Anesthesiology
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Acute respiratory failure may develop in patients with chronic obstructive pulmonary disease because of intrinsic positive end-expiratory pressure (PEEPi) and increased resistive and elastic loads. Proportional assist ventilation is an experimental mode of partial ventilatory support in which the ventilator generates flow to unload the resistive burden (flow assistance: FA) and volume to unload the elastic burden (volume assistance: VA) proportionally to inspiratory muscle effort, and PEEPi can be counterbalanced by application of external PEEP. The authors assessed effects of proportional assist ventilation and optimal ventilatory settings in patients with chronic obstructive pulmonary disease and acute respiratory failure. ⋯ Application of PEEP to counterbalance PEEPi and FA to unload the resistive burden provided the optimal conditions in such patients. Ventilator over-assistance and patient-ventilator asynchrony was observed when VA was added to this setting. The clinical use of proportional assist ventilation should be based on continuous measurements of respiratory mechanics.
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Randomized Controlled Trial Clinical Trial
Local anesthetic administration for awake direct laryngoscopy. Are glossopharyngeal nerve blocks superior?
Glossopharyngeal nerve (GPN) blocks may provide reliable analgesia for awake direct laryngoscopy, although this has not been evaluated prospectively. This study was designed to determine if GPN blocks provide a superior route of local anesthetic administration for awake direct laryngoscopy as measured by hemodynamic, gag, and subjective pain responses. ⋯ Glossopharyngeal nerve blocks do not provide a superior route of local anesthetic administration for awake direct laryngoscopy. Two minutes of 2% viscous lidocaine S&G followed by 10% lidocaine spray was the anesthetic route preferred by participants and laryngoscopists.
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The pharmacokinetics and pharmacodynamics of remifentanil were studied in 65 healthy volunteers using the electroencephalogram (EEG) to measure the opioid effect. In a companion article, the authors developed complex population pharmacokinetic and pharmacodynamic models that incorporated age and lean body mass (LBM) as significant covariates and characterized intersubject pharmacokinetic and pharmacodynamic variability. In the present article, the authors determined whether remifentanil dosing should be adjusted according to age and LBM, or whether these covariate effects were overshadowed by the interindividual variability present in the pharmacokinetics and pharmacodynamics. ⋯ Based on the EEG model, age and LBM are significant demographic factors that must be considered when determining a dosage regimen for remifentanil. This remains true even when interindividual pharmacokinetic and pharmacodynamic variability are incorporated in the analysis.
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Due to potential neurologic sequelae, the risk:benefit ratio of thoracic epidural analgesia is controversial. Surprisingly, however, few available data address neurologic complications. The incidence of neurologic complications occurring after thoracic epidural catheterization was studied in patients scheduled for abdominal or abdominothoracic surgery. ⋯ Thoracic epidural catheterization for abdominal and thoracoabdominal surgery is not associated with a high incidence of serious neurologic complications. In fact, the incidence of puncture- and catheter-related complications is less in the mid and upper than in lower thoracic region, and the predicted maximum risk for permanent neurologic complications (upper bound of the 95% confidence interval) is 0.07%.
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Brief ischemic periods render the myocardium resistant to infarction from subsequent ischemic insults by a process called ischemic preconditioning. Volatile anesthetics have also been shown to be cardioprotective if administered before ischemia. The effect of preconditioning alone and combined with halothane or isoflurane on hemodynamic recovery and preservation of adenosine triphosphate content in isolated rat hearts was evaluated. ⋯ The results indicate that preconditioning, halothane, and isoflurane provide significant protection against ischemia. The combination of preconditioning and halothane or isoflurane did not improve hemodynamic recovery but did increase preservation of adenosine triphosphate.