Anaesthesia For Pre-exisiting Conditions Flashcards

1
Q

what is stated by the Monroe Kellie hypothesis?

A

intracranial cavity is filled with brain, CSF and blood

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2
Q

in what ratios is the intracranial cavity filled?

A

brain - 80%
CSF - 10%
blood - 10%

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3
Q

what can disrupt the blood brain barrier?

A

trauma
inflammation
hypertension

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4
Q

what percentage of cardiac output does the brain receive?

A

~15%

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5
Q

why does the brain receive such a large percentage of cardiac output?

A

has high metabolic rate

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6
Q

what is the consequence of increases in CSF and intracranial blood volume?

A

raised / altered ICP

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7
Q

what is the brain reliant on to support metabolic rate?

A

maintenance of intracranial blood volume

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8
Q

what are the main aims when anaesthetising animals with neurological/brain trauma?

A

maintain cerebral blood flow
reduce or limit increases in ICPh

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9
Q

at is normal ICP?

A

5-12 mmHg

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10
Q

what are the clinical symptoms of riased ICP

A

papilledema
abnormal pulsing of retinal vessels
depression
stupor
coma

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11
Q

what is papilledema?

A

optic disc swelling

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12
Q

what happens if ICP increases?

A

compensatory mechanisms are initiated (e.g. cushings reflex)

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13
Q

what may happen if ICP continues to rise following initiation of compensatory mechanisms?

A

mechanisms may become exhausted

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14
Q

why does the cushings reflex occur?

A

because of the reduction in cerebral blood flow

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15
Q

what is the aim of of the cushings reflex?

A

decrease intracranial volume / pressure

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16
Q

how is the cushings reflex initiated?

A

reduction in blood flow causes an accumulation of CO2 as a result of poor perfusion
CO2 is detected by the brain stem and the sympathetic nervous system responds by increasing MAP to improve perfusion to the brain

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17
Q

what are the signs of the cushings reflex?

A

hypertension
reflex bradycardia
irregular breathing apnoea

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18
Q

what causes the signs of the cushings triad?

A

accumulation of CO2 as a result of poor perfusion
CO2 is detected by the brain stem and the sympathetic nervous system responds by increasing MAP to improve perfusion to the brain

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19
Q

how can an increase in ICP be prevented during patient care?

A

avoid coughing
avoid neck leads
adequate depth prior to intubation
avoid pressure on the neck during restraint
avoid jugular samples
avoid straining to urinate / defecate
avoid vomiting / gagging

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20
Q

how can coughing be avoided in patients at risk of raised ICP?

A

give anti-tussive

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21
Q

what may be involved in the pre-operative assessment of neurological patients?

A

haem and biochem
electrolytes
glucose
PCV
glasgow coma scale (MGCS)

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22
Q

what must be considered around drug choices when anaesthetising neurological patients?

A

should not increase ICP or cause dramatic change to MAP

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23
Q

are opioids indicated for use with neurological patients?

A

yes

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24
Q

what is the effect of opioids on ICP?

A

do not tend to alter cerebral blood flow or increase ICP too much

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25
Q

what are the effects of opioids on the cardiovascular and respiratory systems?

A

minimal, dose dependent, CV and respiratory depression

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26
Q

what opioid should be avoided in patients at risk of raised ICP and why?

A

morphine due to increased incidence of vomiting

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27
Q

are benzodiazepines indicated for use in patients at risk of raised ICP?

A

yes - no effect on ICP

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28
Q

what are the effects of benzodiazepines on the cardiovascular and respiratory systems?

A

no adverse effects

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29
Q

what are the effects of benzodiazepines?

A

reduction in anxiety but can be unreliable

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30
Q

is ACP contraindicated in patients at risk of raised ICP?

A

yes

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31
Q

why is ACP contraindicated in patients at risk of raised ICP?

A

may trigger seizures in patients with intracranial pathology
causes systemic vasodilation which causes hypotension and cerebral vasodilation

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32
Q

what effect does cerebral vasodilation have on ICP?

A

raises ICP as vessels take up more space

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33
Q

are alpha 2 agonists indicated for use in patients with a risk of raised ICP?

A

do not affect ICP but should be used very cautiously

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34
Q

why are alpha 2 agonists not indicated for use in patients with a risk of raised ICP?

A

can cause significant cardiopulmonary dysfunction
will cause an increase in MAP nd bradycardia so masking the cushings effect
can cause vomiting in cats

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35
Q

is ketamine indicated for use in patients at risk of raised ICP?

A

historically not as reported to increase ICP
now found to have neuroprotective properties and when used with other agents no increase in ICP seen

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36
Q

what can happen if ketamine is given alongside propofol?

A

reduction in ICP

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37
Q

what is the benefit of using ketamine in patients at risk of raised ICP?

A

thought to have neuroprotective properties
fewer CV and respiratory depressive effects

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38
Q

what are the main anaesthetic considerations for neuro patients?

A

preoygenate
ensure adequate depth before intubation
use sevolurane
monitor closely
maintain normocapnia
IVFT
mild head elevation
monitor for seizure activity
careful handling and restraint to avoid compression of jugular vein
avoid straining

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39
Q

why is sevoflurane better for patients at risk of raised ICP?

A

maintains cerebral perfusion pressure at higher MAC multiples
iso may slightly raise ICP

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40
Q

why is it important that normocapnia is maintained in neurological cases?

A

increased EtCO2 can lead to vasodilation

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41
Q

what is the purpose of elevation of the patient’s head if they are at risk of raised ICP?

A

aids venous drainage

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42
Q

why may patients with neurological issues need GA?

A

imaging
CSF tap
spinal surgery
treatment of non neuro issues
pre existing disease (epilepsy) but requires surgery

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43
Q

what are the main considerations for a patient undergoing MRI?

A

careful positioning (straightness)
no metal on patient/staff/equipment
safety
access for staff (remote, often outside hospital)
remote monitoring
temperature levels can be difficult to maintain as cold

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44
Q

what type of equipment is used for monitoring in MRI?

A

often specialised
fibreoptic
expensive!
long leads to reach outside unit and avoid metal in the room

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45
Q

what are the common CSF tap locations?

A

cisterna magna
lumbar

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46
Q

what is the anaesthetic consideration when a cisternal CSF sample is being taken?

A

need to bend the neck (nose on chest) to open up the vertebral space - monitor for signs of ET tube kinking

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47
Q

what equipment can be used to maintain patient safety during a cisternal CSF tap?

A

armored ET tube

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48
Q

what is the main consideration with using armored ET tubes?

A

not in MRI as contain metal!

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49
Q

what are the main airway considerations for a neurological patient?

A

lateral intubation may be necessary for neck or spine instability
avoid coughing - ensure anaesthetic plane is deep enough prior to intubation
positioning for cisternal CSF tap

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50
Q

what are the main anaesthetic considerations for a seizure patient?

A

often unknown cause
look at current medication and any interactions
treat as raised ICP
IV access essential
close monitoring pre and post anaesthesia

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51
Q

when is an especially risky phase of anaesthesia for seizure patients?

A

recovery as drugs wear off

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52
Q

what are the main anaesthetic considerations for a neuromuscular patient?

A

may be predisposed to regurgitation and aspiration - check gag reflex, suction ready
weakness of respiratory muscles possible so may need IPPV (check capnography)
rapid induction and recovery
exaggerated response to NMBA in myaesthenia gravis
consider local anaesthesia

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53
Q

what are the main areas to consider when planning for an anesthetic?

A

signalment
history and CE
presenting procedure
considerations
plan

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54
Q

what are the main brachycephalic considerations and how can they be mitigated?

A

airway - ETT selection, head up induction, cuff tube, on wedge, pre oxygenate
eyes - eye lube
skin - care with IV and CSF sampling if skin inflamed
joints - padding and support
GOR - fasting times, GOR, pre-op GI meds

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55
Q

what is the benefit of using butorphanol for a raised ICP patient?

A

anti-tussive

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56
Q

what is the benefit of using dexmedetomidine in a raised ICP patient?

A

vasoconstriction
antagonism possible
short acting

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57
Q

how can vasodilation be avoided in ICP patients?

A

VA low
good premed
consider drugs used

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58
Q

what must be considered about the breathing system used for ICP patients?

A

suitable for IPPV if become hypercapnic

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59
Q

what are some of the reasons that GI patients may present for anaesthesia?

A

planned abdominal surgery
acute abdomen surgery (e.g. GDV)
pre-existing GI condition
diagnostic procedures (e.g. endoscopy)

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60
Q

when may management of GI cases differ?

A

whether they are planned or emergencies

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61
Q

what are the main considerations for planned GI surgery?

A

stabilise patient (there is usually time)
pain management
reflux risk and so aspiration risk - suction and elevation of head until cuff inflated
may be limited access to head if oesophageal surgery
consider dehydration and anorexia
avoid drugs which induce vomiting
pre-oxygenate
may need access through the thorax - ventilation
heat preservation is key

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62
Q

what type of GI surgery may be planned?

A

oesophageal or GI foreign body

63
Q

what is an example of an emergency GI surgery?

A

GDV

64
Q

what is needed on GDV arrival?

A

IV access
IVFT - large volume, fast

65
Q

what is the aim of GDV stabilisation prior to GA?

A

improved CV and respiratory function prior to GA

66
Q

how may a GDV patient be stabilised prior to GA?

A

decompress stomach if able (percutaneous or stomach tube)
IVFT
CVS monitoring

67
Q

how is GDV treated?

A

decompression surgery and gastropexy

68
Q

what altered parameter is often seen in GDV patients?

A

ventricular arrhythmias

69
Q

where do arrhythmias seen in GDV patients originate from?

A

ventricles

70
Q

what are the common intraoperative considerations / risks with GDV surgery?

A

pressure on diaphragm from distended viscera can alter respiration
electrolyte and acid base abnormalities
clotting abnormalities
possible pneumothorax due to stomach position in cranial abdomen

71
Q

what is the issue with blood pressure monitoring during GDV surgery?

A

BP reads ok but perfusion is poor

72
Q

why may BP read as normal in GDV patients when perfusion is poor?R

A

cardiac output reduced due to hypovolaemia and dehydration
SVR increased due to pressure on great vessels by stomach reducing blood flow return to the heart

73
Q

how is BP calculated?

A

BP= SVR x CO

74
Q

what must be monitored in GDV patients in the post op period?

A

ECG to check for ventricular arrhythmia
pain - adequate analgesia

75
Q

what percentage of dogs with GDV may have arrhythmias pre, peri or post op?

A

up to 40%

76
Q

where should GDV patients recover?

A

ICU / intensive monitoring

77
Q

what drugs should be avoided in GDV patients?

A

any that suppress the CVS

78
Q

what is a significant risk in patients with pre-exisiting GI disease?

A

GOR

79
Q

what is crucial when managing patients at risk of GOR?

A

starvation times

80
Q

what are the main considerations for patients with pre-existing GI disease?

A

starvation times due to GOR risk
may be chronic disease - research
current medication
may be on a special diet
may have electrolyte or acid base disturbance so pre-op blood sensible

81
Q

what are some of the considerations for lower GI scope?

A

long starvation time
Kleanprep and enema
bloods and electrolytes checked
place cephalic IVC NOT saphenous for IVFT
keep warm
tail wrapped and area clipped for cleanliness
loss of access for rectal temperatures

82
Q

what is the function of the liver?

A

production of substances
bilirubin excretion
biotransformation of drugs or toxins
metabolism of carbs, proteins and fats
glucose homeostasis
metabolism and so heat production

83
Q

what substances are produced by the liver?

A

urea
clotting factors
albumin

84
Q

how is the liver involved with glucose homeostasis?

A

glycogen storage
gluconeogenesis

85
Q

what can cause hepatic dysfunction?

A

porto-systemic shunt
biliary obstruction or trauma
chronic disease
acute failure
neoplasia

86
Q

what symptoms may be seen with hepatic dysfunction?

A

ascites / oedema
PUPD
anaemia
hypocalcaemia
hypoglycaemia
hypothermia
reduced clotting times
acid base disturbences
jaundice
encephalopathy

87
Q

why is liver dysfunction associated with ascites and oedema?

A

due to hypoproteineamia and hypoalbuminaemia

88
Q

what is hepatic encephalopathy?

A

a collection of neurological abnormalities which can occur due to hepatic disease

89
Q

what causes the signs of hepatic encephalopathy?

A

increased toxins (ammonia) in the blood as the liver is unable to process them properly so they build up.
these toxins then access the CNS and result in encephalopathic signs

90
Q

what are the signs of hepatic encephalopathy?

A

altered demenour
confusion (increasing in severity)
inappetance
disorientation
blindness
occassional aggressive, uncontrolled behaviour
seizures
unrousable
coma
death

91
Q

what are the stages of hepatic encephalopathy?

A

stage 1-4

92
Q

what is the aim of medical management of hepatic encephalopathy?

A

reduce ammonia levels in the blood through absorption or reduction

93
Q

what drug is often used in hepatic encephalopathy patients?

A

lactulose

94
Q

how does lactulose work?

A

transformed by colonic bacteria into organic acids
results in trapping of ammonia ions and so decrease in absorption of ammonia

95
Q

what ion contributes to hepatic encephalopathy signs?

A

ammonia

96
Q

what are liver dysfunction patients prone to under GA?

A

hypothermia
hypoglycaemia

97
Q

why are liver dysfunction patients prone to hypothermia under GA?

A

liver is massive producer of heat due to metabolism

98
Q

why are liver dysfunction patients prone to hypoglycaemia under GA?

A

liver involved in glucose homeostasis

99
Q

what are the effects of low albumin on anaesthesia?

A

reduced protein binding of drugs
oncotic pressure of blood reduced so fluids will not remain in circulation (fluid rescuss more difficult)

100
Q

what is the effect of reduced protein binding of drugs?

A

drug action longer lasting as larger free fraction
overdose effects exacerbated

101
Q

what are the effects of liver dysfunction on anaesthesia?

A

slower biotransformation of drugs
increased risk of haemorrhage due to reduction in clotting factors
electrolyte imbalances
fluid rescussitation more challenging due to reduced oncotic pressure

102
Q

how should hepatic patient’s be managed for GA?

A

stabilisation
cautious and minimal premedication
slow induction with lowest possible dose
analgesia
avoid NSAIDs
maintain temp
monitor glucose
be aware of coagulopathies

103
Q

why should NSAIDs be avoided in hepatic patients?

A

coagulation issues
hepatic and renal excretion (extra work for kidneys)

104
Q

what are the main nursing care points for patients with coagulopathies?

A

care with venepuncture (no jugular sticks)
pressure applied well after samples or IVC removal
avoid rough handling
avoid trauma (e.g. excitable recovery)

105
Q

what pre-anaesthetic blood may be needed for hepatic patients?

A

liver enzymes
bile acids
clotting times
urea
plasma proteins
glucose

106
Q

what is an insulinoma a tumour of?

A

pancreatic islet cells

107
Q

what are the main indications for insulinoma?

A

hypoglycaemia

108
Q

why do insulinomas make patients hypoglycaemic?

A

over production of insulin

109
Q

how can insulinoma be treated?

A

medical - preds, glucose, diazoxide
surgery to remove - may include partial pancreatectomy

110
Q

what should be monitored for following insulinoma removal?

A

pancreatitis
pain
hyperglycaemia or hypoglycaemia - regular BG

111
Q

what additional technique may be used during insulinoma surgery to facilitate removal?

A

NMBA

112
Q

how should diabetic patients be managed when having surgery?

A

stabilise for GA whenever possible
find out routine and try to stick to it
first patient of the day and then home ASAP
monitor glucose
feed as soon as possible in recovery and give insulin

113
Q

what complications can be seen with diabetic patients?

A

hyperglycaemia
dehydration
weight loss
fatty liver
ketoacidosis

114
Q

how may diabetics be managed in terms of starvation times?

A

half meal and half insulin in the moring if vet is happy

115
Q

what drug considerations should be made for patients with diabetes?

A

short acting
good analgesia
IVFT

116
Q

what drug should be avoided for diabetic patients?

A

medetomidine

117
Q

why should medetomidine be avoided in diabetic patients?

A

hyperglycaemia is a risk

118
Q

why may a second IVC be useful in diabetic patients?

A

glucose monitoring

119
Q

in what cats is hyperthyroidism often seen?

A

elderly

120
Q

what are the main presenting signs of hyperthyroidism?

A

highly strung
thin
PUPD
muscle weakness

121
Q

why is muscle weakness of note when anaesthetising a patient?

A

may need ventilation if unable to breathe adequately themselves

122
Q

what is often seen alongside hyperthyroidism?

A

hypertrophic cardiomyopathy

123
Q

how should hyperthyroid cats be managed pre GA?

A

avoid stress
IV induction where possible
ECG
IVFT

124
Q

what drugs should be avoided in hyperthyroid cats?

A

ketamine
medetomidine

125
Q

why should ketamine be avoided in hyperthyroid cats?

A

increases myocardial workload and increases HR

126
Q

why should medetomidine be avoided in hyperthyroid cats?

A

drops CO

127
Q

what may create monitoring challenges in thyroidectomy surgery?

A

access to patient due to surgical site

128
Q

what should patients be monitored for post thyroidectomy?

A

laryngeal paralysis
hypocalcaemia
BP changes

129
Q

what must remain patent at all times in hyperthyroid cats?

A

IVC

130
Q

in what patients is hypothyroidism often seen?

A

elderly dogs

131
Q

what concurrent condition may be seen in many patients with hypothyroidism?

A

megaoesophagus

132
Q

what are some of the anaesthetic considerations for hypothyroidism?

A

decreased GI motility
obesity may affect ventilation
lethargy
prone to bradycardia and hypotension
slow biotransformation of drugs common

133
Q

what is hyperadrenocorticism caused by?

A

pituitary or adrenal tumour leading to glucocorticoid excess
can also be iatrogenic

134
Q

what are the main anaesthetic considerations for hyperadrenocorticism patients?

A

poor muscle tone - may affect ventilation
may be overweight and lethargic
poor thermoregulation
high risk of bruising
risk of PE
PUPD
higher risk of wound infection
may be on medical management

135
Q

why are hyperadrenocorticism patients at risk of PE?

A

hypercoagulability

136
Q

why are hyperadrenocorticism patients at higher risk of wound infections?

A

due to increased glucocorticoids

137
Q

what is the main consideration of patients with hypoadrenocorticism?

A

avoid stress
unable to mount normal stress response
need stabilisation pre GA

138
Q

what electrolyte imbalances are commonly seen with hyperadrenocorticism patients?

A

Na retention
K excretion

139
Q

what electrolyte imbalances are commonly seen with hypoadrenocorticism patients?

A

hyperkalaemia

140
Q

what are the main signs of hypoadrenocorticism?

A

bradycardia
dehydration
weight loss
weakness
lethargy
non-specific

141
Q

what are the main types of renal disease seen?

A

AKI
CKD
urinary tract obstruction or rupture (bladder, ureter or urethra)

142
Q

what are the main effects of kidney disease which can affect anaesthesia?

A

hypoproteinaemia
uraemia
metabolic acidosis
hyperkalaemia
anaemia

143
Q

how does hypoproteinaemia affect anaesthesia?

A

increased free fraction of drug so more to take effect
decreased oncotic pressure to hold fluids in intravascular space

144
Q

how does uraemia affect anaesthesia?

A

CNS depression

145
Q

how does metabolic acidosis affect anaesthesia?

A

decreased renal excretion of drugs
myocardial dysfunction

146
Q

how does potassium disturbance affect anaesthesia?

A

potentially life threatening
may be high or low in kidney patients

147
Q

what can happen to potassium levels in acute kidney injury?

A

increase rapidly as excretion stopped

148
Q

what can happen to potassium levels in CKD?

A

low due to continual potassium leakage

149
Q

how does anaemia affect anaesthesia?

A

potential for reduced O2 carrying capacity

150
Q

what should be done before anesthesia of renal patients?

A

pre op bloods to check current function
IVFT pre op?
full clinical exam

151
Q

why may pre op fluids be helpful for renal patients?

A

maintain circulating volume and hydration to support kidneys

152
Q

what drugs should be used for renal patients?

A

minimal CV, BP and renal effects

153
Q

what are the main effects on GA of renal disease?

A

decreased GFR
ADH release
aldosterone activation
effect on prostaglandins

154
Q
A