Hello there! Hope you are having an enjoyable weekend – I know I am, still cast-free and finally without a limp! A couple weeks ago we offered a cat’s eye view of equine dentistry. This week, I thought it would be important to discuss a little bit further about everything that goes into forming what we call “the anesthetic plan” for your horse’s dental. While your horse is nowhere close to being under general anesthesia, there are anesthetic considerations for every situation involving an equine dental. The first and foremost is safety – for you, the veterinary staff, and your horse. This is the primary reason we ask you to take a step back during your horse’s dental, and let us do the work! Some of the sedatives we use can easily kill a human in fractions of the doses used for the dental, and should only be handled by a veterinarian. The vets are prepared with emergency drugs in case of an accidental overdose or human exposure.
The first thing the Springhill vets do about your horse’s dental happens before your appointment time even arrives. This happens when your horse is already a patient of Springhill Equine, or if you have taken the time to provide complete information about your horse by filling out our new client form and sending it back to us before your appointment (also earning you $5 off your bill!). The vets look at the age, breed, sex, and size of your horse to the best of their ability, and begin to consider what type of sedation would best suit your horse’s physiology. We examine relevant past medical history in our records, and if a dental was performed by Springhill in the past, we consult the last dose used. Between these records, and communication between Dr. Lacher and Dr. King, any past known behavior of the horse (such as needle phobias) or response to sedation (‘He’s a cheap date!’) is taken into account. The doctors arrive on the farm with the foundation of an anesthetic plan in their head – prepared to reconsider our anesthetic approach at every step.
Knowledge of your horse’s behavior is crucial due to another important anesthetic principle called “windup”. Many horses (understandably!) experience anxiety surrounding a dental experience. Stress experienced prior to, during, and in the minutes following sedation causes physiologic responses that can make the horse require more sedation (sometimes A LOT more). We work to minimize that. From the start, we try to move calmly and quietly while sedating the horse, and may give your horse treats to make it a more pleasant experience. Some horses can be very difficult or fearful of intravenous injections, therefore, sometimes more restraint is required to keep everyone involved out of harm’s way. It is important during this time that you let our staff handle the horse. Accidental injection of these drugs into the carotid artery (instead of the jugular vein) will result in the horse experience immediate and profound seizures. We are prepared to deal with these scenarios, however rare. Should this happen, the horse recovers completely with time, except in cases of catastrophic injury. In horses, catastrophic injury is considered a risk with absolutely ANY anesthetic plan – even “acing” your horse for the farrier!
An important part of the anesthetic plan is using the lowest possible dose of each drug, while providing adequate depth of sedation, length of time to complete the dental, and comfort to the horse during the process. Our arsenal contains five main sedatives – xylazine (a.k.a. “Rompun”), Sedivet (romifidine, similar to xylazine), butorphanol (“torb” or Torbugesic), acepromazine (Ace), and detomidine (Dormosedan or “Dorm”). Each of these drugs has its own profile of safety, efficacy and side effects. Before these drugs are even drawn into a syringe for your horse, everything discussed above is considered, as well as an assessment of the horse’s attitude, personality, and comfort level with our presence that day. Environmental factors that may arouse the horse such as wind, temperature, lawn mowers, small children, etc. are also part of the consideration. We listen to the horse’s heart to make sure there are no significant murmurs or arrhythmia’s that could cause an adverse event. Finally, we use the power of synergy to minimize the volume of each drug used by making a cocktail.
I’ll explain by example. When used alone, a whole ml of detomidine may be required to complete a dental on a particular horse. However, Springhill Equine most often uses a triple-threat combination using a “base dose” of xylazine or Sedivet, and add small volumes of the more potent detomidine (Dorm) and Torb. By doing this, we reduce that 1 ml to often 0.2 or 0.3 ml instead. This keeps the dose for this particular drug well within the margin of safety, minimizing its side effects. Likewise for the others in the cocktail (ingredients may vary – e.g. Tennessee Walkers often are better with ace and xylazine cocktails). By using what is termed a “balanced anesthetic technique,” synergy of the sedatives further reduces the required dose. If more sedation is required midway to complete the dental, we try to use the lowest volume of what we feel will be the most effective to finish our work. The next time, we will take into account any “top ups” that were required. The less sedation required for a balanced plane, the more money and time you save!
In summary, there is an enormous amount of thought put into that little syringe that we pull out during your horse’s dental. There are hundreds of thoughts behind it in our doctor’s heads, from possible safety concerns, potential side effects, quality of anesthesia and the plan for next time! If you ever have questions about the sedatives used, you need only ask them and they will happily explain it to you! May your litter box be clean and your food bowl full, until next week!