Anesthesiology
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Anesthesia produces atelectasis in the dependent areas of the lungs by mechanisms that remain unknown. It has been proposed that anesthesia produces a cephalad shift in the end-expiratory position of the diaphragm, which compresses the lungs and produces atelectasis. This study tested the hypothesis that the extent of atelectasis is correlated with the cephalad displacement of the dependent portion of the diaphragm produced by halothane anesthesia in healthy young human subjects. ⋯ The dependent lung atelectasis produced by halothane anesthesia does not appear to be related to changes in the position of any single chest wall structure in these healthy young subjects, but rather to an interaction of several factors that remain to be identified.
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Cervical spine kinetics during airway manipulation are poorly understood. This study was undertaken to quantify the extent and distribution of segmental cervical motion produced by direct laryngoscopy and orotracheal intubation in human subjects without cervical abnormality. ⋯ This investigation quantifies the behavior of the normal cervical spine during direct laryngoscopy with a Macintosh blade. With this maneuver, the vast majority of cervical motion is produced at the occipitoatlantal and atlantoaxial joints. The subaxial cervical segments (C2-C5) are displaced only minimally. This study establishes a highly reliable and reproducible method for analyzing cervical motion in real time.
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Transient focal neurologic deficits have been observed in patients emerging from brain tumor or carotid surgery, and a pharmacologic effect of anesthetic agents has been proposed as the cause of such neurologic dysfunction. Therefore, the effect of sedation with midazolam or fentanyl on motor neurologic function was studied prospectively and preoperatively in patients with carotid disease or mass lesions of the brain. ⋯ Sedation with midazolam or fentanyl can transiently exacerbate or unmask focal motor deficits in patients with prior motor dysfunction.
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Evoked, recurrent electromyographic activity (F waves) reflect alpha-motor neuron excitability. Based on observations that other inhaled anesthetics do so, we hypothesized that nitrous oxide, alone or in combination with isoflurane, would depress F-wave activity and correlate with depression of movement response to tail clamp or electric stimulation. ⋯ Because nitrous oxide depressed F-wave but not M-wave activity, the data suggest a central (spinal) rather than neuromuscular junctional site of action of this agent. The direct correlation between nitrous oxide dose, F-wave amplitude depression, and surgical immobility suggests the possibility of using F-wave activity to predict the likelihood of anesthetic-induced immobility. However, the mechanism of action of nitrous oxide may differ from that of the potent inhaled agents.
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Randomized Controlled Trial Clinical Trial
Preemptive analgesia: intraperitoneal local anesthetic in laparoscopic cholecystectomy. A randomized, double-blind, placebo-controlled study.
A controversy exists over the effectiveness and clinical value of preemptive analgesia. Additional studies are needed to define the optimum intensity, duration, and timing of analgesia relative to incision and surgery. ⋯ The results indicate that intraperitoneal local anesthetic blockade administered before or after surgery preempts postoperative pain relative to an untreated placebo-control condition. However, the timing of administration is also important in that postoperative pain intensity and analgesic consumption are both lower among patients treated with local anesthetic before versus after surgery.