Anesthesia and analgesia
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Anesthesia and analgesia · Oct 2013
ReviewUnderstanding the Mechanism: Mediation Analysis in Randomized and Nonrandomized Studies.
In comparative clinical studies, a common goal is to assess whether an exposure, or intervention, affects the outcome of interest. However, just as important is to understand the mechanism(s) for how the intervention affects outcome. For example, if preoperative anemia was shown to increase the risk of postoperative complications by 15%, it would be important to quantify how much of that effect was due to patients receiving intraoperative transfusions. ⋯ We discuss the proper design and analysis of studies investigating mediation, including the importance of distinguishing mediator variables from confounding variables, the challenge of identifying potential mediators when the exposure is chronic versus acute, and the requirements for claiming mediation. Simple designs are considered, as well as those containing multiple mediators, multiple outcomes, and mixed data types. Methods are illustrated with data collected by the National Surgical Quality Improvement Project (NSQIP) and utilized in a companion paper which assessed the effects of preoperative anemic status on postoperative outcomes.
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Anesthesia and analgesia · Oct 2013
Randomized Controlled TrialAccuracy of Carboxyhemoglobin Detection by Pulse CO-Oximetry During Hypoxemia.
Carbon monoxide poisoning is a significant problem in most countries, and a reliable method of quick diagnosis would greatly improve patient care. Until the recent introduction of a multiwavelength "pulse CO-oximeter" (Masimo Rainbow SET(®) Radical-7), obtaining carboxyhemoglobin (COHb) levels in blood required blood sampling and laboratory analysis. In this study, we sought to determine whether hypoxemia, which can accompany carbon monoxide poisoning, interferes with the accurate detection of COHb. ⋯ In healthy volunteers, the Radical-7 pulse CO-oximeter accurately detects hypoxemia with both low and elevated COHb levels, and accurately detects COHb, but only reads SpCO when SaO2 is more than approximately 85%.
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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
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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Anesthesia and analgesia · Oct 2013
ReviewMeasuring Mitochondrial Oxygen Tension: From Basic Principles to Application in Humans.
The protoporphyrin IX-triplet state lifetime technique (PpIX-TSLT) has been recently introduced as the first method to measure mitochondrial oxygen tension (mitoPO2) in living cells and tissues. The current implementation of the technique is based on oxygen-dependent quenching of the delayed fluorescence lifetime of 5-aminolevulinic-acid-enhanced mitochondrial PpIX. It represents a significant step forward in our ability to comprehensively measure tissue oxygenation. ⋯ Clinical measurements of mitoPO2 are possible as demonstrated by cutaneous measurements in healthy volunteers. Applications of PpIX-TSLT in anesthesiology and intensive care medicine might, e.g., be monitoring mitoPO2 as a resuscitation end point, targeting oxygen homeostasis in the critically ill, and assessing mitochondrial function at the bedside. PpIX-TSLT likely also has applications in other fields also, e.g., providing an oxygen-related feedback signal in photodynamic therapy of malignant tumors.