Anesthesiology
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Letter Comparative Study
Temperature of propofol does not reduce the incidence of injection pain.
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Desflurane, enflurane and isoflurane can be degraded to carbon monoxide (CO) by carbon dioxide absorbents, whereas sevoflurane and halothane form negligible amounts of CO. Carbon monoxide formation is greater with drier absorbent, and with barium hydroxide, than with soda lime. The mechanism, role of absorbent composition and water, and anesthetic structures determining CO formation are unknown. This investigation examined sequential steps in anesthetic degradation to CO. ⋯ A difluoromethoxy group is a structural requirement for haloether degradation to CO. Results are consistent with initial base-catalyzed difluoromethoxy proton abstraction (potassium > sodium hydroxide, thus greater CO formation with barium hydroxide lime vs. soda lime) forming a carbanion (reprotonated by water to regenerate the anesthetic, hence requirements for relatively dry absorbent), carbanion decomposition to a difluorocarbene, and subsequent difluorocarbene reaction to form CO.
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Randomized Controlled Trial Clinical Trial
Non-thermoregulatory shivering in patients recovering from isoflurane or desflurane anesthesia.
Although cold-induced shivering is an obvious source of postanesthetic tremor, other causes may contribute. Consistent with this theory, the authors had previously identified an abnormal clonic component of postoperative shivering and proposed that it might be nonthermoregulatory. A subsequent study, however, failed to identify spontaneous muscular activity in normothermic volunteers. These data suggested that the initial theory was erroneous or that a yet-to-be identified factor associated with surgery might facilitate shivering in patients after operation. Therefore, the authors tested the hypothesis that some postoperative tremor is nonthermoregulatory. ⋯ The incidence of postoperative shivering is inversely related to core temperature. Therefore, it was not surprising that shivering was most common among the hypothermic patients. The major findings, however, were that shivering remained common even among patients who were kept scrupulously normothermic and that many shivered while they were vasodilated. Thus, postoperative patients differ from nonsurgical volunteers in demonstrating a substantial incidence of nonthermoregulatory tremor.