Anesthesia and analgesia
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Anesthesia and analgesia · Jun 2010
Presynaptic actions of general anesthetics are responsible for frequency-dependent modification of synaptic transmission in the rat hippocampal CA1.
In clinical anesthesia, robust surgical stress occasionally causes unintended light anesthesia during operation. To test the hypothesis that neural input condition could modify actions of general anesthetics as a result of presynaptic alteration in the central nervous system, we investigated the mechanisms by which the stimulus frequency modifies synaptic transmission of the rat hippocampus in the presence of general anesthetics. ⋯ IV anesthetics, but not volatile drugs, enhance the discharge of a readily releasable pool of GABA vesicles from presynaptic terminals. Depletion of an active pool of GABA after high-frequency stimuli would produce frequency- and use-dependent recurrent inhibition in the presence of IV anesthetics. The stimulus frequency-dependent modification of synaptic transmission might be responsible for the unsuccessful immobilization or hypnosis during general anesthesia after IV anesthetic administration.
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Anesthesia and analgesia · Jun 2010
A description of intraoperative ventilator management and ventilation strategies in hypoxic patients.
Hypoxia is a common finding in the anesthetized patient. Although there are a variety of methods to address hypoxia, it is not well documented what strategies are used by anesthesiologists when faced with a hypoxic patient. Studies have identified that lung protective ventilation strategies have beneficial effects in both oxygenation and mortality in acute respiratory distress syndrome. We sought to describe the ventilation strategies in anesthetized patients with varying degrees of hypoxemia as defined by the Pao(2) to fraction of inspired oxygen (Fio(2)) (P/F) ratio. ⋯ Similar ventilation strategies in mL/kg PBW and PEEP were used among patients regardless of P/F ratio. The results of this study suggest that anesthesiologists, in general, are treating hypoxemia with higher Fio(2) and PIP. The average Fio(2) and PIP were significantly escalated depending on the P/F ratio.
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Anesthesia and analgesia · Jun 2010
Brief report: effects of positive end-expiratory pressure on internal jugular vein cross-sectional area in anesthetized adults.
We tested whether positive end-expiratory pressure (PEEP) increases right internal jugular vein (RIJV) cross-sectional area (CSA) in 45 ASA physical status I and II adults. All patients received a standardized IV fluid bolus, induction of general anesthesia, tracheal intubation, and mechanical ventilation. We evaluated the CSA of the RIJV using ultrasound without PEEP (control) and with PEEP (10 cm H(2)O) in the supine, level position. Addition of PEEP increased RIJV CSA 0.42 + or - 0.41 cm(2) (mean + or - SD, median 0.34 cm(2), P < 0.001), which represented a 41% mean increase in CSA.
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Anesthesia and analgesia · Jun 2010
Low tidal volume and high positive end-expiratory pressure mechanical ventilation results in increased inflammation and ventilator-associated lung injury in normal lungs.
Protective mechanical ventilation with low tidal volume (Vt) and low plateau pressure reduces mortality and decreases the length of mechanical ventilation in patients with acute respiratory distress syndrome. Mechanical ventilation that will protect normal lungs during major surgical procedures of long duration may improve postoperative outcomes. We performed an animal study comparing 3 ventilation strategies used in the operating room in normal lungs. We compared the effects on pulmonary mechanics, inflammatory mediators, and lung tissue injury. ⋯ Comparing intraoperative strategies, ventilation with high PEEP resulted in increased production of inflammatory markers. Low PEEP resulted in lower levels of inflammatory markers. High Vt/low PEEP resulted in less histologic lung injury.
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Anesthesia and analgesia · Jun 2010
What will anesthesiologists be anesthetizing? Trends in neurosurgical procedure usage.
To anticipate future changes to the practice of neuroanesthesia, we examined the nationwide trends in frequently performed operative neurosurgery. ⋯ The highest volume trends in operative neurosurgery are for spinal fusion (increasing at a rate of approximately 12,000 procedures/y), craniotomy for tumors and other purposes (increasing at a rate of approximately 2,700 procedures/y), and a decrease in shunts (decreasing at a rate of approximately 3,000 per year). The data suggest that intracranial endovascular treatment remains relatively rare, but it is growing exponentially, and lengths of stay are increasing, whereas inhospital deaths are decreasing. The conclusions of this study are limited by the imprecise nature of the ICD-9-CM procedure codes, the categorization scheme we used, and by the sampling methods of the National Inpatient Sample.