Anesthesiology
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Ligation injury of the L5/L6 nerve roots in rats produces behavioral signs representative of clinical conditions of neuropathic pain, including tactile allodynia and thermal and mechanical hyperalgesia. In this model, intrathecal morphine shows no antiallodynic activity, as well as decreased antinociceptive potency and efficacy. This study was designed to explore the antinociceptive activity of intrathecal clonidine alone or in combination with intrathecal morphine (1:3 fixed ratio) in nerve-injured rats. The aims, with this study, were to use nerve-injured animals to determine: (1) whether the antinociceptive potency and efficacy of intrathecal clonidine was altered, and (2) whether the combination of intrathecal morphine and clonidine would act synergistically to produce antinociception. ⋯ These data show that: (1) clonidine, like morphine, loses antinociceptive potency and efficacy after nerve ligation injury, and (2) strongly suggest that a spinal combination of morphine and clonidine synergize under conditions of nerve injury to elicit a significant antinociceptive action when either drug alone may be lacking in efficacy. It is unlikely that the synergy of morphine with clonidine is due to an attenuation of spinal sympathetic outflow by clonidine, because the sympatholytic agent phentolamine produced an opposing effect on morphine antinociception. The data suggest that combinations of morphine and clonidine may prove useful in controlling pain in patients with neuropathic conditions.
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Pulse oximetry is considered a standard of care in both the operating room and the postanesthetic care unit, and it is widely used in all critical care settings. Pulse oximeters may fail to provide valid SpO2 data in various situations that produce low signal-to-noise ratio. Motion artifact is a common cause of oximeter failure and loss of accuracy. This study compares the accuracy and data dropout rates of three current pulse oximeters during standardized motion in healthy volunteers. ⋯ The mechanical motions used in this study significantly affected oximeter function, particularly when the sensors were connected during motion, which requires signal acquisition during motion. The error and dropout rate performance of the Masimo was superior to that of the other two instruments during all test conditions. Masimo uses a new paradigm for oximeter signal processing, which appears to represent a significant advance in low signal-to-noise performance.
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Ischemia-hypoxia followed by reperfusion and reoxygenation injures cells and organs. Previous studies have indicated that isoflurane may protect organs from ischemia-reperfusion or hypoxia-reoxygenation. This study investigated the ability of isoflurane to protect the liver from hypoxia-reoxygenation injury and the mechanisms of this phenomenon. ⋯ The results show that isoflurane protected the liver from an early reoxygenation injury presumably mediated by Kupffer cells. The mechanisms of the inhibitory effects of isoflurane on the injury may involve suppression of extracellular superoxide generation during reoxygenation.
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Halothane induces negative inotropic and lusitropic effects in myocardium. It has been suggested that halothane potentiates beta-adrenoceptor stimulation. However, its effects on the inotropic response to alpha-adrenoceptor stimulation and its effects on the lusitropic effects of alpha- and beta-adrenoceptor stimulation are unknown. ⋯ At clinically relevant concentrations, halothane potentiated the positive inotropic effects of both alpha- and beta-adrenoceptor stimulation. Furthermore, halothane alters the positive lusitropic-effect of beta-adrenoceptor stimulation under low load.