Anesthesia Flashcards
1
Q
Define
Anaesthesia
A
A state with a lack of sensation
2
Q
Define
General anaesthesia
A
A state of unconsciousness produced by anaesthetic agents, with an absence of pain sensation
3
Q
Define
Regional anaesthesia
A
Lack of sensation from interupting sensory nerve conduction to only one region of the body
4
Q
Define
Sedation
A
A state of reduced irratibility or excitment
5
Q
Define
Anxiolysis
A
A state of reduced anxiety
6
Q
Define
Analgesia
A
Insensibility to pain without loss of consciousness
7
Q
Define
Narcosis
A
A state of stuppor or unconsciousness produced by a narcotic
8
Q
Define
Hypnosis
A
An artifically induced state of passivity
9
Q
What are 3 exceptions to the legal requirement of anaesthesia?
A
- Emergency first aid
- Castration (before 7 days for pigs, bulls and sheep when using rings)
- Tail docking (before 7 days for pigs and sheep)
10
Q
List the 3 components of the anaesthetic triad
A
- Analgesia
- Narcosis
- Muscle relaxation
11
Q
List the 5 phases of anaesthesia
A
- Preoperative period
- Pre-anaesthetic medication
- Induction
- Maintenance
- Recovery
12
Q
List 3 risks associated with anaesthesia in small animals
A
- Breed type
- Lack of observation/monitoring
- Species (cats and rabbits have more problems in recovery, dogs are more likely to have respiratory arrest)
13
Q
List the 6 features of an ideal anaesthetic
A
- Safety
- Efficacy
- Predictability
- Convenience
- Cost
- Legality
14
Q
List 3 risks associated with anaesthesia in horses
A
- Duration of anaesthetic is more than 2 hours
- Age of patient is less than 7 days
- Recovery period
15
Q
Why is it relevant to withhold food from an animal before an anaesthetic procedure
A
Withholding food prevents the risk of vomiting, regurgiation and aspiration, and reduces intra-abdominal pressure
16
Q
Define this ASA Classification
ASA I
A
Normal, healthy
17
Q
Define this ASA Classification
ASA II
A
Mild systemic disease/impairment
18
Q
Define this ASA Classification
ASA III
A
More severe systemic disease which is well managed by treatment
19
Q
Define this ASA Classification
ASA IV
A
Severe systemic disease which is not well managed
20
Q
Define this ASA Classification
ASA V
A
Moribund, unlikely to survive 24 hours
21
Q
List the 5 general aspects that you should evaluate in a pre-anaesthetic clinical exam
A
- Breed of the animal
- Animal morphology
- Age
- Organ systems
- Labratory & other tests
22
Q
What is the recommended pre-operative fasting period for a dog and cat
Food & water
A
4-6 hours (food only)
23
Q
What is the recommended pre-operative fasting period for a horse
Food & water
A
6-12 hours (food only)
24
Q
What is the recommended pre-operative fasting period for a cow
Food & water
A
18-24 hours for food, 12-18 hours for water
25
What are the 2 most important systems to examine before anaesthesia
Cardiovascular and respiratory systems
26
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
27
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
28
List 4 things improper patient positioning can affect
| In which animal is this most important?
1. Blood flow
2. Intracranial pressure
3. Muscle perfusion
4. Ventilation
| Horses
29
List 4 ways heat is lost during anaesthesia
1. Conduction
2. Convection
3. Raditation
4. Evaporation
30
How can you prevent hypothermia under anaesthetic?
| Physical factors
Increase environmental temperature, no draughts and use hot water bottles
31
How can you prevent hypothermia under anaesthetic?
| Anaesthetic factors
Use short acting anaesthetics, keep patient as light as possible, and use rebreathers where possible
32
How can you prevent hypothermia under anaesthetic?
| Surgical factors
Avoid unessecary clipping, minimize surgical time, and keep exposed visceral surfaces moist
33
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
34
# Define
Tranquilliser
Agent that affects mood
35
# Define
Sedative
Agent that causes drowsiness
36
# Define
Neuroleptic
Agent that reduces aggression and agitation
37
List the 4 drug classes of sedatives
1. Phenothiazines
2. Butyrophenones
3. Benzodiazepines
4. Alpha-2 agonists
38
What is the mortality rate associated with anaesthesia in dogs and cats?
Dogs: 0.17%
Cats: 0.24%
39
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
40
List 6 things to monitor during anaesthesia
| Think patient and equipment
1. CNS function
2. Cardiovascular function
3. Respiratory function
4. Temperature
5. Anaesthetic equipment
6. Fluids, surgeon, general etc.
41
What are the 4 stages of anaesthetic depth?
Stage I, voluntary excitment
Stage II, involuntary excitment
Stage III, surgical anaesthesia
Stage IV, overdose
42
From which points in anaesthesia is the patient in stage I of anaesthetic depth?
From induction until unconsciousness
43
From which points in anaesthesia is the patient in stage II of anaesthetic depth?
From unconsciousness until rhythmic breathing is present
44
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)
45
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
46
List 5 ways in which we can monitor anaesthetic depth
| Think patient reflexes/systems
1. Cranial nerve reflexes
2. Other reflexes
3. Cardiovascular responses
4. Respiratory responses
5. Skeletomuscular responses
47
Which cranial nerve reflexes do we assess during anaesthesia?
Occular reflexes (palpebral and corneal)
48
Which stage of anaesthesia is the palpebral reflex lost?
| What situation is the exception?
Stage III
| Horses under ketamine anaesthesia
49
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)
50
List 3 examples of reflexes you can use to measure anaesthetic depth other than occular reflexes
1. Laryngeal and pharyngeal reflexes
2. Pedal withdrawl
3. Anal reflex
51
List 3 ways you can assess cardiovascular and respiratory function in anaesthesia
1. Heart rate
2. Blood pressure
3. Ventilation (rate, depth and pattern)
52
What is the first sign of lightening anaesthesia in horses?
Movement
53
___ and ___ are important in maintaining mean arterial blood pressure
| MAP = __ x __
Cardiac output ad systemic vascular resistance
| MAP = CO x SVR
54
What is the driving force for tissue perfusion?
Mean arterial blood pressure (MAP)
55
Which parameter of cardiovascular function is a subject assessment?
Tissue perfusion
56
List 3 ways you can assess HR, arterial pressure and perfusion
1. Palpate the apex beat
2. Auscultation
3. Palpation of peripheral pulses
57
Peripheral pulse palpation gives an indication of ___, whereas palpation of the apex beat does not
Peripheral perfusion
58
Apex beat palpation and auscultation are not good indications of __
| 2 things
Cardiac output and tissue perfusion
59
Which 2 arteries are generally useful for peripheral pulse palpation
| What is another one you can use in dogs?
1. Metacarpal
2. Dorsal pedal
| Lingual artery
60
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
61
What creates the pulse pressure we can feel?
The difference between the systolic and diastolic blood pressures
62
List 2 ways you can assess tissue perfusion
1. Capillary refill time
2. Mucous membrane colour
63
How can you assess renal perfusion?
Measure urine output
63
63
List 2 benefits of 'sighing' the lungs during anaesthesia
1. Prevents atelectasis (lung collapse)
2. Allows us to assess the compliance of the lungs and/or breathing system
64
What does a low 'sigh' compliance indicate?
There is pressure on the chest and/or an obstruction
65
What does a high 'sigh' compliance indicated?
There is a dissconnection or leak in the breathing system
66
List 3 complications of anaesthesia associated with hypothermia
1. Cardiovascular depression
2. Hypocoagulation
3. Hypoventilation
67
Electrical cortical activity __ with increasing anaesthetic depth
Decreases
68
What does an ECG measure?
The electrical activity of the heart
69
List 3 advantages of an ECG
1. Good for diagnosing cardiac arrythmias
2. Good indication of myocardial hypoxia
3. Provides a continuous visual display of heart activity
| Also relatively cheap & easy!
70
List 3 disadvantages/limitations of an ECG
1. Provides no information about mechanical activity
2. Displayed HR can be inaccurate
3. You can observe pulseless electrical activity (machine fault)
71
Describe the standard lead configuration for an ECG
Lead I connects LA-RA
Lead II connects RA-LL
Lead III connects LA-LL
72
List 3 possible causes for bradycardia
1. Vagal stimulation
2. Drugs (ex. opioids)
3. Hypercapnia
73
List 3 possible causes for tachycardia
1. Pain
2. Light anaesthesia
3. Hypotension/hypovolemia
74
List 3 possible causes for premature complexes on an ECG
1. Sympathetic stimulation
2. Cardiac disease
3. Hypercapnia
75
What are 2 indirect ways we can measure blood pressure?
1. Oscillometric
2. Doppler
76
Describe how you would take BP with an oscillometer
Place an inflatable cuff around limb, inflated above systolic pressure and then slowly deflated
The machine will sense the pulses of the arterial wall and give you the readings (systolic pressure is when pulse returns, MAP is the maxmal oscillation amplitude)
77
What indicates the mean aterial pressure on an oscillometric BP reading?
The maximal oscillation amplitude of the aterial wall
78
The width of a BP cuff should be approx. __ of the circumference of the extremity
40%
79
How will the blood pressure change if the cuff is too small?
BP will be overestimated
80
How will the blood pressure change if the cuff is too big?
BP will be underestimated
81
List 3 disadvantages of oscillometric BP measurement
1. Does not work well with low HR, arrythmias or small patients
2. Readings are affected by movement
3. Systolic pressure is overestimated at low pressures (and vice versa)
82
Describe how you would take BP with a doppler
A cuff is placed proximal to the ultrasound probe, inflated to occlude blood flow (above systolic pressure) and then slowly deflated
The pressure at which the audible signal returns is the systolic pressure
83
List 3 disadvantages of doppler BP measurement
1. Can be difficult to place the probe
2. Only gives systolic pressure
3. Less accurate than direct arterial pressure monitoring (hard not to be though)
84
Which method of BP monitoring is continuous: oscillometric or doppler?
Doppler
85
Describe how BP is taken in direct BP monitoring
The physical pressure is conducted via a saline filled tube to a transducer, the transducer changes the physical signal into an electrical signal
86
What does a pulse-oximeter measure?
% oxyen saturation of haemoglobin
| Also pulse rate
87
Describe how pulse-oximetry works
A probe measures the absorption of light by oxyhaemoglobin and deoxyhaemoglobin
| Oxy- and deoxyhaemoglobin absorb light of different wavelengths
88
List 3 factors that can affect the results of pulse-oximetry
1. Pigmented/hairy skin
2. Vasoconstriction
3. Ambient light
89
List 4 respiratory monitoring devices and what they monitor
1. Apnoea monitors (resp. rate)
2. Capnography (alveolar ventilation)
3. Pulse oximetry (O2 saturation of Hb)
4. Blood gas analysis (ventilation, oxygenation and acid-base status)
90
What is capnography?
| What does it show us?
A graphical & continuous representation of PCO2 throughout the respiratory cycle
91
What is the range for normocapnia?
ETCO2 35mmHg - 45 mmHg
92
What is the range for hypercapnia?
| What does it reflect?
ETCO2 > 45mmHg
| Reflects hypoventilation
93
What is the range for hypocapnia?
| What does it reflect?
ETCO2 < 35mmHg
| Reflects hyperventilation
94
Describe a normal capnogram
Respiratory baseline: 0 mmHg
Expiratory upstroke: steep
Alveolar plateu: slowly increasing
Inspiratory down stroke: steep
95
What does increased ETCO2 on a capnogram indicate physiologically?
| 3 things
1. Decreased alveolar ventilation
2. Increased CO2 production
3. Increased inspired CO2
96
What does decreased ETCO2 on a capnogram indicate physiologically?
| 3 things
1. Increased alveolar ventilation
2. Reduced CO2 production
3. Increased alveolar dead space
97
# Define
Ventilaiton
The act of inhaling and exhaling
98
# Define
Oxygenation
Delivery of oxygen to tissues
99
# Define
Hypercapnia
High blood carbon dioxide
| Normal range is 35-45mmHg
100
What monitors PaCO2 levels?
Central chemoreceptors in the medulla
| Medulla in the brain - not kidney :/
101
What monitors PaO2 levels?
Peripheral chemoreceptors
102
List 3 things that are impaired during anaesthesia
1. Airway reflexes
2. Respiratory muscle control
3. Neural control
103
# Define
FiCO2
Fraction of inspired CO2
| Should be 0
104
In which circumstance would FiCO2 not be zero?
Rebreathing (i.e., there is a lot of dead space or you are using a non-rebreathing system)
105
# Define
VCO2
CO2 produced by the body
106
# Define
VA
Minute ventilation (tidal volume x respiratory rate)
107
What is malignant hyperthermia?
A severe reaction to anaesthetic drugs to which the body temp raises to dangerously high levels
108
Which breeds/species are more susceptible to malignant hyperthermia?
Pigs and greyhounds
109
List 3 factors that can impact minute ventilation (VA)
1. Positioning
2. Drugs
3. Hypothermia
110
List 3 causes of hypercapnia
1. Drugs (depressents)
2. Obesity
3. Underlying disease
| Generally reduced alveolar ventilation
111
# Define
SaO2
Percentage of haemoglobin bound to oxygen
112
List 3 physiological signs of hypercapnia
1. Tachypnoea
2. Peripheral vasodilation
3. Tachycardia
113
List 4 ways you can maintain/manage an airway during anaesthesia?
1. Endotracheal tube
2. Laryngeal mask
3. Tracheostomy
4. Mask
114
Explain the function of murphey's eye
To maintain ventilation if the end of the ET tube becomes occluded during anaesthesia
115
List 4 reasons intubating an animal could be difficult
1. Anatomical
2. Physiological
3. Pathological
4. Iatrogenic
116
List some advantages of a laryngeal mask
1. Very easy to place
2. Easy to move
3. Allows for mechanical ventilation
117
List some disadvantages of a laryngeal mask
1. Difficulties if not positioned correctly
2. Possibility for laryngeal trauma
118
List some advantages of a tracheostomy
1. You definitely have an airway
2. You can bypass upper airway pathology
119
List some disadvantages of a tracheostomy
1. Requires more equipment
2. Higher incidence of morbitity
3. More aftercare is needed
120
List some advantages of a mask
1. Very easy to move and place
2. Increases FIO2 (inspired oxygen)
121
List some disadvantages of a mask
1. No airway protection
2. No mechanical ventilation
3. No capnography
122
List 3 reasons why you would use IPPV
1. To assist the patient
2. To assist the anaesthetist
3. To assist the surgeon
123
List some disadvantages of using IPPV
1. There is reduced cardiac output in the patient
2. Can cause lung damage
3. May see respiratory alkalosis
4. Higher cost & complexity
124
List 4 things you need to set up a intermittent positive pressure ventilation (IPPV) system
1. Cuffed ET tube
2. Appropriate breathing system
3. Means of delivery ventilation
4. Method to suppress ventilation (i.e., anaesthetics, opiods, neuromuscular blocking agents)
125
List some advantages of an ET tube
1. Protects the airway
2. Allows for mechanical ventilation
126
List some disadvantages of an ET tube
1. Can cause tracheal damage
2. Possibility for occulsion
3. Tube can become damaged
127
Define complications in anaesthesia
Often predictable disturbances, consequences of anaesthetic drugs, animal status and procedure
128
Define emergencies in anaesthesia
Events that lead rapidly and inevitably to death if untreated or mismanaged
129
Define accidents in anaesthesia
A common result of human error, often preventable
130
List 3 causes of hypercapnia
1. Hypoventilation
2. CO2 rebreathing
3. Increased CO2 production
131
Describe how to treat hypercapnia
Lighten anaesthesia and provide IPPV
Can also use a non-rebreathing system
132
List 3 causes of hypoxaemia
1. Inadequate oxygen supply
2. Hypoventilation
3. V/Q mismatch
133
Describe how to treat hypoxaemia
Pre-oxygenate the patient, increase FiO2 and lighten anaesthesia
134
Describe how you can prevent aspiration in the anaesthetized patient
Secure the airway with the cuff of the ETT, fast before induction, and make sure induction is quick
135
Describe barotrauma
Alveolar damage and potential rupture due to elevated transalveolar pressure
| Cause is increased pressure
136
List 3 consequences of an untreated airway obstruction
1. Exhaustion
2. Pulmonary oedema
3. Acute lung injury
137
Define apnoea
Total respiratory arrest
138
Describe how to treat apnoea
Assure the airway, provide assisted or mechanical ventilation, and lighten the anaesthetic
139
List 5 possible causes of hypotension
1. Hypovolemia
2. Vasodilation
3. Decreased contractility
4. Cardiac arrhythmias
5. Reduced venous return
140
Describe how to treat hypotension
| There are 4 ways
Anticholinergics to increase HR
Fluid therapy to increase preload
Iontropic drugs to increase contractility
Vasopressors to increase afterload
141
Describe how to treat bradycardia
Anticholinergics (atropine)
142
Describe how to treat tachycardia
Treat the underlying cause (nociception, hypoxia, hypotension, etc.)
143
What is the body's response to haemorrhage?
Tachycardia and vasoconstriction
144
List 3 consquences of hypothermia
1. MAC reduction
2. Impaired coagulation
3. Vasoconstriction
145
What is the difference between nociception and pain?
Nociception is unconscious, pain is conscious
146
Describe how to treat anaphylaxis
Adrenaline (bronchodilators and vasopressors)
147
# Define
Cardiac arrest
Sudden cessation of effect cardiac contractions
148
# Define
Respiratory arrest
Sudden cessation of respiratory movements
149
List the events following respiratory arrest that lead to cardiac arrest
1. Hypoxaemia
2. Hypoxic myocardium
3. Arrythmias
4. Cardiac arrest
150
List the events following cardiac arrest that lead to respiratory arrest
1. Tissue hypoperfusion
2. Cerebral hypoxia
3. Hypoxic medullary respiratory centre
4. Respiratory arrest
151
What is the goal of CPR?
To deliver O2 to vital organs until return of spontaneous circulation
152
List 4 signs of cardiac arrest in the anaesthetized patient
1. Decreased ETCO2
2. Cardiac arrythmias
3. Sudden drop of blood pressure
4. Loss of pulse-oximetry signal
153
Describe how to manage the airway in CPR
Check for obstruction and then place an ET tube
Stop anaesthetic delivery and give 100% O2
154
Describe how to manage breathing in CPR
Administer approx. 10 breaths/min, allowing adequate time for deflation (avoid hyperventilation)
Give 100% FiO2
NO doxapram
155
Describe how to manage circulation in CPR
Position the animal in right lateral or dorsal recumbancy
Start compressions ASAP
Obtain IV access
156
Describe the difference between cardiac and thoracic pump chest compressions
| In which case would you use which?
Cardiac pump: chest compressions over the heart, between the 3-6 intercostal space
Thoracic pump: chest compressions of the highest point of the thorax
| Cardiac: <15kg or narrow
Thoracic: >15kg or barrel chest
157
How do cardiac compressions promote blood flow in CPR?
By direct compression of the ventricles
158
How do thoracic compressions promote blood flow in CPR?
By increasing the intrathoracic pressure
159
To which depth should you compress the chest for CPR?
1/3 - 1/2 the width of the chest
160
How long should 1 full interuptted cycle of CPR be?
2 minutes
161
List 4 conditions in which you would consider doing internal cardiac compression
1. Pneumothorax
2. Cardiac tamponade
3. Penetrating chest wounds
4. Intraoperative arrests (you're already in there!)
162
Where should you enter the chest cavity to access the heart for internal cardiac compression?
The 5th intercostal space (during expiration)
163
Which anatomical point can you use to identify where to open the chest for internal cardiac compression?
The olecranon of the forelimb
164
List 4 reasons why ICC would be preferred over ECC
1. Thorax is already open
2. Large dog breeds
3. Disease processes that would make ECC ineffective
4. If ECC is generally ineffective
165
Which monitors should be used when doing CPR?
ECG and capnography
166
Which cardiac rhythms are shockable?
Ventricular tachycardia (big QRS complexes) and ventricular fibrilation (looks like waves)
167
Which cardiac rhythms are non-shockable?
Asystole (flat line) and pulsless electrical activity (non-ordered waves)
168
List 5 routes of drug administration for advanced life support?
1. Central IV
2. Peripheral IV
3. Introsseous
4. Intratracheal
5. Intracardiac
169
Explain the role of vasopressors in advanced life support
They increase vascular resistance in promote blood flow to vital organs
170
Provide 2 examples of vasopressors used for advanced life support
1. Adrenaline
2. Vasopressin
171
List 5 drugs you can give intratracheally
1. Epinephrine
2. Vasopressin
3. Atropine
4. Lidocaine
5. Naloxone
172
Explain the role of anticholinergices in advanced life support
They decrease parasympathetic tone to increase heart rate
173
In which 2 situations would you use atropine for ALS?
| Think about the cardiac rhythms
Asystole or pulseless electrical activity (the heart has stopped)
174
Provide 2 examples of antiarrhytmic drugs
1. Amiodarone
2. Lidocaine
175
What is the recommended primary treatment for ventricular fibrilation and tachycardia
Defibrillation
176
Provide 3 examples of reversal agents, and what they reverse
Naloxone - reverses opioids
Flumazenil - reverses benzodiazepines
Atipamezole - reverses alpha agonists
177
What is the survival rate following CPR in dogs and cats?
2-10%
178
At what point does potentially irreversible ischemic damage occur?
After 6 minutes
179
What are the 3 goals of post cardiac arrest care?
1. Hemodynamic optimization
2. Respiratory optimization
3. Neuroprotection
