Anesthesiology
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Comparative Study Clinical Trial Controlled Clinical Trial
High thoracic epidural anesthesia does not alter airway resistance and attenuates the response to an inhalational provocation test in patients with bronchial hyperreactivity.
The functional relevance of an intact pulmonary sympathetic innervation for airway resistance is unknown. We therefore evaluated whether or not pulmonary sympathetic denervation by thoracic epidural anesthesia decreases the threshold of an inhalational provocation with acetylcholine in 20 patients with documented bronchial hyperreactivity scheduled for elective upper abdominal or thoracic surgery. ⋯ We conclude that in patients with bronchial hyperreactivity 1. blockade of pulmonary sympathetic innervation seems to be of no relevance for airway resistance and 2. both epidural and intravenous bupivacaine substantially attenuate the response to an inhalational provocation with acetylcholine.
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We previously described the use of the nematode Caenorabditis elegans as a genetic model for studying the mechanism of action of volatile anesthetics. All previous strains of C. elegans with altered responses to anesthetics have been identified by screening the response to halothane. The current study was designed to identify classes of mutations by screening for alterations in sensitivity to enflurane, isoflurane, and diethylether. ⋯ The interaction of these mutations indicates that multiple sites of anesthetic action exist and that there are at least three such sites. A pathway for control of sensitivity to volatile anesthetics is proposed.
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Clinical Trial Controlled Clinical Trial
Influence of a subanesthetic concentration of halothane on the ventilatory response to step changes into and out of sustained isocapnic hypoxia in healthy volunteers.
In humans the ventilatory response to isocapnic hypoxia is biphasic: an initial increase in minute ventilation (VE) from baseline, the acute hypoxic response, is followed after 3-5 min by a slow ventilatory decay, the hypoxic ventilatory decline, and a new steady state, 25-40% greater than baseline VE, is reached in about 15-20 min. The transition from 20 min of isocapnic hypoxia into normoxia results in a rapid decrease in VE, the off-response. In humans, halothane, at subanesthetic concentrations, is known to decrease the acute hypoxic response. In order to investigate the effects of halothane on sustained hypoxia we quantified the effects of 0.15 minimum alveolar concentration halothane on the ventilatory response at the onset of 20 min of hypoxia and at the termination of 20 min of hypoxia by normoxia in healthy volunteers. ⋯ Our results indicate that halothane caused VE to be less than control levels during acute and sustained hypoxia as well as when sustained hypoxia is replaced by normoxia. It is argued that the depression of VE during acute hypoxia is attributed to an effect of halothane on the peripheral chemoreceptors. During sustained hypoxia halothane had no effect on the magnitude of the hypoxic ventilatory decrease, which is probably related to an increase by halothane of inhibitory neuromodulators within the central nervous system. With halothane, the ventilatory decrease when sustained hypoxia is replaced by normoxia is related to the removal of the hypoxic drive at the site of the peripheral chemoreceptors.
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Comparative Study
In vitro modeling of spinal anesthesia. A digital video image processing technique and its application to catheter characterization.
Maldistribution of intrathecal local anesthetic has recently been implicated as a contributor to neurotoxic injury. In vitro modeling can be used to understand the distribution of anesthetic agents within the subarachnoid space. We describe an in vitro modeling technique that uses digital video image processing and its application to catheter injection of local anesthetic. ⋯ The digital video image processing technique can be used to quantify anesthetic distribution rapidly within a model of the subarachnoid space without disturbing the distribution. The current results demonstrate a strong dependence of anesthetic distribution on catheter angle, catheter size, and injection rate. Comparisons between 28-G catheters suggest that the difference in reported incidence of cauda equina syndrome associated with different 28-G catheters cannot be explained on the basis of differences in anesthetic distribution.
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Randomized Controlled Trial Comparative Study Clinical Trial
Prophylactic antiemetic treatment with ondansetron in children undergoing tonsillectomy.
Children undergoing tonsillectomy are at high risk for postoperative vomiting. This study was undertaken to compare ondansetron with metoclopramide and droperidol for the prevention of postoperative vomiting after tonsillectomy. ⋯ The intravenous administration of ondansetron 0.15 mg.kg-1 is highly effective in reducing postoperative emesis in children undergoing tonsillectomy. Metoclopramide and droperidol at the doses tested are ineffective in this population.