Anesthesiology
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Previous studies in which volatile anesthetics were exposed to small amounts of dry soda lime, generally controlled at or close to ambient temperatures, have demonstrated a large carbon monoxide (CO) production from desflurane and enflurane, less from isoflurane, and none from halothane and sevoflurane. However, there is a report of increased CO hemoglobin in children who had been induced with sevoflurane that had passed through dry soda lime. Because this clinical report appears to be inconsistent with existing laboratory work, the authors investigated CO production from volatile anesthetics more realistically simulating conditions in clinical absorbers. ⋯ The absorbent temperature increased with all anesthetics but was highest for sevoflurane. The reported magnitude of CO formation from desflurane, enflurane, and isoflurane was confirmed. In contrast, a smaller but significant CO formation from sevoflurane was found, which may account for the CO hemoglobin concentrations reported in infants. With all agents, CO formation appears to be self-limited.
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Clinical Trial
Relation of the static compliance curve and positive end-expiratory pressure to oxygenation during one-lung ventilation.
Positive end-expiratory pressure (PEEP) is commonly applied to the ventilated lung to try to improve oxygenation during one-lung ventilation but is an unreliable therapy and occasionally causes arterial oxygen partial pressure (PaO(2)) to decrease further. The current study examined whether the effects of PEEP on oxygenation depend on the static compliance curve of the lung to which it is applied. ⋯ The effects of the application of external 5 cm H(2)O PEEP on oxygenation during one-lung ventilation correspond to individual changes in the relation between the plateau end-expiratory pressure and the inflection point of the static compliance curve. When the application of PEEP causes the end-expiratory pressure to increase from a low level toward the inflection point, oxygenation is likely to improve. Conversely, if the addition of PEEP causes an increased inflation of the ventilated lung that raises the equilibrium end-expiratory pressure beyond the inflection point, oxygenation is likely to deteriorate.
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A recent study showed that inhaled furosemide greatly improves experimentally induced dyspnea in humans. The objective of the current study is to test the hypothesis that inhaled furosemide suppresses the behavioral response to airway occlusion without changing the behavioral response to a somatic noxious stimulus in anesthetized animals. ⋯ Inhaled furosemide suppressed the behavioral response to airway occlusion in anesthetized animals without affecting the response to somatic noxious stimulus. The authors' animal model of respiratory distress may be applicable to the study of dyspnea in regard to its mechanism and treatment.
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Levobupivacaine, the single levorotatory isomer of bupivacaine, is now available for clinical use. This study was undertaken to determine whether pregnancy affects the systemic toxicity of levobupivacaine and to compare the systemic toxicity of levobupivacaine with that of bupivacaine and ropivacaine. ⋯ Pregnancy increases the risk of convulsions but not of more advanced manifestations of local anesthetic toxicity. The risk of toxicity is greatest with bupivacaine and least with ropivacaine. However, in actual clinical practice, the risk of systemic toxicity may also be affected by the relative potency and effectiveness of these drugs.
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Local anesthetics that produce analgesia of long duration with minimal impairment of autonomic functions are highly desirable for pain management in the clinic. Prenylamine is a known calcium channel blocker, but its local anesthetic blocking effects on voltage-gated sodium channels have not been studied thus far. ⋯ The data presented here demonstrate that prenylamine possesses local anesthetic properties in vitro and elicits prolonged local anesthesia in vivo.