Anesthesiology
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Multicenter Study
Assessing the diagnostic accuracy of pulse pressure variations for the prediction of fluid responsiveness: a "gray zone" approach.
Respiratory arterial pulse pressure variations (PPV) are the best predictors of fluid responsiveness in mechanically ventilated patients during general anesthesia. However, previous studies were performed in a small number of patients and determined a single cutoff point to make clinical discrimination. The authors sought to test the predictive value of PPV in a large, multicenter study and to express it using a gray zone approach. ⋯ Despite a strong predictive value, PPV may be inconclusive (between 9% and 13%) in approximately 25% of patients during general anesthesia.
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Postoperative pain remains a challenging problem in part because the underlying mechanisms are still not well understood. There is a compelling need for translational studies in human models of postoperative pain to bridge the gap between animal models und human clinical studies. ⋯ Ongoing activity of nociceptors underlying nonevoked pain after incision in humans may not be explained by sensitization of nociceptors to heat but triggers the increased painfulness of mechanical stimuli in the area of secondary hyperalgesia. However, the spatial expansion of hyperalgesia seems to rely on at least partly different mechanisms. These findings may contribute to the understanding of pain and hyperalgesia after surgery.
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The permutation entropy, the approximate entropy, and the index of consciousness are some of the most recently studied electroencephalogram-derived indexes. In this work, a thorough comparison of these indexes was performed using propofol anesthesia in a rabbit model. ⋯ Single-scale and multiscale permutation entropies may be promising measures of propofol anesthetic depth when corrected for burst suppression. Additional studies should investigate the information measured by electromyography algorithms from commercial monitors of anesthetic depth. The rabbit may be a promising animal model for electroencephalographic studies because it provides a good-quality signal.
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During deep brain stimulation implant surgery, microelectrode recordings are used to map the location of targeted neurons. The effects produced by propofol or remifentanil on discharge activity of subthalamic neurons were studied intraoperatively to determine whether they alter neuronal activity. ⋯ These results help to characterize the circuit properties and feedback inhibition of subthalamic neurons and demonstrate that both propofol and remifentanil produce only minor alterations of subthalamic neuron discharge activity that should not interfere with deep brain stimulation implant surgery.