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 -‐> 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'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'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

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