Veterinary anesthesia: Understanding risk management, adverse outcomes
Kurt Grimm, DVM, MS, PhD, Dipl. ACVA, Dipl. ACVCP, is a veterinary anesthesiologist, owner of Veterinary Specialist Services in Conifer, Colo., and works with the surgeons at the Veterinary Referral Center of Colorado in Denver. He has edited several texts on anesthesia and pain management.
Grimm spoke with DVM Newsmagazine recently about his field and the challenges of anesthetizing complex patients.DVM: How has the field of anesthesiology changed in recent years? Do you think the advances have kept pace with growth in other areas of veterinary medicine?
Grimm: The profession has changed so much in the last 15 years. When I graduated in 1995 there wasn't a great emphasis on the care of geriatric pets because a lot of sick animals, especially older ones, were euthanized. Today, for a lot people, that's a last resort. So we are dealing with a lot of complex cases, coexisting diseases and cases that we may not have been trained very well to handle but are now forced to manage.
For example, I see many cats with stable chronic kidney disease and horrible dental disease. That's one of the biggest reasons I get called out to private practices — to give anesthesia for generally routine procedures like dentistries but on older patients that have chronic kidney disease.
Additionally, there wasn't a perceived need or a market in private practice for anesthesiologists. Historically, there were so few board-certified anesthesiologists in private practice people didn't think about using our services to manage anesthetic-related risks. In the last decade that started to change. As surgeons have advanced in the level of surgery that they're performing, having an anesthesiologist there can bring the level of anesthesia and monitoring to a higher level.
However, not all cases have to be referred nor should they be. If practitioners are appropriately prepared they can probably do just as good of a job as most of us. But the types of patients that they don't routinely anesthetize or that are very complex — an anesthesiologist is better prepared to deal with the risks and potential complications that may arise during anesthesia.
DVM: What do you recommend for preoperative care, and how might you modify your approach for the more complex patient?
Grimm: You gather history, do diagnostics and identify the things that are impacting the patient. Then you develop an anesthetic plan that tries to mitigate the risks. When you run into cases that have a long list of coexisting problems, the risks increase. Every time you add another element to the equation, it makes things more complex; you must plan to manage all the risks simultaneously. Occasionally we find something we didn't expect to find, and it postpones the surgery or even changes the owner's decision about going forward with surgery.
If a patient has a pre-existing condition that you either know about or suspect based on physical examination, then it's hard to justify not doing pre-anesthetic diagnostic testing to assess the patient's current status.
I think you'll find plenty of people who say packed cell volume and total solids are adequate for preoperative blood work, but a number of us believe that both a complete blood count and serum chemistry are good practices. If something unexpected is found, then you can consider other diagnostic tests — ultrasounds, X-rays, ECGs — to figure out whether it's a serious problem. The odds of finding something significant with young, healthy animals is relatively low, but occasionally one of them will have, for example, elevated BUN and/or creatinine values. It's worth taking time to figure out if it's either a serious problem or simply dehydration, which can be easily corrected with preinduction fluid administration.
The more information you have, then the more informed decisions you can make about what anesthetics to use or, more importantly, not to use, and what you can rule out as a cause of any intraoperative complication.
Sometimes the sicker patients are easier to plan for. Usually they've been well worked up so you have a lot of information and a complete history.