Profound opioids are useful in the critical patient to reduce the need for and detrimental effects of high levels
of inhalant anesthesia. (Use an anticholinergic if needed to maintain normal heart rate.) Oxymorphone, hydromorphone
and fentanyl consistently reduce MAC and can provide excellent analgesia.
Inhalant inductions should be chosen for special situations when injectables are either impossible to administer or contraindicated. It is a common method for induction of small exotic species and lab animals.
Small patients with no accessable veins or that are dangerously aggressive to handle are often induced in a tank using high inhalant concentrations. Choose an induction site close to the room exhaust to help remove any escaping gases. Make sure the tank is connected to a scavenge during the induction. Following removal of the animal from the tank, close the lid and place the tank near the room exhaust or leave it connected to the scavenge.
Critical cases may be induced with isoflurane or sevoflurane after a suitable opioid premedication. Mask inductions should be carried out near the room exhaust. Masks used should have a good fitting diaphragm to reduce escape of gases. Always turn the O2 off when the mask is withdrawn to assess depth or to intubate.
Rapid recovery or out-patient practice in small animals is not a good reason for the extra pollution associated with this technique. Propofol can be used for this purpose, producing a smoother induction, no pollution and often a smoother recovery. It also offers an excellent alternative for cesarian section induction.
