Making Good Choices in Veterinary Anesthesia: Procedural Sedation
By Elana Rybak, DVM, cVMA
In our practice we have various needs for procedural sedation for short procedures such as radiology, BAER testing (Brainstem Auditory Evoked Response testing, AKA - hearing testing), and CT scanning, amongst others. We see a broad range of patients from healthy puppies to geriatric patients with multiple comorbidities. Let’s talk about some different scenarios where procedural sedation is needed, and what some protocols may look like for these cases.
Your first patient is a 5 week old female Dalmation puppy that is presented for BAER testing. The puppy is sweet and friendly, but is very wiggly and just will not sit still! You only need a few minutes to get your testing done, and it is a non-painful procedure so no need for strong pain control. At 5 weeks old, a puppy is still considered a neonate and therefore is going to have an increased sensitivity to anesthetic drugs, a decreased ability to respond to physiologic change, and will be dependent on heart rate for cardiac output and blood pressure maintenance. Another consideration is that experiences that a puppy has in early life can affect its behavior long-term, so gentle handling and positive reinforcement are quite important as well. Thinking about drug selection, due to the dependence on heart rate for cardiac output, drugs that would drastically reduce the heart rate such as Alpha-2 agonists could be problematic in this patient. The simplest, and really quite effective option in this case is good ol’ Butorphanol. We typically use ~0.3mg/kg IM in our young puppy patients for this procedure and it generally offers just the right amount of calming/sedation that we need. It is relatively short-acting and is not a significant cardiovascular depressant so it is quite useful and safe for this type of case.
Your next patient is a 10 year old male neutered Labrador mix with a liver mass who needs an abdominal CT for surgical planning (this scenario could also apply to an abdominal ultrasound with fine needle aspirate sampling). The dog is otherwise healthy, and liver enzymes are only mildly elevated on bloodwork. For CT, we need patients to be completely still for about 10-15 minutes to plan and acquire images (depending on the sites being imaged). An IV catheter is always placed for contrast administration.
Since this dog is otherwise healthy, and CT is a non-painful procedure, we commonly use Butorphanol with Dexdomitor for sedating these types of patients. We often start with a lower dose of Dexdomitor (~2-3 mcg/kg) with 0.2mg/kg of Butorphanol. If we need a little more muscle relaxation, Midazolam (0.1-0.2 mg/kg) can be added to this combination, or if the patient is fractious/aggressive, we may add some Ketamine (0.5-1mg/kg) to the Butorphanol + Dexdomitor combination. If the resulting sedation is not sufficient for immobilization, we can always add additional Dexdomitor dosing in small increments IV, or titrate a low dose of Propofol or Alfaxalone IV to effect. Dexdomitor offers predictable sedation and is reversible, and just because the patient is older does not mean this drug cannot be used, though lower dosages are usually sufficient. Additionally, Butorphanol has excellent sedative properties and works synergistically with Dexdomitor.
Your last patient is a 14 year old female spayed Calico cat with a grade 3/6 heart murmur that needs spinal radiographs taken. The cat is a bit ‘spicy,’ is fairly painful and is not amenable to being stretched for proper positioning in radiology while fully awake. In cases like this, we would likely use a combination like Methadone (0.2-0.3mg/kg) with Alfaxalone (1mg/kg) IM to get this patient both more comfortable/less painful, as well as more relaxed/heavily sedated for proper positioning. Opioids are considered quite safe for patients with cardiovascular disease, and they are reversible. Alfaxalone is able to be dosed IM as well as IV, so it is perfect for cases like this where you are unable to get IV access in the awake patient but perhaps can’t or don’t want to use drugs like Dexdomitor or Ketamine that have more significant cardiovascular effects. Top-offs of Alfaxalone may be needed, but usually a combination like this will get you a much calmer, safer, more comfortable patient to work with.
Ultimately procedural sedation requires a good balance between the procedure planned, the patient’s physiologic needs and the anesthetist’s comfort with medications and protocols. There are many different ways to approach these cases and as long as this balance is reached, safe and effective procedural sedation can be achieved for any patient.