Abdominal Aortic Aneurysm Flashcards
How do arterial aneurysms develop?
- proteolytic degradation
increase in proteolytic enzymes compared to inhibitors
increased activity + expression of MMPs
elastin not synthesised - inflammatory response - cytokine activation of proteins
- biochemical stress - atherosclerosis - intimal layer
- genetics - upregulation of genes coding for ECM degradation
Describe the dimensions of the aorta and places where it commonly forms an aneurysm
average diameter = 28mm thoracic –> 20mm infrarenal
an aorta >3cm = moderate aneurysmal
severe if >5cm
>1.8cm iliac artery = aneurysmal
most begin below renal arteries and before bifurcation of iliac
How can aneurysms be classified?
morphology - saccular or fusiform
true or false
location
size
What is the difference between true and false aneurysms?
TRUE =
involvement of all 3 layers (intima + media + adventitia)
eg atherosclerotic, syphilitic, congenital, ventricular (following an MI)
FALSE =
collection of blood leaking out of artery or vein
blood is confined around the vessel by surrounding tissue
eg from trauma, percutaneous surgery, injections
What does an aneurysm look like histologically?
lymphocyte and macrophage infiltration
media thinning
marked loss of elastin
What are the S&S of an aortic aneurysm?
usually asymptomatic unless there is gross expansion or rupture
Expanding AAA back/flank/abdo/groin pain early satiety nausea vomiting urinary symptoms venous thrombosis fever embolic phenomena (affects toes) pulsatile mass syncope
Ruptured AAA central abdo/back pain groin pain syncope paralysis flank mass pulsatile mass shock
What are the indications for surgical intervention with AA disease?
ruptured
symptomatic
asymptomatic + >5.5cm
asymptomatic + >4cm + increased by 1cm within a year
Hows does AAA cause groin pain?
retroperitoneal space invaded
pressure on L/R femoral nerve
refers pain down to the groin
List some DDx for AAA
Skin/soft tissue - sebaceous cysts, sarcoma, lipoma, hernia
GIT - hepatomegaly, carcinoma of stomach/pancreas
Vascular - AAA, retroperitoneal lymphadenopathy
acute abdo, acute pancreatitis, perforation, renal or biliary colic, inferior MI
What are some of the RF for AAA?
M>F >65yrs peripheral vascular disease smoking COPD previous aneurysm CAD hypertension first-degree relative connective tissue disease - Marfan's, Ehlers-Danlos
What are some of the RF for a ruptured AAA?
hypertension elevated peak aortic wall stress cardiac/renal transplant tobacco rapid expansion baseline line aortic diameter decreased FEV1 F>M
What investigations can be used to diagnose AAA?
examination + history
Lab - FBC, U&Es, LFTS + diff to assess transfusion requirements or infection
Imaging
USS - 100% sensitive and 96% specific
AXR - high false negative
CT - 100% sensitive + more accurate in defining extent and morphology of disease
MRI + gadolinium - better imaging but not suitable for unstable patients
Angiography - may miss AAA if laminated thrombus means lack of calcification –> lumen will appear normal
useful for endovascular repair
What are the mortality figures of elective aortic repair vs emergency repair?
elective
4% risk of death after open-surgery
1% risk after endovascular repair
emergency
40-50% risk after open-surgery
Who would benefit more from an endovascular stent rather than elective surgery?
patients with: severe COPD severe cardiac disease active infection medical problems which preclude operative intervention
How are AAA monitored?
with USS
every 3 months if AAA 4.5-5.4cm
every 2 years if AAA 3.0-4.4cm
Describe open surgical repair of an AAA
midline abdominal or retroperitoneal incision
the aneurysm is opened
replacement of diseased section with a tube or bifurcated prosthetic graft
excludes aneurysm and prevents sac growth
choice of tube graft, bifurcation graft or aortofemoral bypass
Describe EVAR for an AAA
= endovascular aneurysm repair
iliofemoral access
requires infrarenal aortic neck of adequate length, angulation and diameter
endograft = polyester/gore-tex stent with exoskeleton
place it within the lumen of AAA extending down into iliac arteries
deployment of trunk + ipsilateral limb
catheterisation of the contralateral limb
completion
What are the advantages and disadvantages of open surgery and EVAR? What risk must surgeons be aware of at the aortic bifurcation?
Open
Good - problem solved, abdomen explored for other abnormalities, bowels kept warm, better for men <70yrs
Bad - significant incision, 30-90mins cross-clamp, many patients are considered unfit
EVAR
Good - more beneficial than open in the repair of ruptured AAA, only small incision made on the aorta, especially women and men >70yrs
Bad - strict requirements on vessel size to work, complications and re-interventions eg endoleak, stent migration
Risk - ED if autonomic nerves across bifurcation, particularly L side, are damaged
How do you manage AAA?
smoking cessation secondary prevention CV RFs control diabetes control cholesterol control BP anti-platelets eg warfarin or LMWH anti-oxidants and vitamins
Describe the major complications of arterial surgery and how you’d prevent them
MI - cardiac investigation and beta-blockers
Transfusion complications - autologous transfusion techniquest
Infection - prophylactic abx
hypothermia - recirculating warm forced-air blanket (bear hug)
Describe some complications of AAA
Death pneumonia MI Groin/graft infection colon ischaemia renal failure (preoperative creatinine level, intraoperative cholesterol embolisation, hypotension) bowel obstruction incisional hernia
Describe the potential complications of AA surgery
fluid shifts - monitor haemodynamic stability, bleeding, UO, peripheral pulses
Infection - prophylactic abx for first 24hrs
Endoleaks - EVAR - due to pressure on the sac
Cardiac - 0-2 days post-op, HCT >28, control tachycardia
Distal embolisation - look for cyanosis and peripheral pulses
Haemorrhage - ore-op assessment with CT
Renal failure - predicted pre-op
Colon ischaemia
Impaired sexual function - 1/3rd not recovered by 3 years
Late complications - graft infection etc
How might a patient present with a ruptured AAA?
Back pain +/- abdo pain
hypotension
pulsatile abdo mass
How might a patient present with a ruptured thoracic aorta?
increased BP in upper limbs
decreased BP in lower limbs
widened mediastinum on radiography
Describe the emergency management of a patient presenting with a ruptured arterial aneurysm
A - airway
B - breathing
C - HR, BP, Hb, ECG, Bloods for amylase, crossmatch blood for transfusions
D - glucose, GCS
2 IV wide bore cannulae –> aim maintain Hb 70-90 and SBP <100mmHg (to avoid rupturing contained leak)
Prophylactic abx - cefuroxime 1.5g + metronidazole 500mg IV
Surgery - clamp aorta above leak + insert Dacron graft
