Anesthesiology
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Comparative Study
Inhibition of volatile sevoflurane degradation product formation in an anesthesia circuit by a reduction in soda lime temperature.
Sevoflurane reacts with carbon dioxide absorbents, such as soda lime, to release the volatile products compounds A and B. These two products, which have been detected in anesthesia circuits, are among five formed when sevoflurane is degraded by soda lime at increased temperature; the others, compounds C, D, and E, have been detected only in heated sealed systems. The current study attempted to determine the influence of soda lime temperature on compounds A and B generation in an anesthesia circuit and whether a decrease in soda lime temperature could eliminate product formation in the circulating gases. ⋯ This study demonstrates that the release of volatile sevoflurane degradation products in an anesthesia circuit is highly dependent on soda lime temperatures. A reduction of the temperature of soda lime may be a feasible method of preventing the release of significant levels of sevoflurane degradation products without interfering with carbon dioxide absorption or altering the sevoflurane concentration.
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Large (0.5-1.0 MAC), rapid increases of desflurane to concentrations greater than 5% can transiently increase heart rate, mean arterial blood pressure (MAP), sympathetic nerve activity, and plasma epinephrine concentration. We tested the hypothesis that small (1% = 0.14 MAC), rapid increases of desflurane concentration to greater than 5% do not increase heart rate, blood pressure, and plasma catecholamine concentrations. ⋯ Small (1%) increases in desflurane concentration to and greater than 6% can transiently increase heart rate, mean arterial pressure, and plasma epinephrine concentration. These data and those from a previous study indicate that these increases occur with a lesser frequency and magnitude than those associated with a single, rapid step from 4% to 12% end-tidal desflurane.
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Comparative Study
Vecuronium neuromuscular blockade reflects liver function during hepatic autotransplantation in pigs.
Rapid assessment of hepatic function early after reperfusion of the liver graft is of great importance, because it may allow for prompt detection of incipient hepatic graft failure. The current study was undertaken to determine whether the continuous recording of neuromuscular transmission could be used as an on-line assessment of hepatic function during liver transplantation when a muscle relaxant with high hepatic uptake is used. ⋯ These results indicate that, compared with the control studies, there is a similar decrease in the recovery rate of vecuronium-induced neuromuscular blockade and in the metabolic rate of 14C-labeled aminopyrine during the progressive recovery of hepatic function immediately after unclamping of the liver vessels. Metabolism of 14C-labeled aminopyrine increased progressively during the reperfusion phase. Therefore, recording of neuromuscular transmission during liver transplantation could serve as a continuous and easy to perform assessment of liver graft function provided that a muscle relaxant with a high hepatic uptake is used for neuromuscular blockade.
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Volatile anesthetics depress left ventricular mechanical performance during multiple phases of the cardiac cycle. The effects of sevoflurane on systolic and diastolic function have yet to be fully evaluated. This investigation characterized the systemic and coronary hemodynamic, inotropic, and lusitropic actions of sevoflurane in chronically instrumented dogs in the presence and absence of autonomic nervous system (ANS) reflexes. ⋯ Sevoflurane caused direct negative inotropic and lusitropic effects in chronically instrumented dogs with and without ANS blockade.
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Comparative Study
Hearing acuity of anesthesiologists and alarm detection.
With rapid technological advances in anesthesiology, we are acquiring an ever increasing number of auditory alarm systems in the operating room the value of which depend on the hearing acuity of the anesthesiologist monitoring the patient. Presbycusis, the effect of aging on the auditory system, characteristically results in a bilaterally symmetric neurosensory high-frequency hearing loss ( > 2,000 Hz). In this study we attempt to assess the impact of this common hearing disorder on alarm detection. ⋯ Although high-frequency hearing acuity of individuals in our study was better than that of the general population, hearing deficits at high frequencies were of the magnitude to interfere with alarm detection. Also background noise levels vary greatly in different operating rooms. These two problems create a hindrance to alarm detection for certain anesthesiologists. From our data we conclude that the aging human ear may not be capable of accurately detecting some auditory alarms in the operating room. Alarm design should consider hearing acuity because high-frequency alarms may go undetected.