Anesthesiology
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Randomized Controlled Trial Clinical Trial
Effects of combining propofol and alfentanil on ventilation, analgesia, sedation, and emesis in human volunteers.
Propofol and alfentanil frequently are administered together for intravenous sedation. This study investigated pharmacokinetic and pharmacodynamic interactions between propofol and alfentanil, at sedative concentrations, with specific regard to effects on ventilation, analgesia, sedation, and nausea. ⋯ The combination of propofol and alfentanil produced greater sedation and analgesia than that with either drug alone. Propofol offset the emetic effects of alfentanil. Equivalent depression of the carbon dioxide response curve, and elevation of end-tidal carbon dioxide occurred with propofol/alfentanil combined and alfentanil.
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Comparative Study
Adult rat brain-slice preparation for nuclear magnetic resonance spectroscopy studies of hypoxia.
When perfused neonatal brain slices are studied ex vivo with nuclear magnetic resonance (NMR) spectroscopy, it is possible to use 31P detection to monitor levels of intracellular adenosine triphosphate (ATP), cytosolic pH, and other high-energy phosphates and 1H detection to monitor lactate and glutamate. Adult brain slices of high metabolic integrity are more difficult to obtain for such studies, because the adult cranium is thicker, and postdecapitation revival time is shorter. A common clinical anesthesia phenomenon--loss of temperature regulation during anesthesia, with surface cooling and deep hypothermia, was used to obtain high-quality adult rat cerebrocortical slices for NMR studies. ⋯ Perfused, respiring adult brain slices having intact metabolic function can be obtained for NMR spectroscopy studies. Such studies have higher spectral resolution than can be obtained in vivo. During such NMR experiments, one can deliver drugs or molecular probes to brain cells and obtain brain tissue specimens for histologic and immunochemical measures of injury. Important ex vivo NMR spectroscopy studies that are difficult or impossible to perform in vivo are feasible in this model.
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Comparative Study Clinical Trial
Prediction of movement during propofol/nitrous oxide anesthesia. Performance of concentration, electroencephalographic, pupillary, and hemodynamic indicators.
Movement in response to painful stimulation is the end point classically used to assess the potency of anesthetic agents. In this study, the ability of modeled propofol effect-site concentration to predict movement in volunteers during propofol/nitrous oxide anesthesia was tested, then it was compared with the predictive abilities of the Bispectral Index and 95% spectral edge frequency of the electroencephalogram, pupillary reflex amplitude, and systolic arterial blood pressure. In addition, the relationships between simple end points of loss and recovery of consciousness, and pupillary, hemodynamic, and propofol concentration indicators were studied. ⋯ Indicators of pharmacodynamic effect, such as the electroencephalogram, pupillary light reflex, and systolic arterial blood pressure, predict movement as well as effect-site concentration during propofol/nitrous oxide anesthesia. Loss and return of the eyelash reflex correspond to a deeper level of anesthesia than syringe-dropping or recall of the birth date.
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Comparative Study Clinical Trial
Electroencephalogram bispectral analysis predicts the depth of midazolam-induced sedation.
The electroencephalogram (EEG) has been used to study the effects of anesthetic and analgesic drugs on central nervous system function. A prospective study was designed to evaluate the accuracy of various EEG parameters for assessing midazolam-induced sedation during regional anesthesia. ⋯ The EEG-BI appears to be a useful parameter for assessing midazolam-induced sedation and can predict the likelihood of a patient responding to verbal commands or to shaking of the head during midazolam-induced sedation.
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Comparative Study
Comparison of the spinal actions of the mu-opioid remifentanil with alfentanil and morphine in the rat.
mu-Opioids administered spinally produce a potent, dose-dependent analgesic response in preclinical and clinical investigations. Side-effect profile of these compounds may be altered as a function of pharmacokinetics. The effects of intrathecal and intraperitoneal remifentanil, an esterase-metabolized mu opioid, alfentanil, and morphine were compared. ⋯ These observations indicate that remifentanil has a powerful spinal opioid action. Consistent with its lipid-solubility, it has an early onset like alfentanil but displays a shorter duration of action after bolus delivery. Despite lipid solubility, remifentanil has a significant spinal therapeutic ratio. These observations likely reflect the rapid inactivation of systemically redistributed agent by plasma esterases.