Anesthesiology
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Recent clinical studies suggest that the magnitude of the second gas effect is considerably greater on arterial blood partial pressures of volatile agents than on end-expired partial pressures, and a significant second gas effect on blood partial pressures of oxygen and volatile agents occurs even at relatively low rates of nitrous oxide uptake. We set out to further investigate the mechanism of this phenomenon with the help of mathematical modeling. ⋯ Modeling of ventilation-perfusion inhomogeneity confirms that the second gas effect is greater in blood than in expired gas. Gas-based minimum alveolar concentration readings may therefore underestimate the depth of anesthesia during nitrous oxide anesthesia with volatile agents. The effect on minimum alveolar concentration is likely to be most pronounced for the less soluble volatile agents in current use.
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Ketamine is a general anesthetic thought to act by antagonizing N-methyl-D-aspartate receptors. However, ketamine acts on multiple channels, many of which are potential targets-including hyperpolarization-activated cyclic nucleotide-gated and potassium channels. In this study we tested the hypothesis that potassium leak channels contribute to the anesthetic action of ketamine. ⋯ The results of this study show that mechanisms additional to hyperpolarization-activated cyclic nucleotide-gated channel block are likely to explain the anesthetic action of ketamine and suggest facilitatory action at two-pore potassium leak channels.
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Patients with early stage tongue cancer do not frequently complain of tongue pain. Endothelin-1 signaling is upregulated in the cancerous tongue at the early stage. We tested the hypothesis that endothelin-1 signaling contributes to the modulation of tongue nociception. ⋯ β-Endorphin released from the cancer cells via endothelin-1 signaling is involved in analgesic action in mechanical hypersensitivity at the early stage.
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The authors hypothesized that low tidal volume (VT) would minimize ventilator-induced lung injury regardless of the degree of mechanical power. The authors investigated the impact of power, obtained by different combinations of VT and respiratory rate (RR), on ventilator-induced lung injury in experimental mild acute respiratory distress syndrome (ARDS). ⋯ In experimental mild ARDS, even at low VT, high mechanical power promoted ventilator-induced lung injury. To minimize ventilator-induced lung injury, low VT should be combined with low power.
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Systemic toxicity of local anesthetics is predominantly complicated by their myocardial toxicity. Especially long-acting local anesthetics exert a negative inotropic effect that has been described at lower concentrations than defined for blockade of myocardial ion channels. We evaluated the negative inotropic effect of bupivacaine at a concentration described for clinical toxicity testing the hypothesis that negative inotropy is a result of reduced Ca sensitivity rather than blockade of ion channels. ⋯ We provide evidence that the negative inotropic effect of bupivacaine may be caused mainly by a reduction in myofilament sensitivity to Ca.