Anesthesiology
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In contrast to hypnosis, there is no surrogate parameter for analgesia in anesthetized patients. Opioids are titrated to suppress blood pressure response to noxious stimulation. The authors evaluated a novel model predictive controller for closed-loop administration of alfentanil using mean arterial blood pressure and predicted plasma alfentanil concentration (Cp Alf) as input parameters. ⋯ The authors' controller has a similar set-point precision as previous hypnotic controllers and provides adequate alfentanil dosing during surgery. It may help to standardize opioid dosing in research and may be a further step toward a multiple input-multiple output controller.
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Flushing of radial arterial catheters may be associated with retrograde embolization of air or thrombus into the cerebral circulation. For embolization into the central circulation to occur, sufficient pressure must be generated during the flushing process to reverse antegrade blood flow in the arterial blood vessels of the upper extremity. This ultrasound study was designed to examine whether routine radial catheter flushing practices produce retrograde blood flow patterns in the brachial and proximal axillary arteries. ⋯ Rapid manual flushing of radial arterial catheters at rates faster than 1 ml/s produces retrograde flow in the proximal axillary artery.
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Intrathecal morphine infusion leads to intrathecal granulomas. In dogs, the authors examined time course of granuloma formation and the role of concentration in granuloma development. ⋯ Serial magnetic resonance imaging showed a rapid formation and regression of the masses initiated by intrathecal morphine infusion. These masses are dependent on local concentration.
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The gene unc-1 plays a central role in determining volatile anesthetic sensitivity in Caenorhabditis elegans. Because different unc-1 alleles cause strikingly different phenotypes in different volatile anesthetics, the UNC-1 protein is a candidate to directly interact with volatile anesthetics. UNC-1 is a close homologue of the mammalian protein stomatin, for which a mouse knockout was recently constructed. Because the stomatin gene is expressed in dorsal root ganglion cells, the authors hypothesized that the knockout would have an effect on anesthetic sensitivity in mice similar to that seen in nematodes. ⋯ Nematodes and mice with deletions of the stomatin gene both have increased sensitivity to diethyl ether. Neither nematodes nor mice with stomatin deficiencies have significantly altered sensitivity to isoflurane or halothane. The effects of stomatin deficiency cross phylogenetic boundaries and support the importance of this protein in anesthetic response and the use of C. elegans as a model for anesthetic action in mammals.
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The skin microcirculation may be evaluated noninvasively by laser Doppler flowmetry and iontophoresis with acetylcholine and sodium nitroprusside. Wavelet transform of the perfusion signal shows periodic oscillations of five characteristic frequencies in the interval 0.0095-1.6 Hz. The aim of the current study was to investigate alterations in skin microcirculation induced by brachial plexus block, with emphasis on the periodic oscillations. ⋯ Alterations in skin microcirculation induced by brachial plexus block can be evaluated by wavelet transform of the laser Doppler flowmetry signal. Brachial plexus block reduces the oscillatory components within the 0.0095- to 0.021- and 0.021- to 0.052-Hz intervals of the perfusion signal. These alterations are related to inhibition of sympathetic activity and a possible impairment of endothelial function.