Anesthesiology
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In doses typically administered during conscious sedation, remifentanil may be associated with ventilatory depression. However, the time course of ventilatory depression after an initial dose of remifentanil has not been determined previously. ⋯ After administration of 0.5 microg/kg remifentanil, there was a decrease in slope and downward shift of the carbon dioxide ventilatory response curve. This reached its nadir approximately 2.5 min after injection, consistent with the computed onset half-time of 2.9 min. The onset of respiratory depression appears to be somewhat slower than previously reported for the onset of remifentanil-induced electroencephalographic slowing. Recovery of ventilatory drive after a small dose essentially was complete within 15 min.
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Comparative Study
Differential effects of anesthetic and nonanesthetic cyclobutanes on neuronal voltage-gated sodium channels.
Despite their key role in the generation and propagation of action potentials in excitable cells, voltage-gated sodium (Na+) channels have been considered to be insensitive to general anesthetics. The authors tested the sensitivity of neuronal Na+ channels to structurally similar anesthetic (1-chloro-1,2,2-trifluorocyclobutane; F3) and nonanesthetic (1,2-dichlorohexafluorocyclobutane; F6) polyhalogenated cyclobutanes by neurochemical and electrophysiologic methods. ⋯ The anesthetic cyclobutane F3 significantly inhibited Na+ channel-mediated glutamate release and increases in [Ca2+]i. In contrast, the nonanesthetic cyclobutane F6 had no significant effects at predicted anesthetic concentrations. F3 inhibited dorsal root ganglion neuron Na+ channels with a potency and by mechanisms similar to those of conventional volatile anesthetics; F6 was less effective and did not produce voltage-dependent block. This concordance between anesthetic activity and Na+ channel inhibition supports a role for presynaptic Na+ channels as targets for general anesthetic effects and suggests that shifting the voltage-dependence of Na+ channel inactivation is an important property of volatile anesthetic compounds.
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Females have worse outcome than do males after coronary artery bypass grafting; however, gender effects on length of stay (LOS) outcomes, such as duration of intubation or intensive care unit (ICU) LOS, have not been evaluated previously. The authors hypothesized that adjustment for pertinent preoperative covariates would eliminate any significant effect of gender on duration of intubation, LOS in the ICU after extubation, total ICU LOS, postoperative (exclusive of ICU) LOS, or total postoperative LOS. ⋯ Even in the context of accelerated recovery programs, these analyses show that female sex has powerful associations with increased LOS intervals for coronary artery bypass grafting surgery, even after adjustment for preoperative covariates. These effects could result from differences in the ways in which men and women respond to coronary artery disease, anesthesia, and coronary artery bypass grafting surgery, or to bias on the part of healthcare workers.
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Dynamic intraesophageal pressure (Pes) is used to estimate intrapleural pressure (Ppl) to calculate lung compliance and resistance. This study investigated the nonhuman primate Ppl-Pes tissue barrier frequency response and the dynamic response requirements of Pes manometers. ⋯ In monkeys, the Ppl-Pes tissue barrier has a frequency response suitable for Ppl estimation during low-frequency mechanical ventilation, and Pes manometers should have a minimum uniform frequency response up to 8.5 Hz. However, the Ppl-Pes tissue barrier adversely affects the accurate estimation of dynamic Ppl at high frequencies, with varied airway pressure amplitudes and offsets, such as the Ppl encountered during high-frequency oscillatory ventilation.
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Isoflurane depresses the electroencephalographic (EEG) activity and exerts part of its anesthetic effect in the spinal cord. The authors hypothesized that isoflurane would indirectly depress the EEG and subcortical response to noxious stimulation in part by a spinal cord action. ⋯ Isoflurane blunted the EEG and MRF-thalamic response to noxious stimulation in part via an action in the spinal cord.