1
Q
What is a AAA
A
- Localised dilation of the abdominal aorta >3cm
2
Q
When is elective repair of AAA indicated
A
- > 5.5cm
- rapid expansion - >1cm / yr
- symptomatic AAA
3
Q
Describe the pathophysiology of AAA
A
- Loss of elastic fibres and smooth muscle in artery wall over time
- High pressure causes weakening and outpouching
- Main cause is atherosclerosis but can also be caused by other things e.g. Marfan’s / TB
4
Q
What are the risk factors for developing a AAA
A
- Non mod = male, FHx, age > 65
- Mod = smoking, hyperlipidaemia , HTN, PVD
5
Q
What are the options for AAA repair
A
- Endovascular aneurysmal repair
- Open surgical repair
6
Q
What are the pros and cons of each method of AAA repair
A
7
Q
Which type of AAA is EVAR most appropriate for
A
- infrarenal aneurysms – more straightforward so less operating time so EVAR /local anaesthetic more tolerable
8
Q
Describe the process of an EVAR
A
- Performed by interventional cardiology and vascular surgeons
- Femoral artery exposed, angiogram performed to identify region of aneurysm
- Stent applied across this region
- The stent prevents blood flowing into the aneurysmal sac. Eventually blood within this thromboses around the stent
- Additional trouser grafts can be inserted into the common iliac arteries – depends on extent of disease.
9
Q
What investigations / preparations would you make pre operatively for EVAR
A
- Standard pre op + optimise + airway
- MDT approach
- Ix – imaging, CPET, bloods, Lung function/ ECHO?
- Medications review – likely to be on many with co-morbidities – educate pt on which to cont
- Consent
10
Q
Describe the anaesthetic management of EVAR
A
- Options include
o neuraxial – epidural or CSE
o local anaesthetic
o GA - Requirements
o AABGI + Arterial line + urinary catheter + temp
o X matched
o IV heparin intra op + check ACT
o May require protamine
11
Q
How much heparin is given in EVARs? Plus target ACT
A
- 5000 units
- After femoral arteries exposed
- Target ACT 200-250
12
Q
Where do EVARs take place
A
- Specialised radiology suite or hybrid operating theatre – remote anaesthesia
13
Q
What safety precautions are taken in EVAR
A
- Both groins and full abdomen sterilised and draped in case of converting to open in emergency
- X match available
14
Q
What are the complications of an EVAR
A
early:
- bleeding - femoral, aortic rupture/ dissection
- blocked arteries - AKI, bowel, spinal cord or limb ischaemia
- embolisation and stroke
late
- endoleak
- stent migration
- graft infection
15
Q
What patient are at risk of developing AKI in EVAR
A
age > 70
CKD - eGFR < 60
pre op diuretics
cardiac failure / liver disease
HTN or diabetes
pre op dehydration
16
Q
What are the surgical risk factors for AKIs associated with EVARs
A
embolisation of atheroma
bleeding and hypotension
blocked renal artery by stent
prolonged surgery + high contrast load
reperfusion injury after stent released
17
Q
How can the risk of periop AKI be reduced with EVARs
A
good hydration, maintain MAP
avoid nephrotoxins, minimise contrast
careful surgical technique to reduce embolisation risk
18
Q
How are the effects of IV contrast minimised
A
- Give a week for kidneys to recover from pre op contrast/imaging
- IV fluids before contrast
- non iodinated contrasts
- Give N acetyl cysteine
- avoid concurrent use of nephrotoxics
19
Q
What are the issues with remote anaesthesia and set up for the EVAR
A
- Unfamiliar environment
- Less equipment and support
- Less experienced staff in anaesthesia
- Limited light levels
- Less access due to C arm
20
Q
Describe the physiology of an aortic cross clamp application
A
applying clamp
- increased afterload - HTN , arrhythmias, myocardial stress
- ischaemia and vasodilation below clamp
- loss of distal venous capacitance - increased central volume - pulmonary oedema and raised ICP
- depending on location of clamp - ischaemia to kidneys, limb, spinal cord / gut
- risk of embolisation of atheroma
release clamp
- sudden drop in after load - hypotension
- release of mediators
- vasodilation - drop in BP
- hypoerkalaemia and acidosis - arrhythmias and myocardial depression
- reduced central volume - reduced preload and CO
- drop in MAP - risk of myocardial ischaemia
21
Q
What determines the physiological effects of aortic cross camp
A
- Where the aneurysm is determines where it has to be applied
- The higher up , the more physiological consequences
- If renal arteries are involved
22
Q
How are the physiological changes during cross clamping and removing managed?
A
clamping
- HTN management - deepen anaeshtetic, remi TCI, GTN IV
- good O2 delivery - sats and Hb - to myocardium
- avoid clamping where a lot of atheroma
removal
- vasopressors and ionotropes
- release one leg at a time
- adequate filling and optimise Hb before releasing clamp
- treat electrolytes and hyperventilate to remove excess CO2 - helps contractility and rhythm
23
Q
What is the purpose of heparin in open AAA repair
A
- Prevent thrombosis when cross clamp is applied
24
Q
When is heparin for open AAA and how much is given + ACT target
A
before cross clamp applied
100units/ kg
ACT 250-300
more than EVAR
25
26
How is distal perfusion during cross clamp maintained
- gott shunt - shunt between proximal and distal aorta
- partial femorofemoral bypass - from femoral vein to bypass , oxygenation, to femoral artery
- partial left heart bypass - LA cannula and to bypass machine and then to distal limbs. No oxygenation needed just pump
27
What segmental spinal artery is most significant
Artery of adamkiewicz - major supply of lumbrosacral cord
28
What is the significance of artery of adamkiewicz having variable origin
Unclear what affect cross clamp at differnt levels will have. In some people it originates lower and will lead to a more significant risk of spinal cord ischaemia
Typically T12 to L1 but can be T8- L4
29
How is spinal cord perfusion calculated ?
What value should it be ?
SCPP = MAP - CSF pressure
Should be atleast 70mmHg
30
How can spinal cord ischaemia be minimised in those having open aortic repair and clamping
- maintain MAP with adequate volume and vasopressors
- spinal drain - keep CSF pressure below 15mmHg
- clamp as low as possible to reduce risk of blocking artery of adamkiewicz / other significant segmental arteries
- minimise clamp time
- sequential clamping with neurophysiological monitoring to detect significant segmental arteries
31
What is sequential clamping with neurophysiological monitoring
- Use SSEP or MEP – somatosensory evoked potentials or motor evoked potentials
- get baseline recording
- slowly clamp differnt aortic segments and look for changes to these readings
Work out which segmental arteries are significant
32
What type of aneurysmal repairs is spinal cord ischaemia most common in
Thoracoabdominal as the clamp will be higher up
33
What is the mortality rate for a ruptured AAA
80%
34
What are the clinical features of ruptured AAA
Abdo +/- back pain
- Hypotension, tachycardia
- Syncope
- Palpable pulsatile abdo mass
35
Describe the initial management of a ruptured AAA
A to E / resuscitation – O2, MHP (1:1:1), ROTEM
- AMPLE Hx – including anticoagulant meds? Airway exam
- Consent – ITU discussion / M&M risk
- Organisation – tell theatres, ITU bed, consultant vascular surgeon and anaesthetist
o Chair reports commented on lack of mention to organisational issues in preparation
36
What is the BP target during resuscitation of a AAA
70mmHg
permissive hypotension
prevents clot disruption
37
What simple investigations can give indication of degree of blood loss in AAA
- Hypotension and tachycardia
- High lactate
- Low GCS
- Low urine output
38
How would you anaesthetise someone with a ruptured AAA
- Pre induction preparation
o X matched
o Belmont and cell savage ready
o AABGI + arterial line + catheter
o Surgeons scrubbed and ready to operate after induction
- Induction
o Fentanyl/ ketamine/ roc – small doses
- Maintenance
o ROTEM/ ABGs Lethal triad
o Manage physiology of cross clamping
- Post op
o Level 3 ITU
o Continue resuscitation / correction of coagulopathy and electrolytes
o Observe for complications
39
What are the post op complications following AAA repair
bleeding anastomoses
ischaemia - renal, bowel, limb, spinal cord
abdominal compartment syndrome
cholesterol embolisation syndrome
40
What are the risks of induction in AAA rupture
loss of abdo tone - partial tampanding of the AAA
vasodilation - already volume deplete and severe hypotension
myocardial depression
IPPV - reduces preload
overall worsening of shock
41
What are the surgical options for ruptured AAA repair
- open
* EVAR - under local and more haem stable
IMPROVE study - Local anaesthetic subgroups for ruptured AAA repair had lower mortality rates
42
What is the role of local anaesthetic in ruptured AAA management
EVAR under local - not suitable for unilateral grafts
local anaesthetic to balloon tamponade and control bleed whilst waiting for open. once CVS stability improves can GA and open
43
Which type of grafts can local anaesthetic be used for and not
- LA = bifurcated endograft
- Can’t use for unilateral grafts as these require femoral-femoral cross over. Groin to groin dissection is not well tolerated under local
44
What are the reasons a local anaesthetic technique may not be feasible in AAA repair
- Back / abdo pain too severe to tolerate procedure
- Agitation from cerebral hypoperfusion – movement / non cooperative
- Unilateral iliac graft and need for femoral femoral cross over
- Expanding retroperitoneal haematoma may cause respiratory compromise – needs intubating
45
List 3 reasons for ongoing bleeding intra operatively
- Insidious bleeding from groin entry site
- Failure to correct coagulopathy
- Type 1 endo leak – failed seal of stent to vessel wall so ongoing bleed around stent
- Endovascular injury during guidewire / stent manipulation
46
Describe the different types of endoleak
47
What are the causes of renal impairment following ruptured AAA
hypovolaemia / blood loss
embolisation of atheroma
clamping supra renal
renal artery truama intra op
abdominal compartment syndrome
48
How is renal injury in AAA rupture prevented?
- Maintain adequate perfusion – volume resuscitation + pressors
- Avoid nephrotoxins
- Daily U&Es
- High suspicion of abdominal compartment syndrome
49
How is ruptured AAA linked to anterior spinal cord syndrome
- Reduced perfusion of spinal cord from hypotension due to blood loss
- Disruption of segmental spinal arteries – artery of adamkiewicz
50
What is a carotid endarterectomy
- Vascular surgical procedure to remove atheromatous plaques from the carotid artery to reduce the risk of stroke
51
What are the indications for carotid endarterectomy
carotid artery stenosis >50% + TIA / stroke
- referred within 24 hrs of symptoms
- proceedure within 2 week s
52
classification of carotid stenosis?
70-99- severe
50-69 - moderate
53
How does atherosclerosis of carotid contribute to stroke
- Thrombosis of carotid – occlusion and collateral circulation isn’t adequate enough
- Embolization of carotid plaque into cerebral circulation
54
Describe the surgical approach to carotid endartectomy
expose carotid - take care with IJV / EJV and nerves (hypoglossal, ansa cervicalis, vagus)
cross clamp above and below - heparin just before
can use shunt at this point - depends on ipsilateral flow and if pt asleep / awake
verticle incision, remove atheroma
use bovine patch to close (can also use primary closure)
55
What are the complications of carotid endartectomy
stroke
- hypoperfusion/ embolisation of atheroma / bleeding from HTN
- structures - vagus, ansa cervicalis, hypoglossal nerve, recurrent/ superior laryngeal. neck haematoma
- cerebral hyperperfusion syndrome
- high risk of periop MI
- infection
intra op - haemodynamic changes from clamping and carotid baroreceptors / vagus nerve
56
When is a shunt used in carotid endartectomy
- Known poor collateral supply
- GA – cant assess neurology
- Some surgeons just routinely use them
57
What are the complications of using a shunt
- Bubble embolization
- Thrombosis
- Arterial wall dissection
58
Why is a patch used to close the artery ?
- Reduces risk of re-stenosis
59
What are the anaesthetic options for carotid endartectomy?
- GA
- Local / regional =
o Local anaesthetic infiltration
o Superficial + deep cervical plexus block
o Cervical epidural – rare in UK
60
What are the advantages and disadvantages of GA for carotid endartectomy repair
- Pros
o No movement / agitation/ distress
o Controlled ventilation ? neuroprotection
o Reduced stress response
- Cons
o No way to monitor neurology - increased need for shunt and issues associated with this
o Intra op hypotension from GA
o Delayed recovery – post op neurology
o Risks of airway management
61
What are the advantages and disadvantages of using a local technique for carotid endartectomy
- Pros
o Real time neurological monitoring – less need for shunt
o Less haemodynamic instability
o Less airway risks
o Quicker post op recovery and neurological monitoring
o Reduced hospital stays
o Surgical closure at normal BP – reduces post op haematoma risk
- Cons
o Movement / agitation / pain
o Stress response increased from pain / anxiety – risk of myocardial ischaemia
o LA risks
o Risks of local technique – nerve damage/ subarachnoid injection
o May need sedation – risks e.g. loss of airway
62
What did the GALA trial find
- outcome almost identical for GA and LA for carotid endartectomies
- However more recent meta analysis found local has lower haematoma incidence.
63
What are the methods for monitoring the adequacy of cerebral perfusion under GA ?
- Carotid artery stump pressure
- Transcranial doppler USS – use middle cerebral artery
- Near infra red spectroscopy
- EEG
- Jugular venous O2 sats
64
What is cerebral hyperperfusion syndrome
- Dysregulated cerebral blood flow due to sudden increase in carotid artery flow after carotid endarterectomy
- Presents as = severe ipsilateral heacache, focal neurology (hemiplegia, hemianopia, neglect) , seizures
- Accompanied by post op HTN in almost all patients
- Can present up to 1 month after but usually in first 5 days
65
What are the risk factors for developing cerebral hyperperfusion syndrome?
HTN
high grade stenosis
contralateral stenosis
recent contralateral endartectomy
66
What are the reasons for haemodynamic instability during carotid endarterectomy
- Anaesthetic related
o GA – reduced SVR / myocardial depression
o LA – LAST, pain/stress of being awake
- Surgical related
o Bleeding
o Carotid baroreceptors - brady / hypo
o Vagal nerve handling – bradycardia and hypotension
o Cross clamping – HTN (sympathetic response) on clamping and hypotension on release
- Patient factors
o CVS comorbidities
o Strong vagal response
67
How can perioperative stroke risk in patients be minimised?
- Embolic (biggest risk)
o Avoid shunts where possible
o Careful surgical techniq to avoid dislodgment of atheroma or air embolism with shunt
o Perioperative antiplatelet – DAPT
o Heparin before cross clamping
- Ischaemic
o Use of shunt if collateral circulation is inadequate
o Pharmacological management of intra op hypotension
- Haemorrhagic
o Pharmacological management of perioperative HTN
68
Differentials for post op confusion after carotid endartectomy
- Stroke / TIA
- Cerebral hyperperfusion syndrome
- Post op cognitive dysfunction / delirium
- Other non neurological
o Hypoxia – airway compression from haematoma
o Metabolic disturbance – AKI
o Opioid use
FINAL
flashcards
Decks in class (20)
# Cards
-
final SOE - last 2 weeks1012
-
High yield747
-
OBSTETRICS351
-
CRITICAL INCIDENCE139
-
ITU486
-
NEUROLOGY350
-
CRQ / MCQs201
-
OPTHALMIC ANAESTHESIA87
-
physics118
-
ANATOMY & REGIONAL437
-
PAEDS308
-
PERIOPERATIVE MED367
-
MISC & OTHER217
-
CARDIO389
-
Airway / H&N278
-
NAP studies64
-
general167
-
trauma186
-
THORACIC SURGERY and OLV76
-
Vascular68
