Vascular Surgery and Critical Limb Ischemia
The vascular domain tests the ischaemic limb, the carotid bifurcation and the aortic aneurysm. Marks hinge on classification, the six Ps, and the time window for revascularisation.
Chronic limb-threatening ischaemia
- Define by rest pain, ulceration or gangrene with objective evidence: ankle-brachial index <0.4, ankle pressure <50 mmHg, or toe pressure <30 mmHg. Rutherford and Fontaine classifications stage severity.
- Examine for absent pulses, Buerger's test and dependent rubor; duplex first, then CTA or MRA.
- Treatment: risk factor control, antiplatelet, statin, supervised exercise, then revascularisation by angioplasty or bypass according to anatomy. Autologous vein gives the best below-knee bypass patency.
Acute limb ischaemia
- Six Ps: pain, pallor, pulselessness, paraesthesia, paralysis, perishing cold. Rutherford acute categories I (viable) to III (irreversible).
- Embolus: sudden onset, atrial fibrillation, normal contralateral pulses. Thrombosis: background claudication and diseased vessels.
- Heparin immediately; embolectomy for embolism, bypass or thrombolysis for thrombosis; fasciotomy for compartment syndrome; primary amputation if irreversible.
- Time is muscle - target revascularisation within six hours.
Aneurysm and carotid
- AAA repair when ≥5.5 cm in men or ≥5.0 cm in women, with rapid growth or symptoms. EVAR has lower 30-day mortality; open repair has fewer late reinterventions.
- Ruptured AAA: permissive hypotension, avoid aggressive crystalloid, operate immediately.
- Carotid stenosis: symptomatic 70-99% needs endarterectomy within two weeks; 50-69% consider in men; below 50% medical therapy. NASCET stenosis = (1 − narrowest lumen/distal normal lumen) × 100.
- After endarterectomy watch for haematoma and airway compromise; cranial nerve injury causes tongue deviation or hoarseness.
Worked example
A 70-year-old with atrial fibrillation has a three-hour history of a cold, painful left leg, no pulses below the femoral, paraesthesia but no paralysis. Reasoning: Rutherford IIa, probably embolic. Start heparin, do not delay for angiography when the diagnosis is clinical, perform femoral embolectomy, then watch for reperfusion injury and compartment syndrome and investigate the cardiac source.
Traps
- Missing threatened acute ischaemia because a Doppler signal is still present.
- Delaying heparin to obtain angiography.
- Forgetting a saddle embolus at the aortic bifurcation, which gives bilateral symptoms.
- Comparing carotid stenoses measured by ECST and NASCET methods; they are not interchangeable.