Anaesthesia Flashcards Preview

X Clinical Veterinary Nursing Theory > Anaesthesia > Flashcards

Flashcards in Anaesthesia Deck (990)
Loading flashcards...
1
Q

what is anaesthesia?

A

the reversible production of a state of unconsciousness required to perform surgery and diagnostic testing

2
Q

what does anaesthesia rely on?

A

provision of the elements of the anaesthesia triad

3
Q

what is general anaesthesia?

A

a state of unconsciousness produced by anaesthetic agents with absence of pain sensation over the entire body

4
Q

what is regional anaesthesia?

A

insensibility caused by an interruption of sensory nerve conduction in any region of the body

5
Q

what is local anaesthesia?

A

lack of sensation in a localised part of the body

6
Q

define sedation

A

the allaying of irritability or excitement

7
Q

define anxiolysis

A

reduced anxiety

8
Q

define analgesia

A

reduced sensibility to pain

9
Q

define narcosis

A

a sleep like state

10
Q

define hypnosis

A

an artificially induced state of passivity (often used interchangeably with narcosis)

11
Q

what is premedication?

A

a drug/combination of drugs given prior to the induction of general anaesthesia

12
Q

why give premeds?

A

calms patients
aids restraint
provides pre-emptive analgesia
allows a reduction i induction and maintenance drugs
contributes to smooth induction and recovery

13
Q

what is the sequence of events involved in general anaesthesia?

A
owner conversation/consent
pre-operative examination
checklist/ASA classification
premedication
induction
maintenance
recovery and post op. care
14
Q

what happens during the pre-operative phase?

A

owner conversation about general wellbeing and informed consent
admission to the practice

15
Q

what happens during the pre-operative examination phase?

A

full clinical exam
ASA classification
planning stage

16
Q

what happens during the preoperative getting ready phase?

A

set up machine/equipment
prepare medication/drugs/fluids
place IV catheter (?)
premedicate patient

17
Q

what happens during the induction phase of anaesthesia?

A

placement of IV catheter (if not placed before)
pre-oxygenation
administration of pre-med (if not already given)
administration of induction agent (propofol/Alfaxalone)
secure airway (ET Tube, V-Gel, LMA, Facemask)

18
Q

what happens during the maintenance phase of anaesthesia?

A

anaesthesia is maintained throughout by gas, TIVA or injectables
potential placement of local and regional blocks
continue to surgery/diagnostic procedure

19
Q

what is TIVA?

A

total intravenous anaesthesia

20
Q

what happens during the recovery phase of anaesthesia?

A

cessation of gaseous maintenance/CRI/antagonism of injectable drugs (whatever is maintaining anaesthesia)
removal of airway device when safe
move to well ventilated/quiet/calm recovery area

21
Q

what are the 3 elements of the anaesthetic triad?

A

analgesia
narcosis
muscle relaxation

22
Q

can all aspects of the anaesthetic triad be achieved with one drug?

A

no - multi-modal approach needed

23
Q

define balanced anaesthesia

A

anaesthesia produced by smaller doses of two or more agents considered safer than the usual large dose of a single agent

24
Q

what is a key benefit of balanced anaesthesia?

A

side effect of each drug are reduced

25
Q

what are the main reasons for anaesthesia?

A

facilitate surgical/diagnostic/other procedures
prevent pain/ suffering
research
immobility

26
Q

what did the CEPSAF Enquiry look into?

A

relative risk of poor outcome (death) of a patient undergoing anaesthetic. Shows % risk of death

27
Q

what is the overall CEPSAF risk for dogs?

A

0.17%

28
Q

what is the overall CEPSAF anaesthetic risk for cats?

A

0.24%

29
Q

what is the overall CEPSAF anaesthetic risk for rabbits?

A

1.39%

30
Q

what did the CEPSAF Enquiry look into?

A

complications within a 48hr post operative period

31
Q

when did the CEPSAF enquiry find 50% of anaesthetic deaths occurred?

A

within 3 hours of recovery

32
Q

what made anaesthetic risk higher?

A

sick animals
cats
ET tube intubation in cats but not dogs

33
Q

is anaesthetic risk higher in sedation or GA?

A

GA

34
Q

what was horses overall calculated anaesthetic risk according to CEPEF?

A

2.1% (rising to 11.7% for colic cases)

35
Q

what are some species specific issues with anaesthesia?

A
extremes of size
hyper/hypothermia
aggression
drug sensitivities
obesity
36
Q

how do extremes of size pose problems during anaesthetic?

A

very large to very small requiring wide range of equipment

37
Q

how does aggression pose problems during anaesthetic?

A

risk of injury - can’t perform pre op exam and may need extra equipment
stress to animal from handling
may rely on drugs that are not ideal for the animal
may need to extubate early and remove IV lines before animal is fully awake

38
Q

how may drug sensitivities in some breeds pose problems during anaesthetic?

A

some large dogs may require lower mg/kg than their smaller friends

39
Q

how does obesity pose problems during anaesthetic?

A

IM injection is difficult (for premed)
can easily overdose as liver does not match weight
ventilatory compromise due to weight of excess fat on body when positioned for surgery
increased CV workload

40
Q

what are some breed specific issues with anaesthesia relating to brachycephallic dogs?

A

compromised airways (small trachea, extra pharyngeal tissue)
gastro-oesophageal reflux
occular issues (extra lubricant and care required)
skin problems
skeletal issues

41
Q

how may gastro-oesophageal reflux be prevented in brachycephallic dogs?

A

give omeprazole 7 days prior to surgery to reduce stomach acid
use cuffed ET tubes
raise head until cuff inflated

42
Q

what are some breed specific issues with anaesthesia relating to boxers?

A

intolerant to acepromazine which can cause bradycardia and hypotension
cardiomyopathy which can be seen in otherwise healthy animals and cause ventricular tachycardia, arrhythmia and syncope

43
Q

how can breed specific issues with boxers be avoided?

A

don’t give ACP

ECG before procedure to check for cardiomyopathy

44
Q

in what breeds is multi drug resistance seen?

A

collies
sheepdogs
shepherds

45
Q

what does the MDR1 gene do?

A

removes drugs from the brain

46
Q

what happens in animals with MDR1 gene mutation?

A

defect in the P-glycoprotein that transports drugs meaning that toxins cannot be transported away from the brain and so build up which can cause neurological symptoms

47
Q

what are the 3 key drugs that are not managed by animals with the MDR1 gene mutation?

A

ivermectin
butorphanol
acepromazine

48
Q

what are some breed specific issues with anaesthesia relating to greyhounds?

A

lack cytochrome P450 which is an important clearance mechanism and so affects metabolism of drugs
body fat is very low (17%) so will recover slowly, require padding and careful temperature monitoring

49
Q

what are some breed specific issues with anaesthesia relating to dobermen?

A
Von-Willibrand deficiency which affects clotting time
dilated cardiomyopathy (found in 50% of 6 year olds) which causes heart to function less well
50
Q

how should Dobermen be tested for Von Wiliibrand factor deficiency and DCM?

A

BMBT

ECG

51
Q

what is the key legislation associated with anaesthesia?

A

protection of animals (anaesthetics) act
misuse of drugs act and misuse of drugs regulations
veterinary surgeons act - schedule 3

52
Q

where can guidance for anaesthesia be found?

A

AAHA anaesthesia guidelines for dogs and cats
AAFP feline anaesthesia guidelines
Association of Veterinary Anaesthetists
American College of Veterinary Anaesthesia and Analgesia

53
Q

when must the pre-operative assessment take place?

A

before the administration of medication/premedication

54
Q

what observations/questions should be involved in the pre-operative assessment?

A

full history
owner questioning on health/routine/behaviour etc
previous reactions to drugs/anaesthetics
procedure
breed/species
confirmation of pre-operative fasting times

55
Q

what influence does the procedure have on the pre-operative assessment?

A

influences questions asked and elements of the exam

56
Q

what parameters should be included in the pre-operative clinical exam?

A
full clinical exam
MM
CRT
thoracic auscultation
pulse rate and quality
ventilatory effort
temperature
swellings/distention
57
Q

what is assessed during thoracic auscultation in the pre-operative exam?

A

presence of heart murmur, ventilatory effort and RR

58
Q

what pulses should be felt to assess pulse quality and perfusion?

A

peripheral

59
Q

where should the clinical exam of the pre-operative assessment be started from?

A

a distance - note the animals temprament

60
Q

what should be checked for significant findings during the pre-operative assessment?

A

history

61
Q

why is a systematic approach to the clinical exam of a pre-operative assessment important?

A

nothing is missed

repetition will increase speed

62
Q

what are the levels of ASA classification?

A

ASA 1-5 and E

63
Q

what does E denote in the ASA classification?

A

emergancy

64
Q

describe ASA I classification

A

normal healthy animal

65
Q

describe ASA II classification

A

mild systemic disease

66
Q

describe ASA III classification

A

Systemic disease, well compensated or controlled by treatment

67
Q

describe ASA IV classification

A

severe uncompensated systemic disease

68
Q

describe ASA V classification

A

unlikely to survive 24 hours

69
Q

why is using ASA classification important?

A

identifies risk
increase safety of patient
quick

70
Q

according to ASA which catergories are at low risk?

A

I and II

71
Q

according to ASA which categories are at risk?

A

III-IV

72
Q

what is the goal of pre-operative fasting?

A

reduce volume of stomach contents

prevention of GOR, regurgitation and aspiration

73
Q

why is reducing the volume of stomach contents through preop fasting crucial?

A

aids ventilation

74
Q

what is the suggested length of pre-op fasting time for cats?

A

6-8 hours

75
Q

what is the suggested length of pre-op fasting time for dogs?

A

8-10 hrs

76
Q

what is the suggested length of pre-op fasting time for rabbits and small furries?

A

no starvation needed but may be worth withholding for 30mins pre-op to remeove food from mouth

77
Q

what is an effect of prolonged pre-op starvation?

A

increase in GOR

in cats it does not necessarily mean an empty stomach

78
Q

why does prolonged starvation not necessarily mean an empty stomach in cats?

A

stress, meal size and a lack of dietary moisture (dry food) can slow gastric emptying

79
Q

what has been shown to reduce incidence of GOR?

A

feeding small canned food 3 hours pre-op

80
Q

what must be gained at all times for all procedures?

A

informed consent

81
Q

what is involved in informed consent?

A

consent form alongside a discussion with client

82
Q

what should be provided to the client once the consent form is signed?

A

a copy

83
Q

is a consent form a legal document?

A

yes

84
Q

why must a consent form be filled in in a private area?

A

GDPR

allows room for client to ask questions

85
Q

how can communication with owners be most effective?

A

give realistic time frames and stick to them
utilise text/email after initial phone call
keep communication open
listen
give privacy and space

86
Q

who launched anaesthetic safety checklists?

A

WHO in 2008

87
Q

what is the benefit of surgical checklists?

A

reduction in rate of deaths and surgical complications by as much as 1/3

88
Q

what are the 3 categories on the ASA anaesthetic safety checklist?

A

pre-induction
pre-procedure
recovery

89
Q

what are the 3 categories on the recommended procedures section of the ASA checklist?

A

pre-anaesthesia
anaesthetic machine
drugs/equipment

90
Q

what must be considered when using drug/anaesthetic protocols?

A

each patient must be treated as an individual and previously devised protocols must be made to meet patient needs and risk factors

91
Q

what diagnostic tests may be used in a pre-op assessment?

A
bloods
urine
radiography
ECG
echocardiology
ultrasound
92
Q

what is a crucial element of anaesthesia?

A

patient preparation

93
Q

where do the majority of complaints that surround anaesthesia and veterinary medicine arise from?

A

poor communication

94
Q

what are the 2 main options for induction of anaesthesia?

A

injectable

inhalent

95
Q

what are the benefits of IV injected anaesthesia induction?

A

quick (2-10 mins onset)
reliable
expected efficacy
less stress for animal

96
Q

what are the disadvantages of IV injection of anaesthetic induction?

A

relies on presence of IV catheter which may be tricky

97
Q

what are the benefits of IM injected anaesthesia induction?

A
fairly quick (10-20 mins)
reliable if actually IM
98
Q

what are the issues with IM injected anaesthesia induction?

A

in obese animals can be injected into fat (less effective)
painful
slower onset

99
Q

what are the benefits of SC injected anaesthesia induction?

A

easy

less painful than IM

100
Q

what are the disadvantages of SC injected anaesthesia induction?

A

causes pain
longer onset (30-45 mins)
lower efficacy

101
Q

what must be checked before administering a drugs by different routes?

A

what it is licensed for

102
Q

what are the benefits of chamber anaesthesia induction?

A

great for small animals (hamsters/mice)
easy to set up and use
cheap
no technical skill needed

103
Q

what are the disadvantages of chamber anaesthesia induction?

A
very stressful for the animal
difficult to observe/monitor animal
risk of staff exposure
unpleasant
only when injection isn't possible
104
Q

what are the benefits of face mask anaesthesia induction?

A

cheap
easy to set up and use
can give oxygen and/or volatile agent quickly

105
Q

what are the disadvantages of face mask anaesthesia induction?

A

does not protect airway
increases dead space
human exposure to VA/waste gases
not always tolerated - animal should be premedicated wherever possible

106
Q

what are the risks associated with physical restraint during anaesthesia induction?

A
stress
becoming worse/escalation (cats particularly)
respiratory compromise
cardiac arrhythmias
raised ICP/IOP
pressure on jugular
coughing
107
Q

why is positioning of an animal so important?

A

facilitates placement of tubes/catheters/blocks
ensures animal safety (better anaesthesia/procedure)
ensures personnel safety
prevents injury to all

108
Q

what are the 4 main airway management devices?

A
mask
laryngeal mask (LMA)
supraglottic device (V-Gel)
Endotracheal tube
109
Q

what is the advantage of a laryngeal mask?

A

easy to use (sits over larynx)
reduced complications compared to ET tubes
reduced airway pollutants compared to face masks

110
Q

what is the disadvantage of LMA?

A

not really designed for veterinary patients

111
Q

how do supraglottic airway devices (V-Gels) work?

A

species and weight specific design

sits in the pharynx and mimics the anatomy

112
Q

what is the gold standard method for airway protection during anaesthesia?

A

ET tubes

113
Q

what are the main advantages of ET tubes for airway management?

A

allows airway protection
prevents atmospheric exposure
allows accurate provision of anaesthetic gases

114
Q

what is the purpose of murphy’s eye - seen on the distal end of ET tubes?

A

another site for movement of air if the main lumen becomes blocked

115
Q

what is the role of a pilot balloon of an ET tube?

A

allows inflation of the cuff

116
Q

what is the role of the adapter on an ET tube?

A

connects to the breathing system

117
Q

what does the size in mm on the side of ET tubes show?

A

internal diameter

118
Q

what are the 4 main types of ET tube?

A

silicone
PVC
red rubber
armoured

119
Q

what is the role of an armoured ET tube?

A

has internal wire which prevents the tube becoming kinked when a patient has to de positioned awkwardly

120
Q

when must armoured ET tubes never be used?

A

if patient is to be MRI’d

121
Q

what is the point of a cuff on an ET tube?

A

allows tight seal in trachea
if inflated correctly is safe
prevents gas leaking around tube
prevents anything going into patients lung (aspiration)
allows accurate delivery of VA and oxygen
allows direct route to lungs (suction)

122
Q

what are the safest type of ET tube cuffs?

A

high volume, low pressure

cuff pressure is spread over a wide area increasing the safety for the patient and reducing risk of damage

123
Q

why are clear tubes safer?

A

can see debris/dirt

condensation can be viewed to check if tube is in correctly

124
Q

should ET tubes be cleaned?

A

no! single use design

125
Q

how should the correct length of ET tube be measured?

A

incisors to shoulder tip

126
Q

what are the issues associated with an ET tube that is too long?

A

risk of single lung ventilation

increase in dead space

127
Q

what equipment is required for endotracheal intubation?

A
laryngoscope
tubes in a range of sizes
local anaesthetic (cats - intubeaze)
tie
cuff syringe
swab
suction?
mask for preoxygenation
stylet/bougie
128
Q

what size blade on a laryngoscope should be used?

A

one that will reach the epiglottis

129
Q

what must be avoided when intubating/holding an animal for intubation?

A

no fingers in the mouth

130
Q

how are ET tubes secured once they are placed?

A

attached to breathing system

tie is tied around tube and then around the back of the animals head/over the nose

131
Q

describe the correct process for inflation of ET tube cuff

A

** check textbook**

132
Q

what is the gold standard for confirmation of the correct placement of ET tubes?

A

capnograph trace

133
Q

how else can correct placement of ET tube be checked?

A

visualisation of tube between the vocal folds
condensation inside tube
appreciation of air movement

134
Q

why should you not press on the thorax to check for ET tube placement?

A
false positive (air from stomach)
reflux
reduction in functional residual capacity of lungs
135
Q

what is the best position for intubation of rabbits?

A

as upright as possible

136
Q

why is ET tube placement in rabbits so hard?

A

visualisation without endoscopy is very difficult

have to go in blind

137
Q

what are the 6 main common complications during anaesthetic induction?

A
injury (staff or patient)
lack of airway patency
aspiration/regurgitation
hypothermia
effect of anaesthetic agents on CVS and respiratory system
post-induction apnoea
138
Q

what can be done to prevent aspiration/regurgitation on induction?

A

identify at risk patients

head up induction for those at risk

139
Q

what is a common cause of hypothermia on induction?

A

IM premed (blanket over animal in kennel)

140
Q

what can cause post induction apnoea?

A

drug given quickly

expected side effect

141
Q

what must be balanced if post-induction apnoea is seen?

A

hypercapnia which will encourage patient to breathe and hypoxia which is dangerous

142
Q

what must be done as soon as possible after patient is induced?

A
monitor
monitoring equipment attached
assume it is all down to you and check everything
check peripheral pulses
confirm ventilation
143
Q

when are injectable anaesthetic agents used?

A

induction of anaesthesia before administration of an inhalational agent
adjunct to inhalational anaesthesia
short term anaesthesia
TIVA

144
Q

what are the 4 most common injectable anaesthetic agents?

A

propofol
alfaxalone
ketamine
tiletamine/zolazepam

145
Q

what injectable anaesthetic agents are licensed for use in dogs and cats?

A

propofol
alfaxalone
ketamine
tiletamine/zolazepam

146
Q

what injectable anaesthetic agents are licensed for use in horses?

A

ketemine

147
Q

what injectable anaesthetic agents are licensed for use in rabbits?

A

alfaxalone

148
Q

what drugs are used for euthanasia?

A

pentobarbital
secobarbital sodium
cinocaine hydrochloride (Somulose)

149
Q

what factors affect the effect of drugs?

A
blood flow to the brain
amount of non-ionized drug
lipid solubility
molecular size
concentration gradient
protein binding
distribution
metabolism
excretion
150
Q

describe the characteristics of the ideal injectable anaesthetic agent

A
rapid onset
non irritant
minimal cardiopulmonary effects
rapidly metabolised and eliminated
non-cumulative
good analgesia
good muscle relaxation
151
Q

where does propofol have it’s effect?

A

GABA agonist - enhances inhibitory neurons in the CNS

152
Q

does the plasma bound portion of a drug exhibit any effect?

A

no

153
Q

how fast is the onset of action of propofol?

A

rapid

154
Q

what level of plasma protein binding is seen with propofol?

A

high - 96-98%

155
Q

is propofol lipid soluble?

A

yes

156
Q

why will propofol have more effect in hypoalbuminaemic animals?

A

less protein to bind to, more then free to cross blood brain barrier and have effect

157
Q

how is propofol metabolized?

A

in the liver

158
Q

how quickly is propofol metabolized?

A

rapidly

159
Q

is propofol non cumulative?

A

in dogs but not in cats

160
Q

what is common post induction with propofol?

A

post-induction apnoea

161
Q

what are the effects of propofol on the CVS?

A

hypotension due to myocardial depression and peripheral vasodilation

162
Q

does propofol provide analgesia?

A

no

163
Q

what level of muscle relaxation does propofol provide?

A

adequate for surgery - some twitching may be seen

164
Q

what can continued propofol use in cats cause?

A

Heinz body anaemia with consecutive day use

165
Q

is propofol irritant if given perivascularly by accident?

A

no

166
Q

is there pain associated with propofol on injection?

A

yes

167
Q

what form is propofol presented in?

A

egg protein or lipid emulsion

168
Q

what differences in propofol formulations are there?

A

some contain preservatives which mean that they do not need to be discarded after they have been broached and used once

169
Q

what may be added to propofol as a preservative?

A

benzyl alcohol

170
Q

how long can propofol containing benzyl alcohol as a preservative be stored fr after opening?

A

28 days

171
Q

when should preservative containing propofol not be used ?

A

prolonged infusions (e.g. TIVA)

172
Q

what type of anaesthetic is alfaxalone?

A

steroid anaesthetic

173
Q

why is alfaxalone combined with cyclodextrin?

A

alfaxalone itself is insoluble - the addition of this sugar allows it to become soluable

174
Q

what is the theraputic index of alfaxalone?

A

high

175
Q

is alfaxalone irritant?

A

no - although possible some irritation IM

176
Q

what level of plasma protein binding is alfaxalone associated with?

A

20%

177
Q

how quick is the onset of effects of alfaxalone?

A

rapid

178
Q

is alfaxalone rapidly metabolised and eliminated?

A

yes

179
Q

is alfaxalone suited for TIVA?

A

yes as it is non cumulative

180
Q

why is alfaxalone suited to TIVA?

A

it is non cumulative

181
Q

what respiratory effects are seen after anaesthetic induction with alfaxalone?

A

some respiratory depression - post induction apnoea

182
Q

what are the effects of alfaxalone on the CVS?

A

preserves baroreceptor tone so that heart rate will increase with reduced BP. Leads to transient tachycardia

183
Q

why does alfaxone cause transient tachycardia?

A

HR increases as BP goes down as baroreceptor tone is preserved

184
Q

how old should patients be before alfaxone is used due to marketing authorisation?

A

> 12 weeks

185
Q

what type of anaesthetic is ketamine?

A

dissociative anaesthetic - NMDA agonist

186
Q

is ketamine a good muscle relaxant?

A

no - should not be used as sole agent but alongside BDZ or alpha-2 agonist

187
Q

are reflexes maintained when ketamine is given?

A

yes - central eye, palprebal reflex, swallow may be present

188
Q

how does ketamine maintain CV and respiratory function?

A

sympathetic stimulation which causes release of adrenaline that counters the ionotropic effect of ketamine on the heart meaning there is no suppression

189
Q

what is ketamine’s analgesic effect?

A

analgesia and antihyperalgesia

190
Q

how fast is the onset of effect of ketamine?

A

slow

191
Q

is ketamine cumulative?

A

no and neither is metabolite nor-ketamine

192
Q

what may prolong duration of ketamine action?

A

renal dysfunction causing slower removal of nor-ketamine from system. This has a similar effect to ketamine

193
Q

what percentage plasma bound is ketamine?

A

50%

194
Q

how is ketamine often used in horses?

A

IV induction and as part of TIVA techniques for maintenance of anaesthesia

195
Q

when is ketamine often used in cats?

A

IM as sedation or for induction of anaesthesia as part of a triple/quad

196
Q

what is an effect of ketamine that means it must be used cautiously in certain paitents with underlying conditions?

A

increases IOP and ICP

197
Q

how may tiletamine/zolazepam (Zoletil) be administered?

A

IM or IV

198
Q

what is linked to poor recovery from administration of tiletamine/zolazepam (Zoletil)?

A

repeated dosing

199
Q

what s the difference in pharmacokinetics of tiletamine/zolazepam (Zoletil) between cats and dogs?

A

dogs metabolize zolazepam much faster that tiletamine leaving it unbalanced

200
Q

what type of drug is thiopental?

A

barbiturate

201
Q

what type of receptors does thiopental work at?

A

GABA receptor agonist

202
Q

what form does thiopental come in?

A

pwder made up to 2.5 or 5%

203
Q

why may thiopental cause perivascular tissue necrosis?

A

due to its strongly alkaline nature

204
Q

what can be caused by perivascular injection of thiopental?

A

perivascular tissue necrosis

205
Q

how quick is the onset of effect of thiopental?

A

rapid

206
Q

how plasma protein bound it thiopental?

A

high - 80%

207
Q

what happens to thiopental before metabolism?

A

redistribution to tissues and then metabolism

208
Q

in what animals is thiopental associated with prolonged recovery?

A

sight hounds

209
Q

why does thiopental cause prolongued recovery in sighthounds compared to other dog breeds?

A

different metabolic pathways present

210
Q

what effects does thiopental have on CVS?

A

moderate, short lived cardiorespiratory depression and ventricular bigeminy (alternating sinus and PVC)

211
Q

what is ventricular bigeminy?

A

sinus rhythm followed by PVC (premature ventricular contraction)

212
Q

in what animals is the effect of thiopental particularly predictable?

A

horses

213
Q

what 6 factors will affect recovery from injectable anaesthetics?

A
drug factors including dose
species, breed and age
co-morbidities
hypothermia
individual co-morbidities
additional factors - concurrent drug administration
214
Q

what co-morbidities must be considered that will affect recovery from injectable anaesthetics?

A

hepatic function
renal function
cardiovascular function

215
Q

how does cardiovascular function affect recovery from anaesthetics?

A

affect elimination of anaesthetic via distribution and movement to kidneys

216
Q

how will hypothermia affect recovery from injectable anaesthetics?

A

metabolism is slowed and renal plasma flow reduced

217
Q

when may TIVA be used?

A

to reduce exposure to inhalant anaesthetic agents
no access to anaesthetic machines - e.g. horses at a yard
specific conditions for whom TIVA is safer

218
Q

what are the ideal properties of drugs used for TIVA?

A

rapid metabolism and elimination
fast onset
high therapeutic index
pharmacokinetic info available via data sheet

219
Q

what are the most common injectable anaesthetics used in practice?

A

propofol
alfaxalone
ketamine

220
Q

what is the main use of injectable anaesthetics?

A

IV induction (although also used through IM and TIVA)

221
Q

what is the key role of an anaesthetic machine?

A

delivery of oxygen (or other gas) and a volatile agent to the patient

222
Q

what are the 2 ways oxygen may be provided to the anaesthetic machine?

A

small cylinder attached to the trolley the machine is situated on
pipeline feeding from a larger bank outside the theatre

223
Q

what are cylinders made of?

A

molybdenum steel

224
Q

what are the key considerations for the storage of gas cylinders?

A

under cover
dry and clean
ideally indoors - well ventilated, fireproof room
not subjected to extreme heat or cold
away from flammable/combustible materials

225
Q

what cylinders should be stored separately?

A

full and empty

226
Q

what orientation should F, G and J cylinders be stored?

A

vertically

227
Q

what orientation should C, D and E cylinders be stored in?

A

horizontally

228
Q

what signs should be posted around cylinder storage area?

A

no smoking

229
Q

how should cylinders be carried?

A

use trolley or hold correctly

230
Q

what is the role of the cylinder yolk?

A

holds the cylinder in place
provides a gas-tight seal
allows unidirectional flow

231
Q

what is a key safety feature of the cylinder yolk?

A

will only fit a specific gas canister within it which prevents attachment of the wrong type of gas cylinder to the inlet

232
Q

what speed should cylinder yolks be opened?

A

slowly

233
Q

what is the BODOK SEAL?

A

non-combustable neoprene washer with a copper ring

234
Q

what is the role of the BODOK SEAL?

A

prevents gas leak

235
Q

what should be avoided when handling cylinder yolk?

A

over tightening

oils and moisturiser on hands

236
Q

why should oils and moisturiser on hands be avoided when handling the cylinder yolk?

A

fire risk due to high pressures and flammable gases

237
Q

what is the pin index safety system?

A

yoke on the anaesthetic machine has 2 protruding pins which align with 2 holes on the corresponding gas cylinder

238
Q

what is the purpose of the pin index safety system?

A

prevents the incorrect cylinder being fitted to the incorrect inlet

239
Q

how many holes are on the pin index safety system?

A

7

240
Q

what pins are found on an oxygen cylinder?

A

2 and 5

241
Q

what pins are found on a nitrous oxide cylinder?

A

3 and 5

242
Q

what pins are found on a medical air cylinder?

A

1 and 5

243
Q

what pins are found on a carbon dioxide cylinder?

A

1 and 6

244
Q

what pins are found on a entonox cylinder?

A

7

245
Q

where is piped gas supplied from?

A

a main source outside of theatre

246
Q

where does piped gas feed into?

A

colour coded and labelled pipelines

247
Q

what connects the anaesthetic machine to Schrader sockets?

A

flexible pipelines

248
Q

what are Schrader sockets?

A

attachment point for gas pipeline in the wall which will only accept a unique diameter index collar

249
Q

what are the key parts of a gas pipeline from socket to anaesthetic machine?

A

Schrader probe - flexible colour coded pipe - non interchangeable screw thread

250
Q

what is the role of a Schrader probe?

A

prevents misconnection of the wrong gas

251
Q

what is a Schradar probe?

A

unique diameter index collar which matches corresponding Schradar socket

252
Q

what is a non-interchangeable screw thread (NIST)?

A

nut and probe with unique profile for each gas with a one way valve to guarantee unidirectional flow

253
Q

what is the role of NIST?

A

prevents incorrect attachment of wrong gas

254
Q

how many banks of cylinders are linked to a pipeline?

A

two banks

255
Q

why are there always 2 banks of cylinders attached to a pipeline?

A

one in use and one reserve

256
Q

what happens if oxygen in cylinder banks becomes too low?

A

alarm will sound

257
Q

what material is gas pipework made of?

A

copper

258
Q

why is gas pipework made of copper?

A

handles high pressure well

259
Q

where may Schradar sockets (pipeline outlets) be located?

A

in the wall or ceiling mounted

260
Q

what must be done to ensure pipe is secure?

A

tug test

261
Q

what colour are oxygen cylinders?

A

white

262
Q

what colour are medical air cylinders?

A

black with white collar

263
Q

what colour are nitrous oxide cylinders?

A

blue

264
Q

what is the pressure within an oxygen cylinder?

A

13700 Kpa

265
Q

what is the pressure within a nitrous oxide cylinder?

A

4400 Kpa

266
Q

why is the Kpa within nitrous oxide cylinders so much lower than within oxygen cylinders?

A

nitrous oxide is a liquid with vapour on top

267
Q

what is the volume of an oxygen E cylinder?

A

680l

268
Q

what is the volume of an F size oxygen cylinder?

A

1360l

269
Q

what is the volume of an J size oxygen cylinder?

A

6800l

270
Q

what would an E size cylinder be used for?

A

side of machine oxygen supply

271
Q

what would a size J cylinder be used for?

A

piped oxygen supply

272
Q

what is the role of the pressure regulator?

A

regulates gas from the cylinder to anaesthetic machine

273
Q

why is a pressure regulator essential?

A

cylinder pressure is high (>10 000 Kpa) and needs to be reduced to a safe level that will not damage the anaesthetic machine and patient

274
Q

what is a safe pressure level for gas to enter the anaesthetic machine?

A

around 400 kPa

275
Q

what are the 4 key jobs of the pressure regulator?

A

reduces the cylinder pressure to a suitable supply pressure
compensates as the cylinder content decreases
smooths any fluctuations from gas supply
ensures safe delivery of gas at a manageable pressure

276
Q

what is indicated by pressure gauges?

A

pressure of gas within cylinder and pipeline in kPa

277
Q

how can you tell which gauge is for which cylinder?

A

colour coded

278
Q

what is pressure in the cylinder proportional to?

A

volume of gas contained within it

279
Q

what happens to the pressure gauge as the cylinder empties?

A

pressure gauge drops

280
Q

what can the pressure gauge be used to determine?

A

when the cylinder needs to be changed

281
Q

why must you be cautious when reading a nitrous oxide pressure gauge?

A

as nitrous is a liquid which then vaporises as it is used the pressure will remain relatively constant until the liquid is depleted when it will fall quickly

282
Q

when will the oxygen failure alarm sound?

A

when oxygen supply falls below 200 kPa

283
Q

what else should happen alongside the o2 failure alarm sounding?

A

delivery of nitrous oxide should be cut out

284
Q

what may make it possible to deliver 100% N2O to the patient if oxygen fails?

A

if there is pressure in the oxygen line

285
Q

what other mechanism should prevent delivery of 100% N2O?

A

hypoxic guard system

286
Q

what may some machines use to inform you of low oxygen?

A

warning message on the scree

287
Q

do all machines have nitrous oxide cut off?

A

no

288
Q

how does nitrous oxide cut off prevent a hypoxic mixture being delivered to the patient?

A

flow of nitrous oxide is dependent on oxygen pressure

if oxygen pressure falls below 130-70 kPa the nitrous oxide supply will be cut off

289
Q

at what oxygen pressure will the nitrous oxide cut off occur?

A

130-70 kpa

290
Q

is hypoxic guard found on all machines?

A

no

291
Q

how does hypoxic guard work?

A

oxygen and nitrous control valves are mechanically linked

both valves can be adjusted independently but the link maintains the minimum ratio of oxygen:nitrous

292
Q

can nitrous oxide be turned on independently of oxygen on an anaesthetic machine with hypoxic guard?

A

no

293
Q

what ratio of oxygen to nitrous oxide is the lowest allowed by hypoxic guard?

A

20-25%

294
Q

on a machine with hypoxic guard what happens when nitrous oxide is turned on?

A

oxygen flowmeter is activated

295
Q

on a machine with hypoxic guard what happens when oxygen is turned off?

A

so is nitrous oxide

296
Q

where is the check valve/non-return pressure relief safety valve located?

A

downstream of vapouriser

297
Q

what is the role of the check valve/non-return pressure relief safety valve?

A

one way valve preventing backflow of gas into the machine and creation of back pressure

298
Q

when does the check valve/non-return pressure relief safety valve open?

A

when the back bar pressure (location of vapouriser) is >35 kPa

299
Q

what is the purpose of the check valve/non-return pressure relief safety valve?

A

protects the machine not the patient

300
Q

does each gas have it’s own flowmeter?

A

yes

301
Q

what is the key role of a flowmeter?

A

administration of chosen level of fresh gas

302
Q

what do flowmeters measure?

A

flow of gas passing through them

303
Q

why must you be cautious when using low flow gas through a flowmeter?

A

accuracy of +/- 2.5%

304
Q

what happens when flowmeters are turned on?

A

small amount of oxygen is released (residual flow)

305
Q

what is the minimum flow of gas through a flowmeter?

A

200-300 ml/min

306
Q

what are the 3 parts of the flowmeter?

A

flow control valve
tapered transparent tube
lightweight rotating bobbin or ball

307
Q

what is the role of the flow control valve on a flowmeter?

A

allows fine adjustment of gas flow and reduces gas pressure from 420kPa to 100 kPa

308
Q

what is the role of the tapered transparent rube of a flowmeter?

A

visual scale

309
Q

what happens within the tapered transparent tube of the flowmeter when the valve is opened?

A

gas enters

310
Q

what is the role of the lightweight rotating bobbin or ball of a flowmeter?

A

floats within the tube as gas passes around it

311
Q

what does higher floating of the flowmeter bobbin or ball mean?

A

higher flow

312
Q

where should flow be read from on a flowmeter with a bobbin?

A

the top of the bobbin

313
Q

where should flow be read from on a flowmeter with a ball?

A

centre of the ball

314
Q

what is the role of the white dot on the bobbin of a flowmeter?

A

confirms flow by rotating

315
Q

where are vaporisers located?

A

back bar of the anaesthetic machine

316
Q

where are vaporisers located in relation to the flowmeter?

A

downstream

317
Q

what is contained within a vaporiser?

A

volatile liquid anaesthetic agent (e.g. isoflurane

318
Q

what is passed through the vaporiser?

A

gas from the flowmeter

319
Q

what happens to gas from the flowmeter as it passes through the vaporiser?

A

picks up vapor to deliver to the patient

320
Q

what happens to gas when it enters a calibrated vaporiser?

A

splits into 2 streams - bypass channel and chamber above liquid anaesthetic

321
Q

how is the ratio of gas that enters the bypass channel and vapour chamber adjusted?

A

control valve (numbers on top!)

322
Q

what can be done by adjusting the ratio of gas that enters the bypass channel and vapour chamber?

A

concentration of vapor picked up by gas cna be increased or decreased

323
Q

what is the control valve of the vaporiser controlled by?

A

large dial on the front of the vaporiser

324
Q

why is the vaporiser housed in a block of brass?

A

to minimise the effect of temperature cooling

325
Q

what happens as the temperature of the vaporising chamber drops?

A

the bi-metallic strip bends and moves, reducing resistance to flow allowing greater ratio of gas to pass into the chamber (overdose)

326
Q

are calibrated vaporisers agent specific?

A

yes

327
Q

when does cooling occur in calibrated vaporisers?

A

during vaporisation

328
Q

what is a vaporiser sometimes known as?

A

temperature compensation mechanism

329
Q

what is the role of wicks in a calibrated vaporiser?

A

increase surface area for evaporation of anaesthetic liquid

330
Q

what is the role of baffles in calibrated vaporisers?

A

direct incoming gas down closer to the surface of the liquid

331
Q

what must not happen when vaporisers are moved?

A

must not be tipped

332
Q

where are the vaporiser(s) connected to the anaesthetic machine?

A

back bar

333
Q

what is the role of Selectatec and Interlock systems?

A

provides mounting of two vaporisers on the back bar

334
Q

when using Selectatec and Interlock systems can vaporisers be used at once?

A

no - only one can be turned on and gas will only flow through the one in use

335
Q

what attaches to the common gas outlet?

A

breathing system

336
Q

what is the role of the common gas outlet?

A

delivers gas(es) and anaesthetic agent to the patient

337
Q

what happens if the common gas outlet is obstructed?

A

pressure relief safety valve should open to prevent damage to the machine

338
Q

what is the role of oxygen flush?

A

removal of gas quickly in an emergency (not when the patient is attached)

339
Q

what pressure and speed is oxygen supplied by oxygen flush?

A

400kPa and 35-75 l/min

340
Q

what does the oxygen flush bypass?

A

flowmeters and vaporiser

341
Q

what could be caused by using the oxygen flush when the patient is attached?

A

barotrauma (lung damage)

dilution of anaesthetic gases

342
Q

what should be used to fill reservoir bag if empty/low?

A

flowmeter

343
Q

what is scavenging?

A

removal of environmental contaminants

344
Q

what regulations are waste anaesthetic volatile agents and gases subject to?

A

COSHH and Health and Safety at Work Act

345
Q

what are the 2 types of scavenging?

A

active

passive

346
Q

how does active scavenging work?

A

(torbridge)

waste gases and anaesthetic agents are drawn outside of the building by a fan and vent system

347
Q

what is required in an active scavenging system to ensure negative pressure is not applied to the patients breathing system?

A

air break

348
Q

what is the role of the air break in active scavenging?

A

ensure negative pressure is not applied to the patients breathing system

349
Q

how does passive scavenging work?

A

gas is pushed by patients expiratory effort into tubing either leading outside the building or into a canister containing active charcol

350
Q

what is the issue with passive scavenging via a tube leading outside the building?

A

makes it harder for the patient to exhale due to increased resistance

351
Q

what does passive scavenging by activated charcoal not absorb?

A

nitrous oxide

352
Q

why must passive scavenging systems into activated charcoal be weighed regularly?

A

to check if they are used up

353
Q

what are the benefits of passive scavenging?

A

can be moved around

easy to use

354
Q

what are the disadvantages of passive scavenging into active charcoal?

A

needs to be stored carefully before disposal as heat can cause it to release its contents
must be changed regularly

355
Q

how do oxygen concentrators work?

A

takes in air and purifies it using a molecular sieve containing a material called Zeolite that removes nitrogen from the air leaving the remaining air 87-95% oxygen

356
Q

when is oxygen concentration often used?

A

ICU units

oxygen for anaesthesia

357
Q

how must liquid oxygen be stored?

A

-183 degrees

358
Q

what is liquid oxygen stored in?

A

vacuum insulated evapourator

359
Q

where is liquid oxygen stored?

A

outside

360
Q

what happens to liquid oxygen before it can be piped into the hospital?

A

drawn off as required, passed through a vapouriser and turned into gas

361
Q

what regulates the flow of gas from the vacuum insulated evapourator before it enters the pipework system?

A

control panel

362
Q

what is required to ensure adequate oxygen supply in the event of any primary supply system failure?

A

backup cylinder manifolds

363
Q

what are the dangers associated with liquid oxygen?

A

burns
frostbite
hypothermia

364
Q

what are the 8 key patient safety features on anaesthetic machines?

A
pin-index system and NIST for pipelines
colour coded pressure gauges and flowmeters
oxygen flowmeter is touch coded
ratio regulators
nitrous oxide cut out
alarm
air intake valve
reserve oxygen cylinders
365
Q

what is touch coding of the oxygen flowmeter?

A

it is the easiest dial to turn

366
Q

what does chronic exposure to volatile agents increase the risks of?

A

spontaneous miscarriage
congential malformation (men and women affected)
liver and kidney damage

367
Q

what 10 ways can exposure to volatile agents be reduced?

A

well ventilated theatres/recovery areas
IV induction where possible
cuffed ET tubes
connect animal to breathing system before turning on gases
use low flows
check for leaks
flush breathing system with oxygen before disconnecting animal
use key fill vapourisers
fill vaporisers at the end of the day
monitor personnel exposure to anaesthetic gases

368
Q

why do recovery area need to be well ventilated?

A

patients will be breathing out gases

369
Q

how many air changes per hour should their be in theatres and recovery areas?

A

15-20

370
Q

how should the breathing system be flushed with the animal still attached?

A

animal remains connected to system with just oxygen at the end of the procedure

371
Q

why is nitrous oxide no longer used by many practices?

A

very bad for the environment

372
Q

describe the process of preforming an anaesthetic machine check

A

scavenging connected to wall, red block will move up inside to show connection. Check piping and connect to common gas outlet
plug in gases
turn on machine and note residual flow on flowmeter (if expected)
turn O2 flow up to the top, then drop to 4 l/min (repeat with all present pipelines)
turn on N2O with no O2 - this should cut out
disconnect O2 from wall - use flush to clear system - alarm should sound. Replace O2 into wall and tug test
with just O2 - detach scavenge and occlude end. Flowmeter bobbin should move up and down showing no leaks
check vaporiser has enough agent, is securely attached and there is free movement of dial (O2 off at this point)

373
Q

define dead space

A

volume of gas which doesn’t eliminate carbon dioxide

374
Q

define tidal volume

A

volume of gas entering the lung with each inspiration

375
Q

define minute volume

A

volume of gas entering the lungs each minute

376
Q

define metabolic oxygen requirements

A

amount of oxygen required each minute for metabolic processes

377
Q

define rebreathing

A

occurs when the inspired gas(es) reaching the alveoli contain more CO2 than can be accounted for by mere re-inhalation from the patients dead space gas (negligable)

378
Q

what is the formula required to calculate minute volume?

A

tidal volume x respiratory rate

379
Q

what must be detected when using breathing systems?

A

rebreathing

380
Q

what are the 3 key functions of a breathing system?

A

provide oxygen +/- anaesthetic agent
enable IPPV or spontaneous ventilation
enable scavenging of expired gases

381
Q

where does a breathing system attach to the anaesthetic machine?

A

common gas outlet

382
Q

how does the breathing system attach to the patient?

A

via ET tube or mask

383
Q

what does IPPV stand for?

A

intermittent positive pressure ventilation

384
Q

what is the fresh gas flow?

A

oxygen/nitrous/air from flowmeters

385
Q

why is scavenging of expired gases so important?

A

removes CO2

removes waste anaesthetic gases

386
Q

why must CO2 be removed once expired from the patient?

A

causes:
adrenaline release
tachycardia
tachypnoea

387
Q

what condition can high levels of CO2 mimic?

A

light plane of anaesthetic

388
Q

identify the components of this non-rebreathing system and the type of system it is

A
Ayres T-Piece
(clockwise from top)
1. APL valve
2. reservoir bag
3. connector to common gas outlet
4. breathing system tubing
5. connection to ET tube or mask
6. Attachment for scavenging tubing
389
Q

what does APL valve stand for?

A

adjustable pressure limiting valve

390
Q

identify the components of this breathing system and identify the type

A
Circle
(clockwise from right)
1. unidirectional valves - ensure gas flow in one direction
2. attachment to common gas outlet of anaesthetic machine
3. soda lime canister
4. breathing system tubing
5. attachment for scavenging tubing
6. APL limiting valve
7. connection to ET tube/mask
8. reservoir bag
391
Q

what is the role of soda lime in circle breathing system?

A

absorbs CO2

392
Q

what is the approximate value used to calculate tidal volume?

A

10ml/kg

393
Q

what size should the reservoir bag on a breathing system be?

A

3-6x tidal volume

394
Q

what sizes of reservoir bag are available?

A

0.5, 1, 2 and 3 litre (larger are available if needed e.g. horse)

395
Q

why must the reservoir bag be checked before each anaesthetic?

A

as they perish over time

396
Q

what does the APL bag attach to?

A

scavenging system

397
Q

should the APL valve be open or closed?

A

open at all times - can be fatal if left closed

398
Q

why does resistance within a breathing system matter?

A

results in hypoventilation - so increased CO2 - and increases work of breathing

399
Q

what can resistance of a breathing system be influenced by?

A

tubing and valves (unidirectional and APL)

400
Q

what effect does an increase in radius have on resistance?

A

2 x increase in radius will lead to 16 x less resistance

401
Q

what effect does an increase in length of breathing circuit have on resistance?

A

2 x increase in length leads to a 2 x increase in resistance

402
Q

what are the 2 types of breathing system tubing?

A

coaxial and parallel

403
Q

describe coaxial breathing system tubing

A

one tube is inside another

404
Q

describe parallel breathing system

A

2 tubes are side by side

405
Q

what is the resistance like in parallel configurations of breathing systems?

A

less than coaxial

406
Q

what is a negative about parallel breathing system configurations?

A

may increase drug - pull on the ET tube

407
Q

what is it important to be aware of with coaxial breathing systems?

A

inner hose disconnection

408
Q

what is a potential benefit of coaxial breathing system configuration over parallel systems?

A

warming of inspired air is possible (although may not have clinical impact)

409
Q

what is the role of soda lime?

A

absorbs CO2

410
Q

what type of reaction is the absorption of CO2 by soda lime?

A

exothermic

411
Q

what are the products of the absorption of CO2 by soda lime?

A

water and heat

412
Q

how is exhaustion of soda lime in a circle circuit indicated?

A

dye changes colour

413
Q

what is found within soda lime?

A

94% calcium hydroxide (Ca(OH)2)

5% sodium hydroxide (NaOH), silica and dye

414
Q

how much CO2 can one kg of soda lime absorb?

A

120L CO2

415
Q

why must gloves be worn when changing soda lime?

A

it is caustic

416
Q

what are the 2 types of breathing system?

A

Non-rebreathing systems

rebreathing systems

417
Q

how do non-rebreathing systems remove expired CO2?

A

fresh gas flow

418
Q

how do rebreathing systems remove expired carbon dioxide?

A

soda lime

419
Q

give 3 examples of non-rebreathing systems

A

T-Piece
Bain
Lack

420
Q

give an example of a rebreathing system

A

Circle

421
Q

which type of breathing system requires a higher fresh gas flow?

A

non-rebreathing

422
Q

what are the issues with higher fresh gas flow on non-rebreathing systems?

A

increased pollution risk
more heat and moisture lost from patient
more expensive to run

423
Q

what are 3 main benefits of non-rebreathing systems?

A

inspired agent should be the same as that on the vapouriser
low resistance and lightweight
some suitable for IPPV
cheap to purchase

424
Q

what non-rebreathing systems are suitable for IPPV?

A

T-Piece and Bain

425
Q

what are the benefits of lower fresh gas flow?

A

lower pollution risk/environmental impact
heat and moisture retained by soda lime
less expensive to run

426
Q

what are the disadvantages of rebreathing circuits?

A

slow changes in inspired anaesthetic agent concentration

higher resistance

427
Q

what should be done if a rapid increase in volatile agent is required by a patient on a rebreathing system?

A

increased fresh gas flow

428
Q

can rebreathing systems be used for IPPV?

A

yes

429
Q

how is fresh gas flow calculated in non-rebreathing systems?

A

fresh gas flow = minute volume x circuit factor

430
Q

what units is fresh gas flow measured in?

A

ml/kg/min

431
Q

what value can be used for a minute volume calculation if you don’t know the respiratory rate or if the animal is panting?

A

200ml/kg/min

432
Q

what is a circuit factor?

A

the amount by which the calculated tidal volume of the patient is multiplied by in order to administer the correct amount of gas. Each type of circuit has a different circuit factor

433
Q

how is fresh gas flow calculated in rebreathing systems?

A

minimum fresh gas flow = metabolic oxygen consumption

434
Q

what is the minimum fresh gas flow form large animals?

A

5ml/kg

435
Q

what is the minimum fresh gas flow for small animals?

A

10ml/kg

436
Q

what is required at low flows on a rebreathing system?

A

accurate flow meters and vapouriser as the closer the flow is to these values the lower the margin for error

437
Q

in practice how is fresh gas flow managed on a rebreathing circuit?

A

high FGF initially and the reduced to 1L/min in animals up to 100kg

438
Q

what body weight is the Ayres T-Piece used for?

A

up to 10kg but preferably less than 7.5kg

439
Q

what is the calculation for fresh gas flow for Ayres T-piece?

A

FGF = minute volume x 2-3

440
Q

can Ayres T-Piece be used for IPPV?

A

yes

441
Q

why is Ayres T-Piece good for small patients?

A

low resistance and dead space

442
Q

what causes modest drag in an Ayres T-Piece breathing system?

A

2 parallel tubes

443
Q

what has made Ayres T-Piece easier to scavenge?

A

version with APL valve which has an attachment for scavenge

444
Q

what animals is the Ayres T-Piece used for?

A

cats and exotics

445
Q

what weight of animals is the Bain circuit used for?

A

8-20kg with valve (smaller bain without valve may be suitable for smaller animals)

446
Q

how is FGF calculated for a Bain circuit?

A

FGF = minute volume x 2-3

447
Q

what are the benefits of a Bain circuit?

A

can be used for IPPV
low drag and dead space
easy to scavenge

448
Q

what are the issues with a Bain circuit?

A

inner tube can become disconnected (coaxial configuration)

449
Q

how can the integrity of a breathing circuit be tested?

A

connect to common gas outlet, occlude patient end of tubing. Close APL and allow reservoir bag to fill, listen for leaks. open APL valve to release pressure

450
Q

how can the inner tubing of a Bain circuit be tested?

A

using 15ml syringe plunger occlude only inner tube. Place FGF on 4l/min. Should trigger pressure release valve on bakc bar

451
Q

what patients are most suited to the Lack circuit?

A

patients >10kg (mini versions available)

452
Q

what is the drag, resistance and dead space like in a Lack circuit?

A

moderate

453
Q

what is the fresh gas calculation for the Lack?

A

minute volume x 1

454
Q

is a Lack circuit suitable for IPPV?

A

no - occasional breaths are ok, can cause rebreathing

455
Q

why is a Lack circuit not suitable for IPPV?

A

can cause rebreathing

456
Q

what sizes of circle circuit are available?

A
variety - 
human adult >20kg
small animal systems >15kg
smaller ones are available for cats and dogs with paediatric tubing
large animal versions
457
Q

what parts of a circle circuit contribute to resistance?

A

unidirectional valves, soda lime canister and APL valve

458
Q

what is the FGF of circle circuits set as?

A

more than metabolic oxygen requirement (1l/min for animals under 100kg, 0.5-1l/min for animals over 100kg)

459
Q

what factors must be considered when choosing a breathing system for a case?

A
size of animal
valve position and IPPV requirement
ease of scavenging
cleaning and sterilisation
use of nitrous oxide
heat an moisture retention
460
Q

what are the signs of APL valve being accidentally left closed?

A
reservoir bag distends
reduction in thoracic movements
possible leaking around ET tube cuff
tachycardia
hypoxia
461
Q

why are thoracic movements reduced if the APL valve is left closed?

A

animal struggles to breathe against pressure created in circuit

462
Q

what conditions can be caused by the APL valve being left closed?

A

pneumothorax
pneumomediastinum
rupture of lung tissue or trachea
potentially fatal

463
Q

how is accidental closure of the APL valve prevented?

A

systematic approach to system checks and checks when attaching to new system

464
Q

how can excessive resistance in the breathing system be recognised?

A

altered RR (low or occasionally fast)
decreased tidal volume
hypoventilation and hypercapnia - increased end-tidal CO2
hypoxia
altered respiratory pattern (e.g. paradoxical breathing)

465
Q

what can reduced alveolar ventilation due to excessive resistance in the breathing system lead to?

A

light plane of anaesthesia as impact on uptake of VA

466
Q

what may apparatus dead space be formed from?

A

integral part of breathing system (e.g. ET tube connector) or excessively long ET tube protruding from mouth

467
Q

what is the effect of increasing dead space to tidal volume ratio?

A

increases PaCO2

increases work of breathing

468
Q

why does increasing dead space to tidal volume ratio increase the work of breathing in small animals?

A

minute volume needs to increase to maintain PaCO2 at normal levels

469
Q

identify this circuit and it’s weight bracket and circuit factor

A

Ayres T-Piece
less than 10kg - preferably less than 7.5kg
2-3

470
Q

identify this circuit, it’s weight bracket and circuit factor

A

Bain
8-10kg with valve (smaller without valve for smaller animals)
2-3

471
Q

identify this circuit, it’s weight bracket and circuit factor

A

Lack (standard)
over 10kg
1

472
Q

identify this circuit, it’s weight bracket and circuit factor

A

Mini Lack
more than 1kg
1

473
Q

identify this circuit, it’s weight bracket and circuit factor

A

Circle
varies - can have a circuit suitable for any size
not applicable

474
Q

what is meant by the post op period after anaesthesia?

A

procedure is finished and the patient now needs to regain consciousness and start their recovery

475
Q

what are the 2 key steps involved in getting the patient into recovery?

A

preparing for end of anaesthesia

end of anaesthesia

476
Q

what should be done when preparing for the end of anaesthesia?

A

reduce volatile agent or IV agent (whatever is keeping the patient asleep)
turn up to 100% oxygen if using nitrous oxide

477
Q

how can you tell when you need to prepare for the end of anaesthesia?

A

watching the procedure to see when the vet is nearly finished (e.g. skin closure nearly done)

478
Q

why is turning up to 100% on preparation for the end of anaesthesia necessary if nitrous oxide has been used?

A

counteracts hypoxia

479
Q

what should you do at the end of anaesthesia?

A

turn off all anaesthetics

ensure analgesia is in place

480
Q

describe the ideal recovery environment

A
safe and secure
ideally purpose built
well ventilated
warm
accessible and easy to observe patients
close proximity to clinical supplies (e.g. oxygen, catheters, swabs, CPR kit) and staff
481
Q

why is the ideal recovery area well ventilated?

A

animals will be exhaling anaesthetic gases to remove them from the body

482
Q

what are the 4 key types of airway management devices used in veterinary practices?

A

SGAD (V Gel)
ET Tube
LMA
face mask

483
Q

what should be done in recovery in all species if the patient has an intubated trachea?

A

loosen/untie the ties on ET tube ready to remove (extubation)

484
Q

when should the ties on an ET tube be undone in a recovering patient?

A
personal preference
situation dependent (not if you are just about to move the patient)
485
Q

when should the cuff of a cuffed ET tube be deflated during recovery?

A

close to extubation (ideally 1 min before!), not when you turn off volatile agent

486
Q

why should the cuff of a cuffed ET tube be deflated close to extubation?

A

prevention of aspiration and improved airway control

487
Q

what are the signs that show that dogs and rabbits should be extubated?

A

signs that laryngeal reflexes are returning (e.g. swallowing)
other reflexes returning and/or spontaneous movement

488
Q

when should cats be extubated?

A

when showing earlier reflexes (e.g. ear flick and blink) and before swallowing returns

489
Q

why must cats be extubated before swallowing returns?

A

have very sensitive larynxes and there is a danger of laryngospasm if you wait for swallowing

490
Q

when should horses be extubated?

A

respiration rate is a good guide as laryngeal reflexes are weak

491
Q

how should the tube be removed once you have judged it is time?

A

smoothly remove tube without damaging the airway (remember ET tube shape) - don’t wriggle the tube!

492
Q

what happens if the ET tube is removed too early?

A

the patient has an unsupported airway

493
Q

what should you do if the tube has been removed too early?

A

maybe provide supplemental oxygen (flow-by)

have laryngoscope and ET tube ready just in case

494
Q

what may happen if the tube is removed too late?

A

patient may bite tube/damage airway/get distressed/develop laryngospasm (cats)

495
Q

when may late extubation be necessary?

A

in patients at high risk of airway obstruction (e.g. BOAS dogs after airway surgery)

496
Q

what must you do if performing late extubation on patients?

A

monitor carefully

497
Q

can late extubation be performed on cats?

A

no - due to risk of laryngospasm

498
Q

is late extubation well tolerated?

A

mostly in patients that require it due to the fact they live with breathing difficulties - not all though!

499
Q

what should be done with the patients tongue around the time of extubation?

A

pull out to the side of mouth so that it doesn’t obstruct the airway

500
Q

what can be done with the mouth/tongue before extubation to make the patient more comfortable?

A

wet with a damp swab

501
Q

why may you want to gently tug the patients tongue as it is beginning to recover more?

A

sometimes seem to have their tongue stuck out of their mouth - a gentle tug may help them to regain function and pull it back in!

502
Q

following extubation what are the stages of recovery?

A

lift head
assume sternal recumbancy
stand
full recovery with no signs of sedation/ataxia

503
Q

what must be monitored on recovery of all patients no matter their ASA grade?

A

Temperature
Pulse
Respiration

quality of recovery
pain/analgesia

504
Q

what should the frequency of temperature measurement in the post op period depend on?

A

individual case - more if attempting t address hypo/hyperthermia
less if uncomplicated recovery

505
Q

what are the effects of hypothermia on the recovering patient?

A
bradycardia and cardiac arrhythmias
impaired coagulation and wound healing
prolonged duration of action of drugs so slower recovery from anaesthesia
decreased renal plasma flow
decreased oxygen delivery to tissues
shivering may increase o2 requirement
506
Q

at what temperatures can atrial fibrillation be caused?

A

30 degrees C

507
Q

at what body temperatures can ventricular fibrillation be caused?

A

24-28 degrees C

508
Q

why does hypothermia lead to prolonged duration of action of drugs and so slower recovery from anaesthesia?

A

slows metabolism

509
Q

how can hypothermia during and after anaesthetic be minimised?

A

warm from time of premed - particularly IM
warm throughout perioperative period
use heating devices
ensure warm environmental temperature

510
Q

how can an animal be warmed throughout the peri-operative period?

A

insulation
warmed fluids
HME or rebreathing system
perform skin prep/clipping before anaesthesia to reduce anaesthetic time

511
Q

what is a HME?

A

heat and moisture exchanger put between ET tube and breathing system to raise heat and humidity of inspired air

512
Q

what can cause hyperthermia in the anaesthetised/recovering patient?

A

decreased heat loss
excessive external heat
increased metabolic production of heat due to underlying process

513
Q

what are the physiological effects of hyperthermia?

A

increased basal metabolic rate
increased oxygen requirement
parenchymal cell damage

514
Q

by how much does basal metabolic rate increase for every degree C above normal temperature?

A

13%

515
Q

what effect can a temperature of >41 degrees C have on the body?

A

irreversible brain damage

516
Q

what effect can a temperature of >43 degrees C have on the body?

A

death

517
Q

if using wheat bags what must happen to ensure the patient is not burned?

A

wrapped in a towel and never in direct contact with the patient

518
Q

when checking pulse what are you assessing?

A

circulation

519
Q

what pulses are best to check quality of circulation?

A

peripheral

520
Q

what else should be checked as a measure of circulation?

A

MM

CRT

521
Q

what equipment may be used to assess circulation?

A

pulse ox is desirable but usually impractical after a certain point in recovery!
auscultate chest with stethoscope
ECG if required

522
Q

what types of obstruction must be checked for to ensure a patent airway?

A

oral obstruction

anatomical obstruction

523
Q

what may an oral airway obstruction be caused by?

A

mouth packs
saliva
vomit

524
Q

what may an anatomical obstruction be caused by?

A

head stuck in corner of the cage and neck kinked

525
Q

when should an animal be placed in its kennel?

A

only once it is able to lift it’s head

526
Q

what can be done with a patient if concerned about the risk of inhalation of saliva/blood/vomit?

A

patient placed in head down position

527
Q

what must you do if your patient is in head down position with the kennel door open?

A

must be observed at all times

528
Q

what must be removed from the kennel while the patient is recovering?

A

water bowl - semi conscious patient may drown in it

529
Q

what must be observed when looking at a patients respiration?

A

that they are breathing!
resp rate in breaths per minute
note pattern
auscultate

530
Q

what should be noted about the patients respiratory pattern?

A

deep vs shallow

thoracic or abdominal

531
Q

what should be done if you are concerned about a patients breathing?

A

provision of oxygen supplementation

532
Q

what are the main types of oxygen supplementation?

A

oxygen cage/tent
face mask
nasal oxygen
flow by

533
Q

what animals is an oxygen tent suitable for?

A

smaller patients only

534
Q

what are the issues with face mask and nasal oxygen to provide oxygen supplementation?

A

may not be tolerated and can make respiration worse if patient is stressed by them

535
Q

what is the ideal recovery?

A

calm and stress free for all

536
Q

what behavior is often seen in recovery?

A

excitement

537
Q

what should be done if the patient is excitable on recovery?

A

monitor and observe - potentially resedate

538
Q

what must be provided to ensure patient cannot injure himself or staff during recovery?

A

suitable cage/box and remove obstructions

539
Q

in what animals is a controlled recovery essential to prevent serious injury?

A

horses

540
Q

what is the ideal way of measuring pain?

A

recognised pain scoring system

541
Q

what should additional analgesics be given based on?

A

patients pain score and not based on what time they last had a pain killer

542
Q

what behaviours may indicate pain in animals?

A
inappetance
reluctance to walk/move/jump/stand
difficulty in mobility
vocalisation
panting
lip-smacking
yawning
aggression
sleeping more
reacting badly to being touched
543
Q

why do some animals not exhibit many pain behaviours at all?

A

prey vs predator - prey animals cannot afford to be seen as weak

544
Q

what are the main physiological signs of pain?

A

increased: HR, RR, temp and BP

545
Q

what are the subjective pain assessment tools?

A

simple descriptive scales
numerical rating scales
visual analogue scales

546
Q

what are the more precise pain assessment tools for animals?

A

composite scales
grimace scales
behavioral assessment

547
Q

why are composite pain scales preferable to more subjective measurements?

A

have a prescribed point for analgesia

less subjective!

548
Q

when are grimace scales useful?

A

in patients who don’t show pain in traditional ways (e.g. rabbits)

549
Q

how should assessment using a grimace scale be done?

A

over a short period of time and ideally remotely

550
Q

what do grimace scales look at?

A

pain face - eye and ear position are recognised as good indicators of pain in some species

551
Q

what other area must be considered as well as pain when assessing patient comfort?

A
full bladder
cold
too hot
wet bedding
tight stitches
clipper rash
need to defecate
fear/anxiety
552
Q

what must be done with IV catheters during recovery?

A

flushed, patent with fluids flowing

properly covered and suitably padded

553
Q

what must be done when removing IV catheters?

A

apply pressure to the area to ensure haematoma doesn’t form

554
Q

what should be checked before recovering the animal?

A

wound checked and dressing/creams applied if needed
check consent form for any additional procedures
check that nothing is swelling due to over tight dressings

555
Q

what may be needed if the patient is interfering with the wound?

A

extra dressings/collar/suit

556
Q

when checking the surgical wound what are you looking for?

A

bleeding or swelling

557
Q

what are the key considerations when nursing the recovering patient?

A

clean, dry, warm and quiet
toilet needs met
water and food when appropriate
TLC

558
Q

when should animals be fed post op?

A

when awake/able to stand and swallow except for specific surgeries

559
Q

what procedures may mean that patients cannot be fed once they are awake and able to stand?

A

GI surgery (controlled feeding)
Sedation /CRIs
follow up imaging needed

560
Q

what type of food should be given post op?

A

bland, soft food

561
Q

what meal size and frequency is ideal post op?

A

little and often

562
Q

what may be necessary when feeding small mammals in recovery?

A

assisted feeding

563
Q

why is it so crucial that rabbits eat soon after surgery?

A

at risk of ilius and gut stasis

564
Q

where should post op data be recorded?

A

specific continuation sheet (hospital record) or on the back of anaesthetic record card

565
Q

why should all post op care be noted down?

A

in case of an adverse event can demonstrate that care was provided

566
Q

why must a general anaesthesia record be completed for every patient?

A

legal document

567
Q

when should each round of parameter checks be completed?

A

minimum of 5 minutes

568
Q

what parameters are measured during general anaesthesia monitoring?

A
HR
BP
resp rate
temperature
pulse ox
drug doses (inc. O2 and volatile agent)
569
Q

when should anaesthetic monitoring take place?

A

from time of premed to time of recovery

570
Q

what other information, aside from monitoring record should be included on the anaesthetic record?

A

animal details

staff involved

571
Q

where should anaesthetic records be stored?

A

animal file

572
Q

who assigned guidelines for assessing depth of anaesthesia?

A

Guedel

573
Q

why is Guedel’s work on anaesthesia planes not totally reliable with veterinary patients?

A

rare that only inhalant drugs are given. Balanced anaesthetic technique will influence reflex and autonomic responses

574
Q

what parameters are relied upon when monitoring patients under a balanced anaesthetic technique?

A

physiological parameters

575
Q

how many stages of anaesthesia are there?

A

4

576
Q

name the stages of anaesthesia

A

stage 1-4

577
Q

which anaesthesia stage is divided into 3 planes?

A

stage 3

578
Q

what are the names of the 3 planes of stage 3 of anaesthesia?

A

plane 1, 2 and 3

579
Q

when does stage 1 of anaesthesia occur?

A

begins at time of induction and lasts until unconsciousness is present

580
Q

what are the physiological effects seen during stage 1 of anaesthesia?

A

pulse and resp rates are often elevated, breath holding may occur and pupils may dilate

581
Q

when does stage 2 of anaesthesia occur?

A

lasts from onset of unconsciousness until rhythmic breathing is present

582
Q

what reflexes are present during stage 2 of anaesthesia?

A

all cranial nerve reflexes are present and may be hyperactive

583
Q

describe eye position in stage 2 of anaesthesia

A

eye may appear wide and open with pupil dilated - the eye will soon rotate to ventromedial position

584
Q

describe signs of plane 1 of stage 3 of anaesthesia

A

respiration becomes regular and deep, spontaneous limb movement is absent but pinch reflex may be brisk. Nystagmus, if present, will start to slow and disappear

585
Q

describe eye position during plane 1 of stage 3 of anaesthesia

A

eyeball is now ventromedial, opening the eye will show the sclera

586
Q

what is plane 1 of stage 3 of anaesthesia suitable for?

A

minor procedures (e.g. abscess lancing and skin suturing)

587
Q

describe plane 2 of stage 3 of anaesthesia

A

palpebral reflex is sluggish or absent although corneal reflexes remain.
Muscles appear relaxed, pedal reflex begins to go
Tidal volume may decrease as resp rate settles.
HR and BP may be slightly reduced

588
Q

describe eye position during plane 2 of stage 3 of anaesthesia

A

eye position is ventromedial and the eyelids my be partially seperated

589
Q

what procedures is plane 2 of stage 3 of anaesthesia adequate for?

A

most surgical procedures

590
Q

describe plane 3 of stage 3 of anaesthesia

A

pedal reflex is lost
abdominal muscles are relaxed
HR and BP may be low

591
Q

what is the pedal reflex?

A

pinching between patients toes to see when they withdraw their foot and the speed at which they do

592
Q

describe the eye position of plane 3 of stage 3 of anaesthesia?

A

eyeball becomes central and eyelids begin to open

pupillary diameter increases

593
Q

describe physiological signs of stage 4 of anaesthesia

A

progressive respiratory failure
pulse may be rapid or very slow and become inpalpable
CRT becomes prolongued
sometimes may see accessory respiratory muscle activity - twitching in the throat (can be confused with light plane of anaesthesia)

594
Q

describe the eye position during stage 4 of anaesthesia

A

central eye with no palpebral reflex

595
Q

what is happening during stage 4 of anaesthesia?

A

anaesthetic overdose

596
Q

why should an anaesthetic be monitored?

A

volatile agents are used which have a profound effect on the patient
it is a legal requirement
there can be quick changes in the animals equipment

597
Q

what can be monitored during anaesthesia?

A
depth of anaesthesia
CVS
respiratory system
inhalent/drug administration
body temperature
urine output
blood glucose 
blood gases
neuromuscular function
598
Q

why should inhalant/drug admin be monitored?

A

avoid dose dependent effects

599
Q

what parameters can be monitored during general anaesthetic with minimal equipment?

A
temperature
ventilation pattern
resp rate
pulse quality
heart rate
thoracic auscultation
mucous membranes
CRT
eye position
600
Q

what parameters can be monitored during anaesthesia but require more specialist equipment?

A
pulse ox
capnography
spirometry
ECG
BP
601
Q

what is an oesophageal stethoscope used for?

A

listening to heart and breath sounds in the anaesthetised animal

602
Q

where should the oesophageal stethoscope be placed?

A

via the oesophagus to the level of the heart base

603
Q

how should an oesophageal stethoscope be placed?

A

palpate apex beat and measure stethoscope against the animals lateral neck and thorax, listen as you pass the stethoscope into the oesophagus and stop once you can hear heart sounds

604
Q

describe correct eye position in an adequate plane of anaesthesia

A

ventromedial position with absent palpebral reflex

605
Q

describe eye position in an light plane of anaesthesia

A

central with palpebral reflex

606
Q

describe eye position in a deep plane of anaesthesia

A

central with no palpebral reflex

607
Q

what must be monitored alongside anaesthesia?

A

patient reaction to any drugs given - side effects or adverse response

608
Q

describe the depth of this plane of anaesthesia:
increased HR
increased resp rate
mucous membranes pink
CRT - brisk
central eye position with slight palpebral reflex

A

too light

609
Q

Describe the depth of this plane of anaesthesia:
steady HR
slightly reduced resp rate
mucous membranes pink
CRT <2 secs
ventromedially rotated eye position with no palpebral reflex

A

adequate

610
Q

describe the depth of this plane of anaesthesia:
steady HR
slightly reduced resp rate
mucous membranes pink/pale pink
CRT 2-3 seconds
central eye position with no palpebral reflex

A

too deep

611
Q

what are the key tips for good anaesthetic monitoring?

A
focus
no distractions
treat patients as if they were yours
make the recording sheet legible
ask for help
612
Q

what body system does blood pressure indicate the function of?

A

CVS and perfusion

613
Q

what is arterial blood pressure a measure of?

A

the pressure exerted by blood on the walls of the blood vessels

614
Q

what is arterial blood pressure an indirect indicator of?

A

blood flow

615
Q

why is it so critical that blood pressure is monitored in the anaesthetised patient?

A

most drugs used cause suppression of the CVS, respiration and BP leading to hypotension

616
Q

what are the 2 key methods of blood pressure measurement?

A

indirect / non-invasive (NIBP)

direct / invasive (IBP)

617