What Happens When A Pet Is Anesthetized?

Q&A with Veterinary Anesthesiologist Rebecca Krimins, DVM, MS
Q: While the majority of veterinary anesthesiologists are employed by veterinary teaching hospitals., you’ve opted to work in private practice, Veterinary Imaging of the Chesapeake (VIoC). Why is having a veterinary anesthesiologist so important in this type of practice?
A: When a patient whether a human or animal—is undergoing an MRI, the patient must remain absolutely motionless throughout the procedure. The only way to ensure this with an animal is to anesthetize it. My job is to develop, implement and oversee an individualized anesthesia protocol that brings the animal safely through the procedure and recovery. So many different diseases that are treatable and even curable can only be definitively diagnosed using MRI; it’s gratifying being part of that process.
I also develop anesthetic protocols for referring veterinarians who have questions on how best to manage their patients that have complex or unusual issues.
Q. What do you mean by an anesthetic protocol?
A. It’s an individualized plan for managing the patient that includes everything from the drugs used for pain, sedation and general anesthesia, to when and how they’re to be used, what monitoring will be used, anticipated monitoring parameters, and how to respond if there are any adverse events.
Over the past year at VIoC, we’ve done MRIs of everything from an Australian snake-necked turtle to a chicken and a 220-pound dog. Our MRI would likely accommodate up to a 400-pound animal; and I can create an anesthetic protocol for virtually any species.
Q. You require that all animals that are going to have an MRI have a radiograph of their chest, blood work, and you ask referring vets for a patient history. Why?
A: I want as complete a picture of the patient as possible so that I can develop the best anesthesia protocol for that patient. I don’t meet the owners before the procedure. What I know is based on the patient history from the referring veterinarian, the test results and my examination.
I want to know if there are any reasons that the animal might have a reaction to the anesthesia, such as heart problems or kidney disease; whether there are any known medical conditions such as seizure disorders or diabetes; and what prescribed and over-the-counter medications and supplements the animal may be taking. The blood work lets us know the electrolyte levels, the kidney and liver function and other vital information. Liver function, for example, is very important since most anesthesia is metabolized through the liver, although there are other drugs we can use if there are liver problems.
Q. What does your examination involve?
A. Just prior to the MRI, I assess the patient by connecting the patient to monitors and taking the blood pressure, pulse ox, temperature, an electrocardiogram (EKG) and by reviewing the prescreening tests and information. If I see a problem, I may change the anesthesia protocol or, if necessary, hold off on doing the MRI.
Q. Can you take us through the steps in anesthetizing an animal for MRI?
A. We start by sedating them with an injectable drug. Some animals—like Labrador Retrievers, for example—can be hyper, while other patients can have pain, which contributes to their anxiety. We want them to be relaxed and calm, so I take my time at this stage.
Once I have the patient sedated, I again reevaluate; this type of evaluation and reevaluation goes on throughout the course of the procedure and recovery.
Next we pre-oxygenate the patient; this is important as we don’t want the patient to become hypoxic during the procedure. Only then do we proceed with induction, during which we give a specific drug to transition the patient from being sedated to being under general anesthesia; and we intubate the patient.
Next we enter the maintenance phase. The animal is inhaling the anesthesia—and sometimes oxygen, as well—the entire time they’re in the MRI. This is possible because at VIoC we have an MRI-compatible ventilator, which is really the gold standard in veterinary MRIs.
The imaging typically takes an hour. In some circumstances once it’s completed and the results have been provided to the surgeon, we transport the patient directly to surgery. Otherwise we’ll continue to monitor the patient until it’s fully awake and ready to go home.
Often patients are awake within minutes. Since the majority of patients being scanned aren’t healthy, they need to be carefully monitored. Sometimes they are anxious and need more sedative, or they need pain medication. They can lose body temperature, so they’re placed on heated air pads. A young animal might be fine in 30 minutes—meaning they’ve recovered with a strong heartbeat and respiration—where an older animal might need hours or an overnight stay to recover.
Q. How long does it take to get the results of the MRI scan?
A. If it’s an emergency MRI, we can have it read immediately by our boarded radiologist. Since the scans can be sent in real time to any veterinarian, including our radiologist, we can be really efficient in getting a timely diagnosis, especially in an emergency situation. The standard results are typically provided in 24 to 48 hours.
Q. You’ve said that there’s an art—not just a science—to anesthesia. What do you mean by that?
A. Part of the art of anesthesia is keeping the patient from being too light or too deep. You can have five 90-pound Labrador Retrievers and they’ll each need their own anesthesia protocol since they’ll metabolize the anesthesia differently. Throughout the whole process, I’m assessing every patient at every moment and making adjustments as needed.