British journal of anaesthesia
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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.
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Randomized Controlled Trial Comparative Study Clinical Trial
Comparison of four non-depolarizing neuromuscular blocking drugs in the suppression of the oculocardiac reflex during strabismus surgery in children.
Eighty children (aged 2-12 yr) undergoing strabismus surgery were randomly assigned to receive tubocurarine, alcuronium, pancuronium or vecuronium during anaesthesia with thiopentone, fentanyl and nitrous oxide in oxygen. Heart rate and rhythm were recorded before and after the induction of anaesthesia and before and during traction on an extraocular muscle. End-tidal carbon dioxide concentration and the degree of neuromuscular blockade were monitored. Alcuronium seemed to give more protection against the oculocardiac reflex (defined as a 20% decrease in heart rate) than did tubocurarine, pancuronium or vecuronium.
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Comparative Study
Antagonism of the muscarinic effects of edrophonium with atropine or glycopyrrolate. A comparative study.
The efficacy of atropine or glycopyrrolate in doses of 10 or 20 micrograms kg-1 and 5 or 10 micrograms kg-1, respectively, has been compared when administered to block the muscarinic effects of edrophonium 0.5 mg kg-1 administered for the reversal of neuromuscular blockade. Both doses of atropine and the higher dose of glycopyrrolate prevented any edrophonium-induced decreases in heart rate; glycopyrrolate at this dose was associated with tachycardia. ⋯ The control of oropharyngeal secretions was adequate even with the lower doses of both anticholinergic agents. Atropine 10 micrograms kg-1 appears to be a better anticholinergic agent for use with edrophonium.
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The ventilatory response to carbon dioxide was studied in 12 unpremedicated children, aged 20-68 months, weighing between 10 and 20 kg, under nitrous oxide-halothane anaesthesia. Tidal volume (VT) and end-tidal carbon dioxide tension (PE'CO2) were continuously measured by pneumotachograph and capnograph. Minute ventilation (VE), respiratory rate (f), mean inspiratory flow (Vl) and effective inspiratory cycle (Tl/Ttot) were calculated during anaesthesia at three different inspired halothane concentrations (0.5, 1 and 1.5%). ⋯ When the inspired concentration of halothane was increased, the slope decreased significantly (39% of initial value at 1% inspired halothane, 26% at 1.5%). The addition of carbon dioxide produced significant increases in VE, VT and Vl but no change in respiratory rate. No statistical difference was observed in the slope of carbon dioxide response between the initial and "control" periods which were measured at the same inspired halothane concentration (0.5%).