JC02 (Surgery) - Peripheral Vascular Ischaemia and Acute vascular emergencies Flashcards
Risk factors for chronic limb ischaemia (5)
□ Smoking**
□ DM
□ Hyperlipidaemia
□ Pre-existing arterial disease: coronary artery disease, stroke/TIA, carotid disease
□ Family history of vascular disease
Typical presentation of non-critical limb ischaemia?
Non-critical ischaemia:
→ Asymptomatic
→ Intermittent claudication:
- Reproducible discomfort of a defined group of muscles
- Induced by exercise and relieved by rest
Typical presentation of critical limb ischaemia?
→ Rest pain: continuous, severe unremitting pain at toes or forefoot
→ Tissue loss: ulcers or gangrene at pressure areas
Describe arterial ulcer:
- Symptom
- Site
- Size
- Edge
- Base
- Discharge
- Depth
□ Symptom: rest pain ± inciting episode of trauma □ Site: over pressure areas □ Size/shape: variable size, often elliptical □ Edge: punched out (if non-healing) or sloping (if healing) □ Base: pale, dry □ Depth: typically very deep ± exposure of bone, ligament, tendon □ Discharge: thin clear serous exudate
Describe dry gangrene:
- Description
- Cause
- Line of demarcation
- Management
→ Hard, dry, dark, crinkled mass
→ Distinct line of demarcation
→ auto-amputate
Describe wet gangrene:
- Description
- Cause
- Line of demarcation
- Management
→ Moist, swollen, often blistered, with discharge
→ Infection spreads proximally, line of demarcation spreads
→ Emergency debridement or amputation to avoid spreading gangrene and sepsis
4 major causes of chronic limb ischemia
□ Atherosclerosis: most common
□ Vasculitis, eg. takayasu arteritis, Behcet’s disease
□ Buerger’s disease (thromboangiitis obliterans)
□ Entrapment syndrome (e.g. Popliteal artery entrapment syndrome (PAES) - abnormally positioned or enlarged calf muscle presses on popliteal artery)
Assessment for entrapment syndrome which may cause chronic limb ischaemia
- test for ↓pulse with foot in passive dorsiflexion or active plantarflexion
- exercise test (i.e. post-exercise ABI)
4 major sites of arterial occlusion in lower limbs
Aortoiliac
Iliac
Femoro-popliteal
Distal
Signs and symptoms for aortoiliac arterial occlusion
Claudication in bilateral buttocks, thighs, calves
Usually no rest pain (unless concomitant distal disease)
Impotence in LeRiche’s syndrome (caused by occlusion at terminal bifurcation of aorta. It is characterized by the tetrad of buttock: claudication, impotence (M), absent femoral pulse and ± aortoiliac bruit.)
Signs and symptoms for iliac arterial occlusion
Claudication in unilateral thigh and calf ± buttocks
Signs and symptoms for Femoro-popliteal arterial occlusion
Claudication in unilateral calf
Rest pain if critical
Tissue loss
Signs and symptoms for Distal Lower limb arterial occlusion
Tissue loss
Outline assessments/ tests for lower limb ischaemia
- Ankle‐Brachial Index (ABI) and exercise testing
- Duplex Ultrasound
- Arteriography (planning for surgery, not for Dx)
Formula for Ankle‐Brachial Index (ABI)
Typical ABI ranges for arterial occlusion
ABI = ipsilateral ankle systolic BP/ higher arm systolic BP
Normal = 0.90 – 1.30
Arterial occlusive disease = ≤0.9 (diagnostic)
0.40 – 0.90 = moderate - claudication
<0.4 = severe - rest pain, tissue loss
Indication for exercise testing for arterial occlusion
ABI normal (0.9-1.3) but symptomatic for arterial occlusion e.g. claudication
Normal waveforms in arterial blood flow in lower limb on Doppler ultrasound
□ Triphasic (normal): forward flow (systole)
+ reverse then forward flow (diastole)
□ Biphasic: forward flow (systole) + reverse flow (diastole) → single-level arterial occlusion
□ Monophasic: forward flow alone → multi-level occlusion
3 modalities of arteriography?
□ Conventional angiography: gold-standard for planning intervention (invasive)
□ CT angiography: initial imaging of choice (non-invasive)
□ MR angiography: non-contrast alternative
Management of intermittent claudication? (5)
Improve survival:
□ Risk factor modification: smoking cessation, DM control, HTN control, lipid control
□ Lifelong antiplatelets: aspirin and/or clopidogrel
Improve symptoms:
□ Supervised exercise training
□ Drugs - platelet-aggregation inhibitors : cilostazol, naftidrofuryl, pentoxifylline
□ Endovascular surgery
Main indications for surgical management of chronic limb ischaemia?
□ Treating disabling claudication in non-critical ischaemia after refractory to conservative treatment
□ Limb salvage in critical ischaemia
4 choices for surgical management of chronic limb ischaemia?
□ Balloon angioplasty + stenting
□ Arterial bypass
□ Endarterectomy
□ Amputation
5 considerations for surgical management of chronic limb ischaemia?
□ Treat inflow before outflow disease, i.e. treat aortoiliac disease first
□ Consider length and degree of occlusion: short stenosis are better treated by endovascular Tx
□ Consider availability of venous grafts: normal, healthy veins are required for arterial bypass
□ Consider life expectancy of pt: those with ≤2y life expectancy are unlikely to benefit
□ Consider presenting symptom of pt: prefer bypass for rest pain
Define the TASC II classification (type A,B,C,D)
TASC II classification: Based on overall success rates of treating different lesions using endovascular/surgical means
□ Type A: short and focal → endovascular therapy
□ Type B: prefer endovascular Tx
□ Type C: prefer open revascularization
□ Type D: prefer surgery as primary Tx for low-to-moderate risk patients
Types of surgical bypass surgery for aortoiliac, above knee and below knee arterial occlusion?
Aortoiliac disease:
Aortofemoral (1st choice)
Axillofemoral (high-risk)
Femorofemoral cross-over (unilateral iliac occlusion)
Above knee:
Femoropopliteal bypass
Below knee:
Femoro-anterior tibial bypass
Femoro-posterior tibial bypass
Indications for surgical amputation in chronically ischemic limb? (3)
→ Dead: non-viable ischaemia, gangrene
→ Dangerous: potential to affect other healthy tissues - Eg. wet gangrene, spreading cellulitis, crush injury, malignancy
→ Damned nuisance: severe effect on quality of life but relief impossible - Eg. severe intractable rest pain, paralysis, contractures
Explain why revascularization is required before amputation of ischemic limb? (2)
→ If proximal blood supply is poor, amputation wound cannot heal
→ Potentially convert a safe dry gangrene into an open wound, prone to infection!
(Revascularization does not apply for major amputation (no point for revascularization as limb cannot be salvaged))
Difference between below knee and above knee amputation?
→ Below knee (BKA): better mobility but poor healing (poor knee collaterals): usually need a flap along popliteal fossa (better blood supply)
→ Above knee (AKA): poorer mobility but better healing
Define Buerger’s disease, 2 risk factors and 3 clinical manifestations?
Buerger’s disease: recurrent progressive inflammation of small/medium vessels of hands and feet
Risk factors/epidemiology:
□ Age/gender: usually young (30-40s) male
□ Smokers
S/S: □ Arterial occlusive disease: rest pain, digital ulcers, gangrene □ Superficial thrombophlebitis □ Raynaud’s phenomenon
Define acute limb ischaemia
sudden decrease in limb perfusion that threatens viability of limb
presenting within 2 weeks of acute event
4 major causes of acute limb ischaemia?
Arterial embolism: commonest cause (60-80%)
Acute thrombosis: thrombosis of a previously stenotic but patent vessel
Arterial trauma
Arterial dissection: false lumen compress onto the true lumen
Symptoms and signs of acute limb ischaemia
Clinical presentation (6Ps): 3 symptoms: → Pain: sudden onset, severe → Paraesthesia and numbness → Paralysis: poor prognostic sign 3 signs: → Pallor and colour changes: → Pulselessness → Perishingly cold
Define progressive changes in pain after onset of acute arterial ischaemia?
- Begins distally and progresses proximally with ↑ severity with time
- Gradually ↓pain as nerve endings die off from ischaemia
Describe progressive changes in skin color of acute ischaemic limb?
0-6h: white, neurosensory deficits → reversible
6-12h: mottled (vasodilatation) that blanches → partially reversible
> 12h: fixed, non-blanchable blue staining (due to thrombosed + ruptured capillaries) → irreversible
Name of classification for acute limb ischemia severity
Rutherford (SVS/ISCVS) classification
Viable (I)
Marginally threatened (IIa)
Immediately threatened (IIb)
Non-viable (III)
Outline 5 metrics to differentiate embolic vs thrombotic cause of acute limb ischaemia
Cause:
- Embolic: AF, AAA, recent MI, VHD
- Thrombotic: Usually none
Previous claudication
- Embolic: None
- Thrombotic: Present
History:
- Embolic: acute onset (sec/min) of symptoms, complete occlusion, multiple sites
- Thrombotic: Subacute onset (hours/ days), incomplete occlusion, single site
P/E:
- Embolic: Contralateral pulse present, Limb usually white (complete occlusion)
- Thrombotic: Contralateral pulse absent, Limb usually dusky (incomplete occlusion)
Compare typical angiography findings for embolic vs thrombotic arterial occlusion.
Embolic: Minimal atherosclerosis, Sharp cut-off with few collaterals
Thrombotic: Diffuse atherosclerosis, Irregular cut-off with well-developed collaterals
Imaging modalities for acute limb ischaemia?
- Doppler US: viability and level of obstruction
- Urgent CTA/conventional angiogram - if viable or marginally threatened
- On-table angiogram if immediately threatened
Surgical management options for acute limb ischaemia? (2)
embolectomy
intra-arterial thrombolysis ± angioplasty
Indications for embolectomy and IA thrombolysis ± angioplasty for acute limb ischaemia
Embolectomy:
- Immediately threatened (class IIb): thrombolysis is usually too slow
- Proximal thrombus: more accessible to embolectomy
- Older thrombus (eg. from aneurysm sac) or non-thrombotic
IA thrombolysis:
- Background stenotic artery: calcific plaques may pop the embolectomy balloon
- Previous stenting/vascular anastomosis: risk of dislodging stent/rupturing vessel for embolectomy
2 major complications from delayed treatment of acute limb ischaemia
Management
Compartment syndrome: tissue edema causing pain
> emergent fasciotomy to relieve edema
Rhabdomyolysis: reperfusion refluxes lactate, enzymes from damaged muscles, causing acute renal failure, arrhythmia, ARDS
> Hydration, IV bicarbonate, Dialysis
Post-operative management of acute limb ischaemia
→ Post-op angiogram to confirm restoration of circulation
→ Warfarin to prevent further embolism
Causes of arterial embolism
- Cardiac (80%): Atrial Fibrillation (70%), LV mural thrombus in AMI (20%), prosthetic heart valves, IE
- Non-cardiac: atheroma/thrombus from atherosclerotic plaque, thrombus from aneurysm
Common sites for arterial embolisms to lodge in lower limb
bifurcation of femoral a. (commonest), trifurcation of popliteal a. (2nd), aortic bifurcation, EIA/IIA
Causes of acute thrombosis
atherosclerotic plaque (commonest),
aneurysm,
graft stenosis,
arteritides,
thrombophilia
Causes of acute arterial trauma
→ Endovascular instrumentation → AV fistula → Fractures/dislocations → Compartment syndrome → Penetrating trauma with vascular injury
