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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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.
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Comparative Study
Effects of pentobarbital and isoflurane on regional cerebral oxygen extraction and consumption with middle cerebral artery occlusion in rats.
When compared with barbiturates, isoflurane may lack protective effects during focal cerebral ischemia. The reason for this difference is not clear. In this study, regional cerebral blood flow (rCBF), arterial and venous O2 saturation, and O2 extraction were compared in the ischemic cortex and in the nonischemic brain regions of rats anesthetized with isoflurane or pentobarbital using a microspectrophotometric technique that directly measures the O2 saturation of blood in the small arteries and veins. ⋯ Because the rCBF was less and the O2 extraction was similar, O2 consumption in the focal ischemic area of the brain during pentobarbital anesthesia must have been less than that during isoflurane anesthesia.
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Few studies have been reported on the direct depressive effects of sevoflurane on myocardial contractility in humans. Direct assessment of contractile state is possible by examining the slope of left ventricular end-systolic wall stress (LVESWS) versus velocity of circumferential fiber shortening with heart rate corrected (Vcfc) relationship with echocardiography. Using this contractile index, the effects of sevoflurane/nitrous oxide were compared with that of enflurane/nitrous oxide on myocardia contractility in humans. ⋯ The results of the present study suggest that sevoflurane has fewer depressant effects on cardiac function than does enflurane.