ACVC 2019: Veterinary anesthesia basics and beyond

Kolesova/stock.adobe.comEstablishing a strong foundational knowledge of anesthesia is critical for any veterinary technician who will be involved in administering anesthesia or monitoring anesthetized patients. At the 2019 Atlantic Coast Veterinary Conference, Heather Carter, BS, LVT, VTS (Anesthesia/Analgesia), offered her insight on all things anesthesia. In one session, she addressed the questions most frequently asked by veterinary technicians about anesthesia.

Patient evaluation and preparation

Q: Do I have to do an exam on a patient if the doctor already did one?

Affirmative, Carter said: “It is imperative that the anesthetist have a baseline knowledge of their patient's vital signs, and that means always evaluating the patient yourself.” Familiarity with each individual patient gives you a much better understanding of their needs under anesthesia.

This evaluation should include:

Vital signs

Pain score

Demeanor, mentation and overall condition

Status of current blood work

Medical history

CPR directive.

Q: What is involved in patient preparation?

Before administering any drug or anesthetic, make sure the patient been fasted properly, Carter explained. Additionally, when examining the patient's blood work, check to see if fluids are needed before anesthesia. Then, confirm the procedure and the surgical location, she said.

Q: What's the difference between dead space and resistance?

Dead space occurs when inhaled gases mix with exhaled gases in areas where they are not supposed to, said Carter. You can mitigate dead space, she said, by cutting endotracheal tubes to end at the incisors. Resistance occurs as a result of a narrowing airway or inappropriate breathing circuit. “To reduce resistance, ensure that you're using the right circuit for the patient,” Carter said.

Equipment maintenance

Q: What does baralyme do?

Baralyme removes the CO₂ from the rebreathing circuit in a closed circuit anesthesia system, Carter explained, and should be changed every four to six hours.

Q: What does an f/Air canister do?

The f/Air canister removes CO₂ from the breathing circuits, Carter explained. These canisters can trap a minimum of 50 g of gas, then must be replaced.

Q: What is the calculation for a reservoir bag?

Multiply the tidal volume-calculated at 10 to 20 mL/kg-by five and round up to get the correct calculation.

Monitoring

Q: When does monitoring start?

Monitoring should begin when your patient receives a premedication, Carter said, except when you're patient is compromised in some way. Monitoring in these patients should begin before drug administration.

Monitoring the patient before anesthesia is administered allows for any necessary adjustments to be made in the anesthetic plan. For example, an ECG obtained during pre-oxygenation could reveal a cardiac arrhythmia that had the potential to make an anesthetic event much more risky, Carter explained.

Q: What parameters should be monitored?

Carter said the following parameters should be monitored:

Heart rate and rhythm

Peripheral capillary oxygen saturation

End-tidal CO₂

Blood pressure

Mucous membranes/capillary refill time

Respiration rate and effort

Temperature

“If monitoring equipment is limited is limited in your practice, use your senses to evaluate eye position and changes in respiratory effort,” Carter advised.

Q: Why is capnography important?

The capnograph is one of the most important machines that veterinary technicians need to be able to monitor and understand. “Capnography does not lie,” Carter said. “It allows the anesthesia team to detect leaks in a circuit, occlusions in an endotracheal tube and the beginning of cardiac arrest.”

Q: Why do some patients keep waking up?

Patients wake up during anesthesia for a few reasons, including inadequate premedication. “Evaluating the drugs that are currently on board as well as the status of procedure will point toward the correct course of action,” Carter said. A patient may require a ketamine bolus to combat windup for example, Carter said. What not to do if your patient wakes up: Don't increase isoflurane/sevoflurane.

Q: How do you fix hypothermia?

A hypothermic patient will be slow to recover and slow to heal. What's more, Carter said, “these patients usually has other anesthetic complications going on as well.” That's why hypothermia prevention is key, and that's done by providing the patient with adequate heat support before, during and after any anesthetic event. Carter' go-to for helping her patients say warm? “I'm a big fan of putting sandwich bags on paws,” she said