British journal of anaesthesia
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Randomized Controlled Trial Clinical Trial
Dose-response relationships for neostigmine antagonism of vecuronium-induced neuromuscular block in adults and the elderly.
We have studied the dose-response relationship for neostigmine in 36 adult (ages 18-50 yr) and 36 elderly (ages > 70 yr) subjects during antagonism of neuromuscular block induced by vecuronium. All patients received vecuronium 0.08 mg kg-1 and neuromuscular block was monitored mechanomyo-graphically using the train-of-four (TOF) mode of stimulation. Six patients of each age group were allocated randomly to receive neostigmine 5, 15, 25, 35 or 45 micrograms kg-1 or saline at 10% recovery of T1 (first response in the TOF). ⋯ There was a significant difference (P < 0.05) in the time to spontaneous recovery of T1 to 10% between the adults (24 (SD 5.5) min) and the elderly (33 (7.8) min). Dose-response curves for neostigmine were parallel in the two age groups, but those for the elderly were significantly to the right of the curves for the adults. This suggests an apparently lesser relative potency of neostigmine, or the requirement of a larger dose, in the elderly for attaining antagonism of a moderately intense vecuronium block at the same time as in adults.
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We studied recovery in 25 adult patients, ASA I, undergoing elective orthopaedic procedures after anaesthesia with 0.65 MAC desflurane (n = 16) or isoflurane (n = 9) with 60% nitrous oxide in oxygen. Early emergence from anaesthesia was assessed in the operating room by measuring time to spontaneous movement, cough, response to painful pinch, tracheal extubation, opening of the eyes and stating correct age, name and body parts. The return of cognitive functions in the late recovery phase was assessed in the post-anaesthesia care unit (PACU) by post-anaesthesia recovery scores (PARS), the Trieger dot test (TDT), and the digit substitution test (DST). ⋯ Recovery times were not increased by increased duration of desflurane anaesthesia. The desflurane patients showed no delirium, minimal sedation and less shivering during the entire postoperative course. We conclude that desflurane anaesthesia was superior to isoflurane anaesthesia, not only in emergence, but also in the recovery of cognitive functions.
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We studied 16 healthy ASA physical status I patients (aged 13-71 yr for sevoflurane and 22-74 yr for isoflurane) to determine maximum blood concentrations on awakening (MBCawake) from sevoflurane and isoflurane anaesthesia, and determined if age and duration of anaesthesia significantly influenced MBCawake. After operation, the end-tidal concentration of anaesthetics was decreased gradually. During recovery from anaesthesia, patients were asked repeatedly to open their eyes. ⋯ There was no significant correlation between age and blood:gas partition coefficient for sevoflurane and isoflurane. Awakening alveolar concentrations (MACawake) calculated from MBCawake were 0.61 (SE 0.05)% for sevoflurane and 0.39 (0.02)% for isoflurane, and correlated significantly with age. The ratios of awakening alveolar concentration to MAC were reasonably constant--0.33 for sevoflurane and 0.33 for isoflurane.
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Comparative Study
Comparison of the use of the laryngeal mask and face mask by inexperienced personnel.
Ten junior doctors with no postgraduate anaesthetic experience attempted to ventilate the lungs of 50 anaesthetized patients, using either a laryngeal mask or a Guedel airway and face mask. Success was defined as the production of two successive tidal volumes exceeding 800 ml within 40 s. The failure rate was significantly greater using the laryngeal mask compared with the face mask (P < 0.05) and the average time was significantly longer with the laryngeal mask than with the face mask (P < 0.01). The results from this investigation suggest the laryngeal mask airway cannot be recommended as a resuscitation device for use by inexperienced operators.