Articles: intubation.
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Randomized Controlled Trial Clinical Trial
Modification by alfentanil of the haemodynamic response to tracheal intubation in elderly patients. A dose-response study.
Fifty-five elderly patients undergoing elective ophthalmological surgery were randomly allocated to four groups. Following the induction of anaesthesia with thiopentone (given over 2 min) and the administration of atracurium 0.6 mg kg-1, patients received alfentanil 400, 600, 800 or 1000 micrograms. Intubation of the trachea was performed 90 s later. ⋯ In each of the groups there was a significant decrease in systolic arterial pressure and a significant increase in heart rate on induction of anaesthesia. In those patients who received either 400 or 600 micrograms of alfentanil, arterial pressure increased immediately after tracheal intubation, whereas in those receiving alfentanil 800 or 1000 micrograms, arterial pressure decreased immediately after tracheal intubation, and when measured 10 min after intubation. It is suggested that alfentanil 600 micrograms (10 micrograms kg-1) constitutes the optimal dose with which to obtund the haemodynamic response to tracheal intubation in elderly patients, and to minimize cardiovascular depression after tracheal intubation.
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Comparative Study
Pressure support compensation for inspiratory work due to endotracheal tubes and demand continuous positive airway pressure.
We evaluated the use of pressure support to compensate for the added inspiratory work of breathing due to the resistances of endotracheal tubes and a ventilator demand-valve system for continuous positive airway pressure (CPAP). A mechanical model was used to simulate spontaneous breathing at five respiratory rates through 7-mm, 8-mm, and 9-mm endotracheal tubes with and without a ventilator demand CPAP circuit. Added work was measured as the integral of the product of airway pressure and volume during inspiration. ⋯ For each endotracheal tube and VT/TI, a level of pressure support (range, 2 to 20 cm H2O) was found which eliminated added work in the spontaneously breathing subject. This level correlated well with that predicted from the data derived using the mechanical model. We conclude that when adjusting for an endotracheal tube's diameter and VT/TI, pressure support can be used to compensate for the added inspiratory work due to artificial airway resistances.
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The haemodynamic response to tracheal intubation was compared in 303 patients in whom anaesthesia was induced with either thiopentone 4 mg/kg, etomidate 0.3 mg/kg or propofol 2.5 mg/kg, with and without fentanyl 2 micrograms/kg. There was after propofol alone a significant decrease in arterial blood pressure, which did not increase above control values after intubation. ⋯ Increases in heart rate occurred with all agents after laryngoscopy. The use of fentanyl resulted in arterial pressures lower than those after the induction agent alone, and in an attenuation, but not abolition of the responses to laryngoscopy and intubation.