Anesthesia and analgesia
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Anesthesia and analgesia · Sep 2011
Randomized Controlled TrialAn exploration of remifentanil-propofol combinations that lead to a loss of response to esophageal instrumentation, a loss of responsiveness, and/or onset of intolerable ventilatory depression.
Remifentanil and propofol are increasingly used for short-duration procedures in spontaneously breathing patients. In this setting, it is preferable to block the response to moderate stimuli while avoiding loss of responsiveness (LOR) and intolerable ventilatory depression (IVD). In this study, we explored selected effects of combinations of remifentanil-propofol effect-site concentrations (Ces) that lead to a loss of response to esophageal instrumentation (EI), LOR, and/or onset of IVD. A secondary aim was to use these observations to create response surface models for each effect measure. We hypothesized that (1) in a large percentage of volunteers, selected remifentanil and propofol Ces would allow EI but avoid LOR and IVD, and (2) the drug interaction for these effects would be synergistic. ⋯ Selected remifentanil-propofol concentration pairs, especially higher propofol-lower remifentanil concentration pairs, can block the response to EI while avoiding IVD in spontaneously breathing volunteers. It is, however, difficult to block the response to EI and avoid both LOR and IVD. It may be necessary to accept some discomfort and blunt rather than block the response to EI to consistently avoid LOR and IVD.
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Anesthesia and analgesia · Sep 2011
Comparative StudyThe effect of ventilator performance on airway pressure release ventilation: a model lung study.
Using a model lung connected to six different ventilators, with each ventilator in the airway pressure release ventilation mode, we measured differences in intrinsic positive end-expiratory pressure (PEEPi) during the expiratory phase and calculated the inspiratory and expiratory pressure time product (PTP) as an index of work of breathing during the inspiratory phase. ⋯ PEEPi varied significantly among ventilators. Inspiratory and expiratory work of breathing varied between ventilators when spontaneous breathing occurred during the ventilator's inspiratory phase.
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Anesthesia and analgesia · Sep 2011
Comparative StudyThe ability of pulse pressure variations obtained with CNAP™ device to predict fluid responsiveness in the operating room.
Respiratory-induced pulse pressure variations obtained with an arterial line (ΔPP(ART)) indicate fluid responsiveness in mechanically ventilated patients. The Infinity® CNAP™ SmartPod® (Dräger Medical AG & Co. KG, Lübeck, Germany) provides noninvasive continuous beat-to-beat arterial blood pressure measurements and a near real-time pressure waveform. We hypothesized that respiratory-induced pulse pressure variations obtained with the CNAP system (ΔPP(CNAP)) predict fluid responsiveness as well as ΔPP(ART) predicts fluid responsiveness in mechanically ventilated patients during general anesthesia. ⋯ A value of ΔPP(CNAP) >11% has a sensitivity of at least 62% in predicting preload-dependent responders to VE in mechanically ventilated patients during general anesthesia.
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Anesthesia and analgesia · Sep 2011
Comparative StudyEnhanced analgesic responses after preferential delivery of morphine and fentanyl to the olfactory epithelium in rats.
Centrally acting opioid analgesics such as morphine and fentanyl are effective, but their efficacy is often limited by a delayed response or side effects resulting from systemic first pass before reaching the brain and the central nervous system (CNS). It is generally accepted that drugs applied to the nasal cavity can directly access the brain and the CNS, which could provide therapeutic advantages such as rapid onset and lower systemic exposure. The olfactory region of the nasal cavity has been implicated in facilitating this direct nose-to-CNS transfer. If the fraction of opioid administered to the olfactory region could be improved, there could be a larger fraction of drug directly delivered to the CNS, mediating greater therapeutic benefit. ⋯ Deposition of opioids to the olfactory region within the nasal cavity could have a significant impact on drug distribution and pharmacodynamic effect, and thus should be considered in future nasally administered opioid studies.
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Anesthesia and analgesia · Sep 2011
Gamma-aminobutyric acid type A receptor β3 subunit forebrain-specific knockout mice are resistant to the amnestic effect of isoflurane.
β3 containing γ-aminobutyric acid type A receptors (GABA(A)-Rs) mediate behavioral end points of IV anesthetics such as immobility and hypnosis. A knockout mouse with targeted forebrain deletion of the β3 subunit of the GABA(A)-R shows reduced sensitivity to the hypnotic effect of etomidate, as measured by the loss of righting reflex. The end points of amnesia and immobility produced by an inhaled anesthetic have yet to be evaluated in this conditional knockout. ⋯ These results suggest that β3 containing GABA(A)-Rs in the forebrain contribute to hippocampal-dependent memory suppressed by isoflurane, but not etomidate.