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Anesthesiology: Lecture 13 Dog and Cat

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Steps of anesthesia
- preanesthetica evalulation and preperation

- pre- med

- anesthetic induction

- maintenance and monitoring

- recovery
What is part of your patient assessment?
- medical hisotry

- full PE

- age : doses will change

- temperment

- breed ( ie: greyhound, brachycephalic)

- basic haematology: PCV, TP, Gluc, BUN
What is part of your medical hx?
- Past problems, previous adverse drug responses

- Anesthetic events

- Present problems

- medication
What are some diagnostic test you can do?
- Complete blood count, serum chemistry, urinalysis advisable

- rads

- Murmurs, arrhythmias (ECG, echocardiography)

- Type of procedure → what complications might you expect
Until when should you delay the anesthetic?
-Further assessment is performed

‐ Patient is stabilized

‐ Anesthetic risk established
Patient Assessment
What are your communicating with the owner?
-Owner comprehension and permission

- Obtain wriFen informed consent
What are requirements for food and water?

What animals should you be careful with water restrictions? 2

What animals require a shorter fasting time? Why?

What is the time for 6 - 16 week animals? 16 or older?
• Allow free access to water

- Care with old animals and animals with increased fluid requirements

• Recommend fasting before anesthesia

- Young animals: require shorter fasting
times (hypoglycemia)

‐ 6-‐16 weeks: 4 hours
‐ 16 weeks: 6-‐8 hours
What are options for premed?
1. ace

2. dexmedetomidine

3. midazolam

4. opiod
What is ace commonly given with?

What do higher doses of ace do?

When is maximum sedation?

What does ace do to your gas dose?

How long do its effects last?

Is there a reversal?

What does ace do to vomiting? When should it be given if using an opiod?
1. opiod

2. don't increase degree of sedation, but side effects and duration

3. Maximum sedaMon aier 30-‐40 min

4. Reduces dose of major anestheMc agent by 30%

5. Long lasMng (6-‐8 hours)

6. No reversal

7. Antiemetic (ideally 15min before opioid)
What are the effects of ace on the cardiovascular system? 2 ***

What effect does it have on the spleen?
1. Alpha-‐1 antagonist→ peripheral vasodilation

2. protects against epinephrine induced arrythmias

- epinepheril reversal

- splenic sequestration of rbc, dog decreased pcv by 30%
What are other non cardio/resp effects of ace?
Ptosis and prolaspse of third eyelid
Do cats get as sedate with ace as dogs?
seldom

- Will block morphine induced excitement
What age of dog should you be careful in using ace in?
puppies (< 2 months)
What are contraindications of ace in dogs?
- Hypovolemia
- Boxers
- Giant breeds?
- Seizure-‐prone?
Why is it a concern to use it in boxers?
- fainting

- vagal syncope

- can only tx symptoms with IVF and atropine vasoconstrictor
What is dexmedetomidine?
• Dextrorotary enanMomer of racemic mixture medetomidine

• Approximately twice as potent as medetomidine

• Supplied as 0.5mg/mL

• Allows to use the same injection volume

• Because dexmed diluMon has the same potency as med
Why is dex used?
Most selective alpha-‐2 agonist available

- sedation

- analgesia

- muscle relaxation
WHat animals is it rec. for only?
only for young, healthy patients
What inpact with dex have on the use of other drugs?
Significant drug-‐sparing effect
What does it do for vomiting?
emetic action in carnivores
What can happen to the dose of dex if you use it with an opidos?
can reduce it
What is atipamezole?
- reversal
What are cardiovascular effects of dex? 3
• Vasoconstriction
decrease in heart rate
Reduction in cardiac output

• Avoid concurrent use of anMcholinergics
What animals should you avoid dex use in? 2 Why?
• Avoid in brachycephalics (upper airway obstruction because of massive relaxation)

• Avoid in small animals less than 12 weeks of age → Reduces endogenous insulin secreMon: hyperglycemia
Why is midazolam used?

What animals does it provide minimal sedation when used alone?

In what patients is more sedation seen? 3

What kind of muscle relaxation does it provide?

How can it be reversed?

What drug is it best combined with?
• Water‐soluble, good absorption IM

• Minimal sedation
excitiction in healthy cats and dog

• Sedation in pediatric, geriatric or ill patients

• Central mediated muscle relaxation

• Anticonvulsant

• Reversal with Flumazenil

• Best combined with opioids
What are effects of midazolam in the CV system?
minimal effects
Where is it metabolized?
How long does it last compared to diazepam?

What procedure should you not use it in?
- liver, inactive metabolites

- shorter

- c-sections
PRemed for dogs?
Premed for cats
Why do cats often need higher doses?
- higher metabolic rates and smaller Surface area
Heavy Sedation for cats

What might you use for a more reliable sedation?

What kind of procedures might you use heavy sedation for?

What must you always do if you are doing a heavy sedation? 2
Anesthetic Induction set up
AnestheMc Equipment Check:

• Ensure ET tubes and intubation aids are readily available

• Anesthesia machine

-‐ Select appropriate breathing system
-‐ Perform leak test
-‐ Check: Oxygen, Inhalant, CO2 absorbent, Waste scavenging

• Monitoring equipment
What is part of your patient prep at induction?

What kind of patients must you stabilize?

What physic parameter must you check?

Why preO2?
• Venous access -‐ catheter placement

• Stabilize hemodynamically instable paMents

• Assess heart rate, pulse quality and respiratory rate

• Connect monitoring equipment (appropriate for disease condiMon)

• Quiet environment

• Pre-‐oxygenatioon: reduces risk of hypoxemia
What can you use for dog induction drugs?
1. THIOPENTAL (10 mg/kg IV) Give half and rest to effect

2. PROPOFOL (2-‐4 mg/kg IV) Give half and rest to effect

3. DIAZEPAM (0.2-‐0.5 mg/kg IV)
KETAMINE (5-‐10 mg/kg IV)
Give to effect

4. ALFAXALONE (1-‐2 mg/kg IV) Give to effect

5. MASK INDUCTION

• Isoflurane
• Sevoflurane
• Halothane
Cat induction
What are reasons for placing a ETT? 3
• Maintain and protect a patent airway
• Apply IPPV
• For maintenance of inhalant anesthesia
What are types of ETT?
- Cuffed (inflated with air to produce a leak proof seal

- Plain (used in birds complete tracheal rings)

- Guarded
Murpheys Eye
in case hole is plugged
What are steps you take before intubation?
‐ Check ET tube cuff for leak

‐ Have mulMple sizes available - use the largest possible

‐ Pre-‐measure ET tube length (incisor teeth - midneck)
Intubation technique dog:

What position can the dog be in?
What are complications that can arise with cuff inflation?
Over-inflation:

• Stretching of tracheal wall

• Compression of lumen

• HerniaMon of cuff → one side is weaker and over inflates and wraps around front of hole and cannot breath
Intubation tech for cat

Why is it more difficult then a cat?

What is the max lido to use?
- < 2 kg, spray 1/2 spry delivers 10mg, very close to toxic dose

- use syringe instead
How can you verify correct ETT placement?
• Direct visualizaMon (use laryngoscope)

• Rebreathing bag

• Chest excursions

• PalpaMon of ONE trachea below the larynx

• AuscultaMon of both sides of the animal's chest

• Capnography→100% indicator you are in
What can you use for maintenance of anesthesia?
1. INHALATIONAL techniques

Isoflurane (1-‐2%)
Sevoflurane (2-‐3%)
Halothane (1-‐2%)

2. • INJECTABLE techniques

• Propofol (0.2-‐0.5 mg/kg/min)
• Alfaxalone (0.1-‐0.2 mg/kg/min)
• Thiopental (1-‐2 mg/kg bolus)
What can you use to monitor CNS and depth?
eye reflexes
What are indictors that you are light?
• Palpebral reflex
• Tear formation
• Eye position is central
What are indicators that you are Sx?
• No palpebral reflex
• Less tear formaMon
• Eye posiMon is ventral
What are indicators that you are too deep?
no palpebral reflex, central eye, cornea dry -‐&gt; LIGHTEN
What are you monitoring during?
• Peripheral pulses (rate, rhythm, quality)

• ObservaMon of chest excursions, re-‐breathing bag

• Doppler (blood pressure, heart rate)

• Pulse oximeter

• Capnogram

• ECG
What life support can you give?
• Provide Oxygen and Support Ventilation

• Fluid therapy

-‐ Lactated Ringers or Normosol R
-‐ 10 mL/kg/hr
-‐ Do not use dextrose

• Provide analgesia

• Consider mulMmodal anesthesia

• Good body positioning, especially if old, don&#039;t overextend limbs or head, sore after

if hanging of table, will be swollen
How is heat lost?
Radiation, conduction, convection and evaporation

its a concern

remember it starts in premed where ace vasodialtes and they are left in a kennel
What are ways to prevent heat loss?
• Careful use of scrub solutions and alcohol!

• Circulating warm water blankets, hot water bottles

• Forced warm air (BAIR huggers)

• Heat lamps, electrical mats be careful
What is the critical phase of anesthesia?
recovery
What should be going on during recovery?
• Continue monitoring, patient support and record keeping

• Airway, Respiration: Supply oxygen

• Circulation: Fluids

• Level of consciousness

• Body temperature

• Pain management

• Patient comfort
When are dogs extubated? cats?
-‐ Dogs: on return of swallow reflex
-‐ Cats: ear twitch
What can happen to the BT of cats in recovery?
increase, hyperthermic
What special precautions should we take with bracycephalics?

What kind of induction protocol is best to use?
1. Avoid heavy sedation (may exacerbate dyspnoe)

- Acepromazine (0.01-‐0.02mg/kg)
Butorphanol (0.2mg/kg)

2. Pre-‐oxygenate

3. Rapid and short acting induction protocol

Propofol -‐ Alfaxalone - Ketamine / Valium

4. Gentle intubation with appropriately sized ET tube, don&#039;t want to make more swelling and edema
Why do we preO2 brachia's?
- never know if intubation will be smooth
What is the best way to maintain and recovery brachcephalics?
• Isoflurane or sevoflurane for maintenance

• Late extubation

• Position in sternal

• Continue monitoring post extubation

• Have O2 ready, be prepared to re-‐intubate
What is the altered physiology of the dam that needs a c section?

What happens to CO?

Why is there often chronic hyperventilation?

What should the anaesthetic drug requirement be reduced by?
• Cardiac output increase → higher metabolic demand

• Chronic hyperventilation to meet increased oxygen demands

• Any drug that can cross blood-‐brain barrier can cross placenta as well (e.g. Diazepam accumulates in fetus)

• Be careful - prone to regurgitation

• AnestheMc requirement is reduced 25-‐40%
What can you do to decrease anesthetic time for the dam?
- do as much before such as place iv, scrub and shaves
What could you premed a csection with?

What considerations should you make when choosing a premed?
• Try to avoid, if possible

• Choose drug with short duraMon or with specific antagonist

• Use lowest possible dose
Describe induction of a pregnant dam?

Why preO2?

What kind of agent should you use for induction?
• Pre-‐oxygenate! (prevents hypoxia from induction apnea)

• IV agent: quick acMng and short duraMon: propofol, alfaxalone
Describe maintenance?
• Secure airway: INTUBATE!

• Use local anesthetic technique (infiltraMon, epidural)

• Monitor blood pressure and provide IV fluid support

• Provide supplemental oxygen
What should you have available if you use an opiod for pain?
- naloxon to reverse neonatal opiod depression
When would it be best to give an opiod?
after fetus delivery
What are other methods of pain relief?
- local anesthetics

- infiltrative line block or splash block