British journal of anaesthesia
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Comparative Study
Neuromuscular blocking and autonomic effects of vecuronium and atracurium in the anaesthetized cat.
The effects of vecuronium and atracurium on neuromuscular transmission, on the responses of the heart rate to vagal stimulation and on the responses to preganglionic stimulation of the nictitating membrane were compared in the chloralose-anaesthetized cat. Vecuronium was four times more potent than atracurium as a neuromuscular blocking agent, whereas the two compounds had similar potencies in blocking the effects of stimulation of the cardiac vagus. The vagal/neuromuscular ratios measured at 50% inhibition were 96 for vecuronium and 25 for atracurium. ⋯ Both compounds had longer time-courses of action than suxamethonium. Very large doses of vecuronium decreased the responses of the preganglionic stimulation of the nictitating membrane, suggesting that at high doses the compound possesses ganglion blocking activity. Large doses of atracurium also decrease the nictitating membrane responses and, in some cats, contractions of the nictitating membrane associated with increases in heart rate and arterial pressure were observed.
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The pharmacokinetics of ketamine 2 mg kg-1 i.v. and 6 mg kg-1 i.m. were investigated in nine children undergoing minor surgery. After either route of administration plasma ketamine concentrations were similar to those found in adult patients receiving the same dose, except at later times after i.v. injection, when concentrations were smaller in children. Also, absorption after i.m. injection appeared to be more rapid in children. ⋯ Concentrations of ketamine upon awakening in a further group of nine children receiving ketamine as the sole anaesthetic showed large inter-individual variation. The concentrations were greater than those previously reported for adults. The greater dose requirements in children, compared with adults, are probably attributable to pharmacodynamic rather than pharmacokinetic factors.
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Pulmonary gas exchange was studied in association with high frequency ventilation and its relation to the duration of insufflation and end-expiratory pressure investigated. Alveolar deadspace, alveolar ventilation and the alveolar-arterial oxygen difference were obtained in cats receiving a constant minute ventilation. ⋯ A positive end-expiratory pressure (PEEP) decreased the alveolar deadspace in high frequency ventilation. Thus, with the low compressible volume ventilator, more efficient high frequency ventilation can be achieved with a short period of insufflation plus low PEEP.
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Comparative Study
High frequency jet ventilation v. manual jet ventilation during bronchoscopy in patients with tracheo-bronchial stenosis.
Six patients with airway stenosis were submitted to bronchoscopy under general anaesthesia. Each was ventilated with a gas mixture of 50% oxygen and nitrogen using successively manual jet insufflation (JV) using the Sanders technique at 20 b.p.m., and high frequency jet ventilation (HFJV) at rates of 150, 300 and 500 b.p.m. ⋯ At the faster rate some degree of hypoxaemia and hypercarbia were noted. The correlation between PaCO2 and transcutaneous carbon dioxide tension was satisfactory.
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Randomized Controlled Trial Comparative Study Clinical Trial
Pattern of change of bronchomotor tone following reversal of neuromuscular blockade. Comparison between atropine and glycopyrrolate.
Specific airways conductance (s. Gaw) was measured using the forced airflow oscillation method, to study the effect of two regimens, commonly used for the reversal of neuromuscular blockade, on bronchomotor tone. Patients who had received neuromuscular blockers and had undergone elective surgery were randomly allocated to receive neostigmine 50 microgram kg-1 given concurrently with either atropine 20 microgram kg-1 (10 patients) or glycopyrrolate 10 microgram kg-1 (10 patients). ⋯ Gaw between the two groups, higher values being found in the atropine group. At 10 min, no significant difference was seen between the groups, although both showed a significant decrease in s. Gaw compared with baseline values (P less than 0.05).