Anesthesiology
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Comparative Study
pH-stat management reduces the cerebral metabolic rate for oxygen during profound hypothermia (17 degrees C). A study during cardiopulmonary bypass in rabbits.
Greater cerebral metabolic suppression may increase the brain's tolerance to ischemia. Previous studies examining the magnitude of metabolic suppression afforded by profound hypothermia suggest that the greater arterial carbon dioxide tension of pH-stat management may increase metabolic suppression when compared with alpha-stat management. ⋯ At 17 degrees C, CMRO2 with pH-stat management is 35-40% less than that with alpha-stat management and is independent of CBF or arterial pressure differences between the techniques.
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Comparative Study
Myocyte contractile responsiveness after hypothermic, hyperkalemic cardioplegic arrest. Disparity between exogenous calcium and beta-adrenergic stimulation.
Acute left ventricular dysfunction is commonly encountered after hypothermic, hyperkalemic cardioplegic arrest (HHCA) and often requires inotropic intervention for successful separation from cardiopulmonary bypass. However, the basic mechanisms involved in depressed left ventricular function and the cellular basis for the differential effects of inotropic drugs after HHCA are unknown. Accordingly, the goal of this study was to determine the effects of calcium (Ca2+) and beta-adrenergic receptor agonists (beta AR) stimulation on isolated myocyte contractile function after HHCA. ⋯ The minimal improvement in myocyte contractile function after HHCA with increased extracellular Ca2+ suggests that Ca2+ depletion is not the primary mechanism for depressed myocyte contractility after HHCA. On the other hand, because beta AR administration improved myocyte contractile function after HHCA, the cellular basis for the effects of beta AR stimulation after HHCA is probably not increased myocyte Ca2+ but rather alternative mechanisms, such as changes in myofilament sensitivity to Ca2+. These results also suggest that the abnormalities in left ventricular function after HHCA result from the direct effects of hyperkalemic induced electromechanical uncoupling as well as relative hypoxic conditions.
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Clinical Trial
Effects of propofol sedation on seizures and intracranially recorded epileptiform activity in patients with partial epilepsy.
Case reports suggesting both pro- and anticonvulsant effect(s) of propofol have been published in recent years. The effects of sedative doses of propofol on epileptiform activities in patients suffering from intractable partial epilepsy were systematically investigated. ⋯ We were unable to demonstrate a significant change in epileptiform activity with sedative doses of propofol in patients suffering from complex partial epilepsy.
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Comparative Study
Abnormal action potential responses to halothane in heart muscle isolated from malignant hyperthermia-susceptible pigs.
During human and porcine malignant hyperthermia (MH), cardiac dysrhythmias and altered myocardial function can be observed. It is unknown whether a primary abnormality in cardiac muscle contributes to the cardiac symptoms during MH. An abnormal response to halothane has recently been demonstrated in action potentials (APs) from MH-susceptible (MHS) human skeletal muscles. We investigated the electrophysiologic properties in trabeculae isolated from the right ventricles of normal (MHN) and MHS pigs. ⋯ This in vitro study demonstrates that halothane produces abnormal alterations in the dynamic electric properties of the ventricular excitable membrane from MHS pigs. These results suggest a latent defect in the myocardium of MHS pigs that becomes apparent in the presence of MH-triggering agents.
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Comparative Study
Microcirculatory perfusion during volume therapy. A comparative study using crystalloid or colloid in awake animals.
Because of the passage of water and salt molecules into the interstitial space, volume replacement with crystalloid solutions requires an amount at least four times that of lost blood. The resulting tissue edema may interfere with nutritive capillary perfusion and oxygen delivery. To prove this hypothesis, the effects of isovolemic hemodilution (hematocrit 30%) with Ringer's lactate solution or dextran 60 on tissue perfusion and oxygenation were investigated in awake Syrian golden hamsters. ⋯ In this model, volume replacement with artificial colloids yielded hemodynamic stability and adequate tissue oxygen supply, whereas administration of crystalloids alone jeopardized tissue perfusion and oxygenation.