Anesthesiology
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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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Mivacurium, a nondepolarizing muscle relaxant, is metabolized by plasma cholinesterase. Although edrophonium does not alter plasma cholinesterase activity, we have observed that doses of edrophonium that antagonize paralysis from other nondepolarizing muscle relaxants are less effective with mivacurium. We speculated that edrophonium might after metabolism of mivacurium, thereby hindering antagonism of paralysis. Accordingly, we determined the effect of edrophonium on neuromuscular function and plasma mivacurium concentrations during constant mivacurium infusion. ⋯ Edrophonium doses that antagonize d-tubocurarine and vecuronium are less effective in antagonizing the neuromuscular effects of mivacurium during constant infusion. Edrophonium increases plasma mivacurium concentrations, partly or completely explaining its limited efficacy; the mechanism by which edrophonium increases mivacurium concentrations remains unexplained. Our results demonstrate that antagonism of mivacurium by edrophonium is impaired, and therefore we question whether edrophonium should be used to antagonize mivacurium.
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Comparative Study Clinical Trial Controlled Clinical Trial
Thermoregulatory vasoconstriction impairs active core cooling.
Many clinicians now consider hypothermia indicated during neurosurgery. Active cooling often will be required to reach target temperatures < 34 degrees C sufficiently rapidly and nearly always will be required if the target temperature is 32 degrees C. However, the efficacy even of active cooling might be impaired by thermoregulatory vasoconstriction, which reduces cutaneous heat loss and constrains metabolic heat to the core thermal compartment. The authors therefore tested the hypothesis that the efficacy of active cooling is reduced by thermoregulatory vasoconstriction. ⋯ Vasoconstriction did not produce a full core temperature "plateau," because of the extreme microenvironment provided by forced-air cooling. However, it markedly decreased the rate at which hypothermia developed. The approximately 1-h delay in reaching core temperatures of 33 degrees C and 32 degrees C could be clinically important, depending on the target temperature and the time required to reach critical portions of the operation.
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Randomized Controlled Trial Comparative Study Clinical Trial
Arterial oxygenation during one-lung ventilation. A comparison of enflurane and isoflurane.
Because maintaining arterial oxygenation (PaO2) during one-lung ventilation (OLV) can be a clinical problem, it is useful to be aware of factors that influence PaO2 in this situation and are under the control of the anesthesiologist. It is unknown whether, among the commonly used volatile anesthetic agents, one is associated with higher PaO2 levels. Clinical studies suggest that isoflurane provides superior PaO2 during OLV than does halothane. These have not been compared to enflurane. The authors studied PaO2 and hemodynamics during OLV with 1 MAC enflurane versus 1 MAC isoflurane. ⋯ During OLV, the PaO2 values with 1 MAC isoflurane were greater than those with enflurane. The dependence of PaO2 on cardiac output does not support the hypothesis that an increase in cardiac output will cause a decrease in hypoxic pulmonary vasoconstriction and a decrease in PaO2 during OLV.
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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.