Veterinary Technician National Examination (VTNE) guideStudy & preparation
VTNE Anesthesia: The Anesthetic Plan, Breathing Circuits, Intubation and Monitoring Targets
Anesthesia is 20 of the VTNE's 150 scored items. Here are its six tasks and the practical standards behind them from AAHA's 2020 anesthesia guidelines: the four phases, circuit choice and oxygen flows, the leak test, intubation checks, the monitoring thresholds that signal trouble, and recovery.
Short answer
Anesthesia is 20 of the VTNE's 150 scored items (13%). AAVSB's outline lists six tasks: applying physiology to anesthesia, helping plan and carry out the anesthetic plan, preparing and maintaining equipment, intubating, and monitoring the patient before, during and after anesthesia. AAHA's 2020 guidelines give the practical standards: rebreathing circuits for patients over about 3–5 kg at 20–40 mL/kg/min of oxygen (minimum 500 mL/min), non-rebreathing circuits for smaller patients at about 200–400 mL/kg/min, a leak test before every patient, and thresholds such as hypotension below a mean of 60–70 mm Hg and SpO2 below 95%.
Anesthesia is easiest to learn in sequence: what to check before induction, what to watch during maintenance, and what still matters after the vaporizer is off. The numbers in this guide come from AAHA's 2020 Anesthesia and Monitoring Guidelines for Dogs and Cats; your program's texts may phrase some ranges differently.
What the VTNE anesthesia domain covers
AAVSB's 2023 content outline gives Anesthesia 20 scored items and six task statements, paraphrased:
- A. Apply anatomy, physiology and pathophysiology to anesthesia
- B. Assist in developing and carrying out the anesthetic plan
- C. Prepare anesthetic equipment and supplies for operator and patient safety
- D. Maintain anesthetic equipment so it works reliably
- E. Establish and maintain a patent airway by endotracheal intubation
- F. Monitor and respond to patient status before, during and after anesthesia
Three knowledge statements are specific to anesthesia: pre- and post-anesthetic assessment and care; induction, maintenance, monitoring and recovery, "including stages of anesthesia and troubleshooting"; and pre-anesthetic and anesthetic drug reactions, indications, contraindications, side effects and interactions. A fourth, shared with other domains, covers the care, maintenance and use of equipment, anesthetic and monitoring equipment included. Drug classes and reversal agents are covered in the VTNE pharmacology guide.
The four phases of anesthesia and the ASA scale
AAHA describes anesthesia as a continuum that starts at home (fasting and any prescribed medications) and, in the hospital, runs through four phases: preanesthesia, induction, maintenance and recovery. Preanesthesia includes a full evaluation, stabilization if needed, equipment preparation, drug selection and "precise calculation of drug dosages for all phases."
Patients are categorized on the American Society of Anesthesiologists (ASA) patient status scale, scored 1 to 5. AAHA cites studies in which a move from ASA 1 or 2 to 3, or from 3 to 4 or 5, increased the odds of anesthesia-related death in dogs and cats.
Two current points on preparation from AAHA's guidelines:
- Fasting. AAHA says the recommended fast for healthy adult patients has decreased, and an abbreviated fast is particularly important for diabetic and neonatal patients. Its 2024 fluid guidelines add that for most patients it's unnecessary to withhold water before anesthesia
- Fluids. The 2024 AAHA Fluid Therapy Guidelines give initial anesthetic fluid rates of 5 mL/kg/h for dogs and 3–5 mL/kg/h for cats with normal heart and kidney function. The arithmetic is in the VTNE math guide
Breathing circuits and oxygen flow on the VTNE
AAHA's equipment section is where many technician-level numbers live:
| Non-rebreathing circuit (NRC) | Rebreathing circuit (RC, circle system) | |
|---|---|---|
| Typical patient | Smaller patients; RCs are typically used above about 3–5 kg (6.6–11 lb) | Patients above about 3–5 kg; pediatric RCs can serve smaller patients if no NRC is available |
| What prevents CO2 rebreathing | High oxygen flow | One-way valves and CO2 absorbent |
| Oxygen flow | About 200–400 mL/kg/min, adjusted to keep inspired CO2 below 5 mm Hg | 20–40 mL/kg/min during maintenance, with a minimum of 500 mL/min for accurate vaporizer output; 2–3 L/min when depth must change quickly |
| Key hazard | Never use the oxygen flush valve: it sends high-pressure flow straight into the airway | Faulty one-way valves or exhausted absorbent let CO2 build up |
Worked with Passy's numbers: a 4-kg cat on an NRC needs about 800–1,600 mL/min. A 30-kg dog on an RC needs 600–1,200 mL/min. A 10-kg dog on an RC works out to 200–400 mL/min, which is below AAHA's 500 mL/min minimum, so 500 mL/min it is. Don't skip that last check.
AAHA also recommends keeping equipment dead space to about 2–3 mL/kg or less, using low-dead-space pediatric circuits in small patients, and adding a manometer and a safety pop-off valve to the circuit.
The leak test and scavenging
AAHA says to leak test the machine and circuit before every patient and after changing any circuit component:
- Close the adjustable pressure-limiting (pop-off) valve.
- Occlude the patient end of the circuit and raise the pressure to 20–30 cm H2O with the oxygen flow.
- Turn the oxygen off. The manometer reading should hold steady.
- If it holds, open the pop-off valve first, then release the occlusion. If it drops, take the machine out of use and troubleshoot.
Scavenging protects staff from waste anesthetic gas, and AAHA notes that active systems are "far more effective" than passive ones such as activated charcoal canisters. AAHA's tip for learning the machine: follow the oxygen from its source through the machine and circuit to the patient, then to the reservoir bag and finally to the scavenger. The anesthesia-equipment flashcards planned for full VTNE prep cover the same components.
Endotracheal intubation: sizing, confirmation and the cuff check
From AAHA's intubation guidance:
- Length. The tube's proximal end should sit at or just outside the incisors, with the tip midway between the larynx and the thoracic inlet
- Diameter. Use the largest tube that passes easily through the arytenoid cartilages without trauma
- Confirming placement. Direct visualization between the arytenoids, movement of the rebreathing bag, condensation in the tube on exhalation and a definitive end-tidal CO2 tracing
- Cuff check. With oxygen flowing, close the pop-off valve, give a manual breath to 15–20 cm H2O and listen at the mouth for a hiss. If you hear one, inflate the cuff slowly during a breath until it stops, then open the pop-off valve immediately and secure the tube. Overinflation can damage the trachea
- Repositioning. Disconnect the tube from the circuit before turning the patient, because rotation can tear the trachea. AAHA calls tracheal tears "a significant issue" in intubated cats
Monitoring targets and the complications they signal
AAHA defines a surgical plane as an absent palpebral reflex, mild jaw tone and no purposeful movement, and pairs electronic monitors with hands-on assessment. Its thresholds for the most common complications:
| Parameter | AAHA threshold |
|---|---|
| Hypotension | Systolic below 80–90 mm Hg, mean below 60–70 mm Hg, diastolic below 40 mm Hg |
| Hypertension | Mean above 120–140 mm Hg or systolic above 160–180 mm Hg |
| Tachycardia under anesthesia | Above 180 bpm in cats; above 150–190 bpm in dogs (large to small) |
| End-tidal CO2 | About 35–45 mm Hg awake; about 40–50 (up to 55) mm Hg at an appropriate surgical plane; start positive pressure ventilation above 60 mm Hg |
| Hypoxemia | SpO2 below 95%; severe below 90% |
| Hypothermia | Core temperature below 98°F |
The order of response matters as much as the numbers. With rising CO2, AAHA says to first make sure the cause isn't excessive anesthetic depth before ventilating. With a low SpO2 reading, check that the patient is intubated, connected and receiving oxygen before you adjust the probe. Tachycardia should prompt a list of causes (noxious stimulus, hypoxemia, hypercarbia, hypovolemia, drugs), not an automatic increase in depth. For questions on these decisions, the 195 Anesthesia questions planned for full VTNE prep follow the same outline.
Recovery: still part of the anesthesia domain
AAHA reports that between 47% and 60% of anesthetic-related deaths in dogs and cats, respectively, occur in the postoperative period, most within the first 3 hours, so monitoring continues with the same vigilance. Its recovery points:
- Keep watching heart and respiratory rate, SpO2, blood pressure and temperature until the patient is alert, normothermic and ambulatory (unless it wasn't ambulatory before)
- Leave the IV catheter in place until the patient is extubated, sternal and stable
- Extubate when respiratory rate and SpO2 are normal and the patient can protect its airway by swallowing vigorously; deflate the cuff immediately before pulling the tube
- After dental procedures or rhinoscopy, AAHA suggests keeping the nose slightly lower than the back of the head and leaving the cuff slightly inflated during extubation, to bring debris out with the tube
Two VTNE-style anesthesia questions, written by Passy
These are original practice questions, not VTNE items.
1. A 3-kg cat will be maintained on inhalant anesthesia with a non-rebreathing circuit. Which oxygen flow fits AAHA's guidance?
- A. 60–120 mL/min
- B. 500 mL/min, the circle-system minimum
- C. 600–1,200 mL/min
- D. 3–5 L/min regardless of weight
Answer: C. AAHA's NRC range is about 200–400 mL/kg/min: 3 × 200 = 600 and 3 × 400 = 1,200 mL/min. Option A applies the rebreathing range (20–40 mL/kg/min) to the wrong circuit, and B is the rebreathing-circuit minimum.
2. During maintenance, a dog's end-tidal CO2 rises to 64 mm Hg. What should the technician check first?
- A. Whether the anesthetic depth is excessive
- B. Whether the pulse oximeter probe needs moistening
- C. Whether the blood pressure cuff has slipped
- D. Whether the dog needs a fluid bolus
Answer: A. AAHA says to first rule out excessive anesthetic depth (check the vaporizer setting and the patient's plane) and to start positive pressure ventilation when end-tidal CO2 is above 60 mm Hg.
Studying the VTNE anesthesia domain
As a Passy suggestion, study it in the same order as the anesthetic event: preanesthesia (ASA status, fasting, equipment checks), induction and intubation, maintenance (circuit, flow, monitoring targets), and recovery. Learn each number with the action it triggers. The outline also names "stages of anesthesia," which this guide doesn't teach; AAVSB's reference list includes several anesthesia texts for technicians, such as Thomas and Lerche's Anesthesia and Analgesia for Veterinary Technicians (2024) and Grubb and colleagues' Anesthesia and Pain Management for Veterinary Nurses and Technicians (2024).
Anesthesia overlaps with Surgical Nursing and Pain Management, so mix the three once each feels solid; the VTNE surgical nursing guide covers the sterile side of the same procedures. When you're ready to mix, practice that moves across all 10 domains is planned for full VTNE prep, and the free VTNE practice questions are a mixed set you can try now.
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Official sources
Exam policies can change. Use these primary sources for the most current details.