Anesthesia and the dental patient (Proceedings)

More and more general veterinary practices are considering the addition of dentistry to the list of services they hope to provide. DVM Magazine 2003 State of the Profession Survey indicated that 44% of those surveyed expect to expand the dental services they already provide. In addition to considering staffing, equipment and scheduling, the practice should look closely at the anesthesia protocols and applications currently employed within the practice. Will your current protocols provide the safety necessary for the long anesthetic procedures that advanced dentistry necessitates?

Pre-operative patient evaluation

Anesthesia always carries some risk to the patient. To minimize the risk, pre-operative patient evaluation should be ordered for each patient. The practice should decide on what parameters are required for each age group. A suggestion as to what that testing can look like would be:

Pediatric

• Physical examination

• PCV/TS, Creatinine

• Urinalysis

Adult

• Physical examination

• CBC/ 12 panel profile

• Urinalysis

Geriatric patients

• Physical examination

• CBC/Superchem/UA

• Additional tests as needed based on history and physical exam

• T-4

• Ultrasound

• Chest radiographs

Some practices have a protocol of running pre-operative blood work the morning of the procedure. That gives the team the absolute most current picture of the state of that patient's health. Other practices will recommend to the client to have the testing performed a couple days prior. If abnormalities in the lab work arise, it may be necessary to run additional tests and cancel the appointment. If all patient evaluation is performed 2-14 days in advance, the veterinarian has the time and opportunity to evaluate the results and make decisions about care and proper scheduling. Regardless, the veterinarian should review the results. I also advocate that the technician review them as well. In a safe, team-oriented environment, this provides another level of safety having additional review and case discussion.

Patient temperament assessment

When a patient is examined by the veterinarian, an assessment of the personality of the patient should be made. Is this patient calm and confident in stressful situations? Does the patient resort to fight or flight in the face of restraint? This is an important evaluation. When it is determined that the patient accelerates once placed in a cage or as the staff handles the patient, these patients should receive special scheduling. Most of these pets will do infinitely better when they remain with their owners. Schedule these patients as the first procedure. Do not admit them to a cage. Sedate the patient in an exam room with the owner present. Select appropriate drugs and leave the patient with the owner. Keep the area quiet and turn down the lights. Encourage the owner to speak softly and to handle in a reassuring manner. Leave the area for 10 minutes. Quietly check on the pet until you notice the appropriate level of sedation.

As patients panic, they experience a whole cascade of hormonal changes. The body does this as a survival technique. Unfortunately, those changes make anesthetizing the patient more difficult. More drugs are required and ultimately you tend to use more than you would under better circumstances. Then as the anesthetic eventually overwhelms the patient, the blood pressure tends to drop dramatically and often dangerously.

Also, if these frightened patients are admitted, and the whole experience is horrible for them, the likelihood of their returning without amplified fear is very low.

Pre-operative drugs

Patients receive pre-operative drugs for a number of reasons:

1. To allay apprehension

2. To reduce the amount of induction agent required

3. To provide a balanced anesthetic approach

Today's anesthetic buzz word is "balanced" anesthesia. Balanced anesthesia refers to a multimodal approach to analgesia. The brain interprets pain from different pathways. Selecting a combination of drugs to address as many of these pathways as possible will provide optimal patient comfort.

We also now know that it is easier to prevent pain than to treat pain. Pre-emptive analgesia includes providing appropriate analgesic is the pre-operative injection.

NSAIDs (Nonsteroidal anti-inflammatory agents)

These agents can be given pre-emptively to patients that have normal blood pressures and normal kidney function. If there is any question as to how the blood pressure will be during the anesthetic procedure, it may be best to administer this class of drugs when you are sure the patient will be normotensive through the procedure.

Anticholinergic agents

Controversial as to whether these drugs should be added routinely to the pre-op injection or not. This classification of drug increases heart rate therefore counteracts the bradycardic effects of the sedative. The use of anticholinergics is contraindicated in tachycardic patients or patients with known cardiac issues.

• Atropine

• Glycopyrrolate

Analgesic agents

One component of the pre-op injection is pain control. Often a pure mu agonist is selected.

• Morphine

• Hydromorphone

• Fentanyl

     o These drugs have a high potential for abuse, so elegant record keeping is vital.

     o Usually cause initial vomiting, but this does ensure an empty stomach prior to general anesthesia.

     o Reversible with Naloxone

Partial agonist

• Buprenorphine

     o In cats this will provide a high level of pain relief in cats. Another benefit of this drug is that it can be administered transmucosally in the cat. The pH of the cat's mouth provides an almost 100% bioavailable environment.

• The same is not true in the dog. It is found to provide a lower level of pain control in the dog, and cannot be used transmucosally.

Agonist-antagonist

• Butorphanol

     o Unfortunately, it is relatively expensive and provides only about 30 minutes of mild pain control. It does have sedative properties, but sedation should not be confused with analgesia.

Sedative agents

A sedative is usually added to calm the patient.

• Diazepam

• Midazolam

• Acepromazine

• Dexmedetomidine

Induction agent

These are agents that are administered to effect in order to place the endotracheal tube.

• Pentothal

• Propofol

• Ketamine/Valium

• Etomidate

Inhalant agents

These are the volatile gasses that are used to maintain general anesthesia.

• Isoflurane

• Sevoflurane

Regional nerve blocks

• Bupivicaine

• Lidocaine

This is an adjunct to the anesthetic procedure. As the nerves are blocked, the patient requires less inhalant anesthesia. This skill alone will help keep blood pressure within normal limits

Additional anesthetic strategies

Turning the patient

In dentistry, the patients need to be turned frequently. Minimize the number of turns required by planning out the order of treatments. Also, disconnect the endotracheal tube from the corrugated tubing and reattach when in proper position.

Also, turn these patients slowly. It is suggested to turn the patients under instead of rolling them over. The main point is to do this slowly. Flipping the patient quickly disrupts any pooling blood and wreaks havoc on the blood pressure.

Intravenous fluid therapy

Although there are no required standards for the provision of anesthesia, it is strongly recommended that a patent IV catheter be in place and IV fluids provided. This can influence the blood pressure dramatically. Unless contraindicated by a patient's cardiac status, start IV fluids at 10ml/kg/hr for the anesthetic rate.

Patient warmth

As patients are under anesthesia, temperature regulation is impaired. It is easier to keep a patient warm than to attempt to increase their warmth once they chill. At the start of the dentistry, the patient should be on a heat source but not one that can cause a thermal burn. A couple of towels at double thickness over the heat source should provide warmth from below. Bair Huggers® are heaters that force the warmed air through a blanket that goes over the patient. Covering the feet with bubble wrap and the head with a stockinette hat can reduce the amount of heat escape through those routes.

Dentistry cases can be some of the longest anesthetic procedures and are often performed on very geriatric cases. Success is measured by your ability to perform anesthesia while maintaining healthy parameters. The temperature of the patient remains between 98-101 degrees. The heart rate remains in the normal range, the MAP is greater than 70 (systolic greater than 100). Heart rate, respiration, pulse ox, capnography and cardiac rhythm are all normal. Monitoring these cases is vital. One of the most critical parameters to watch is the blood pressure. Success is not measured by the fact that the patient slept through the procedure and went home and there were no complaints.

Leave your ego at the door!

If when you are monitoring your patient and any of the parameters are not within your comfort zone, take appropriate steps to correct the situation. But, if attempts to correct fail, don't fight it. Wake this patient up and reschedule the procedure with a different anesthetic protocol.