Canadian journal of anaesthesia = Journal canadien d'anesthésie
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Comparative Study
Time-cycled inverse ratio ventilation does not improve gas exchange during anaesthesia.
Inverse ratio ventilation (IRV) has been reported to improve oxygenation at lower peak airway pressures in patients with respiratory failure. Therefore we hypothesised that IRV might also improve oxygen exchange during anaesthesia. Conventional ratio ventilation (CRV) and IRV were compared in 24 low-risk surgical patients who were paralysed and whose lungs were ventilated with air/O2 by a non-rebreathing circuit and a Siemens 900-C servo ventilator. ⋯ Multivariate models were tested to identify variables which predicted O2 exchange during CRV. Patient age was the only predictor consistently significant in all models. We conclude that age is an important determinant of impaired pulmonary oxygen exchange during anaesthesia, and that increasing mean AWP by TC-IRV has no beneficial effects on pulmonary mechanics or gas exchange.
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This study examined the effect of flumazenil, a benzodiazepine antagonist, on aqueous humour pressure in dogs receiving either midazolam or no benzodiazepine. Twenty-four halothane-anaesthetized dogs were assigned to one of four groups. Group I (n = 6) received saline iv at 0, 45 and 90 min. ⋯ In Groups 3 and 4, midazolam decreased aqueous humour pressure from 18 +/- 2 mmHg (mean +/- SD) to 14 +/- 3 mmHg (P less than 0.001) and from 34 +/- 5 mmHg to 31 +/- 3 mmHg (P less than 0.01) respectively. Flumazenil given during continuous infusion of midazolam produced increases of aqueous humour pressure of 2 +/- 1 (P less than 0.01) to 5 +/- 2 mmHg (P less than 0.01) that lasted less than or equal to 12 min. It is concluded that at both normal and elevated aqueous humour pressures flumazenil produces statistically significant but clinically unimportant increases of aqueous humour pressure in anaesthetized dogs receiving midazolam, but not in dogs given no benzodiazepine.
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Randomized Controlled Trial Comparative Study Clinical Trial
Comparison of two esmolol bolus doses on the haemodynamic response and seizure duration during electroconvulsive therapy.
Twelve ASA physical status I-III patients were enrolled in a double-blind, prospective, randomized, three-way, within-patient crossover study designed to determine the effect of two standard esmolol bolus doses (100 and 200 mg) on the haemodynamic response and seizure duration during electro-convulsive therapy (ECT). Esmolol or placebo was administered one minute prior to induction of anaesthesia and exactly two minutes before ECT. Both the 100 and 200 mg bolus doses significantly blunted the maximum increase in heart rate (HR) and mean arterial pressure (MAP) following ECT in comparison with placebo. ⋯ No significant difference was found between the two esmolol doses at corresponding measurement points before and after ECT. Treatment with esmolol 200 mg resulted in a significantly shorter mean seizure duration than with placebo. As the 200 mg dose caused a shorter seizure duration and the haemodynamic effects of 100 mg and 200 mg doses were similar, it was concluded that the 100 mg esmolol bolus dose was the better dose for ECT.
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The present study employed train-of-four (TOF) stimulation at a current of 20 mA to assess the incidence and degree of residual neuromuscular blockade in 64 randomly selected Post Anesthesia Care Unit (PACU) patients. Group C (Control, n = 10) had received anaesthesia without nondepolarizing muscle relaxant; Group V (n = 25) had received vecuronium; and Group P (n = 29) had received pancuronium. At the end of surgery, each patient had been considered by his anaesthetist to have adequate neuromuscular function on the basis of clinical signs and tactile or visual evaluation of responses to TOF stimulation. ⋯ This study indicates that residual curarization may be commonly encountered following long-acting relaxants despite qualitative intraoperative TOF monitoring. The present incidence, detected at a current of 20 mA, is consistent with previous reports which employed supramaximal TOF stimulation. We conclude that despite intraoperative monitoring, residual curarization following long-acting nondepolarizing agents is common and that it may be detected with TOF at a low stimulating current (20 mA).
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Neostigmine 0.06 mg.kg-1 or edrophonium 1 mg.kg-1 were administered to two groups of 15 patients each for antagonism of pipecuronium-induced neuromuscular block at 20% spontaneous recovery of the first twitch (T1) of the train-of-four (TOF) stimulation. The mean onset of action (+/-SEM) of edrophonium (18.1 +/- 2.4 sec) was significantly more rapid (P less than 0.01) than that of neostigmine (47.6 +/- 4 sec), as were the times taken to attain a TOF ratio of 0.25 and 0.5. Nevertheless, the reversal time (time taken from the end of injection of the antagonist until TOF ratio value had reached 0.75) was significantly shorter (P less than 0.01) in the neostigmine than in the edrophonium group (499.3 +/- 62 vs 767 +/- 52 sec respectively). ⋯ Administration of one additional dose (one-third of the initial dose) of the same antagonist resulted in adequate antagonism in the remaining five patients in the neostigmine group and in nine patients in the edrophonium group. Two such doses were required in the remaining three patients in the latter group. The mean total dose of neostigmine and edrophonium employed in this study was 0.067 +/- 0.002 and 1.3 +/- 0.05 mg.kg-1, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)