Peripheral Vascular Disease III - Abdominal Aortic Aneurysm (AAA) Flashcards
what is an aneurysm?
dilation of a vessel by more and 50% of its normal diameter
what is the normal aortic diameter?
1.2-2.0cm
what are the 2 types of aneurysm?
1) true aneurysm
2) false aneurysm
in true aneurysm, describe the vessel wall?
= the vessel wall is intact (all 3 layers)
in false aneurysm, describe the vessel wall?
= there is a breach in the vessel wall (surrounding structures act as vessel wall)
what are the 3 shapes of an aneurysm?
1) saccular
2) fusiform
3) mycotic
how do mycotic aneurysms arise?
- arises secondary to an infectious process, involving all 3 layers of the artery
related to pathogenesis, what happens in abdominal aortic aneurysm?
= medial degeneration
what happens in medial degeneration?
- regulation of elastin/collagen in aortic wall
- aneurysmal dialtion
- increase in aortic wall stress
- progressive dilation
who is at the greatest risk of developing abdominal aortic aneurysm?
1) increases with age
2) make gender
3) smoking
4) hypertension
5) diabetes
6) raised cholesterol
what commonly happens in people with AAA?
popliteal aneurysms
what do the majority of AAA present with?
people who present with this, what are they at risk or?
asymptomatic
Risk of = rupture
if people with AAA present with symptoms, what are they?
In people who present with symptoms, what can you exclude?
1) pain
- can mimic renal colic
2) trashing
= bits of plaque break off and travel through aorta
3) rupture
You can exclude rupture.
what sort of pain is AAA rupture?
sudden onset of epigastric, central pain.
- may radiate through back
what may rupture of AAA mimic?
mimic renal colic
what does rupture of AAA result in?
collapse
on examination, what might you find in a patient with ruptured AAA?
- may look well
- hypo/hypertension
- pulsatile, expansile mass +/- tender
- transmitter pulse
- peripheral pulses
what are the 2 types of rupture?
1) retroperitoneal, contained rupture
2) free intra-peritoneal rupture = fatal
how can you image AAA?
- duplex ultrasound
= asymptomatic/surveillance
in the duplex ultrasound, what are you looking at?
AP diameter and involvement of iliac arteries
= it only tells you there is an AAA or not and its AP diameter
what other imaging can you do for AAA?
CT scan
what are you looking at in a CT scan?
= arterial phase
- IV contrast
- commence when contrast is in arterial system
what is the only imaging method to identify ruptured AAA?
CT scan
what are the 2 ways of managing an AAA?
1) open repair
2) endo-vascular aneurysm repair (EVAR)
to repair an AAA, what 4 things can open repair involve?
1) laparotomy
2) clamp aorta + iliac
3) Dacron graft
4) tube vs bifurcated graft
what is the other way of managing an AAA?
endo-vascular aneurysm repair
what happens in endo-vascular aneurysm repair?
- exclude AAA from inside the vessel
- inserted via peripheral artery
- X-ray guided
- modular components
what are the 3 types of acute limb threat?
1) acute limb iscahemia
2) acute or chronic limb iscahemia
3) diabetic foot sepsis
what is acute limb ischaemia?
sudden loss of blood supply to a limb
what causes acute limb ischaemia?
= occlusion of native artery or bypass graft
what causes sudden occlusion in acute limb ischaemia?
1) embolism
2) athero-embolism
3) arterial dissection
4) trauma
5) extrinsic compression
what are the 6 features of acute limb ischaemia?
What 2 important features are important to gather in a history for people at risk of acute limb ischaemia?
1) pain (due to lack of blood supply to nerves)
2) pallor
3) pulseless
4) perishingly cold
5) paraesthesia = pins & needles/altered sensation
6) paralysis
- no prior history of claudication
- known cause for embolism
describe the pain suffered in acute limb iscahemia.
- severe, sudden onset, resistant to analgesia
what happens with the calf muscles in acute limb ischaemia?
- calf/muscles tenderness with tight compartment indicates muscle necrosis often irreversible iscahemia
describe the pallor of the limb involved in acute limb ischaemia.
Initially
= limb white with empty veins
Later
= capillaries fill with stagnated de-oxygenated blood giving a mottled appearance
- Arteries distal to occlusion fill with propagated thrombus with rupture of capillaries
is blanching mottling salvageable?
is non-blachnig mottling reversible?
yes - if prompt re-vascualrisation
no - it is irreversible ischaemia
why does paraesthesia/parlysis occur in acute limb ischaemia?
- sensorimotor deficit are indicative of muscle & nerve ischaemia
what time feature is acute limb iscahemia salvable?
0-4hours
- white foot
- painful
- sensorimotor deficit
what time feature is acute limb iscahemia partially reversible?
4-12hours
- mottled
- blanches on pressure
what time feature is acute limb iscahemia non-salvageable?
> 12hours
- fixed mottling
- non-blanching
- compartments render/red
- paralysis
how do you manage acute limb ischaemia?
1) ABC – resuscitate and investigate
2) FBC, U/Es, CK, Coag +/- Troponin
3) ECG – MI, dysrhythmia
4) CXR – underlying malignancy
5) anti-coagulants
= stops propagation of thrombus
- may improve perfusion
6) arterial imaging
if limb is salvageable, what do you do?
= embolectomy +/- fascioteomies +/- thrombolysis
what 3 things does diabetic foot sepsis encompass?
1) diabetic neuropathy
2) peripheral vascular disease
3) infection
what does this triad in diabetic foot sepsis lead to?
- tissue ulceration
- necrosis
- gangrene
what causes diabetic foot sepsis?
- simple puncture wound
- infection from nail plate or inter-digital space
- from neuro-iscahemic ulcer (occurs on areas of increased pressure)
why is diabetic foot sepsis a problem?
= within the foot the intrinsic muscles of digits are confine within rigid compartments
- bounded by planter fascia, metatarsal bones and interosseous fascia
- infection tracks in soft tissues into this rigid compartment
what happens if the build up of pus cannot escape?
- pressure builds up in rigid compartment leading to impairment of capillary blood flow & further iscahemia & further tissue damage
= can rapidly progress to sepsis & limb loss
what 5 systemic things happen as a result of diabetic foot sepsis?
- pyrexia
- tachycardia
- tachypnoeic
- confused
- kussmauls breathing
what 7 local features happens as a result of diabetic foot sepsis?
- swollen affected foot
- swollen forefoot
- tenderness
- ulcer with pus extruding
- erythema, may track up limb
- patches of developing necrosis
- crepitus in soft tissue of foot
- pedal pulse may or may not be present
how would you manage diabetic foot sepsis?
1) antibiotics
- gram +ve cocci (S. aureus + streptococcus sp)
- gram -ve bacilli (E. coli, klebsiella sp, enterobacter, proteus sp and pseudomonas sp.)
- anaerobes (bacteroides)
2) rapid surgical debridement of infected tissue
3) remove all infected tissue
4) wound open to encourage drainage
