Anesthesia and analgesia
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Anesthesia and analgesia · Oct 2013
ReviewNoninvasive Hemoglobin Monitoring: How Accurate Is Enough?
Evaluating the accuracy of medical devices has traditionally been a blend of statistical analyses, at times without contextualizing the clinical application. There have been a number of recent publications on the accuracy of a continuous noninvasive hemoglobin measurement device, the Masimo Radical-7 Pulse Co-oximeter, focusing on the traditional statistical metrics of bias and precision. In this review, which contains material presented at the Innovations and Applications of Monitoring Perfusion, Oxygenation, and Ventilation (IAMPOV) Symposium at Yale University in 2012, we critically investigated these metrics as applied to the new technology, exploring what is required of a noninvasive hemoglobin monitor and whether the conventional statistics adequately answer our questions about clinical accuracy. ⋯ This hemoglobin error grid can be used to evaluate the required clinical accuracy (±g/dL) of a hemoglobin measurement device to provide more conclusive evidence on whether to transfuse an individual patient. The important decision to transfuse a patient usually requires both an accurate hemoglobin measurement and a physiologic reason to elect transfusion. It is our opinion that the published accuracy data of the Masimo Radical-7 is not good enough to make the transfusion decision.
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Pediatric advanced life support training and guidelines are typically designed for first-responders and out-of-hospital resuscitation. Guidelines and scenarios that are more applicable to the perioperative environment would be beneficial for anesthesiologists. The goal of this article is to review resuscitation of pediatric patients during the perioperative period. ⋯ In an effort to provide information of maximum benefit to anesthesiologists, we include common pediatric perioperative arrest scenarios with detailed description of their management. We also provide a section on postresuscitation management and review the techniques for maintaining the child's hemodynamic and metabolic stability. Finally, 3 appendices are included: an example of an intraoperative arrest record that provides feedback for interventions; a table of key medications for pediatric perioperative resuscitation; and a review of defibrillator use and simulation exercises to promote effective defibrillation.
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Anesthesia and analgesia · Oct 2013
ReviewReduction of Myocardial Infarct Size with Ischemic "Conditioning": Physiologic and Technical Considerations.
A wealth of evidence has revealed that the heart can be "conditioned" and rendered less vulnerable to ischemia-reperfusion injury via the upregulation of endogenous protective signaling pathways. Three distinct conditioning strategies have been identified: (1) preconditioning, the phenomenon where brief episodes of myocardial ischemia (too brief to cause cardiomyocyte death) limit necrosis caused by a subsequent sustained ischemic insult; (2) postconditioning, the concept that relief of myocardial ischemia in a staged or stuttered manner attenuates lethal ischemia-reperfusion injury; and (3) remote conditioning, or upregulation of a cardioprotective phenotype initiated by ischemia in a remote organ or tissue and "transported" to the heart. ⋯ There is, however, a potentially important caveat to the clinical translation of myocardial conditioning: emerging data suggest that the efficacy of ischemic conditioning is compromised in aging, diabetic, and hypertensive cohorts, the specific populations in which myocardial protection is most relevant. Successful clinical application of myocardial conditioning will therefore require an understanding of the potential confounding consequences of these comorbidities on the "conditioned" phenotype.
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Anesthesia and analgesia · Oct 2013
Comparative StudyThe Hemodynamic Response to Dexmedetomidine Loading Dose in Children With and Without Pulmonary Hypertension.
Dexmedetomidine, an α-2 receptor agonist, is widely used in children with cardiac disease. Significant hemodynamic responses, including systemic and pulmonary vasoconstriction, have been reported after dexmedetomidine administration. Our primary goal of this prospective, observational study was to quantify the effects of dexmedetomidine initial loading doses on mean pulmonary artery pressure (PAP) in children with and without pulmonary hypertension. ⋯ Dexmedetomidine initial loading doses were associated with significant systemic vasoconstriction and hypertension, but a similar response was not observed in the pulmonary vasculature, even in children with pulmonary hypertension. Dexmedetomidine does not appear to be contraindicated in children with pulmonary hypertension.
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Anesthesia and analgesia · Oct 2013
Randomized Controlled TrialFactors Affecting the Performance of 5 Cerebral Oximeters During Hypoxia in Healthy Volunteers.
Cerebral oximetry is a noninvasive optical technology that measures frontal cortex blood hemoglobin-oxygen saturation. Commercially available cerebral oximeters have not been evaluated independently. Unlike pulse oximeters, there are currently no Food and Drug Administration standards for performance or accuracy. We tested the hypothesis that cerebral oximeters accurately measure a fixed ratio of the oxygen saturation in cerebral mixed venous and arterial blood. ⋯ While responsive to desaturation, cerebral oximeters exhibited large variation in reading errors between subjects, with mean bias possibly related to variations in the ratio of arterial and venous blood in the sampling area of the brain. This ratio is probably not fixed, as assumed by the manufacturers, but dynamically changes with hypoxia. Better understanding these factors could improve the performance of cerebral oximeters and help establish saturation or blood flow thresholds for brain well-being.