Some ventilatory effects of XXXX as sole anaesthetic agent.

@entity1 @entity308 @entity871 @entity1009 @entity26 @entity1875 @entity544
Ventilatory effects of @entity1875 , used as a sole agent for the induction and maintenance of general anaesthesia, were studied in 14 healthy unpremedicated @entity1 . Subarachnoid anaesthesia was established before induction of general anaesthesia. Induction was with @entity1875 2.5 mg kg-1 given while the @entity1 breathed 100% @entity26 . We intended to start an infusion of @entity1875 100 micrograms kg-1 @entity1009 ; maintain it for at least 25 min; make a first set of quasi-steady-state observations; double the infusion; and repeat observations after 25 min. The single induction bolus plus single rate infusion was not totally satisfactory: further boluses were usually needed. At induction there was apnoea in all but three @entity1 , sometimes lasting more than 3 min; hyperventilation before induction, combined with @entity871 , probably exaggerated this. Established ventilatory rates were generally 30% higher than awake. One @entity1 became bradypnoeic. Tidal volume and minute ventilation, and the Tl:Ttot ratio, were reduced. Doubling the infusion rate had no clear effect on frequency or tidal volume, but it further reduced the Tl:Ttot ratio and caused an increase in PE'CO2 of 1 kPa. The ventilatory response to @entity544 was 58% of baseline awake control (95% confidence limits +/- 26%) at the lower infusion rate, with further slight @entity308 when the infusion rate was doubled. Doubling the rate of infusion of @entity1875 did not give twice the effect on ventilation, and probably is not giving twice the "depth" of anaesthesia. We cannot say if this is for pharmacokinetic or pharmacodynamic reasons.
