Anesthesiology
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Volatile anesthetics depress global left ventricular function by altering intracellular calcium (Ca2+) homeostasis at several sites within the myocyte. Although extracellular Ca2+ partially reverses the negative inotropic effects of volatile anesthetics, the actions of extracellular Ca2+ on anesthetic-induced diastolic dysfunction are unexplored. This investigation examined and compared the direct effects of extracellular Ca2+ on left ventricular systolic and diastolic function in conscious and anesthetized dogs. ⋯ Although CaCl2 produced positive inotropic effects in both the conscious and anesthetized states, CaCl2 did not alter diastolic function in conscious dogs. In contrast, CaCl2 reversed halothane- and isoflurane-induced negative lusitropic actions. The results of the present investigation suggest that improvement of left ventricular performance by CaCl2 during volatile anesthesia may be related to actions in diastole as well as systole.
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There is increasing interest among anesthesiologists in the use of continuous infusion of intravenous drugs. The therapeutic effect of most drugs is a function of the concentration at the site of drug effect, which in turn is determined by the plasma concentration. Constant plasma concentrations can be maintained by computer-controlled infusion pumps. However, such equipment is not yet widely available and will be expensive. ⋯ Other than the assumption of linear kinetics, the algorithm is independent of pharmacokinetic models. Implementation does not require computer-based numerical analysis.
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Propofol anesthesia often is associated with marked decreases in arterial blood pressure. Previous investigations in vivo have provided conflicting reasons for this clinical finding, including propofol-induced decreases in preload or afterload and/or direct myocardial depressant effects. Interpretation of the results of these studies is complicated by use of indices of myocardial contractility that may only indirectly indicate changes in inotropic state or are significantly dependent on ventricular loading conditions. ⋯ The results indicate that the significant decrease in systemic arterial blood pressure observed during continuous propofol anesthesia in dogs is a result of direct negative inotropic actions of propofol along with its direct effects upon arterial and venous vascular tone.
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The spinal mechanisms underlying the hyperesthetic state during inflammation are little understood. To gain a better understanding of these mechanisms, this study evaluated the effects of intrathecal morphine; MK-801, an N-methyl-D aspartic (NMDA) antagonist; and CP-96,345, an NK1 antagonist, on the hyperesthesia observed after carageenan injection of the rat paw. ⋯ These data indicate that (1) an NMDA receptor, but not an NK1 receptor, plays an important role in maintaining the hyperesthesia after carageenan injection; and (2) NMDA antagonism has a simple additive interaction with morphine in the carageenan model of inflammatory hyperesthesia.
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Comment Letter Biography Historical Article
Preemptive analgesia or anoci-association.