Canadian journal of anaesthesia = Journal canadien d'anesthésie
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Comparative Study
Airway irritation produced by volatile anaesthetics during brief inhalation: comparison of halothane, enflurane, isoflurane and sevoflurane.
Eleven male volunteers were studied to compare the airway irritation produced by the four anaesthetic agents: halothane, enflurane, isoflurane and sevoflurane at two concentrations, equivalent to one and two MAC. Tidal volume, respiratory frequency and functional residual capacity changes induced by 15 sec inhalation of the anaesthetics were measured using respiratory inductive plethysmograph. Appearance of the cough reflex was also observed. ⋯ The orders of appearance of the cough reflex and of subjective airway irritation were similar. Sevoflurane did not elicit a cough reflex. It is concluded that sevoflurane was the least irritant anaesthetic and is considered to be the most suitable for inhalational induction of anaesthesia.
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Randomized Controlled Trial Clinical Trial
pH adjustment of mepivacaine decreases the incidence of tourniquet pain during axillary brachial plexus anaesthesia.
The effect of pH adjustment of mepivacaine on the incidence of tourniquet pain during axillary brachial plexus anaesthesia was studied. Thirty-nine patients scheduled for hand surgery, during which use of pneumatic tourniquet for longer than 60 min was planned, were randomized into two groups. Both received axillary brachial plexus block with 40 ml, 1.4% mepivacaine, 1:200,000 epinephrine. ⋯ Tourniquet; pain was defined as poorly localized and distinct from an inadequate axillary block by a blinded observer. More tourniquet pain occurred in the control group. The authors conclude that alkalinization of mepivacaine for axillary brachial plexus anaesthesia may be indicated in cases where use of pneumatic tourniquet for long periods is planned.
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This study in dogs determined the effect of systemic cooling and arterial hypocarbia during cardiopulmonary bypass (CPB) on the requirements for enflurane anaesthesia (MAC) before and after CPB. Twelve mongrel dogs were each anaesthetized with enflurane in oxygen on two separate occasions. End-tidal enflurane concentration was measured with a Puritan-Bennett Anaesthesia Agent Monitor. ⋯ Analysis of the data, using ANOVA for repeated measures, revealed MAC 3 (1.95 +/- 0.33%, post-CPB) to be reduced when compared with MAC 1 (2.18 +/- 0.28%, P < 0.01) or MAC 2 (2.10 +/- 0.22%, P < 0.01), determined before CPB. Multivariate repeated measures analysis revealed no independent effects of hypothermia or arterial hypocarbia during CPB, on MAC reduction. By the time of the second experiment in each dog (two weeks later), MAC had returned to baseline levels.(ABSTRACT TRUNCATED AT 250 WORDS)
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Desflurane is a volatile anaesthetic that combines low blood gas solubility (blood/gas partition coefficient = 0.42 at 37 degrees C), moderate potency (MAC = 6-7%), and high volatility (vapour pressure = 681 mmHg at 20 degrees C, boiling point = 23.5 degrees C). The volatility and potency of desflurane prevent its safe use in vaporizers of traditional design. We present a mathematical model which demonstrates the potential for desflurane overdose if contemporary vaporizers are misfilled with desflurane. ⋯ The calculated desflurane output of a misfilled enflurane vaporizer at a dial setting of 1% and a temperature of 22 degrees C is 57.8%, or 9.6 MAC. For misfilled enflurane, isoflurane, and halothane vaporizers at dial settings equivalent to one MAC at 22 degrees C, the calculated desflurane output is 14.0, 10.2, and 7.8 MAC, respectively. We conclude that the safe delivery of desflurane will require engineering safeguards, additional monitoring, and education of the anesthesia community.