TECH UPDATE

Intermittent Sedation-Assisted Recovery; the ‘Liquid Rope’

By Travis Otremba, LVT,CVT

Recovering horses from inhalant anesthesia can be a challenge. Horses are, in general, large and can become quite uncoordinated as they arouse from anesthesia.

The anesthetics we use have an affinity for fat and muscle, and many horses can have plenty of both. Compounding matters, those anesthetic agents cause emergent delirium, hallucinations and dissociative behaviors in the horse. Add in a tight sympathetic tone, with a fightor-flight response that is almost always engaged, and you have a recipe for a potential train-wreck recovery.

In cases where recovery carries an increased risk, rope-recoveries are common. A head and tail rope, with 2 assistants, 1 on each respective rope, help the horse to steady itself once aroused and attempting to stand. The rope-recovery limits the “free” movement of the horse within the recovery stall, thus decreasing the risk of injury.

However, what happens when staffing is at a shortage, and there aren’t any extra bodies to help you recover the patient? Or, you might not have ropes or the setup to use them properly. What if the horse will not tolerate being tied to the wall? Or will it panic when it realizes there is a rope tied on its tail?

When these challenges arise, I turn to the “liquid rope” recovery; a 1-individual, intermittent sedationassisted recovery that can help to ensure a quiet and low-risk standing from general anesthesia.

At Ocala Equine Hospital, we have a heavy and fast-paced orthopedic case load. Ensuring a good and efficient recovery from anesthesia is paramount to our success. Often, horses just need a little extra help other than a free, unassisted recovery but may not require or tolerate an actual rope recovery.

It’s for these patients that the intermittent sedation recovery method works well.

The protocol is similar in technique to a rope recovery, i.e., the horse is positioned on a pad, back to the doors, the anesthetist directly behind the withers and a towel covers the eye. The extension-set from the IVC is draped over so the anesthetist can access it easily.

Everything about this set up is almost identical to a rope recovery, there is just 1 caveat: no ropes, and it only uses 1 person; no second assistant needed.

The liquid rope enables the horse to clear itself of the anesthesia used during surgery and awaken more calmly, reducing its risk for injury.

Images courtesy of Travis Otremba

Chemical restraint now replaces any physical restraint, and the anesthetist relies on intermittent sedation. By intermittent sedation, I mean small boluses of a sedative (almost always xylazine due to its fast-acting and fast-clearing properties), given at specific increments during the recovery phase.

I like to split the timing of this sedation into 3 different areas:

1. pre-arousal,

2. arousal and

3. standing.

Since there is no physical restraint being applied to the horse, i.e. no halter, ropes or humans to lay on it, I tend to give most of my sedation boluses during the prearousal phase. The goal is to delay arousal in this phase. As I stated before, horses can arouse very uncoordinated, fractious and panicked.

To decrease that chance, I prefer to delay their arousal and give them a chance to blow off a lot of the inhalant. When I see my horses coming back to consciousness around the 15-minute mark, I will delay that to about 30–40 minutes post end of inhalant anesthesia.

To do this, a fast-acting but short-living alpha-2 sedative works well and that is why I use xylazine, almost exclusively. Alpha-2 sedatives are potentiated by inhalants, so understanding that relationship gives the anesthetist an edge to keep them down without overdosing. Small boluses can really go a long way to keeping the horse unconscious while still breathing off the excess gas, creating a clearer animal once it wakes up.

Once the horse is positioned on the mat in recovery, I like to give the first small bolus of xylazine, just before removing the endotracheal tube. If they are still fairly deep with inhalant, this could cause a small bout of apnea, but if not, it will facilitate a stimulant-free extubation and not arouse the horse. At this point, the horse is positioned, extubated and breathing well.

As the horse comes up the levels of unconsciousness, take note of breathing patterns, light sensitivity in the eye and any tensing of the horse. Small boluses of xylazine may be administered as changes in respiration occurs or light sensitivity in the eye starts to return. Generally, around every 8–10 minutes a small bolus of xylazine is given.

If there is some early tensing in the neck or limbs, a larger dose might be advantageous as you might be getting a bit too close to arousal.

As the horse slowly comes up to consciousness, ear movement is a fairly consistent sign that the horse is back to consciousness and is responding to its environment. However, any leg movement, neck movement, or swallowing should be treated as arousal.

This is one of the most important doses, in my opinion, as it slows the horse’s panic or abolishes the emergent delirium caused by inhalant anesthesia. Since the arousal has been delayed, and the horse has had time to breathe off anesthetics, there is no longer a significant amount of inhalant within the horse to potentiate a small bump of xylazine, so a larger dose is generally warranted.

As well, I tend to talk to them in a low, soothing voice and pet their neck as they are returning to consciousness, giving them some calming encouragement. Horses are social animals, and many will respond positively to the calm voice.

The towel is still over the eye, and as long as the horse is quiet I may remove it, but I’ll leave it on if the animal is significantly light sensitive or wants to move. On the chance the horse immediately rolls to sternal and has an abrupt arousal, a bump of xylazine should help to quiet the ‘flight’ reflex, and a lot of times the horse will lay back to a semi-sternal recumbency, or stand strong and quick.

On average, they should have the appearance of lighter sedation, not so much so their nose is on the floor.

Soon, the horse should be standing. It may be tempting to encourage the horse to stand at this time, but resist that urge and allow them the time to wake up quietly on their own and without pressure.

Again, talking to them during this stage is a great tool to help keep them calm. Once the horse makes the effort to stand, be prepared to leave the stall and close it up. The horse should be quiet, slightly sedate but alert. Keep in mind, a small amount of stored drug in the muscle or fat may get squeezed into circulation due to the sudden engagement of muscles.

Nystagmus, muscle twitching and a ‘stunned’ appearance may be seen.

Once they are standing, however, that will diminish quickly and within a few minutes the horse should appear normal. Having the stall ready to be shut up, though, is important for safety for everyone—including the horse—in case they go down or have a harder recovery.

Once standing, if they are a bit wound up or need more pain management, a small amount of butorphanol or detomidine may be beneficial to quiet them again and give the anesthetist time to get the horse organized before heading back to their stall.

In all, this recovery works well to get a horse from general anesthetic recumbency to standing, when there is increased risk to the surgery site, or the patient presents a risk to themselves by allowing a free recovery.

By delaying arousal, quieting the flight response and keeping them calm, the intermittent-sedation-assisted recovery method is useful for anesthetists in equine surgery to get their horses standing. Furthermore, as a 1-person recovery, it is easily incorporated in a variety of practices to ensure a high standard of care for the horse. MeV

Teaching Points

The main goal of intermittent sedation is to delay arousal to give the horse time to burn off the anesthetics given during surgery before it returns to consciousness.

You might find that 1 bolus sends them deeper or multiple bumps within a short time might be needed to keep them unconscious.

By keeping the bumps of sedation small, the anesthetist can add more if warranted, but not start to accumulate a lot of xylazine in the horse.

Experience will help in differentiating the subtle changes that clue you in that arousal is coming, but staying alert to the horse and having a plan is necessary to success.

About the Author

Born and raised in Michigan, Travis graduated from Baker College, Jackson, and obtained his credentials as a licensed veterinary technician. Travis worked for 8 years as a small-animal technician in general practice, as well as a short time in surgical oncology in his home state. Following his passion for horses, Travis made the move to Ocala, Fla., in 2014, to work for Ocala Equine Hospital. With a focus solely on anesthesia, he completed a 4-month mentorship with Eric Abrahamsen, DVM, DACVAA, and became a surgery technician, anesthesia. Since then, he has been credentialed in Florida as a certified veterinary technician.

For more information:

AAEVT Equine Manual for Veterinary Technicians, DeNotta, S, et.al. Wiley Blackwell, 2023. Enhanced Chemical Restraint, Abrahamsen, EJ, DVM,DACVA. 2014.