Originally appeared as Ask the Vet by Dr. Shawn Ashley in Pug Talk Magazine (Nov/Dec.92 issue)
Anesthesia whether in human or veterinary medicine is a serious subject and should not be taken lightly. No matter how many precautions there can always be unforeseen risks and complications. Risk factors to consider are age related heart, lung, liver, and kidney disease, obesity, pregnancy, chronic illness, circulatory shock, and various built-in breed predispositions. Pugs, unfortunately, have many of these built in anomalies.
Brachycephalic dogs have shortened muzzles which decrease nasal air exchange space and increase air resistance through this stenotic area. This air resistance can give rise to laryngeal spasms and tracheal collapse; thus, closing the primary windpipe leading to suffocation.
These breeds often have enlongated soft palates* which can interfere with the normal function of the epiglottis. The epiglottis is a cartilage responsible in closing over the trachea when swallowing. This interference can lead to aspiration pneumonia and/or or respiratory compromise. These factors must be considered when choosing a particular anesthetic regimen.
Some risk factors can be alleviated by maintaining proper weight, requestion presurgical bloodwork and discussing your veterinarian's chosen anesthetic regimes prior to a surgical procedure. Regimens will vary with each individual case and with each differing procedure.
As every cut does not require stitches, the same holds true for anesthesia --not every procedure requires full endotracheal tube gas anesthesia. There are many regimens. The BEST for your pet is the one your veterinarian is most comfortable with after all risk factors have been considered. However, there are new agents that have been incorporated into veterinary medicine that do lower the risk factor even further.
On of these agents is the anesthetic gas Isoflurane (Aerrane). It is a nonflammable, stable agent that is the most modern in veterinary medicine and the most widely used in human surgery. It is the least soluble of the inhaled anesthetics, which means very little is absorbed by the blood and tissues and near to none is metabolized by the body. Most is simply exhaled off by the patient. These properties make for rapid recovery times in long procedures and short procedures become Iess stressful day surgeries.
At good surgical depths Isoflurance does not routinely sensitize the heart to arrhythmias or reduce cardiac output, maintaining good tissue perfusion. This makes it the anesthetic of choice in patients with heart, kidney, or liver disease. Isoflurane is compatible with all approved pre- anesthesia regimens and may be used in open, semi-open, semi-closed, or closed anesthetic delivery systems. It has a high vapor pressure, is stable in soda lime, is resistant to breakdown by sunlight, does not react with metal, and may types of vaporizers can be converted over to deliver it.
There is no documented toxicity to chronic exposure to isoflurane. This makes it a plus for the staff as well as the patient. However, scavenger systems should be attached to all anesthetic machines regardless of the chosen gas!
The biggest and possibly the only drawback to isoflurane is the cost; yet, its safety is quickly offseting this factor. The price is becoming more and more comparable with other anesthetic inhalants and its properties are a definite crowd pleaser. It is not a matter of whether a veterinarian will be using isoflurane. It is just a matter of time! Pug owners are urged to ask for the anesthetic by name.
| Isoflurane | Halothane | Metboxy Flurane | |
| %usage* | 13 | 15 | 25.5 |
| control depth/recovery | v. rapid | rapid | slow |
| induction time | rapid | slower | v. slow |
| cardiac output | maintained | reduced | maintained |
| metabolism** | .17%liver | 20%liver | 50%liver |
| toxicity** | none known | liver | kidney |
| respiration | depressed | depressed | depressed |
*based on recent AAHA Journal survey of practicing vets in VT. Back.
**chronic exposure w/o scavengers can lead to disease. Back.