British journal of anaesthesia
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Randomized Controlled Trial Clinical Trial
The cricoid yoke--a device for providing consistent and reproducible cricoid pressure.
An instrument is described which, when used during the accelerated induction technique, ensures that consistent and adequate cricoid pressure can be applied. Mothers undergoing general anaesthesia for elective Caesarean section were studied in order to illustrate the clinical application of the instrument. The consequences to intubating conditions of applying adequate cricoid pressure, and an assessment of the instrument's control over the incidence of regurgitation during operation were investigated.
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The effects of overnight fasting on gastric contents and on the symptoms associated with fasting were studied prospectively in female outpatients. Group A (n = 66) were patients scheduled for first trimester therapeutic abortion; group B (n = 66) were scheduled for minor gynaecological surgery. It was demonstrated that overnight fasting (15 +/- 3 h) did not guarantee an empty stomach (volume 22 +/- 13 ml) and that gastric acidity was high (pH 1.6 +/- 0.5). ⋯ Before anaesthesia, 50% of all patients had symptoms of moderate to severe hunger, while 44% of patients had symptoms of moderate to severe thirst. Neither the severity of symptoms of fasting nor the duration of fast correlated with gastric volume or pH. Patients in group A had significantly greater symptoms of hunger; however, they also had fasted for significantly longer (P less than 0.002).
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The most important clinical properties of local anaesthetic agents are potency, onset, duration of action and relative blockade of sensory and motor fibres. These qualities are related primarily to the physicochemical properties of the various compounds. ⋯ In general, the local anaesthetics for infiltration, peripheral nerve blockade, and extradural anaesthesia can be classified into three groups: agents of low potency and short duration, for example procaine and chloroprocaine; agents of moderate potency and duration, for example lignocaine, mepivacaine and prilocaine; and agents of high potency and long duration, for example amethocaine, bupivacaine and etidocaine. These local anaesthetics also vary in terms of onset: chloroprocaine, lignocaine, mepivacaine, prilocaine and etidocaine have a rapid onset, while procaine, amethocaine and bupivacaine are characterized by a longer latency period.