Anesthesiology
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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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Randomized Controlled Trial Comparative Study Clinical Trial
Does spinal anesthesia result in a more complete sympathetic block than that from epidural anesthesia?
Spinal and epidural injection of local anesthetics are used to produce sympathetic block to diagnose and treat certain chronic pain syndromes. It is not clear whether either form of regional anesthesia produces a complete sympathetic block. Spinal anesthesia using tetracaine has been reported to produce a decrease in plasma catecholamine concentrations. This has not been demonstrated for epidural anesthesia in humans with level of anesthesia below C8. One possible explanation is that spinal anesthesia results in a more complete sympathetic block than epidural anesthesia. To examine this question, a cross-over study was performed in young, healthy volunteers. ⋯ Spinal anesthesia did not result in a more complete attenuation of the sympathetic response to a CPT than did epidural anesthesia. In response to the CPT, spinal anesthesia blocked the increase in cardiac index, and epidural anesthesia resulted in a decrease in total peripheral resistance compared to the pre-anesthesia state. The differences between the techniques are not significant and are of uncertain clinical implications.
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Multicenter Study Clinical Trial
Postoperative apnea in former preterm infants after inguinal herniorrhaphy. A combined analysis.
Controversy exists as to the risk for postoperative apnea in former preterm infants. The conclusions of published studies are limited by the small number of patients. ⋯ The analysis suggests that, if it is assumed that the statistical models used are equally valid over the full range of ages considered and that the average rate of apnea reported across the studies analyzed is accurate and representative of actual rates in all institutions, the probability of apnea in nonanemic infants free of recovery-room apnea is not less than 5%, with 95% statistical confidence until postconceptual age was 48 weeks with gestational age 35 weeks. This risk is not less than 1%, with 95% statistical confidence, for that same subset of infants, until postconceptual age was 56 weeks with gestational age 32 weeks or postconceptual age was 54 weeks and gestational age 35 weeks. Older infants with apnea in the recovery room or anemia also should be admitted and monitored. The data do not allow prediction with confidence up to what age this precaution should continue to be taken for infants with anemia. The data were insufficient to allow recommendations regarding how long infants should be observed in recovery. There is additional uncertainty in the results due to the dramatically different rates of detected apnea in different institutions, which appear to be related to the use of different monitoring devices. Given the limitations of this combined analysis, each physician and institution must decide what is an acceptable risk for postoperative apnea.
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Randomized Controlled Trial Comparative Study Clinical Trial
Effects of fentanyl on sympathetic activation associated with the administration of desflurane.
Activation of the sympathetic nervous system occurs when desflurane is inspired shortly after anesthetic induction and when the inspired concentration of desflurane is rapidly increased during steady-state periods of anesthesia. The purpose of this study was to determine the effectiveness and dose response of fentanyl pretreatment in attenuating the neurocirculatory responses to desflurane in healthy human volunteers. ⋯ The administration of desflurane was associated with increases in SNA, HR, MAP, and CVP. Maximum sympathetic activation and hemodynamic responses occurred 4-5 min after initiating desflurane during induction and 2-3 min after increasing the inspired concentration of desflurane during the "transition" period. Although fentanyl partially attenuated the hemodynamic component in a dose-dependent fashion during the "transition" period, it did not significantly diminish the response during induction.
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Clinical Trial
The maximum depth of an atracurium neuromuscular block antagonized by edrophonium to effect adequate recovery.
The inability of edrophonium to rapidly reverse a deep nondepolarizing neuromuscular block may be due to inadequate dosage or a ceiling effect to antagonism of neuromuscular block by edrophonium. A ceiling effect means that only a certain level of neuromuscular block could be antagonized by edrophonium. Neuromuscular block greater than this could not be completely antagonized irrespective of the dose of edrophonium administered. The purpose of this study was to determine whether a ceiling effect occurred for antagonism of an atracurium-induced neuromuscular block by edrophonium and, if so, the maximum level of block that could be antagonized by edrophonium. ⋯ There is a maximum level of neuromuscular block that can be antagonized by edrophonium to effect adequate recovery. The level corresponds approximately to the reappearance of the fourth response to TOF stimulation. It is probably safest to wait until this level of block occurs before edrophonium is given for reversal. Earlier administration will not hasten recovery.