European journal of anaesthesiology
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Randomized Controlled Trial Clinical Trial
Administration of vecuronium, atracurium and pancuronium in divided doses: effect on onset and duration of action.
The time to onset of neuromuscular block (as assessed by single twitch stimulation at 0.1 Hz) and the duration to 25% recovery of twitch height were measured after administration of vecuronium 0.1 mg kg-1, atracurium 0.5 mg kg-1 or pancuronium 0.1 mg kg-1, administered either as a single bolus or in divided doses, 10% being administered 4 min prior to the remaining 90%. The patients were anaesthetized with thiopentone, nitrous oxide in oxygen and i.v. fentanyl. There was no significant difference between the single- and divided-dose groups, either in the onset times (2.8 and 2.9 min for vecuronium, 2.7 and 2.4 min for atracurium and 3.3 min each for pancuronium for single- and divided-dose groups, respectively) or the duration to 25% recovery of twitch height (35 and 29 min for vecuronium, 45 and 39 min for atracurium and 87 and 93 min for pancuronium for single- and divided-dose groups, respectively).
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This review describes the distribution of ventilation and blood flow in the anaesthetized subject, during spontaneous breathing and after muscle paralysis. Within minutes after induction of anaesthesia, the diaphragm is shifted cranially (supine position), functional residual capacity is reduced and collapse of dependent lung regions can be seen by means of computed tomography. These changes occur whether anaesthesia is intravenous (barbiturate) or inhalational (halothane) and whether ventilation is spontaneous or mechanical. ⋯ This causes a ventilation/perfusion mismatch, the hall-mark of which is shunt. Additional factors such as airway closure and release of hypoxic pulmonary vasoconstriction may contribute to the gas exchange disturbance. The major features of the lung function impairment are already present during spontaneous breathing in the anaesthetized subject, and muscle paralysis adds only little to the disturbance.
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The pharmacokinetics and hepatic disposition of pipecuronium have been investigated in cats with normal and absent renal function. A combined fluorimetric and chromatographic technique was used to determine the concentrations of pipecuronium and its metabolites in the samples. Following intravenous injection of 150 micrograms kg-1, pipecuronium disappeared from the plasma bi-exponentially with half-lives of 9.8 +/- 5.4, 77.7 +/- 9.7 min and 7.2 +/- 5.0, 100, 6 +/- 23.7 min; the Vd was 362.3 +/- 74.9 ml kg-1 and 123.7 +/- 14.6 ml kg-1 and the clearance was 5.0 +/- 0.9 ml min-1 kg-1 and 1.0 +/- 0.1 ml min-1 in the animals with and without renal function, respectively. ⋯ Neither temporary hepatic exclusion nor intraportal administration of pipecuronium indicated any significant role of the liver in handling pipecuronium. Renal excretion seems to be the predominant route of elimination. No metabolites were found in this study.