British journal of anaesthesia
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Flow-volume loops were monitored continuously in 39 patients undergoing thoracic surgery requiring one-lung ventilation. In 26 of the 39 patients (67%), auto-positive end-expiratory pressure (auto-PEEP) was seen on the flow-volume curves during both two-lung and one-lung ventilation. Eighty-seven percent of the patients whose trachea was intubated with a smaller size (35- and 37-French gauge) double-lumen tracheal tube exhibited auto-PEEP, compared with patients in whom the tube used was larger (39- or 41-French gauge: 54% and 50%, respectively). Before operation, mean airway resistance was significantly greater in patients who exhibited auto-PEEP during anaesthesia (2.4 cm H2O litre-1 s) than in patients without auto-PEEP (1.7 cm H2O litre-1 s).
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Interaction of the steroidal neuromuscular blocking drugs pancuronium, pipecuronium, rocuronium and vecuronium with cardiac muscarinic receptors in rat hearts was investigated in vitro by a tritiated N-methyl hyoscine binding assay. We showed an interaction with cardiac muscarinic receptors with a rank order of potency pancuronium > vecuronium > pipecuronium > rocuronium and demonstrated complex binding characteristics for pancuronium, vecuronium and rocuronium, with "Hill coefficient" of less than unity. We conclude that the haemodynamic differences seen during the use of these neuromuscular blocking drugs may be a result of their interactions with cardiac M2 muscarinic receptors.