Easing pets into anesthesia

Tasha McNerney, BS, CVT, CVPP, VTS (Anesthesia and Analgesia) discusses centers on induction agents to facilitate a rapid and smooth transition from consciousness to unconsciousness in veterinary patients, preparing them for intubation and maintenance on inhalant anesthesia in this most recent installment of Pet Connections.

Below is a full transcript, edited lightly for clarity.

Tasha McNerney, BS, CVT, CVPP, VTS (Anesthesia and Analgesia): Hey everyone, it's Tasha McNerney and I am here to talk to you guys today about induction agents. So induction agents are drugs that we give intravenously, sometimes intramuscularly, and the purpose of these drugs is that we want to produce a rapid and smooth transition from consciousness to unconsciousness, and then we want the ability to intubate our patients and maintain them on inhalant anesthesia.

Now, the goal of these induction agents is to very quickly achieve that level of unconsciousness, that loss of reflex muscle relaxation, but we also don't want to do it so fast that we interrupt their cardiovascular or respiratory function. Key about induction agents here is that this is going to be a fast process. Usually, these agents are administered IV, fairly rapidly. Common examples of the ones that you're going to use in practice are going to be things like propofol, maybe alfaxalone, maybe a combination of ketamine and a benzodiazepine, or even a drug like etomidate. The choice is really going to depend on what you have available at your clinic, and the timing of the procedure, the level of pain anticipated, [and] whether or not you're including something like ketamine prior to giving your propofol. That'll all be determined by the actual patient and the procedure being done and their ASA status.

Induction is almost always administered together with oxygenation, if it's not overly stressful for the patient, and then it's rapidly followed by intubation and then delivery of 100% oxygen and your inhaled anesthetic gasses.

You've probably all seen this play out before, because you're probably familiar with giving propofol as a main induction agent in your practice.

All right, now let's talk a little bit about propofol, because propofol is one of the most common induction agents that we use in veterinary medicine. Now, the great thing about propofol is it's very rapid. Not only is it rapid in its onset, right? It works within seconds when you give it [through] IV, but also it's rapid in its metabolism, which means it has a very rapid redistribution and metabolism, so those patients recover pretty quickly from a propofol induction or single bolus of propofol. It allows for a very smooth induction and smooth recovery as well, and usually is associated with less of a like hangover effect than maybe some other induction agents, like a ketamine Valium induction.

Now it should be administered slowly, because if you administer it too fast, you're going to see some of those negative side effects, mainly apnea, right? And we don't want that in our patients. Also, something to consider about propofol is it does have a vasodilatory effect, so it may not be the best choice in patients that already are experiencing something like septic shock or who are very hypovolemic, but for the most part, propofol is a really nice induction agent, and we like to maybe add in some ketamine and do maybe a ketofol induction. But because it has such a rapid onset and a rapid redistribution, it makes it almost a perfect choice for a lot of patients that you're going to put under anesthesia.