exchange can be maintained at relatively low airway pressures with high perfluorocarbon doses for several hours.