How to Knock Out a Horse

I woke up the other morning and realized that our clinical year is already halfway gone. I'm amazed I'm actually still alive at this point, not to mention actually beginning to have some semblance of confidence and aptitude for this thing that is supposed to be my job (in less than 9 months). I've gotten through more than half of my clinical rotations at this point, not limited to but including wildlife medicine, oncology, cardiology, small and large animal medicine, and ambulatory practice (driving around making farm calls for things like dairies, alpaca farms, and backyard goats and sheep). Each of these has had their fair share of fantastic stories, and I should have been keeping up with them, but clinical year doesn't leave much time for things besides eating and sleeping (or attempting to). Some rotations I've liked better than others, some I was completely scared out of my mind, and some that I had early on I'm wishing I could have a do over (I could do it so much better now!). Let's fast forward past that to the rotation I'm currently on. Anesthesia.

Now I will have to admit, the prospect of this rotation was terrifying to me. With good reason. Anesthesia can be scary. You're using a lot of different drugs that can have a lot of different side effects, many if not most of the animals we anesthetize here are not systemically healthy, and things can go wrong. Heart rates can drop too low or shoot sky high, breathing effort can be sub-par, blood pressure can plummet, patients can get very cold. The scariest part for most of us, as we're just learning the ropes, is what we call 'induction'. This is where we use our drug of choice (most often propfol, of Michael Jackson fame, but there are others) to bring the animal from conscious to unconscious and able to be intubated. (i.e. you need to make this animal so sleepy that it will not protest you sticking a tube into its trachea). This can be a tense time. We like to titrate our induction drugs exactly to effect, avoiding giving more than the animal needs. Timing has to be pretty perfect; you need to get that tube in there before the animal starts waking up, gagging, potentially biting the tube. And intubation is not the easiest task. Dogs have long faces, it can be difficult to see far into the back of their mouths to see what you are doing. Sometimes the size tube you think will work is in fact the wrong size (we often have three or four different tubes on our trays, ready to go if this happens). And cats do this delightful thing where their larynx spasms if you touch it too soon, and then you are never getting that tube it. 

So, if you're good, you induce the animal, get it intubated, get it hooked up to oxygen and inhalant anesthetic, and then set up your plethora of monitoring equipment. Your heart rate looks fine, pressures are ok, animal is  doing fairly well breathing on it's own. Phew. You give a sigh of relief and get ready for the next scary part, whatever that may be.

Now if you think induction of a cat or a dog is scary (and we do), that brings me to the horses. You may be wondering how we knock a horse down, get it intubated, and get it onto a surgical table and into the operating room. Now THIS can be scary. The horse gets lead into a padded induction stall, with a swinging padded board that will be used to slowly squish the horse up against the wall so that it falls as gracefully as a thousand pound animal can fall. Horses often balk walking into the stall. It's scary in there, not wide open, and there are weird things around. Once they are standing in a relatively accomodating position, they get their premedication, which is a heavy dose of sedative to prepare them for the induction agent. The induction drug is then given when the horse is nice and sleepy, and this is where the squeeze board comes in handy. Two people at the front of the horse, four of five on the squeeze board, and you gently push the horse into the wall and cross your fingers that it just slides down gracefully. This isn't always the case. Horse can drop awkwardly, they can go down and get back up, they can freak out and kick the board out and send you flying across the room. Tense. And once the horse drops, you've gotta hustle and get the endotracheal tube in and get that thing into surgery and hooked up before it decides its not actually that asleep. A horse trach tube is one of the most ridiculous things I've ever seen; about three feet long with a diameter of like three inches, with the attachment on the end of the tube it looks like a giant plunger. Luckily, it's easier than you would think to get that tube in. 

Anesthetizing like a boss

But still, you're a little nervous, and while you're frantically trying to get a giant plunger down a horse's trachea, everyone else in in the stall is hooking the horse's legs up to the hoist to move it onto the surgical table. If you don't watch yourself, you could turn around and be bowled over by a horse swinging upside down by its legs. Careful.

Even scarier than knocking the horse down is waking the horse back up. They get hoisted up by the crane again and moved onto a very thick pad in a padded room with a padded floor (sound like this is about to get dangerous?). Ropes are tied to the tail and to a soft recovery halter to help the horse when it tries to stand. A brave soul gets in there to pull out the trach tube once the horse is breathing well enough, and then skedaddles out of there before he gets trapped and kicked into a wall by a delirious, gigantic animal.
The horse will lay quietly, sleeping, for a while, and you are watching through a tiny peep hole for the excitement to begin. Then once they decide they're awake, they usually don't mess around. They usually try to pick their head up first, do a little head flopping, try to roll up onto their chest. Once the animal gets itself sternal, the smart horses will just sit there a little while longer, waiting until they are ready to stand. Others are not as smart. They try to stand, lose their footing, stumble across the stall and collide with the wall. Faceplant into a corner and sit there for a while. Fall backwards into the door you are watching through and smash your nose if you get careless and let your face get too close. They often stumble around and end up standing with one or more feet on the two foot thick mat they were previously lying on, which doesn't really help the balancing situation. Some other brave soul can go in and try to slowly coax the horse to step of the mat, at which point someone beckons frantically for some students to get on the ropes on the other side of the wall and pull the mat up out of the way (this activity requires me to dangle my entire body weight on the rope). Eventually the horse will be standing well enough it can be walked by two people, one on the halter and one holding its tail, back to its stall. If all goes well, your horse is just fine. Many leave the recovery stall with scrapes and bumps from stumbling around. One horse today went face first into a corner and laid there with her face pressed into the floor for a while. Another woke up and stumbled around, then decided she was very awake and paced tight, stumbly circles interjected with angry whinnies. It can look very dramatic.
Unluckier ones than these can injure themselves, damage a surgical repair just done, hurt an eye, or even worse, break a leg. Fortunately, these injuries do not happen that often, but they are a very real threat when anesthetizing such a giant animal. We do our very best to keep the many people involved out of harm's way too, but there are many stories of broken legs and broken noses that get tossed around when everyone is sitting around waiting for the horse to start walking up. They become legendary.
After anesthetizing quite a few horse cases thus far, induction and recovery of small animals seems a little bit less scary! While an angry malamute may intimidate me before it's asleep, at least it can't ACTUALLY kill me. I think I can handle it :-)