Anesthesiology
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Hypotension after spinal anesthesia for cesarean section remains a common and serious complication despite the use of uterine displacement and volume preloading. The current study revaluated the role of crystalloid volume preloading in this context. ⋯ The study confirms that hypotension associated with spinal anesthesia for cesarean section cannot be eliminated by volume preloading in the supine wedged patient. The relatively small reduction in incidence of hypotension challenges our perception of the value of crystalloid preload. Though volume preload in the elective cesarean section is advocated, the requirement for a mandatory administration of a fixed volume before spinal anesthesia for urgent cases has been abandoned.
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Dexmedetomidine, a highly selective alpha 2-adrenoreceptor agonist, decreases central sympathetic activity and reduces the anesthetic requirement of halothane. Preliminary studies show that dexmedetomidine improves the outcome from ischemic injury and, therefore, may have potential therapeutic value. ⋯ Results from this study indicate that postischemic administration of dexmedetomidine, in a dose that reduces the anesthetic requirements by 50%, has a neuroprotective effect in this model of focal cerebral ischemia.
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Previous studies have shown that pulse oximeters whose sensors are positioned improperly may yield erroneously low saturation (SpO2) values on normoxemic subjects. The behavior of oximeters with malpositioned sensors during hypoxemia has not been studied. The current study is aimed at determining the behavior of several different pulse oximeters over a wide range of arterial oxygen saturation (SaO2). ⋯ The calibration curves of the pulse oximeters studied were changed greatly by sensor malpositioning. At low SaO2 values, these changes could cause the oximeter to indicate that a patient was only mildly hypoxemic when, in fact, hypoxemia was profound. It is recommended that sensor position be checked frequently and that inaccessible sensor locations be avoided whenever possible.
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Noxious cutaneous stimuli enhance spinal excitability. The behavioral correlate to this response is found in the rat formalin test, in which formalin injection into the hindpaw evokes signs of nociception (flinching and licking of the injected paw) with acute (phase 1) and delayed-hyperalgesic (phase 2) components. ⋯ These observations offer systematic support for the powerful interaction between NSAIDs and opioids and certain other analgesics in clinical pain states. These studies also demonstrate that spinal synergy is not a common property of all interactions. Thus, the NSAID synergy appears to occur with agents that exert a concurrent action both pre- and postsynaptic to the primary afferents.