Anesthesiology
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Although the intensity of neurostimulation (i.e., charge) is a product of current intensity and pulse duration, the effects of the latter on the amplitude of evoked response and subjective discomfort are unknown. Therefore, the authors investigated the effects of current intensity and pulse width, and their interaction with electrode placement and polarity, on force translation (FTR), accelerography (ACG), and electromyography (EMG) at the adductor pollics muscle. ⋯ The total current charge required for evoking a supramaximal neuromuscular response is much higher than previously appreciated, and electrode polarity is important in attaining a supramaximal plateau. Failure to attain (and maintain) a supramaximal stimulus allows changes in the effectiveness of neurostimulation, thus influencing the magnitude of the evoked neuromuscular response and confounding measurements of neuromuscular block.
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Intrathecal carbachol produces consistent analgesia in animals without appreciable adverse effects. Little is known about the ability of this drug to provide analgesia as stimulus intensity is increased. Likewise, there are few data regarding interactions between carbachol and other intrathecal analgesics. ⋯ Intrathecal carbachol provides analgesia to noxious thermal stimulation of the hind paw in rats. It is relatively less effective at providing analgesia than intrathecal morphine or clonidine when stimulus intensity is raised. Intrathecal carbachol is synergistic when combined with intrathecal morphine or clonidine.