Clinical induction and maintenance

What is the aim of induction

• Produce state of anaesthesia

• Suppress reflexes to allow endotracheal intubation

What are the induction injectable agents

• Propofol

• Alfaxalone

• Ketamine

• Thiopental

• Etomidate

What are pharmacokinetics

• Absorption, distribution, metabolism, elimination

• Onset, offset

What are pharmacodynamics

• Systemic effects

• Quality of induction of recovery

• Therapeutic margin

What are physicochemical properties

• Formulation

• Shelf life

• Drug compatibility

What are patient specific factors

• Species

• Breed

• Temperament

• Co-morbidities

• Pregnancy

What species are induction drugs licensed in

What are dog physiological consideration

• Variation in sizes and temperament

• IV usually readily accessible

What should not be used in sighthounds

Thiopental

What should be prioritised in brachycephalics

Airway access

What is important with dogs with heart disease

Maintain cardiac output

What cat physiological considerations are there

Common diseases such as CKD in older cats and hyperthyroidism

What is a reliable route of administration in cats

IV

Why should you care with propofol in cats

Heinz body anaemia reported following doses over sequential days

When should you take care with ketamine in cats

If they have anuric AKI as it is eliminated unchanged via the kidneys

What are the practicality problems for horses

Use drugs with lower volume so unlikely to be able to induce to effect due to safety

What is a risk in farm animals

High aspiration risk due to salivation and regurgitation

What are specific considerations for exotics

• Small size so small drug volume

• Diverse range in physiology

• Lack of familiarity

• IV access difficult

• Prone to stress

• High mortality rate

What are specific considerations for wildlife

• Safety

• Diverse range in physiology

• Capture myopathy

What are the issues with mask induction

• Highly stressful

• High concentration required

• Profound CV effects

• High risk of exposure

• Mortality risk

What are the routes of administration of injectables

What is the purpose of airway management

• Oxygen and anaesthetic delivery

• Airway protection against reflux and aspiration

• Provides means to ventilate

What are the approaches to airway management

• Endotracheal intubation

• Supraglottic airway devices

• Face mask

How do you ET intubate small animals

• Laryngoscope for visulisation of artenoids and glottis

• Do not touch the epiglottis

How do you ET intubate a cat

• Laryngospasm risk

• Lidocaine spray required

• Uncuffed or cuffed

How do you ET intubate a horse

• Large silicon ET tube

• Blind placement

• Bite block or gag required

How do you ET intubate small ruminants

• Narrow gape

• Straighten head and neck

• Long laryngoscope blade

• Stylet

How do you ET intubate cattle

Manually displace epiglottis and arytenoids

What is the aim of cuff inflation

• Provide seal to protect airways

• Minimise anaesthetic exposure

• Means to ventilate

What are the methods of cuff inflation

• Minimal occlusive pressure against 20cmH₂O pressure

• Cuff syringe with built in manometer

What are supraglottic airway devices

• Peri-laryngeal seal via inflatable cushion

• LMA developed for humans but can be used in dogs

• V-gel developed for cats and rabbits

What are alternative methods of airway access

• Temporary tracheotomy

• Pharyngostomy

• Airway insufflation

• Endoscopic guidance

What are the inhalation maintenance agents

• Isoflurane

• Sevoflurane

What are the total intravenous anaesthesia agents

• Propofol boli / infusion

• Alfaxalone boli / infusion

• Triple drip

What is in a triple drip

• Ketamine

• Guaphensen

• Alpha-2 agonist

What do inhalation agents require

• Anaesthetic machine

• Vaporiser

• Breathing system

When is total intravenous anaesthesia required

• Field anaesthesia

• Indicated for procedures involving respiratory tract

How do you manually assess maintenance agents

• Palpebral reflexes

• Eye positioning

• Jaw tone

• Trends of vitals

What do gas analysers give you

End tidal anaesthetic agent

Which pig breeds are genetically predisposed so malignant hyperthermia

• Landrance

• Pietrain

• Duroc

• Poland china

What is the pathophysiology of malignant hyperthermia

1. Dysfunctioned ryanodine-sensitive Ca²⁺ channels

2. Lead to excess intracellular Ca²⁺ release and sustained muscle ontraction

3. Dramatic CO₂ and heat production

4. Subsequent metabolic and respiratory acidosis, cell death, DIC and mortality

What species are the maintenance agents licensed in

What negative environmental effects do inhalation agents have

• Greenhouse gas

• Ozone depletion

What are negative environmental effects of injectable agents

• Energy consumption via manufacture, sterilisation, packing, transport, disposal, electricity, wastage

• Contamination of local body of water