ANESTHESIA TEST #1 REVIEW

DEFINITIONS

What is ax?

→ loss of sensation

What is GA?

→ reversible CNS depression caused by anesthetic agents, resulting in:

• LOC

• pain loss

• amnesia

• ⬇ mobilit

What is the diff btw local, regional and topical ax?

→ local: targets sm area
→ regional (nerve blocks): affects lrg nerve areas
→ topical: limited to skin and SQ tissue

What is neuroleptanalgesia?

→ very deep sedation + analgesia produced by an opioid + tranquillizer
→ NOT true ax, but provides deep sedation and pain relief

What is anxiolytics vs anxiolysis?

→ anxiolytics

• Drugs that reduce anxiety, causing anxiolysis

• i.e. sedatives and tranquilizers

→ anxiolysis

• Reduction of anxiety (like analgesia = reduction of pain)

What is a sedative?

→ drug causing CNS depression
→ ⬇ awareness and drowsiness; patient remains minimally aware of surroundings

What is a tranquilizer?

→ causes calm WITHOUT drowsiness
→ patient is unwilling to move but remains conscious and aware of the environment, without concern

What is vapour pressure? Should this be low or high in value?

→ tendency of a liquid to evaporate @ rm temp

• ⬆ vapour pressure = evaporates readily = more volatile

• ⬇ vapour pressure = evaporates less readily = less volatile

→ should be HIGH so the liquid readily becomes a gas/vapour

What is solubility coefficient? Should this be high or low in value?

→ how easily a gas dissolves in blood compared to alveolar gas

Solubility coefficient = anesthetic in tissue ÷ anesthetic in alveolar gas

→ should be LOW

• Less dissolves in blood, so more remains available to reach the brain

• Faster induction + recovery

What is M.A.C? Should this be high or low in value?

→ minimum alveolar concentration
→ lowest [] of ax gas that prevents gross movement in 50% of patients exposed to a painful stimulus
→ should be LOW = greater potency, so less ax is needed

Out of vapour pressure, solubility coefficient and M.A.C, which one is most important (in theory)?

→ solubility coefficient = MOST important because it determines how quickly ax is absorbed, affecting induction, recovery and changes in ax depth

What is fresh gas?

→ O₂ that has picked up inhalant ax vapour, becoming fresh gas

What are vital signs?

→ measurements showing how the body is functioning, esp. cardio and resp systems

• HR, RR, BP, temp and O₂

What is muscle tone?

→ resistance/tension in a muscle when relaxed or moved
→ ⬇ muscle tone during ax generally means greater relaxation

What are reflexes?

→ automatic, involuntary responses to a stimulus
→ help assess ax depth; generally ⬇ as ax deepens

What is HR and how can it be monitored during ax?

→ HR = # of heartbeats/min (bpm)

Methods:

• Auscultation w a stethoscope

• Palpating a pulse

• ECG = electrical activity

• Pulse oximeter = pulse rate

What is resp rate and how is it monitored?

→ RR = # of breaths/min

Methods:

• Observe chest movement

• Watch breathing bag move w resp

• Capnography = monitors exhaled CO₂ and assesses ventilation

What is pulse quality and how is it monitored?

→ strength and feel of pulse, helping assess blood flow

• N = regular and strong

• Pulse rate should = HR

• Difference = pulse deficit, indicating a circulatory problem

• How: palpate a peripheral pulse (e.g. femoral pulse inside hind leg) and assess strength/regularity

What are mucous membrane colour and CRT and how are they monitored?

→ MM: gum colour, helps assess oxygenation/circulation
→ CRT: time for colour to return after gums are pressed until they blanch

• How: inspect gums, gently press and assess CRT

• Pink gums + CRT <2 sec are generally reassuring

What is BP and how is it monitored?

→ BP = force of blood against blood vessel walls

Methods:

• Non-invasive: BP cuff w Doppler or oscillometric equipment

• Invasive: arterial catheter connected to pressure transducer

What is SpO2 and how is it monitored?

→ estimates % of haemoglobin carrying O₂
→ use a pulse oximeter on the tongue, lip or another suitable tissue site

• Awake: >90%

• Anesthetized: >95%

What is EtCO2 and how is it monitored?

→ CO₂ measured @ the end of exhalation
→ use a capnograph connected to the breathing circuit

• Typical target: 35–45 mmHg

• Assesses ventilation and helps detect breathing/circulation problems

How is body temp monitored during ax?

→ temp probe or thermometer (e.g. oesophageal or rectal probe)

• Ax can cause hypothermia

• Monitor regularly and provide warming support when needed

What is the palpebral reflex and how is it monitored?

→ blink when skin near the inner or outer corner of the eye is touched
→ gently touch medial/lateral canthus and observe for a blink

• Generally decreases as ax deepens

What is the pedal w drawal reflex and how is it monitored?

→ limb withdrawal in response to a stimulus

• Squeeze a digit and observe for withdrawal (leg ideally extended)

• N absent under sx ax and gone after induction

• Decreasing response can indicate increasing ax depth; interpret w other signs

How can eye position help assess anesthetic depth?

→ observe eyeball position and pupil size

• Position and pupil responses can change w ax depth

• Interpret w vital signs, muscle tone and other reflexes because drugs can affect them

QUESTIONS

What do we mean when we define anesthesia as a continuum of care?

→ ax begins and ends @ home; patient safety and care matter b4, during and after ax

List ways to improve anesthetic safety

→ cognitive aids
→ train staff + good team communication
→ diligent monitoring
→ detailed records
→ professional patient care
→ appropriate analgesia + anxiolytics
→ good client communication

When is it best to use an individual vs standard ax plan okay? What are 1-2 pros & cons of each?

→ Individual plan

• Best for higher-risk patients (ASA III+) and non-routine procedures

• Pros: tailored to patient risks/needs; drug choices/doses can be adjusted

• Cons: more time-consuming/complex; requires more knowledge/planning

→ Standardized plan

• Best for lower-risk patients and routine procedures

• Pros: simple, efficient and consistent

• Cons: less flexible; may not suit higher-risk patients

What is balanced anesthesia?

→ combining multiple drugs/drug classes for safe, effective ax while ⬇ -ve effects of individual drugs

• Multiple drug classes/targets affect different pain pathways

• Drug combinations can be adjusted as needed

• Provides multimodal ax and better perioperative analgesia

What are the 4 phases of anesthesia (slide 15 unit #1)

1. Pre Ax – planning + set up

2. Induction – getting patient under GA

3. Maintenance – maintaining desired ax depth

4. Recovery – return to consciousness + monitoring

What is involved in the preanesthetic evaluation of the patient?

→ Hx
→ PE: TPR, heart/lung auscultation, MM/CRT, oral cavity/pharynx, hydration
→ age, breed, gender, size, temperament/activity, wt, BCS
→ Dx
→ ASA risk classification
→ ID patient-specific anesthetic risks

Name some recommended pre ax dx

→ PCV/TP, CBC, blood chems, urinalysis, rads/imaging, ECG

What should be included in release forms?

→ informed consent
→ emergency contact
→ written estimate
→ resuscitation status

What are the ASA classifications of patient risk?

→ ASA = American Society of Anesthesiologists

• ASA I = minimum risk: healthy patient, no underlying disease

• ASA II = slight risk: mild systemic disturbance, no clinical signs

• ASA III = moderate risk: systemic disease/disturbance w mild clinical signs

• ASA IV = high risk: severe systemic disease/disturbance

• ASA V = grave risk: life-threatening systemic disease/disturbance

Do you know the most common fasting and water recommendations pre ax?

→ Food: w hold for 4–6 hrs up to 12 hrs b4 GA to ⬇ vomiting/aspiration risk
→ Water: usually NOT w held; helps prevent dehydration and clears GI tract faster

• Remove water b4 pre meds (timing varies)

Name some goals and benefits of giving pre anesthetic drugs

→ ⬇ anxiety and calm/sedate patient
→ analgesia b4, during + after sx
→ synergistic effects btw drugs (balanced ax)
→ ⬇ amount of ax agent needed
→ counteract -ve side effects of other drugs

What are the pre med drug categories w examples?

1. Opioids: fentanyl, morphine, hydromorphone, methadone, buprenorphine, butorphanol

2. Alpha-2 agonists: dexmedetomidine, xylazine

3. Benzodiazepines: midazolam, diazepam

4. Phenothiazines: acepromazine

5. Dissociative: ketamine

6. Neurosteroids: alfaxalone

7. Anxiolytics/PVP: gaba, trazodone

What are the major effects of the 7 pre med drug categories and when should each be avoided?

Drug category	Major effects	Avoid / use caution
1) Opioids	Analgesia/pain relief (some sedation)	Head trauma, resp depression, bradycardia
2) Alpha-2 agonists	Sedation, analgesia, muscle relaxation	Heart disease, liver dysfunction, old/young patients
3) Benzodiazepines	Anxiolysis, muscle relaxation, anticonvulsant effects	Liver compromise; paradoxical excitement in healthy young patients
4) Phenothiazines	Tranquilization, antiemetic effects, mild sedation	Hypotension, seizure-prone patients, liver dysfunction, geriatrics
5) Dissociatives	Dissociative ax, analgesia	Head trauma, seizures, cardiac disease
6) Neurosteroids	Sedation + ax	Lrg injection vols = resp depression
7) Anxiolytics/PVP	⬇ fear, anxiety, stress	Excessive sedation in debilitated patients; GI upset

What are the major diff btw opioids regarding duration, analgesia and side effects?

Drug	Duration	Analgesia	Key side effects / facts
Fentanyl	20–30 min (short)	Strongest	Resp depression; bradycardia w bolus, CRI or patch
Morphine	2–4 hr (long)	Strong	Vomiting IM; histamine release IV; bradycardia
Hydromorphone	2–4 hr (long)	Strong	Similar to morphine but no histamine release; may cause hyperthermia in cats
Methadone	2–4 hr (long)	Strong	NMDA antagonist; less vomiting than morphine; sedation + resp depression
Buprenorphine	4–8 hr (long)	Moderate	Partial mu agonist; slow onset; minimal sedation; useful in cats OTM
Butorphanol	20–90 min (mid)	Weakest (mild–moderate)	Limited analgesia; kappa agonist/mu antagonist; useful as sedative w a tranq

List several important reasons anticholinergics are less popular in pre med combos now

→ no proven overall benefit to ax risk/outcomes
→ can cause harm and ⬆ risk
→ effects may last longer than needed

• Many drug effects ⬇ b4 induction

• Maintenance ax already causes profound CNS depression

• Good analgesia ⬇ amount of ax needed more effectively

• ⬇ resp/ocular secretions and peristalsis may be undesirable

IMPORTANT: anticholinergics can still tx mild bradycardia during ax ONLY when indicated

Why are anticholinergics and alpha 2 agonists should NOT be administered together?

→ NOT combined w alpha-2 agonists because they can:

• ⬆ BP to around 150–160 mmHg, potentially damaging organs

• ⬆ cardiac output, increasing the heart’s O₂ requirement and risk in patients w undx problems

What is the role of induction agents?

→ cause unconsciousness for endotracheal intubation b4 inhalant ax maintenance
→ can also provide short-term injectable ax as a single bolus, repeated boluses or CRI

What is the benefit of preoxygenation?

→ 100% O₂ for 3 mins saturates haemoglobin and provides an O₂ reserve for approx. 6 mins

Esp. important for:

• Brachycephalic breeds

• Airway disease/breathing difficulties

• Expected difficult intubations

• Pregnancy (fetal oxygenation)

What does it mean to dose to effect and why is it done?

→ give sm amounts of induction drug gradually until desired effect, rather than the entire calculated dose @ once

• Give 1/4–1/2 calculated dose @ short intervals until jaw tone relaxes + laryngeal reflex is absent, allowing ET intubation

• Do NOT exceed max calculated dose

Advantages:

• ⬇ risk of apnea + resp depression

• Prevents overdosing; gives only what patient needs

• Allows adjustment for pre meds + patient condition

What are the major pros and cons of phenols (propofol)?

→ Pros

• Fast onset + short duration = easy to titrate

• Smooth induction/recovery

• Safe for repeat dosing in dogs/cats

→ Cons

• Apnea, resp depression, bradycardia, hypotension

• No analgesia

• Avoid in cats w moderate–severe liver disease; caution w low protein

What are the major pros and cons of neurosteroids (alfaxalone)?

→ Pros

• Fast onset + short duration = easy to titrate

• IV or IM; useful for fractious/sm patients

• Alternative to propofol for non-IV induction

→ Cons

• Apnea + hypotension, esp. w rapid IV injection

• Possible hypoxia, arrhythmias, excitement/twitching

• Caution in pregnant, lactating or debilitated animals

What are the major pros and cons of dissociatives (ketamine)?

→ Pros

• Analgesia + sedation

• Useful for balanced induction; ⬇ propofol dose

→ Cons

• Muscle rigidity, tachycardia, hypertension, salivation, rough recovery

• Avoid in severe cardiac/liver disease, increased intracranial/intraocular pressure or psychosis

• Caution w renal disease in cats

NOTE: benzodiazepines ⬇ adverse effects

What are the major pros and cons of inhalants (isoflurane) for induction?

→ used via mask/chamber when patients cannot be safely handled or tolerate other induction

→ Pros

• Useful when injectable induction isn't suitable

→ Cons

• Slow, stressful, difficult to monitor (excitement phase)

• No rapid, secure airway

• Airway irritation, hypotension, resp depression

• Waste gas exposure/environmental contamination

What are the major pros and cons of barbiturates (thiopental)?

→ no longer available for vet use in Canada

→ Pros

• Controls seizures

• ⬇ intracranial pressure

→ Cons

• Resp/cardio depression

• NO analgesia

• Extravasation causes tissue damage

• Accumulates in fat = prolonged recovery w repeated doses

What are the major pros and cons of etomidate?

→ not licensed for vet use in Canada

→ Pros

• Ideal for patients w cardio disease

→ Cons

• Myoclonus, paddling, vocalization, vein irritation

• Risk of adrenocortical suppression

• $$$

Why do we usually give a dissociative drug w a benzodiazepine?

→ ⬇ ketamine side effects:

• Muscle rigidity

• Seizures

• Rough recovery

Which drug can only be given IV and what can be safely mixed w it in the “ syringe?

→ diazepam (benzodiazepine) can ONLY be given IV
→ ketamine is the only other injectable drug safe to mix in the same syringe w diazepam

What are the pros and cons of mask or chamber induction w gas anesthetics?

→ Pros

• No IV catheter/injection required

• Useful for patients difficult to handle or catheterize

→ Cons

• Can be stressful

• ⬆ staff exposure to waste anesthetic gases

• Generally slower than IV induction

• Risk of resp depression

Name 3 +ve and 2 -ve regarding using anesthetic gases to maintain anesthesia

→ Positives

1. Quick/easy titration of ax depth

2. Less drug metabolism, allowing longer/safer ax

3. Controlled O₂ supplementation through a patent airway (ET tube)

→ Negatives

1. More equipment + costs

2. Waste ax gases cause environmental pollution

What would make an ideal anesthetic gas?

→ Safe + advantageous for patient

• Good muscle relaxation + post-op analgesia

• Quick induction + recovery = easy adjustment of ax depth

• Minimal cardio, resp, renal, hepatic side effects

• Minimal retention by body fat

→ Low cost

→ Safe for anesthetist

• Non-explosive + non-flammable

• No side effects

How is ax gas delivered to a patient via machine when it starts from a liquid form?

How does ax gas work in the body (simple explanation)?

1. Inhaled: patient breathes ax gas through ET tube

2. Absorbed: gas passes from lung alveoli into bloodstream

3. Distributed: blood carries ax to brain + other organs

4. Anesthesia: ax reaches brain, producing/maintaining ax

5. Continuous delivery: ax must be continuously supplied to maintain a [] gradient btw blood + alveoli

6. Removal: vaporizer off; most ax leaves through lungs during expiration, allowing consciousness to return

What are the main diff btw isoflurane and sevoflurane?

Characteristic	Isoflurane	Sevoflurane
Solubility coefficient	1.4	0.63
MAC	1.5%	2.4%
Speed	Rapid induction/recovery	Very rapid induction/recovery
Potency (MAC)	Higher	Lower
$$$	Less expensive	7–8× more expensive
Vaporizer	Precision vaporizer	Own special vaporizer

NOTE: ⬇ solubility = faster changes in ax depth; ⬇ MAC = greater potency

What are pros and cons of isoflurane?

→ Pros

• Rapid induction + recovery

• Lower MAC = more potent

• Best for cardiac patients

• <1% hepatic metabolism

• Safe for geriatric patients, neonates + anesthetists

• Cheaper

→ Cons

• More resp depression

• Bad odour may cause breath-holding in non-premedicated patients

• Little/no analgesia

• May cause excitement during recovery, esp. when used alone

NOTE: most common in sm vet practice

What are pros and cons of sevoflurane?

→ Pros

• Faster induction + recovery and changes in ax depth

• Slightly less resp depression

• Similar cardio side effects

• <3% hepatic + nephronic metabolism

→ Cons

• Higher MAC = less potent, so more is required

• 7–8× more $$$

• Requires own special vaporizer

NOTE: most common in exotics, avian patients, research, referral + specialized vet practices

What are the biggest drawbacks of each of the hx ax agents we discussed?

→ Halothane

• Cardiac arrhythmias

• Significant resp depression

• Liver damage

→ Methoxyflurane

• Kidney damage (nephrotoxicity)

• High blood solubility = slow induction + recovery

→ Diethyl ether

• Highly flammable + explosive (major fire risk)

• Resp tract irritation + increased secretions

• Slow induction + recovery

What is diffusion hypoxia as it relates to nitrous oxide?

→ when N₂O is stopped, it rapidly moves from blood into alveoli, diluting O₂

• Temporarily ⬇ O₂ available to breathe

• Prevention: administer 100% O₂ for several mins after discontinuing N₂O

What is the diff btw the stages and planes of ax?

→ Stages: overall progression from awake to dangerously deep ax
→ Planes: depth within Stage III (sx ax)

• Stage I: disorientation just b4 LOC

• Stage II: excitement/dysphoria, movement, vocalization, potentially exaggerated reflexes

• Stage III: true ax, divided into 4 planes

• Stage IV: terminal stage

What stage is the goal for intubation? What stage is the goal for sx?

→ Intubation:

• Stage III, Plane 1

• Light ax; laryngeal reflex must be absent

→ Sx:

• Stage III, Plane 2

• Medium ax; ideal sx depth

What is the purpose of patient monitoring?

→ Assess ax depth + patient response
→ Monitor vital signs + heart function
→ Detect problems early so they can be corrected b4 life-threatening
→ Maintain patient safety throughout ax + recovery

What is the best way to monitor and how often?

→ Best: continuous monitoring using hands-on assessment + equipment together

• Assess HR, RR, pulse quality, MM colour, CRT + ax depth

• Use ECG, pulse oximetry, capnography + BP monitoring as appropriate

→ Frequency

• During ax: record most parameters q 5 mins minimum

• After extubation: record q 15 mins until parameters are N

What is the n range of parameters under ax?

→ HR (Stage III, Plane 2)

• Dogs: >80 bpm; sm breeds >100 bpm; lrg breeds >60 bpm

• Cats: >100 bpm

→ RR (Stage III, Plane 2)

• 8–20 breaths/min

→ SpO₂

• >95%

→ EtCO₂

• 35–45 mmHg

→ BP

• Systolic: 90–160 mmHg

• MAP: 60–100 mmHg

→ Temp

• Dogs: <37°C = hypothermia

• Cats: <38°C = hypothermia

• <35°C = severe hypothermia

What monitoring equipment will we learn to use and what does each measure?

→ ECG: electrical activity + heart rhythm
→ Pulse oximeter: arterial haemoglobin O₂ saturation (SpO₂) + pulse rate
→ Capnometer/capnograph: RR + EtCO₂; waveform assesses resp frequency, depth + quality
→ BP monitor: blood pressure
→ Thermometer/temp probe: body temp
→ Anesthetic gas analyzer: [] of inhalant anesthetic/O₂ in breathing system (depending on analyzer)
→ Ax machine manometer: pressure in breathing system

What are some reasons for keeping detailed records?

→ Patient safety: ID changes/problems early
→ Track trends: vital signs + ax depth over time
→ Guide tx: support decisions during ax
→ Communication: keep vet team informed
→ Legal documentation: record care provided
→ Future reference: help plan ax for future procedures

Why is the recovery period so important?

→ patient remains @ risk as ax wears off

• Airway/breathing: ensure patient can breathe + protect airway

• Vital signs: monitor HR, RR, oxygenation + temp

• Temp: prevent/tx hypothermia

• Complications: detect resp depression/delayed recovery early

• Comfort/safety: assess pain, keep warm + prevent injury

NOTE: most ax deaths in vet med occur during the 3 hrs immediately post-op

How long after the end of ax should the patient be monitored?

→ continue until parameters return to N
→ after extubation, record parameters q 15 mins until N
→ recovery extends until the animal has N parameters + can hold sternal recumbency, or until it returns home w N functions

What are the indications that it is time or almost time to extubate a dog? A cat?

→ Dog

• Remove tube after swallowing

• Brachycephalic: leave tube in as long as tolerated; remove b4 dog chews it

→ Cat

• Remove b4 swallowing

• @ first sign of movement (e.g. ear twitch)

KEY DIFF: cats have a more sensitive larynx and ⬆ laryngospasm risk, so they are generally extubated at a lighter recovery plane than dogs, as soon as appropriate protective reflexes return

What is a laryngospasm?

→ exaggerated, prolonged laryngeal reflex causing closure of arytenoid cartilages, partially/fully obstructing airflow

→ Causes: irritation/inflammation from rough intubation or prolonged ET tube presence

→ Signs: wheezing/dyspneic sounds on inspiration, possible apnea, anxiety, thrashing + cyanosis

What are methods of preventing laryngospasm and tx mild case?

→ Prevention

• Xylocaine spray 1–2 min b4 intubation

• Sm amount of Xylocaine gel on ET tube

• Laryngoscope + gentle technique; avoid touching cartilages

• Remove tube promptly b4 patient fully awake

• Sternal recumbency when possible, head supported, neck extended + no airway pressure

→ Tx

• Pink MM: supplement O₂ by mask/chamber/flow-by

• Muddy MM or persistent sounds: manually extend head/neck + gently pull tongue if swallowing reflex is insufficient

What should you have in case of prolonged laryngospasm?

→ supplies for re-induction w injectable agent, reintubation + O₂
→ cyanosis/apnea persists: re-induce w injectable agent (not a mask) for reintubation + O₂
→ dexamethasone may be given IV to ⬇ inflammation @ vet's discretion

What is w brachycephalic?

→ Anatomical features: stenotic nares, narrowed trachea, elongated soft palate, possible obesity
→ Signs: loud inspiratory sounds (snoring/stertor)
→ Prevention: leave ET tube in as long as possible
→ Tx: same general approach as laryngospasm, including O₂ supplementation + airway management

How do we prevent and tx hypothermia? What types of heating should we avoid?

→ Prevention/tx

• Insulation + external heat: blankets, heated oat bags, circulating warm water pads

• Monitor temp; avoid warming too quickly

• Remove external heat w/in 1°C of target, then use insulation only

→ Avoid

• Electrical heating pads/discs due to thermal burn risk

• Overheating

What are the names of possible interventions for stormy or dysphoric recoveries and for prolonged recoveries?

→ Stormy recoveries

• Semiconscious excitement/hallucinations (commonly w ketamine)

  • Quiet, dark, padded recovery area

  • ⬇ stimulation

  • Consider diazepam or acepromazine

• Vocalization/paddling in unconscious animals (associated w barbiturate inductions or minimal/worn-off pre meds)

  • Gently reassure

  • Consider IV diazepam or another sedative/anxiolytic

• If pain suspected: give analgesics

→ Prolonged recoveries

• Gentle stimulation (never be rough or yell)

• IV fluids

• Restore body temp

• Consider reversal agent if applicable