Anesthesiology
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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.
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Cannulation of the internal jugular vein (IJV) is associated with a 95% success rate when external landmarks are used. Anatomic variability has been implicated as the cause for difficulty in cannulation without ultrasound. In contrast to an IJV located lateral to the carotid artery (CA), an IJV overlying the CA may result in CA puncture. The authors' purpose in this study was to examine, using ultrasound, the anatomic relation of the IJV and CA as viewed from the perspective of a cannulating needle. ⋯ In a majority of patients, the IJV is not lateral to the CA in an ultrasound imaging plane positioned in the direction of a cannulating needle. Instead, the IJV overlies the CA in 54% of patients overall, predisposing these patients to CA puncture if the cannulating needle traverses the IJV.
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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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Comparative Study
Comparative pharmacology of cisatracurium (51W89), atracurium, and five isomers in cats.
Atracurium has four chiral centers and the marketed product is a mixture of ten optical and geometric isomers. Six of the isomers were prepared and evaluated for neuromuscular blocking activity and autonomic effects in anesthetized cats. This study reports the comparative pharmacology of the six isomers and atracurium that led to the selection of one isomer, cisatracurium (Nimbex, 51W89) for clinical development. ⋯ Cisatracurium has neuromuscular blocking effects identical to those of atracurium, is more potent, and does not produce cardiovascular effects or increase plasma histamine concentrations.