Anaesthesia
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Comparative Study
Arterial to end-tidal carbon dioxide tension difference during laparoscopy. Magnitude and effect of anaesthetic technique.
The relationship between arterial carbon dioxide tension and end-tidal carbon dioxide tension was studied in 25 patients during laparoscopy. Thirteen patients received general anaesthesia and 12 epidural anaesthesia. ⋯ The reasons for this difference are probably associated with the physiological changes induced by CO2 pneumoperitoneum and steep Trendelenburg positioning. The choice of anaesthetic technique did not affect the arterial to end-tidal carbon dioxide tension difference significantly (p greater than 0.9).
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Propofol offers many advantages as a total intravenous anaesthetic agent compared with other agents. However, considerable experience is necessary in order to give an uncomplicated anaesthetic. ⋯ A strong statistical relationship was found between measured blood propofol concentrations and the corresponding computer predictions (y = -0.50 + 1.36x). No significant differences in this relationship were found between patients who breathed spontaneously (y = -0.71x + 1.43x) and those who received intermittent positive pressure ventilation (y = -0.33 + 1.32x).
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Ten patients, whose lungs were ventilated initially with intermittent positive pressure ventilation at conventional rates after myocardial revascularisation or cardiac valvular surgery, were weaned using a valveless high frequency jet ventilator at a constant rate of 50 breaths/minute. The withdrawal of ventilation was achieved, when clinical criteria permitted, by reduction of the tidal volume preset on the jet ventilator in successive stages; this was effected by stepwise decreases in the jet driving pressure. ⋯ Synchronisation of the patient's breathing with the valveless ventilator is not required and weaning is tolerated well by the patient. Arterial oxygen tension and saturation were maintained throughout weaning and did not decline after extubation of the trachea.