Anaesthesia Flashcards
What occurs in the pre-op phase of anaesthesia?
Owner consent and admission to practice Full exam/history, ASA classification and planning stage Set up machine/equipment Prepare meds/drugs/fluids Premed patient
What happens in the induction phase of anaesthesia?
IV catheter placement
Pre-oxygenation
Admin of induction agent
Security of airway
What happens in the maintenance phase of anaesthesia?
Maintain anaesthesia - gas/TIVA/injectable
Placement of local/regional blocks
Continue to surgery/diagnostics
What happens in the recovery phase of anaesthesia?
Cessation of gaseous maintenance/CRIs
Antagonism of injectable drugs
Removal of airways device
Move to recovery area
What is the anaesthesia triad?
Analgesia
Narcosis
Muscle relaxation
What did the CEPSAF enquiry discover?
50% of deaths occurred within 3 hours of recovery
Sick animals had higher risk than healthy ones
Risk significantly higher with GA than sedation
Cats had twofold increase in risk
What are the species-specific problems seen?
Extremes of size Hyper-/hypothermia Aggression/risk of injury Drug sensitivities in breeds Obesity
List some breed-specific problems with anaesthetic drug use.
Brachycephalic
Boxers = ACP / cardiomyopathy
Collies/sheepdogs/shepherds = MDR1 gene
Greyhounds = lack of cytochrome P450 / body fat
Dobermann = Von Willebrand factor / dilated cardiomyopathy
Miniature schnauzer = females sick sinus syndrome
What can VNs do/not do in terms of inducing/maintaining anaesthesia?
Can administer a specific amount of meds directed by VS / act as VS hands to maintain
Cannot admin meds incrementally or to effect
What information needs to be gathered from an owner during the pre-op assessment?
Full history Owner questioning - any concerns? Previous reactions to drugs? Breed/species Confirm pre-op fasting times
What is assessed in the pre-op clinical examination?
MMs/CRT Thoracic auscultation Heart murmur? Pulse quality and effort Ventilatory effort Temperature Swellings/distension Temperament
What is the goal of pre-op fasting?
To reduce the volume of the stomach contents
To prevent GOR/regurgitation and aspiration
What are the recommended guidelines for pre-op fasting?
Cats = 6-8 hours
Dogs = 8-10 hours
Rabbits/small furries = no starvation but may withhold food ~30 mins pre-op
What diagnostic tests may be run prior to anaesthesia induction?
Bloods Urine Radiography ECG Echocardiology Ultrasound
What are the injectable anaesthetic agents and what animals are they licensed for?
Propofol - dogs, cats
Alfaxalone - dogs, cats, rabbits
Ketamine - horses, dogs, cats
Tiletamine / zolazepam - dogs, cats
What are the injectable drugs for euthanasia?
Pentobarbital Secobarbital sodium (quinalbarbital sodium) plus cincocaine hydrochloride = Somulose
What factors affect the effect of anaesthetic injectables?
Blood flow to brain Amount of non-ionised drug Lipid solubility Molecular size Conc. gradient Protein binding Distribution Metabolism Excretion
What makes the ideal injectable anaesthetic agent?
Rapid onset Non-irritant Minimal cardiopulmonary effects Rapid metabolism and elimination Non-cumulative Good analgesia Good muscle relaxation
What are the key points regarding propofol as an injectable anaesthetic?
Rapid onset of action Highly plasma protein bound (96-98%) and lipid soluble Rapidly metabolised and eliminated Non-cumulative in DOGS No analgesia Fair muscle relaxant Non-irritant Post-induction apnoea, hypotension, Heinz body anaemia in cats
What are the key points regarding alfaxalone as an injectable anaesthetic?
Non-irritant (?IM) 20% plasma protein bound Rapid onset Rapid metabolism and elimination Non-cumulative Preserves baroreceptor tone Some respiratory depression
What are some key points regarding ketamine as an injectable anaesthetic?
Poor muscle relaxation (not used as sole agent) Reflexes maintained Maintains CVS/respiraotyr function Analgesia/antihyperalgesia Slow onset Non-cumulative 50% plasma protein bound Increase intraocular-/intracranial pressure
What factors affect recovery from injectable anaesthetics?
Drug factors, e.g. dose
Species, breed and age
Co-morbidities, e.g. CVS/hepatic/renal function
When is TIVA useful and what are its ideal properties?
Used to reduce exposure to inhalants, or “in the field” when machines are not available
Ideal properties = rapid metabolism and elimination, fast onset, high therapeutic index, pharmacokinetics available
In which three ways can anaesthesia be induced by injection and what are the advantages/disadvantages of each?
IV = quickest onset (2-10mins), reliable, less stress BUT relies on IV catheter - IV only for Propofol/Alfaxalone
IM = fairly quick (10-20mins), reliable if actually IM BUT can be painful, slower onset
SC = easy to administer, less painful than IM BUT can cause pain, longer onset (30-45mins), lower efficacy
Which two ways can anaesthesia be induced through inhalation and what are the advantages/disadvantages?
Chamber inductions = easy to set up/use, cheap, no technical skill BUT very stressful, difficult to observe patient, risk of exposure
Face masks = cheap, easy to set up/use, can give oxygen/VAs quickly BUT does not protect airway, increases dead space, risk of exposure
Describe the laryngeal mask airway (LMA).
Easy to use - sits over airway
Reduced complications compared to ETT
Reduced airway pollutants compared to face mask
Not really designed for veterinary species
Describe the supraglottic airway device (V-GEL).
Species specific / weight specific design
Training needed before use
Describe ET tubes.
Allows airway protection
Prevents atmospheric exposure
Allows accurate provision of anaesthetic agents
Some have a cuff system
What is the point of a cuff on an ET tube?
Allows a tight seal in the trachea Prevents gas leaking around tube Prevents contents going into patient lung Allows accurate delivery of VAs/oxygen Allows direct route to lungs
What equipment should you prepare for ET intubation?
Laryngoscope Tubes - range of sizes (length = incisors to shoulder tip) Local anaesthetics (cats) Tie Cuff syringe Swab/suction/mask for preoxygenation
What are the common complications during induction?
Injury - us or them Lack of airway patency Aspiration/regurgitation Hypothermia CVS/respiratory system dysfunction Post-induction apnoea
List the patient safety features on anaesthetic machines.
Pin-index system and NIST for pipelines Colour-coded pressure gauges and flowmeters Oxygen flowmeter "touch coded" Ratio regulators Nitrous oxide cut-out Alarm whistle Air intake valve Reserve oxygen cylinders
What is the difference between active and passive scavenging?
Active = waste gases/anaesthetic agents drawn outside of building by a fan and vent system, requires an air break to prevent negative pressure being applied to patient breathing system
Passive = gas is pushed by patient expiratory effort into tubing either into tubing leading outside of building or into a canister containing activated charcoal