Impact of the Anesthetic Circuit
The anesthetic circuit may limit the rate of recovery, just as
it limits induction. If the patient is not disconnected from the circuit on cessation
of anesthetic delivery, the patient may continue to inspire anesthetic. To reduce
the inspired level to zero or almost zero, several factors must be taken into account.
The anesthetic within the circuit must be washed out. The rubber or plastic components
of the circuit and the soda lime within the circuit have absorbed anesthetic (see
Table 5-3
) that can be released
back into the gas phase,[66]
and this anesthetic
also must be washed out. The patient's exhaled air contains anesthetic that cannot
be rebreathed if the inspired anesthetic concentration is to approach zero. The
effect of each of these factors to raise the inspired anesthetic concentration can
be overcome by the use of high inflow rates of oxygen (≥5 L/min).
