British journal of anaesthesia
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Comparative Study
Recovery of respiration following neuromuscular blockade with atracurium and alcuronium.
Eleven fit unpremedicated patients took part in the study. Group I (five patients) received atracurium 0.3 mg kg-1 and group II (six patients) received alcuronium 0.2 mg kg-1. The simultaneous recovery of respiration, judged by serial measurements of the tidal volume and blood-gas values, and peripheral neuromuscular function, judged by the response of the adductor pollicis muscle, were studied. ⋯ Adequate recovery of respiratory muscle function was present in group I within 15 min of the onset of spontaneous respiration, whereas in group II this recovery took 30 min. At this time there was marked peripheral neuromuscular blockade with the peak tetanic height value less than 25% of control in both groups. It was concluded that recovery of the respiratory muscles from neuromuscular block by atracurium and alcuronium occurred more rapidly than the recovery of the small muscles of the hand, but that adequate tidal volume, in the absence of other clinical signs, should not be regarded as a reliable indication of complete return of neuromuscular function.
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Physiological (VDphys) and anatomical (VDanat) deadspaces were measured in seven anaesthetized, paralysed and intubated adult patients ventilated at normal and high frequencies. To maintain a constant PaCO2 while increasing the ventilation frequency from 15 to 120 b.p.m., the mean VT was decreased from 454 +/- 62 ml (mean +/- SD) to 117 +/- 9 ml. ⋯ This study showed that the deadspace volume measured conventionally was not a constant factor, was mainly a function of VT and was a determinant of tidal and minute volume requirement even during high frequency ventilation. The variable VDphys showed a wide variation between subjects, and appeared to have a mean minimal value of approximately 1.1 ml kg-1 at 80 b.p.m. in adult human subjects with a tracheal tube in situ--a value about half the VDphys measured at conventional normal tidal volumes and ventilation frequencies.
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The problems of selection of tracheal tubes, and the need for a rationale, are outlined. Tracheal tubes of 7.5 mm and 8.5 mm i.d. are recommended for female and male patients, respectively. ⋯ To provide a seal with low pressure-high volume cuffed tubes, cuff sizes of 20.5 mm and 27.5 mm are recommended for female and male patients, respectively. The mechanism of sealing with low pressure-high volume cuffs is reviewed.
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We report a patient with achondroplasia who presented for emergency Caesarean section. Endotracheal intubation was not difficult. The reaction of this patient to drugs such as thiopentone and tubocurarine, judged on body weight basis, was normal.
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The effects of frequency, tidal volume and added deadspace on carbon dioxide clearance were measured during high frequency jet ventilation at 1, 3 and 5 Hz in dogs. With a short, small volume deadspace, carbon dioxide clearance increased with minute volume at each frequency, but for a given minute volume the clearance decreased with increase in frequency. At 5 Hz, carbon dioxide clearance was less than carbon dioxide production. ⋯ At 5 Hz, an increased volume of added deadspace had little effect on carbon dioxide clearance, but increased length, without change in volume, decreased clearance. Carbon dioxide clearance was increased by placing the jet at the lung end of the tracheostomy tube. It is concluded that at 1 Hz, carbon dioxide elimination is governed by bulk flow, but at 5 Hz other mechanisms are important.