Induction of anaesthesia Flashcards
1
Q
Name 3 induction methods that can be used?
A
- injectable agents (IM,IV, IP, SC)
- Induction chamber/ masks (birds)
- Immersion/ contact (Fish - passes over gills or absorbed by skin)
2
Q
Name 12 things that make the ideal anaesthetic?
A
- Water soluble
- Long shelf-life
- stable when exposed to light
- small volume reuired
- no local toxicity
- no effect on vital organ function
- Minimal individual variation
8, safe therapeutic ratio (ketamine 10x induction dose kills paient, propofol -2-3x will kill the patient) - onset
- short duration - patients should recover well
- non-toxic metabolites
- no histamine release
3
Q
Which is the most commonly used anaesthetic in the UK for cats and dogs?
A
Propofol ‘milk of amnesia’
4
Q
what is propofol and what is its drug content?
A
Alkyl phenol, white emulsion, 10mg/ml
5
Q
name 5 things in propofol?
A
- soyabean oil
- glycerol
- egg lecithin
- no preservative
- NaOH (changes pH)
6
Q
Name one promlem with propofol?
A
It supports bacteria and endotoxin
7
Q
How quickly to use the vial once opened?
A
Within 24 hours
8
Q
what was the problem with propoflo plus (zoetis) which lasted for 28 days?
A
More pain on injection
9
Q
How quickly does propofol work?
A
Very rapid onset of action (30-40 seconds head down)
10
Q
How long is the period of unconsciousness?
A
5-8 mins
11
Q
what is the pharmacokinetic features of the drug?
A
Highly lipophilic and high Vd. Will cross the BBB.
12
Q
What is the recovery like with propofol and why?
A
rapid, smooth emergence due to redistribution and efficient metabolism - metabolites inactive (Hepatic metabolism)
13
Q
What does propofol do to ventilation?
A
Respiratory depression IPPV
14
Q
What do you need to do if you suspect post induction apnoea?
A
Half the speed of injection
15
Q
What is the recovery like with propofol?
A
Rapid and smooth recovery
16
Q
is propofol suitable for top-ups and TIVA and when would you use this?
A
Yes, if you don’t want to put the animal on gas.
17
Q
What does propofol do for muscle relaxation?
A
Usually okay
18
Q
Is propofol an analgesic?
A
NO - no analgesic properties - does reduce ICP (intra-cranial pressure) - use if head trauma or ocular ulcer.
19
Q
Why hold the animal tightly when administering propofol?
A
Because it stings a lot.
20
Q
What dose of propofol would you administer?
A
1-7mg/kg - depends on pre-meds
21
Q
In what animals should you be very careful when using propofol?
A
In patients with shock or sepsis.
22
Q
What should you do in old dogs and cats using propofol?
A
Decrease the dose
23
Q
Name two diseases in which propofol is fine to administer?
A
renal compromise and hepatopathy
24
Q
What can propofol be combined with to dilute?
A
5% dextrose
25
In what animals is propofol licensed?
Dogs and cats
26
Name 8 problems associated with using propofol?
1. Rigidity, twitching
2. Apnoea
3. Profound bradycardia
4. Care in hypoproteinaemia
5. Heinz body anaemia in cats (clumped RBCs)
6. Use for patients with pancreatitis/ hyperlipoproteinaemia or diabetic hyperlipidaemia.
7. pain on injection
8. . Local reaction (clear formulation, discontinued)
27
Name a common thiobarbituate used?
Thiopentone sodium
28
What is thiopentone sodium?
A sodium salt powder
29
What is the property of thiopentone sodium
Highly lipophilic and highly alkaline solution (pH 14)
30
Is thiopentone sodium commonly used?
No, difficult to source and no longer licensed in cats, dogs or horses.
31
Name 4 effects of thiopentone sodium?
1. rapid loss of consciousness
2. respiratory depression
3. cardiovascular depession
4. peripheral vasodilation
32
What is the length of time the thiopentone works?
Ultra short-acting
33
What does thiopentone sodium do in the blood?
highly protein bound and displaced by flunixin and phenylbutazone
34
Why does pH affect the response?
Because the unionised fraction can penetrate the cell.
35
What else is important in terms of fraction unbound of thiopentone sodium?
The plasma protein concentration
36
What is the danger of administering to pregnant animals?
Thiopentone sodium crosses the placenta
37
Where is thiopentone sodium metabolised?
In the liver
38
In what species is there a long recovery from thiopentone and why?
Sighthounds - metabolism and body fat.
39
What is the dosage of thiopentone and when would you reduce?
10-25mg/kg - reduce more if pre-med was alpha 2 agonists.
40
How quickly should you administer thiopentone?
Give 1/2-1/3 dose over 30 seconds
41
What is its primary use today and why?
Used in horses to 'top up' - can use in horses that are kicking on the table.
works faster than ketamine top-ups.
42
Name a contraindication of using thiopentone and how is this prevented?
Fractious animals with minimal IV access - can cause enormous sloughing of the skin if injected around the vein --> always administer with a catheter and not a needle.
43
Name 6 illnesses in which it would NOT be appropriate to administer thiopentone?
1. Hypoproteinaemic patients
2. CHF, arrythmias (unless lidocaine given)
3. liver disease
4. Renal disease (increases potassium --> worsen arrythmias)
5. anaemia/ hypovolaemia
6. Hypothyroid/ hypoarenocorticoid patients (hypotension can be difficult to control)
44
What is NTK?
Oxybarbiturates (pentobarbitone)
45
What is NTK similar to in structure?
Thiopentones.
46
What is the solution of NTK?
6% (60mg/ml)
47
What is the onset like using NTK and why?
Slower onset of action than thiopentone due to less plasma protein binding and less lipid solublility.
48
is pentobarbitone commonly used?
No longer available!
49
Name 4 reasons why NTK is no longer used?
1. slow recovery
2. difficult to source
3. CVS and respiratory depression
4. Irritant
50
Name another form of anaesthetic?
Injectable steroid anaesthetics - saffan
51
Are injectable steroid anaesthetics used common?
No longer available in the UK in this form.
52
Name 2 examples of an injectable steroid anaesthetic?
Alphaxalone (6mg/ml) and alphadonolone (3mg/ml)
53
How do the two compare?
Alphaxolone is more potent and alphadonolone
54
By what are injectable steroid anaesthetics solubolised by?
Cremaphor EL
55
In what species were injectable steroid anaesthetics used?
Pigs and ruminants
56
What is a major contraindication of using injectable steroid anaesthetics?
They cause a massive histamine release
57
What do injectable steroid anaesthetics cause in some cats?
anaphylaxis.
58
Name two side effects of the massive histamine release associated with injecatble steroid?
Swollen larynx and swollen paws.
59
What is the formulation of alphalaxone without cremaphor?
A HPBCD (hydroxypropyl-beta-cyclodextrin) - donut shaped molecule (hydrophillic on the outside and lipophilic on the inside.
60
what is the trade name of alfaxalone?
alfaxan
61
In what species is alfaxalone used?
Dogs and cats.
62
How does alfaxalone cause anaesthesia?
By inhibiting the GABA receptor.
63
What does alfaxalone look like?
Clear, colourless solution - neuroactive.
64
How quickly is alfaxalone cleared from the body and why?
Very rapidly - short plasma elimination hald-life.
65
How can alfaxalone be used to maintain anaesthesia?
Repeated boluses or as TIVA
66
How quickly is the induction agent given if an injectable steroid anaesthetic?
Over 60 seconds.
67
Does alfaxalone or propofol lead to better recovery?
Propofol
68
What is occassionally seen with alfaxalone recovery and what is required?
Occasional apnoea and IPPV might be needed.
69
Name 3 good properties associated with alfaxalone?
1. cardiovascularly stable
2. NO HISTAMINE RELEASE
3. good muscle relaxant
70
Why should animals not be disturbed during recovery with alfaxalone?
Because excitement can occur.
71
Name two dissociative agents?
Ketamine and Tiletamine (Europe and USA)
72
What is the pH of the dissociative agents and what does this mean?
Weak organic acid (pH 3.5_ therefore stings on injection, especially IM.
73
Describe dissociative agent composition?
Racemic 10% solution (100mg/ml)
74
How can dissociative agents be administered?
IV, IM, SC, IP, PO, epidural space
75
Why do you normally have to combine ketamine with something else?
Causes rigidity therefore combine with something that causes muscle relaxation e.g. benzodiazepines.
76
What is the induction rate of ketamine?
Very rapid
77
What does ketamine cause when introduced?
Minimal respiratory effects, bronchodilation (good for asthma!)
78
What is a very beneficial property of ketamine?
GOOD ANALGESIA!
79
what do CVS effects of ketamine depend on?
Dose
80
name 4 things that are increased following ketamine administration?
1. jerky movements
2. muscle tone
3. salivation
4. lacrimation
81
What is the recovery process for ketamine?
Stormy if disturbed or not adequately pre-medicated
82
What effect does ketamine have on eyes?
Depth assessment is different because eyes open.
83
What is an issue associated with the eyes being open?
Corneal drying - use lacrilube.
84
What is common in patients when combined with alpha 2 agonists?
Vomiting - avoid in patients with GI obstruction.
85
Name 4 conditions in which you should avoid the use of ketamine?
1. Increased ICP
2. Occular surgery
3. Fever
4. Hyperthyroids
86
What type of drug is ketamine legally?
Schedule 2
87
What is zoletil 100?
250mg tiletamine and 250mg zolazepam
88
how much sterile water needs to be added to zoletil 100?
5ml sterile water.
89
what is zoletil 100 used for?
Dog and cat anaesthesia.
90
Give an example of an imidazole anaesthetic?
Etomidate (not licensed)
91
What are 3 things that remain stable when using etomidate?
1. HR
2. ABP (arterial blood pressure)
3. CO
92
Name 4 contraindications of etomidate?
1. Myoclonus
2. Phlebitis
3. Pain on injection
4. Addision crisis
93
Is etomidate (imidazole anaesthetic) commonly used ?
Not in the UK
94
What kind of induction agent would you use for horses?
IV induction agent.
95
Name three ways anaesthesia can be topped up in horses?
IV Top-ups
inhalation
TIVA
96
How can anaesthesia be induced in foals?
Inhalation - associated with increased death rates.
97
What is the most common induction agent used in horses?
Ketamine
98
How does ketamine have to be used and why?
In combination with something else - causes seizures if used alone.
99
What is the safety margin of ketamine?
Very wide.
100
What is ketamine commonly used in combination with in horses?
. ACP
Alpha 2 agonists (sedative)
BZDs (not licensed)
Guaifenesein
101
In what species is Guifenesein (GGE) licensed?
In horses.
102
What is the function of guifenesein?
It is a centrally acting muscle relaxant
103
What is it used as part of?
TIVA - called 'triple drip'
104
What is the best solution of guifenesein to use?
5% or 10%
105
What does guifenesein substitute?
The use of benzodiazepines (midazolam or diazepam)
106
can guifenesein be used in horses alone?
Good in foals alone, do not use in adults alone.
107
What does giufenesein cause if not injected correctly?
Causes sloughing of the skin - always use a catheter.
108
Name a common induction combination for horses?
Acepromazine, detomidine, ketamine and isoflourane
109
How is most anaesthesia done in ruminants?
With the animal standing
110
How is anaesthesia administered in ruminants?
IV - calves could use a mask
111
What might some cows drink?
Chloral hydrate
112
Why do ruminants require cuffed intubation?
regurgitation
113
Where are most anaesthetic agents administered in the pig? what are the other options?
deep IM in the neck
- could use IV or mask
114
Name three induction agents used in pigs?
1. ketamine
2. Propofol
3. Alfaxalone
115
What can occur in pigs after exposure to an anaesthetic inhalant and how is it treated?
Malignant hypothermia
Treated with dantrolene.
116
Why is intubation of pigs difficult?
Larynx angle and mouth does not open far
117
What is the main risk when inducing exotics?
Hypothermia or hyperthermia (increased SA to BW ratio)
118
What is the death rate for rabbits under anaesthetisa?
1/72
119
Name 4 problems of rabbit anaesthtsia?
1. hypothermia
2. prolonged recovery - GI disturbances
3. difficult intubation
4. respiratory obstruction leading to cyanosis.
120
What two things are advisable in rabbit anaesthesia?
Pre-medication and pre-oxygenate
121
Name two licensed induction agents in rabbits?
Fentanyl/ fluanisone
Alfaxalone
122
Name 4 induction examples in rabbits?
1. Fentanyl/ fluanisone recipie
2. Ketamine, medetomidine, Opioid
3. BZD and opioid, followed by alfaxalone or propofol 15 mins later
4. alfaxalone
123
Name 3 pieces of equipment which can help with rabbit intubation?
Laryngeal masks, V-gels, nasal intubation,
'Fleknell laryngoscope'
124
What is common in birds and what is a good idea?
High GA mortality, IPPV is a good idea.
125
What means that conditions change quickly in birds?
they have high metabolism
126
How long should birds be fasted for?
Not too long (especially budgies and small pet birds). Raptors and waterfoul - 4-6 hours to make sure crop is empty.
127
What is unique about birds and intubation - what kind of tube should be used?
They have complete tracheal rings.
Use Cole intubation tubes.
128
What happens if birds are put onto their backs - what is beneficial?
they become bradycardic - IPPV beneficial.
129
What two positions can birds not breath very well and why?
If you lie birds on their sternum or on their backs - they do not have a diaphragm.
130
How are most bird injections performed?
Using an inhalant e.g. isoflurane in oxygen.
131
Why is intubation reccomended in birds?
Apnoea common
132
What is another technique used to intubate birds?
Can use air sac cannulation - push ET tube inside air sac.
133
How many different species of reptiles?
6400 - need to know anatomy
134
What makes reptiles so difficult to anaesthetise and maintain?
Blood shunting
135
What happens to heart rate in reptiles under GA?
It does not really change.
136
What is needed to aid respiration in reptiles?
IPPV - respiration is abolised at surgical planes.
137
What type of reptiles are particularly difficult to induce with gas?
Chelonia
138
What response is used in large, fractious lizards to restrain for injection?
vagal-vagal response.
139
What is used for gas induction of reptiles?
Isoflurane or sevoflurane
140
what are the injectable agents used in reptiles?
Alfaxalone or propofol
141
What works alone as TIVA for chelonia?
Alfaxalone
142
Name two combinations which can be used to sedate large fractious patients?
Ketamine/ midazolam
| ketamine/ medetomidine
143
What can be used for analgesia in reptiles?
Butorphanol +/- NSAID
| buprenorphine in some too
144
Why is intubation difficult in chelonia?
Fleshy, large tongue.
145
What remains closed when reptiles are not breathing?
Glottis.
146
In what order to snakes induce and recover?
They induce from head to tail and recover from tail to head.
147
What is a reptiles response to gas concentrations?
They respond very slowly to gas concentrations
148
How do we test to see if a reptile is recovering from anaesthsia?
Toe and tail pinch and tongue retraction reflexes.
corneal and palpebral reflexes.
149
What is an invaluable monitoring system in reptiles?
Doppler flow monitor.
150
What is unique about ECG and the heart in reptiles?
Heart can still contract after death and you could get an ECG reading for about 3 days after death.
151
If administering an injectable anaesthetic to lizards, which vein would be used?
Central coccygeal vein e.g propogol 3-5mg/kg
152
Where is the tracheal opening in lizards?
The base of the tongue, on the floor of the oral cavity.
153
How often is IPPV administered in lizards?
1x2 times a minute
154
What can cause cardiac arrest in reptiles?
any sudden change in position
155
What needs monitoring throughout reptile GA?
Temperature
156
How long does recovery take for some reptiles?
24-48 hours
157
What also helps reptiles wake up?
Intraosseous or IV access and fluids (1-2ml/kg/hour)
158
Why do reptiles wake upquicker when ventilated with room air before recovery?
Because high pCo2 stimulates ventilation and is suppressed by high O2.
159
Where is blood best sampled from in chelonians?
Jugular vein - avoid lymph contamination
160
Name 5 induction routes for chelonia?
1. oral
2. IV
3. Intracoelomic
4. Epicoelomic
5. Intraosseous
161
Is anaesthesia well tolerated in chelonians?
yes
162
Where is the rima glottis in chelonians?
2/3 along the tongue mid line
163
What kind of circuit would you use for chelonians?
A T piece circuit - deliver iso/sevo and oxygen
- also use IPPV
164
What are the 2 most common types of captive snakes?
Colubridae
| boidae
165
When might sedation be needed in snakes?
Blood samples and detailed examination
166
How is blood usually collected from snakes?
Cardiocentesis or from the tail vein
167
How can fluids be administered to snakes?
SC or intracoelomic
168
How often should IPPV be administered to snakes?
1-4 X a minute
169
What is commonly used as an injectable agent in fish and amphibians?
MS-222 in water
| -tricaine methanesulphonate
170
Which species of fish might require injectable agent?
Lungfish
171
What is MS-222 buffered with?
Sodium bicarbonate
172
Why does tricaine mehanesulphonate need to be removed from the tank once anaethetised?
because it is cumulative
173
When can you remove amphibians and fish from water?
When surgery less than 5 mins and keep moistured.
174
What is required in fish and amphibians for longer procedures?
Oxygenated water over gills +/- anaesthetic solution (1ml every 30 secs to keep them anaesthetised)
175
What dilution of MS-222 is used for amphibians?
1:25 000 dilution in sterile water
176
Name 5 methods of anaesthesia in amphibians?
1. Phenoxyethanol
2. Benzocaine (in acetol)
3. Ketamine IM (50mg/ml)
4. Bubble iso or sevo through water)
5. iso in KY jelly
177
How can the plane of anaesthesia be changed in amphibians?
- water + anaesthetic to deepen
| - just water to lighten
