Anaesthesia
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Randomized Controlled Trial Clinical Trial
The effect of humidification and smoking habit on the incidence of adverse airway events during deepening of anaesthesia with desflurane.
The effect of two levels of humidification on the incidence of adverse airway events was studied in 58 adult female patients during deepening of anaesthesia using up to 12% desflurane. Humidification was provided by a breathing system filter with either low moisture-conserving performance (17.2 mg x l(-1) at 0.5 1 tidal volume, Group L) or high moisture-conserving performance (33.5 mg x l(-1) at 0.5 1 tidal volume, Group H). Forty-eight per cent of patients smoked and there were more smokers in Group L than in Group H. ⋯ When both humidity and age were included in the analysis, there was a significant smoking-humidity interaction (p < 0.05), such that high humidity decreased the incidence of coughing in nonsmokers but not in smokers. The incidence of laryngospasm was significantly lower in Group H than in Group L (p < 0.05). We conclude that when patients inspire high concentrations of desflurane during induction of anaesthesia, increasing humidification to the levels achieved in this study decreases the incidence of coughing among nonsmokers and of laryngospasm in both smokers and nonsmokers.
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In the South Thames (West) region of the United Kingdom, during a 6-year period from 1993 to 1998, there was a significant increase in the Caesarean section rate accompanied by a significant decrease in the use of general anaesthesia for operative delivery. During this time, there were 36 failed tracheal intubations occurring in 8970 obstetric general anaesthetics (incidence 1/249). There was no significant difference in the incidence of failed tracheal intubation in each of the six years. In 24 of the 26 cases for which the patients' notes could be examined, there was either no recording of preoperative assessment, a failure to follow an accepted protocol for failed tracheal intubation, or no follow-up.
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A patient with cerebral infarction was certified clinically brainstem dead. However, 4 h after the diagnosis of death, while the patient was being ventilated using the biphasic positive airway pressure mode, the 'assist' indicator light on the Drager Evita 2 ventilator illuminated intermittently. There was no evidence of spontaneous breathing. 'Triggering' was probably caused by a decrease in airway pressure in time with cardiac contraction. The trigger flow rate is crucial as factors other than the patient's inspiratory effort can initiate flow from the ventilator with very sensitive settings.