Anesthesia Flashcards
Define
Anaesthesia
A state with a lack of sensation
Define
General anaesthesia
A state of unconsciousness produced by anaesthetic agents, with an absence of pain sensation
Define
Regional anaesthesia
Lack of sensation from interupting sensory nerve conduction to only one region of the body
Define
Sedation
A state of reduced irratibility or excitment
Define
Anxiolysis
A state of reduced anxiety
Define
Analgesia
Insensibility to pain without loss of consciousness
Define
Narcosis
A state of stuppor or unconsciousness produced by a narcotic
Define
Hypnosis
An artifically induced state of passivity
What are 3 exceptions to the legal requirement of anaesthesia?
- Emergency first aid
- Castration (before 7 days for pigs, bulls and sheep when using rings)
- Tail docking (before 7 days for pigs and sheep)
List the 3 components of the anaesthetic triad
- Analgesia
- Narcosis
- Muscle relaxation
List the 5 phases of anaesthesia
- Preoperative period
- Pre-anaesthetic medication
- Induction
- Maintenance
- Recovery
List 3 risks associated with anaesthesia in small animals
- Breed type
- Lack of observation/monitoring
- Species (cats and rabbits have more problems in recovery, dogs are more likely to have respiratory arrest)
List the 6 features of an ideal anaesthetic
- Safety
- Efficacy
- Predictability
- Convenience
- Cost
- Legality
List 3 risks associated with anaesthesia in horses
- Duration of anaesthetic is more than 2 hours
- Age of patient is less than 7 days
- Recovery period
Why is it relevant to withhold food from an animal before an anaesthetic procedure
Withholding food prevents the risk of vomiting, regurgiation and aspiration, and reduces intra-abdominal pressure
Define this ASA Classification
ASA I
Normal, healthy
Define this ASA Classification
ASA II
Mild systemic disease/impairment
Define this ASA Classification
ASA III
More severe systemic disease which is well managed by treatment
Define this ASA Classification
ASA IV
Severe systemic disease which is not well managed
Define this ASA Classification
ASA V
Moribund, unlikely to survive 24 hours
List the 5 general aspects that you should evaluate in a pre-anaesthetic clinical exam
- Breed of the animal
- Animal morphology
- Age
- Organ systems
- Labratory & other tests
What is the recommended pre-operative fasting period for a dog and cat
Food & water
4-6 hours (food only)
What is the recommended pre-operative fasting period for a horse
Food & water
6-12 hours (food only)
What is the recommended pre-operative fasting period for a cow
Food & water
18-24 hours for food, 12-18 hours for water
What are the 2 most important systems to examine before anaesthesia
Cardiovascular and respiratory systems
What is a particular risk factor to consider when anaesthesing a neonatal/pediatric animal
Just list one example
Younger animals have a reduced thermoregulatory capacity, so there is a greater risk of hypothermia
What is a particular risk factor to consider when anaesthesing a geriatric animal
Just list one example
Older animals have reduced cardiovascular and respiratory reserves
List 4 things improper patient positioning can affect
In which animal is this most important?
- Blood flow
- Intracranial pressure
- Muscle perfusion
- Ventilation
Horses
List 4 ways heat is lost during anaesthesia
- Conduction
- Convection
- Raditation
- Evaporation
How can you prevent hypothermia under anaesthetic?
Physical factors
Increase environmental temperature, no draughts and use hot water bottles
How can you prevent hypothermia under anaesthetic?
Anaesthetic factors
Use short acting anaesthetics, keep patient as light as possible, and use rebreathers where possible
How can you prevent hypothermia under anaesthetic?
Surgical factors
Avoid unessecary clipping, minimize surgical time, and keep exposed visceral surfaces moist
When would you extubate a dog vs a cat
Why is it different?
Dog: when they swallow
Cat: before they swallow
In cats, you risk laryngospasm if you wait until they swallow
Define
Tranquilliser
Agent that affects mood
Define
Sedative
Agent that causes drowsiness
Define
Neuroleptic
Agent that reduces aggression and agitation
List the 4 drug classes of sedatives
- Phenothiazines
- Butyrophenones
- Benzodiazepines
- Alpha-2 agonists
What is the mortality rate associated with anaesthesia in dogs and cats?
Dogs: 0.17%
Cats: 0.24%
Why is monitoring during anaesthesia critical?
Anaesthesia impairs the function of the respiratory, cardiovascular and thermoregulatory systems
Monitoring helps us notice negative trends in these systems, and correct them early on
List 6 things to monitor during anaesthesia
Think patient and equipment
- CNS function
- Cardiovascular function
- Respiratory function
- Temperature
- Anaesthetic equipment
- Fluids, surgeon, general etc.
What are the 4 stages of anaesthetic depth?
Stage I, voluntary excitment
Stage II, involuntary excitment
Stage III, surgical anaesthesia
Stage IV, overdose
From which points in anaesthesia is the patient in stage I of anaesthetic depth?
From induction until unconsciousness
From which points in anaesthesia is the patient in stage II of anaesthetic depth?
From unconsciousness until rhythmic breathing is present
How is stage III of anaesthetic depth divided?
Plane 1, light surgical anaesthesia
Plane 2, satisfactory for most procedures
Plane 3, satisfactory for most procedures
Plane 4, very deep anaesthesia (not usually required)
From which points in anaesthesia is the patient in stage IV of anaesthetic depth?
From very deep anaesthesia (plane 4) to respiratory paralysis and death
List 5 ways in which we can monitor anaesthetic depth
Think patient reflexes/systems
- Cranial nerve reflexes
- Other reflexes
- Cardiovascular responses
- Respiratory responses
- Skeletomuscular responses
Which cranial nerve reflexes do we assess during anaesthesia?
Occular reflexes (palpebral and corneal)
Which stage of anaesthesia is the palpebral reflex lost?
What situation is the exception?
Stage III
Horses under ketamine anaesthesia
Why is the palpebral reflex better than the corneal reflex for monitoring anaesthetic depth?
The corneal reflex can still be present after cardiac arrest, and you risk corneal trauma if you check it too often
The palpebral is good for most species because it is present when anaesthesia is light, and lost when there is sufficient anaesthesia (stage III)
List 3 examples of reflexes you can use to measure anaesthetic depth other than occular reflexes
- Laryngeal and pharyngeal reflexes
- Pedal withdrawl
- Anal reflex
List 3 ways you can assess cardiovascular and respiratory function in anaesthesia
- Heart rate
- Blood pressure
- Ventilation (rate, depth and pattern)
What is the first sign of lightening anaesthesia in horses?
Movement
___ and ___ are important in maintaining mean arterial blood pressure
MAP = __ x __
Cardiac output ad systemic vascular resistance
MAP = CO x SVR
What is the driving force for tissue perfusion?
Mean arterial blood pressure (MAP)
Which parameter of cardiovascular function is a subject assessment?
Tissue perfusion
List 3 ways you can assess HR, arterial pressure and perfusion
- Palpate the apex beat
- Auscultation
- Palpation of peripheral pulses
Peripheral pulse palpation gives an indication of ___, whereas palpation of the apex beat does not
Peripheral perfusion
Apex beat palpation and auscultation are not good indications of __
2 things
Cardiac output and tissue perfusion
Which 2 arteries are generally useful for peripheral pulse palpation
What is another one you can use in dogs?
- Metacarpal
- Dorsal pedal
Lingual artery
Which artery do you commonly use for pulse palpation in horses
What other ones can you use? (3)
The facial artery
Can also use the palatine, auricular or dorsal metatarsal
What creates the pulse pressure we can feel?
The difference between the systolic and diastolic blood pressures
List 2 ways you can assess tissue perfusion
- Capillary refill time
- Mucous membrane colour
How can you assess renal perfusion?
Measure urine output
List 2 benefits of ‘sighing’ the lungs during anaesthesia
- Prevents atelectasis (lung collapse)
- Allows us to assess the compliance of the lungs and/or breathing system
What does a low ‘sigh’ compliance indicate?
There is pressure on the chest and/or an obstruction
What does a high ‘sigh’ compliance indicated?
There is a dissconnection or leak in the breathing system
List 3 complications of anaesthesia associated with hypothermia
- Cardiovascular depression
- Hypocoagulation
- Hypoventilation
Electrical cortical activity __ with increasing anaesthetic depth
Decreases
What does an ECG measure?
The electrical activity of the heart
List 3 advantages of an ECG
- Good for diagnosing cardiac arrythmias
- Good indication of myocardial hypoxia
- Provides a continuous visual display of heart activity
Also relatively cheap & easy!
List 3 disadvantages/limitations of an ECG
- Provides no information about mechanical activity
- Displayed HR can be inaccurate
- You can observe pulseless electrical activity (machine fault)