A comparison of intravenous and gaseous induction of anaesthesia : the clinical and pharmacoeconomic benefits in day-case patients.
The very first anaesthetics were gaseous. These early slow, irritant or flammable
drugs were ultimately displaced by intravenous agents, despite other beneficial properties.
Preliminary work with two new insoluble, potentially rapid-acting nonflammable
anaesthetics showed desflurane, the less soluble, to be too irritant while sevoflurane was
smooth and well-tolerated. This thesis set out to examine possible clinical andlor financial
benefits from the use of sevoflurane in day case patients.
A double-blind comparison showed sevoflurane to induce anaesthesia almost as
rapidly as the most common intravenous drug, but to minimise apnoea and hypotension,
with a smoother transition to the maintenance phase and faster emergence from brief day
case anaesthesia. While a few patients found gaseous induction unpleasant, this was not
confirmed by an audit of sevoflurane's more widespread use.
Further work evaluated alternative, vital capacity, induction techniques. However,
simple tidal breathing was found to be equally effective but more consistent, appearing to
be the method of choice, even compared with the most recent, optimised delivery of
intravenous anaesthetics. Gaseous induction was shown to facilitate airway maintenance
with either a face mask or laryngeal mask. Double-blind comparisons showed that it also
provided acceptable conditions for tracheal intubation in the small minority of day case
patients in whom this is required.
Compared to the usual intravenous anaesthetic, gaseous induction with sevoflurane
was shown to be less expensive under most common circumstances. Gaseous induction also
reduced anaesthetic consumption during the subsequent maintenance phase, making it the
most efficient way in which to use inhalation anaesthetics.
Having reestablished gaseous induction as an important technique with clinical and
financial benefits in modem day case practice, this thesis concludes with suggestions for
future research to further refine the process and find solutions to some minor problems,
such as occasional patient reticence and the possibility of increased postoperative nausea.