Anesthesia for Dentistry

Dentistry is becoming so much more common in general veterinary practice and that is exciting! It is excellent for the animals, the human animal bond, and all the practice employees.

Dentistry is exciting stuff!

Dentistry is also a complex problem as it is not just the dentistry we have to consider. We must think about safety through, what is often, a prolonged anesthesia, pain management, and an effective dentistry.

As veterinary technicians, there are lots of aspects we can assist with and things we can advocate for! In this article, we are going to cover some of the things I consider and do on a regular basis with my dental patients.

Ideally, we would like to see young animals with early stages of disease (i.e., stage 1 or 2 periodontal disease). These patients have, typically, lower anesthetic risk and the dentistry will be prompt because the work we will have is not too extensive.

These are just not the patients we see. All too often we see patients with later stage periodontal disease requiring multiple extractions and a lot of work for cleaning. These animals are also older, usually older than 5. With every year of age, anesthetic risk increases. This is something we all know.

We need to continue to educate our client base about the nature of periodontal disease to hopefully have younger animals having prophylactic work done.

These animals have considerations that veterinarians must think through as they design an anesthetic protocol.

Most of our dental patients are going to sit in ASA 2 or 3 (potentially 4 but unlikely in most circumstances).

Patients with ASA classes 1 – 3 can be safely anesthetized using standard protocols and techniques. All patients above class 3 should be stabilized prior to general anesthetic (try to return them as close to a class 1 as possible).

Veterinarians will use individualized protocols that are designed to minimize risk to the patient.

In all patients, intravenous fluids are a must, and we must always be thinking about ways to minimize total anesthetic time.

Based on the patient’s status, the best course of action may be to postpone anesthesia to a later date and/or select another course of treatment which is not frequently possible with dentistry.

As I mentioned above, a patient’s ASA score is often forgotten and rarely recorded. I encourage all of you reading this article to incorporate and document this extremely useful anesthetic classification system.

We have other things that need to be considered for all dentistry patients regardless of their classification of physical status.

All dentistry patients must have adequate analgesia, they must be kept warm throughout, blood pressure must be protected, and in small or young patients we must consider the length of the fast and the procedure and watch blood glucose.

We will be talking about all these things individually.

We have so many options for sedation now, which is awesome. The focus of this article is not intended to talk about the individual drugs specifically, but is to stress the function and importance of sedation as it relates to dentistry. I will give a brief list of some of the common agents I have used in my career. They are:

• Acepromazine (drug class: Phenothiazine)
• Dexmedetomidine and Medetomidine (drug class: Alpha – 2 – Agonist)
• Opiates (various ones)
• Midazolam (drug class: Benzodiazepine)

I certainly prefer when veterinarians take an individual approach to sedation and anesthesia. Meaning that I prefer tailored drug protocols to each patient (based off data collection) rather than ‘blanket’ protocols.

Sedation is a critical part of the anesthesia process as it ‘sets the tone’, so to speak. Ideally the sedation protocol should not only relax the patient, but should also provide a good level of pre-emptive analgesia. We know we will be causing pain. Effective pre-emptive analgesia is a very important part of a multi-modal approach. This is typically achieved by combining a sedative agent and an opiate for sedation.

Please do make note of the fact that I have left Anticholinergics off this list (Atropine & Glycopyrrolate). They are now only indicated for use as needed rather than as a pre-medication, unless patient circumstances make them necessary.

Sedation levels are evaluated by a subjective system. The person assessing the animal after sedation has taken effect should decide if the patient has mild, moderate, or profound level of sedation.

With appropriate sedation you should see moderate to profound levels of sedation. This minimizes patient stress, allows for low doses of induction agent, and due to decent pre – emptive analgesia you should be able to maintain your patient on lower levels of inhalant which is ideal.

Mild levels of sedation increase the likelihood of excitement phases through induction and the patients often tend to require higher levels of inhalant throughout.

I would also like to note, it is nice to use reversible agents where possible.

Like sedation protocol, we have lots of options here. They can include the following:

• Alfaxan
• Propofol
• Ketamine/Diazepam (becoming largely phased out because of the above better options)

The one purpose of induction is to facilitate general anesthesia and intubation. Controlling the airway is of the utmost importance when conducting general anesthesia. These agents are all highly effective at performing this task.

We must remember that all induction agent doses should be titrated and given to affect. It is typical to see 1/4 or 1/3 doses of the total patient volume given at a time. This decision is guided by the level of the patient’s sedation; the more profound the level of sedation the less induction agent needed. This process must happen promptly, but patients should still be briefly assessed for induction related apnea which can be relatively common especially with large boluses.

Under no circumstances is ‘masking down’ a patient appropriate. It poses signifi cant risk for the patient and the staff.

In most general veterinary practices, anesthetic maintenance is done with one of two inhalant agents (both are related). They are:

1. Isoflurane
2. Sevoflurane

Both these agents are similar in the way they work, but they do have some differences with some of their qualities (i.e., partition coefficient, MAC, vapor pressure).

They are excellent at maintaining general anesthesia when used appropriately. As with most anesthetic agents, they are not to be taken for granted, however.

A dentistry is often a lengthy procedure and our patients are often older (as we already stated). Our inhalant agents are terrible for causing hypotension. The more you turn the dial up on the inhalant, the more your patient’s blood pressure is going to go down. Isofl urane causes hypotension by decreasing vascular resistance; this occurs more profoundly at higher levels.

We must do everything we can to protect our patient’s blood pressures, especially our older patients or patients with elevated blood urea nitrogen (BUN) and creatinine levels. Part of that is ensuring that our inhalant is delivered at the lowest possible levels that ensure our patients are anesthetized. This can be accomplished by the already mentioned and powerful, multi-model analgesia.

If your patient can be maintained at 0.5 % or 1.0 % Isoflurane, that is ideal. You will do more to protect their blood pressure by doing this than with anything else!

If I am considering running a patient at even 2.0 % Isoflurane, I am thinking about other ways I can help my patient and I am talking with my attending veterinarian.

Pain management is a huge topic as it relates to dentistry. Expect to see discussion regarding that in an upcoming article!

Earlier on in the scil Vet Academy lecture RVT’s & Dental Anesthesia: Where can we help? we talked about a few other anesthesia related concerns that many dental patients have.

These included the following.

• Hypothermia
• Hypotension
• Hypoglycemia
• Analgesia

I want to spend a little bit of time on the topics we have not covered in depth just yet.

The first is heat loss! Hypothermia is a huge concern with all anesthesia patients, but with dentistry that is more so because they tend to under GA for a long time and we are dealing with water around the mouth and head. Their heat loss can be pronounced. Heat loss is a significant issue as it relates to anesthesia.

The effects of unmanaged postoperative hypothermia are very real!

They include:

• Slower recovery from general anesthesia, decreased ability to process anesthetic drugs
• Increased risk of infection
• Impairs platelet function
• Post–operative shivering increases oxygen consumption demand
• Coma
• Death

We must keep patients warm! As it relates to dentistry, we should be doing the following:

• Pre-warm during the sedation period if possible – this can be one way to prevent heat loss the best!
• Warm IV fl uids to 38 degrees Celsius and keep them warm
• Avoid cold dentistry rooms
• BAIR hugger, socks on feet, etc

These are all things we, as technicians can easily do. We must incorporate regular checks of temperature throughout dentistry either every 15 minutes by probe or continuously with a multi-parameter monitor.

Remember, older and smaller patients will lose heat faster than healthy larger adult patients, respectively.

A vet once told me ‘if you can do no good, at least do no harm.’ This has always stuck with me and I always consider it with blood pressure.

If we become relaxed about this parameter, we may not see the damage right away, but we could see it 6 months down the road when an older patient with high end normal BUN and CREA presents after a lengthy dental procedure and is now in renal failure. The last thing we want to do is compromise tissue perfusion to vital organs.

There are multiple monitoring devices that allow you to measure blood pressure which I am sure you all know. Multi-parameter monitors and Dopplers (with appropriate equipment additions) are certainly the leaders.

Cuff size is critical to obtaining a good reading. A cuff that is too loose can give you falsely low readings and a cuff that it too tight can give you falsely high readings.

The parameter we monitor primarily is MAP (Mean Arterial Pressure). We should be aiming for a wonderful MAP of 100 mmHg if we can! That is ideal. If we cannot obtain that, then we must remain above 60 mmHg. Trending down to 60 mmHg or below that number is unacceptable and we must start interventions for that.

As I mentioned earlier, keeping the inhalant levels low will do more than anything to keep blood pressure up! Remember that and all the skills we have talked about thus far to keep inhalant levels low.

Your next defense, if low inhalant is not helping, is crystalloid fluid therapy. All patients should be on a crystalloids IV fluid treatment during any anesthetic procedure. With veterinarian direction you can provide a fluid bolus.

Crystalloids fluids have small particles that will stay in the vascular space for a short time hence helping blood pressure. This is something I always discuss with the veterinarian before proceeding.

A last option would be synthetic colloids. They are being used more cautiously now as some studies in human medicine are finding side effects after their use in some patients well after anesthesia.

If colloids are used, crystalloid fluid rates should be reduced, and the bolus should be done cautiously. Colloids have large particles and will stay within the vascular space for a longer time, making them volume expanders.

In most cases, I find keeping inhalant low to be the single most helpful thing that can be done!

Blood glucose is something I have started monitoring closer in recent years and I do find it to be impactful in some cases. Very small patients, regardless of species, have a faster metabolic rate. Their blood glucose will drop faster than larger patients, especially when you consider a lengthy fast, a prolonged dental procedure and a recovery in which they may or may not eat depending on how they feel.

With longer anesthetics we should be taking a blood glucose at the start and then taking one every 30 – 60 minutes to monitor, depending on the veterinarian’s wishes.

If the patient’s blood glucose drops too low, we must be talking about ways to compensate for that as it will significantly impact the patient’s ability to recover.

This would all be done with veterinarian guidance as blood glucose being too high is also dangerous. Taking blood glucose is very easy. All that is needed is a small prick of the ear and then the reading can be obtained with a properly set glucometer.

Anesthetic recovery is something that should not be taken lightly. We need to closely watch patients until they can control their own heads and can largely stay sternal.

Recovery is one of those times that things can change very rapidly. Extubation for dentistry should be done cautiously because of the amount of water we have used in the mouth. Prior to them starting to wake up, make sure you rinse the mouth and clear any debris or gauze used during the procedure. Ensure to also dry out the mouth, check the vestibule area as water really likes to pool there.

Prolonged anesthetic recovery can happen. Consider all the things we have previous discussed to help! Heat, blood glucose, oxygen support, drug reversals (alpha-2-agonists).

As technicians, we must remember that we play a critical role in anesthesia and dentistry! We must remain engaged and educated to be as effective as we can be. We are wonderful patient advocates on so many levels. Advocate for effective dentals and safe anesthesia for all your patients! They will thank you for it!

Beckman, D. B. (2016, September 9). Dental Nerve Blocks in Dogs and Cats Enhance Anesthesia Safety. Dental Nerve Blocks in Dogs and Cats Enhance Anesthesia Safety. https:// veterinarydentistry.net/dental-nerve-blocksdogs- cats/

Hale, F. (2007, July 1). Local Anesthesia in Veterinary Dentistry. Local Anesthesia in Veterinary Dentistry. www.toothvet.ca PDFfi les/LocalAnesthesia.pdf American Society of Anesthesiologists (ASA) Physical Status Scale. (n.d.).

American Society of Anesthesiologists (ASA) Physical Status Scale. Retrieved November 20, 2020, from www.avtaa-vts.org/asa-ratings.pml