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Acute and chronic ischaemia of the limb
VASCULAR
Arteritis/vasculitis is an atypical arterial disease and presents in young patients with raised inflammatory markers. Buerger’s disease (thromboangitis obliterans) typically affects male smokers in their third or fourth decade. In scleroderma and systemic lupus erythematosis, the cutaneous manifestations may lead to the diagnosis. Takayasu’s arteritis occasionally affects the arteries of the lower limb.
Acute and chronic ischaemia of the limb Marcus Brooks Michael P Jenkins
Congenital anomalies: coarctation of the aorta may present with intermittent claudication and hypertension of the upper limb. Persistence of the embryological sciatic artery results in the failure of development of the iliofemoral arteries (rare). The popliteal artery may be damaged by entrapment or cystic adventitial disease. Entrapment occurs when the popliteal artery lies medial (not between the heads) of the gastrocnemius and is compressed by knee flexion. Cystic adventitial disease is a poorly understood pathological process in which cysts develop in the adventitia of the artery.
Incidence Intermittent claudication (the most common manifestation of limb ischaemia) affects 5–7% of the UK population. In 1995, the Vascular Surgical Society of Great Britain and Ireland estimated an incidence of critical ischaemia of the limb of 40 per 100,000 population per year. The incidence in the UK may be increasing due to an ageing population and improved survival from coronary and cerebrovascular disease.
Fibrosis: fibromuscular dysplasia presents in young adults with ‘beaded’ arterial stenoses. Retroperitoneal fibrosis or radiotherapy may damage the aorta and iliac arteries, thereby compromising inflow to the leg.
Aetiology Atherosclerosis is the primary cause of limb ischaemia in the UK. The risk factors are: • smoking • diabetes mellitus • increasing age • family history • hyperlipidaemia • hypertension • raised level of homocysteine in serum • male sex.
Trauma: blunt and penetrating trauma can lead to arterial compromise. Fractures and joint dislocations of the long bones are the most common causes. In blunt trauma, loss of limb pulses is usually due to intimal disruption or dissection (rather than transection).
Intermittent claudication Patients with intermittent claudication have adequate blood flow to supply the limb and its muscle groups at rest. Walking results in the onset of pain due to muscle ischaemia that, in more severe cases, may be associated with paraesthesiae due to the shunting of blood away from the sensory nerves.
Thrombosis/emboli: emboli occur secondary to: • atrial thrombus (atrial fibrillation or myxoma) • ventricular thrombus (post-myocardial infarction) • aneurysmal disease of the aorta, iliac or popliteal arteries. The risk of embolization is low in asymptomatic popliteal aneurysms with a diameter of <2.5 cm, but the risk also depends on the amount of thrombus present. Arterial thrombosis is associated with hypercoagulable states: • malignancy • polycythaemia • thrombocythaemia • factor V Leiden deficiency/deficiency of protein C or protein S/lupus anticoagulant.
Clinical features Patients present in the fifth, sixth or seventh decade with pain in the calf, thigh or buttock that is initiated by walking and relieved by rest. The distance walked before the onset of pain is reproducible on a flat surface and reduced on an incline. Pain confined to the calf suggests disease of the superficial femoral artery. Thigh or buttock pain suggests disease in the aortoiliac segment; Leriche’s syndrome is the association of such pain with erectile dysfunction. The main differential diagnoses are spinal claudication, venous claudication and the radicular pain of nerve root entrapment. Spinal claudication: the spinal canal narrows during extension and opens with flexion. Patients with spinal stenosis develop pain in the buttock, thigh or calf on prolonged standing that is alleviated by knee flexion. This ‘shooting’ pain is associated with paraesthesiae, weakness and heaviness of the legs. The onset of pain at rest and walking, and the need to lean forward or sit to gain relief, help to differentiate these symptoms from those of limb ischaemia.
Marcus Brooks is a Specialist Registrar in Vascular Surgery at the Regional Vascular Unit, St Mary’s Hospital, London, UK.
Venous claudication is an uncommon condition diagnosed only in active young adults with extensive occlusions of the iliofemoral deep vein. Exercise results in a ‘bursting’ sensation, generalized
Michael P Jenkins is a Consultant Vascular Surgeon at the Regional Vascular Unit, St Mary’s Hospital, London, UK.
SURGERY 22:12
331
© 2004 The Medicine Publishing Company Ltd
VASCULAR
pain and swelling of the limb. Stopping walking relieves pain slowly, and the limb must be elevated for complete relief. Associated conditions and risk factors In the assessment of the patient with intermittent claudication, symptoms of cerebrovascular disease (stroke, transient ischaemic attack, amaurosis fugax), coronary artery disease (chest pain, palpitations, exertional dyspnoea) and diabetes mellitus (polydipsia, polyuria, lethargy) must be sought. Risk factors for vascular disease must be identified. Examination The pulse and blood pressure are recorded. The legs are inspected for signs of critical ischaemia (see below) and co-existent pathology (musculoskeletal, neurological, venous). The brachial, carotid, aortic, femoral, popliteal and pedal pulses are palpated. Auscultation for bruits is performed at the carotid bifurcation, infrarenal aorta, common femoral arteries and adductor hiatus. The ankle–brachial pressure index (see below) is measured in both lower limbs.
a
Critical ischaemia of the foot. a The foot rests horizontally and is pale. The hallux is necrotic and venous guttering is seen. b The dependent limb exhibits rubor.
Critical ischaemia of the limb The European Consensus Document (1989) defined critical ischaemia of the limb as ‘persistently recurring rest pain requiring analgesia for more than two weeks, or ulceration or gangrene of the foot in the presence of an ankle systolic pressure less than 50 mmHg (or a toe pressure less than 30 mmHg in diabetic patients)’.
1
Arterial ulcers are characterized by: • a grey-white base (which may be deep and contain exposed bone, joints or tendons) • a ‘punched-out’ edge • signs of ischaemia in the surrounding skin. Common sites are the digits and areas of boney prominence.
Clinical features Patients present with pain, ulceration or gangrene. True ischaemic ‘rest pain’ is a constant and unremitting pain in the fore-foot relieved only by dependency of the limb and opioid analgesia. The onset of pain may follow a period of worsening claudication. Tissue loss and ulceration are often associated with minor trauma. The assessment of the pre-morbid mobility and living circumstances of the patient aid decision-making and rehabilitation. A history of varicose veins (see page 321), coronary artery bypass or previous arterial surgery helps determine the feasibility of using the long saphenous vein as a conduit for arterial reconstruction.
Gangrene should be termed ‘tissue-loss’ or ‘necrosis’. The necrotic tissue is insensate and may be dry and demarcated or wet with signs of infection.
Acute ‘threatened’ limb Acute onset of ischaemia in a previously normal limb is usually due to embolism. In patients with pre-existing arterial disease, a sudden deterioration (‘acute-on-chronic ischaemia’) may be due to: • acute thrombosis of a pre-existing stenosis • loss of a major collateral • occlusion of a bypass graft.
Examination The appearances of a critically ischaemic limb depend on the: • severity of ischaemia • rapidity of onset • development of collaterals • angle of elevation. Prolonged dependency may result in oedema and changes of venous stasis. The interdigital spaces and heels must be inspected. The peripheral vascular system is fully examined by: • palpation • auscultation • measurement of ankle–brachial pressure indices.
Clinical features The patient presents with sudden onset of pain at rest or rapid deterioration in claudication distance, ulcers or gangrene. A history of atrial fibrillation, intermittent claudication or critical ischaemia (or a previous bypass graft) usually confirms the diagnosis. Examination The contralateral limb must be examined; normal pulses in this limb suggest an embolic cause in the affected limb. In an acute presentation, the affected limb is: • pale • perishing cold
Pre-gangrene: the early signs of critical ischaemia are a cool, pale limb with venous guttering (Figure 1). Elevation exacerbates pallor and subsequent dependency is accompanied by ischaemic rubor (Buerger’s test).
SURGERY 22:12
b
332
© 2004 The Medicine Publishing Company Ltd
VASCULAR
• pulseless • paraesthetic • paralysed. This can be remembered as ‘the five Ps’. In acute-on-chronic ischaemia, the signs are variable, but skin pallor and mottling, muscle tenderness and loss of movement or sensation are indicative. Fixed-tissue staining, complete loss of sensation and rigidity suggest irreversible damage of soft tissue.
Colour duplex ultrasound is a useful first-line investigation, but is operator-dependent and can be limited by bowel gas obscuring the aortoiliac segment and calcification obscuring the distal vessels. The degree of stenosis is estimated visually and by velocity criteria (Figure 2). MR and CT angiography: multi-planar spiral scanners and specialized image capture software are needed. Excellent views can be obtained as far distally as the crural vessels with newer contrast media. Faster scanners and improved resolution will lead to MR and CT angiography becoming the diagnostic investigations of choice in the UK.
Investigations Ankle–brachial pressure index: the ratio of the systolic pressure at the ankle compared with that in the brachial artery is measured using a hand-held Doppler flowmeter and sphygmomanometer. The ratio is: • >0.9 in normal subjects • 0.6–0.9 in intermittent claudication • <0.5 in critical limb ischaemia. The arteries are often calcified in diabetic patients, leading to falsely elevated readings.
Management Intermittent claudication Intermittent claudication is usually managed conservatively; <7% of patients progress to critical ischaemia of the limb. Risk factors: patients with intermittent claudication have a twoto-four-fold increased risk of death from ischaemic heart disease and stroke compared with an age-matched population. Risk factors must therefore be managed aggressively; enrolment in smoking cessation programmes, and prescription of anti-platelet agents, statins and nicotine replacement therapy (if needed) are mandatory. First-line treatment is aspirin; clopidogrel or dipyridamole are reserved for patients who are unresponsive or who cannot tolerate aspirin. Intermittent claudication can be improved by conservative management alone in 30–50% of patients in the UK.
Intra-arterial digital subtraction angiography has been the ‘gold standard’ investigation in the UK for many years, but is invasive and exposes the patient to the risks of: • haematoma (3%) • arterial dissection (0.5%) • distal embolization (0.5%) • contrast reactions (0.02%). Patients with serum creatinine >120 µmol/l are at risk of contrast-induced nephropathy, a risk reduced by: • stopping non-steroidal drugs • intravenous pre-hydration • administration of N-acetyl cysteine.
Structured exercise programmes: a recent Cochrane Collaboration meta-analysis of nine clinical trials confirmed significant benefit in pain-free and maximum walking distances by structured twiceweekly exercise programmes led by nurses. Drug therapy: cilostazol has been shown to increase walking distance compared with placebo in clinical trials, but has yet to be evaluated outside of this setting. Percutaneous angioplasty: the results of percutaneous angioplasty of the aorta (90% primary patency at five years) and iliac arteries (60–80% primary patency at five years) for claudication are excellent. Stenting does not confer long-term benefit and is reserved for: • failure of primary angioplasty • residual stenosis >50% • procedure-related arterial dissection. Angioplasty of discrete stenoses or short occlusions of the superficial femoral artery lesions have a 50% primary patency at five years. The authors reserve angioplasty for patients with: • disease of the aortoiliac segment • walking limitation that is disabling • a suitable superficial femoral artery lesion.
a
b
Critical ischaemia of the limb Limb loss will occur at some stage without intervention. Patients have a significantly reduced life expectancy due to comorbidity; 25% will die within one year and 50% will die within five years. Limb salvage by arterial reconstruction is beneficial compared to
2 Non-invasive investigation: arterial duplex ultrasound. a Direct reduction in diameter (arrow) at the point of stenosis. b Change in arterial waveform based on the change in velocity at the stenosis.
SURGERY 22:12
333
© 2004 The Medicine Publishing Company Ltd
VASCULAR
primary amputation when the following quality-of-life indicators are analysed: • duration of hospital stay • avoidance of institutionalization • cost. Critical ischaemia is a consequence of two-level disease, and the inflow to the legs should be carefully examined. Achieving successful revascularization requires good inflow into the limb and an adequate target vessel supplying the foot.
reveal underlying arterial stenoses. Thrombolysis of an occluded prosthetic graft usually reveals a pre-existing problem which needs intervention. Contraindications include: • previous stroke or intracranial bleed within eight weeks • surgery within two weeks • recent bleeding in the gastrointestinal tract • recent trauma • the acute threatened limb (see below). Primary amputation is reserved for the 14% to 20% of patients who have unreconstructable disease or extensive loss of tissue.
Angioplasty: in enthusiastic centres in the UK, 50–75% of patients with critical ischaemia of the limb have been reported as suitable for subintimal angioplasty. This technique is usually reserved for superficial femoral, popliteal or tibial artery occlusions of >15 cm (Figure 3). Successful recanalization of the artery (by creation of a new subintimal channel) has been reported in up to 80% of patients, with limb salvage rates of 50–89% at two years. Such impressive data are not always reproducible.
Acute threatened limb The acute threatened limb is a surgical emergency. Patients require supplemental oxygen, intravenous fluid, aspirin, heparin and opioid analgesia. Loss of movement or sensation are indications for urgent revascularization to prevent limb loss and there is no time for thrombolysis in these circumstances.
Distal arterial bypass: the long saphenous vein is the conduit of choice; many randomized controlled clinical trials report primary patency rates of 50–75% at five years for autologous vein grafts compared with 37–43% for prosthetic grafts. An arm vein is a second-line choice. Prosthetic bypass should be reserved for patients in whom no vein is available. Results of prosthetic conduits are improved by using a collar or cuff of vein interposed between the native target vessel and the conduit in below-knee bypass (Miller cuff, St Mary’s boot, Taylor patch). There is no evidence as to whether vein should be left in situ (with the valves destroyed by a valvotome) or reversed. Aspirin helps to preserve graft patency, and duplex graft surveillance programmes improve graft patency (but not necessarily limb salvage).
Embolectomy: emboli can be retrieved using a Fogarty catheter under local anaesthesia, but the majority of patients will have underlying atherosclerotic disease and need bypass surgery. Under such circumstances, angiography is essential, with on-table angiography if preoperative imaging is unavailable. Distal arterial bypass: after revascularization (ideally using a venous conduit as previously described) compartmental fasciotomies should be performed to prevent reperfusion-associated oedema leading to a compartment syndrome. Muscle condition can also be inspected. Primary amputation is performed when the leg is not viable. Skin matting muscle tenderness with sensory and motor loss all suggest lack of viability. The risks of revascularizing a non-viable limb include reperfusion-associated arrhythmias, hyperkalaemia and rhabdomyolysis, and are associated with a high mortality.
Intra-arterial thrombolysis: direct intra-arterial infusion of tissue plasminogen activator is used to dissolve acute thrombus and
a
FURTHER READING Beard J D, Gaines P A (Editors). A companion to specialist surgical practice: vascular and endovascular surgery. 2nd edition. London: W B Saunders, 2001. Earnshaw J, Murie J (Editors). The evidence for vascular surgery. London: TFM, 1999.
b
Subintimal percutaneous angioplasty. a Before the procedure (arrow). b After the procedure (arrow). 3
SURGERY 22:12
334
© 2004 The Medicine Publishing Company Ltd
Arteritis/vasculitis is an atypical arterial disease and presents in young patients with raised inflammatory markers. Buerger’s disease (thromboangitis obliterans) typically affects male smokers in their third or fourth decade. In scleroderma and systemic lupus erythematosis, the cutaneous manifestations may lead to the diagnosis. Takayasu’s arteritis occasionally affects the arteries of the lower limb.
Acute and chronic ischaemia of the limb Marcus Brooks Michael P Jenkins
Congenital anomalies: coarctation of the aorta may present with intermittent claudication and hypertension of the upper limb. Persistence of the embryological sciatic artery results in the failure of development of the iliofemoral arteries (rare). The popliteal artery may be damaged by entrapment or cystic adventitial disease. Entrapment occurs when the popliteal artery lies medial (not between the heads) of the gastrocnemius and is compressed by knee flexion. Cystic adventitial disease is a poorly understood pathological process in which cysts develop in the adventitia of the artery.
Incidence Intermittent claudication (the most common manifestation of limb ischaemia) affects 5–7% of the UK population. In 1995, the Vascular Surgical Society of Great Britain and Ireland estimated an incidence of critical ischaemia of the limb of 40 per 100,000 population per year. The incidence in the UK may be increasing due to an ageing population and improved survival from coronary and cerebrovascular disease.
Fibrosis: fibromuscular dysplasia presents in young adults with ‘beaded’ arterial stenoses. Retroperitoneal fibrosis or radiotherapy may damage the aorta and iliac arteries, thereby compromising inflow to the leg.
Aetiology Atherosclerosis is the primary cause of limb ischaemia in the UK. The risk factors are: • smoking • diabetes mellitus • increasing age • family history • hyperlipidaemia • hypertension • raised level of homocysteine in serum • male sex.
Trauma: blunt and penetrating trauma can lead to arterial compromise. Fractures and joint dislocations of the long bones are the most common causes. In blunt trauma, loss of limb pulses is usually due to intimal disruption or dissection (rather than transection).
Intermittent claudication Patients with intermittent claudication have adequate blood flow to supply the limb and its muscle groups at rest. Walking results in the onset of pain due to muscle ischaemia that, in more severe cases, may be associated with paraesthesiae due to the shunting of blood away from the sensory nerves.
Thrombosis/emboli: emboli occur secondary to: • atrial thrombus (atrial fibrillation or myxoma) • ventricular thrombus (post-myocardial infarction) • aneurysmal disease of the aorta, iliac or popliteal arteries. The risk of embolization is low in asymptomatic popliteal aneurysms with a diameter of <2.5 cm, but the risk also depends on the amount of thrombus present. Arterial thrombosis is associated with hypercoagulable states: • malignancy • polycythaemia • thrombocythaemia • factor V Leiden deficiency/deficiency of protein C or protein S/lupus anticoagulant.
Clinical features Patients present in the fifth, sixth or seventh decade with pain in the calf, thigh or buttock that is initiated by walking and relieved by rest. The distance walked before the onset of pain is reproducible on a flat surface and reduced on an incline. Pain confined to the calf suggests disease of the superficial femoral artery. Thigh or buttock pain suggests disease in the aortoiliac segment; Leriche’s syndrome is the association of such pain with erectile dysfunction. The main differential diagnoses are spinal claudication, venous claudication and the radicular pain of nerve root entrapment. Spinal claudication: the spinal canal narrows during extension and opens with flexion. Patients with spinal stenosis develop pain in the buttock, thigh or calf on prolonged standing that is alleviated by knee flexion. This ‘shooting’ pain is associated with paraesthesiae, weakness and heaviness of the legs. The onset of pain at rest and walking, and the need to lean forward or sit to gain relief, help to differentiate these symptoms from those of limb ischaemia.
Marcus Brooks is a Specialist Registrar in Vascular Surgery at the Regional Vascular Unit, St Mary’s Hospital, London, UK.
Venous claudication is an uncommon condition diagnosed only in active young adults with extensive occlusions of the iliofemoral deep vein. Exercise results in a ‘bursting’ sensation, generalized
Michael P Jenkins is a Consultant Vascular Surgeon at the Regional Vascular Unit, St Mary’s Hospital, London, UK.
SURGERY 22:12
331
© 2004 The Medicine Publishing Company Ltd
VASCULAR
pain and swelling of the limb. Stopping walking relieves pain slowly, and the limb must be elevated for complete relief. Associated conditions and risk factors In the assessment of the patient with intermittent claudication, symptoms of cerebrovascular disease (stroke, transient ischaemic attack, amaurosis fugax), coronary artery disease (chest pain, palpitations, exertional dyspnoea) and diabetes mellitus (polydipsia, polyuria, lethargy) must be sought. Risk factors for vascular disease must be identified. Examination The pulse and blood pressure are recorded. The legs are inspected for signs of critical ischaemia (see below) and co-existent pathology (musculoskeletal, neurological, venous). The brachial, carotid, aortic, femoral, popliteal and pedal pulses are palpated. Auscultation for bruits is performed at the carotid bifurcation, infrarenal aorta, common femoral arteries and adductor hiatus. The ankle–brachial pressure index (see below) is measured in both lower limbs.
a
Critical ischaemia of the foot. a The foot rests horizontally and is pale. The hallux is necrotic and venous guttering is seen. b The dependent limb exhibits rubor.
Critical ischaemia of the limb The European Consensus Document (1989) defined critical ischaemia of the limb as ‘persistently recurring rest pain requiring analgesia for more than two weeks, or ulceration or gangrene of the foot in the presence of an ankle systolic pressure less than 50 mmHg (or a toe pressure less than 30 mmHg in diabetic patients)’.
1
Arterial ulcers are characterized by: • a grey-white base (which may be deep and contain exposed bone, joints or tendons) • a ‘punched-out’ edge • signs of ischaemia in the surrounding skin. Common sites are the digits and areas of boney prominence.
Clinical features Patients present with pain, ulceration or gangrene. True ischaemic ‘rest pain’ is a constant and unremitting pain in the fore-foot relieved only by dependency of the limb and opioid analgesia. The onset of pain may follow a period of worsening claudication. Tissue loss and ulceration are often associated with minor trauma. The assessment of the pre-morbid mobility and living circumstances of the patient aid decision-making and rehabilitation. A history of varicose veins (see page 321), coronary artery bypass or previous arterial surgery helps determine the feasibility of using the long saphenous vein as a conduit for arterial reconstruction.
Gangrene should be termed ‘tissue-loss’ or ‘necrosis’. The necrotic tissue is insensate and may be dry and demarcated or wet with signs of infection.
Acute ‘threatened’ limb Acute onset of ischaemia in a previously normal limb is usually due to embolism. In patients with pre-existing arterial disease, a sudden deterioration (‘acute-on-chronic ischaemia’) may be due to: • acute thrombosis of a pre-existing stenosis • loss of a major collateral • occlusion of a bypass graft.
Examination The appearances of a critically ischaemic limb depend on the: • severity of ischaemia • rapidity of onset • development of collaterals • angle of elevation. Prolonged dependency may result in oedema and changes of venous stasis. The interdigital spaces and heels must be inspected. The peripheral vascular system is fully examined by: • palpation • auscultation • measurement of ankle–brachial pressure indices.
Clinical features The patient presents with sudden onset of pain at rest or rapid deterioration in claudication distance, ulcers or gangrene. A history of atrial fibrillation, intermittent claudication or critical ischaemia (or a previous bypass graft) usually confirms the diagnosis. Examination The contralateral limb must be examined; normal pulses in this limb suggest an embolic cause in the affected limb. In an acute presentation, the affected limb is: • pale • perishing cold
Pre-gangrene: the early signs of critical ischaemia are a cool, pale limb with venous guttering (Figure 1). Elevation exacerbates pallor and subsequent dependency is accompanied by ischaemic rubor (Buerger’s test).
SURGERY 22:12
b
332
© 2004 The Medicine Publishing Company Ltd
VASCULAR
• pulseless • paraesthetic • paralysed. This can be remembered as ‘the five Ps’. In acute-on-chronic ischaemia, the signs are variable, but skin pallor and mottling, muscle tenderness and loss of movement or sensation are indicative. Fixed-tissue staining, complete loss of sensation and rigidity suggest irreversible damage of soft tissue.
Colour duplex ultrasound is a useful first-line investigation, but is operator-dependent and can be limited by bowel gas obscuring the aortoiliac segment and calcification obscuring the distal vessels. The degree of stenosis is estimated visually and by velocity criteria (Figure 2). MR and CT angiography: multi-planar spiral scanners and specialized image capture software are needed. Excellent views can be obtained as far distally as the crural vessels with newer contrast media. Faster scanners and improved resolution will lead to MR and CT angiography becoming the diagnostic investigations of choice in the UK.
Investigations Ankle–brachial pressure index: the ratio of the systolic pressure at the ankle compared with that in the brachial artery is measured using a hand-held Doppler flowmeter and sphygmomanometer. The ratio is: • >0.9 in normal subjects • 0.6–0.9 in intermittent claudication • <0.5 in critical limb ischaemia. The arteries are often calcified in diabetic patients, leading to falsely elevated readings.
Management Intermittent claudication Intermittent claudication is usually managed conservatively; <7% of patients progress to critical ischaemia of the limb. Risk factors: patients with intermittent claudication have a twoto-four-fold increased risk of death from ischaemic heart disease and stroke compared with an age-matched population. Risk factors must therefore be managed aggressively; enrolment in smoking cessation programmes, and prescription of anti-platelet agents, statins and nicotine replacement therapy (if needed) are mandatory. First-line treatment is aspirin; clopidogrel or dipyridamole are reserved for patients who are unresponsive or who cannot tolerate aspirin. Intermittent claudication can be improved by conservative management alone in 30–50% of patients in the UK.
Intra-arterial digital subtraction angiography has been the ‘gold standard’ investigation in the UK for many years, but is invasive and exposes the patient to the risks of: • haematoma (3%) • arterial dissection (0.5%) • distal embolization (0.5%) • contrast reactions (0.02%). Patients with serum creatinine >120 µmol/l are at risk of contrast-induced nephropathy, a risk reduced by: • stopping non-steroidal drugs • intravenous pre-hydration • administration of N-acetyl cysteine.
Structured exercise programmes: a recent Cochrane Collaboration meta-analysis of nine clinical trials confirmed significant benefit in pain-free and maximum walking distances by structured twiceweekly exercise programmes led by nurses. Drug therapy: cilostazol has been shown to increase walking distance compared with placebo in clinical trials, but has yet to be evaluated outside of this setting. Percutaneous angioplasty: the results of percutaneous angioplasty of the aorta (90% primary patency at five years) and iliac arteries (60–80% primary patency at five years) for claudication are excellent. Stenting does not confer long-term benefit and is reserved for: • failure of primary angioplasty • residual stenosis >50% • procedure-related arterial dissection. Angioplasty of discrete stenoses or short occlusions of the superficial femoral artery lesions have a 50% primary patency at five years. The authors reserve angioplasty for patients with: • disease of the aortoiliac segment • walking limitation that is disabling • a suitable superficial femoral artery lesion.
a
b
Critical ischaemia of the limb Limb loss will occur at some stage without intervention. Patients have a significantly reduced life expectancy due to comorbidity; 25% will die within one year and 50% will die within five years. Limb salvage by arterial reconstruction is beneficial compared to
2 Non-invasive investigation: arterial duplex ultrasound. a Direct reduction in diameter (arrow) at the point of stenosis. b Change in arterial waveform based on the change in velocity at the stenosis.
SURGERY 22:12
333
© 2004 The Medicine Publishing Company Ltd
VASCULAR
primary amputation when the following quality-of-life indicators are analysed: • duration of hospital stay • avoidance of institutionalization • cost. Critical ischaemia is a consequence of two-level disease, and the inflow to the legs should be carefully examined. Achieving successful revascularization requires good inflow into the limb and an adequate target vessel supplying the foot.
reveal underlying arterial stenoses. Thrombolysis of an occluded prosthetic graft usually reveals a pre-existing problem which needs intervention. Contraindications include: • previous stroke or intracranial bleed within eight weeks • surgery within two weeks • recent bleeding in the gastrointestinal tract • recent trauma • the acute threatened limb (see below). Primary amputation is reserved for the 14% to 20% of patients who have unreconstructable disease or extensive loss of tissue.
Angioplasty: in enthusiastic centres in the UK, 50–75% of patients with critical ischaemia of the limb have been reported as suitable for subintimal angioplasty. This technique is usually reserved for superficial femoral, popliteal or tibial artery occlusions of >15 cm (Figure 3). Successful recanalization of the artery (by creation of a new subintimal channel) has been reported in up to 80% of patients, with limb salvage rates of 50–89% at two years. Such impressive data are not always reproducible.
Acute threatened limb The acute threatened limb is a surgical emergency. Patients require supplemental oxygen, intravenous fluid, aspirin, heparin and opioid analgesia. Loss of movement or sensation are indications for urgent revascularization to prevent limb loss and there is no time for thrombolysis in these circumstances.
Distal arterial bypass: the long saphenous vein is the conduit of choice; many randomized controlled clinical trials report primary patency rates of 50–75% at five years for autologous vein grafts compared with 37–43% for prosthetic grafts. An arm vein is a second-line choice. Prosthetic bypass should be reserved for patients in whom no vein is available. Results of prosthetic conduits are improved by using a collar or cuff of vein interposed between the native target vessel and the conduit in below-knee bypass (Miller cuff, St Mary’s boot, Taylor patch). There is no evidence as to whether vein should be left in situ (with the valves destroyed by a valvotome) or reversed. Aspirin helps to preserve graft patency, and duplex graft surveillance programmes improve graft patency (but not necessarily limb salvage).
Embolectomy: emboli can be retrieved using a Fogarty catheter under local anaesthesia, but the majority of patients will have underlying atherosclerotic disease and need bypass surgery. Under such circumstances, angiography is essential, with on-table angiography if preoperative imaging is unavailable. Distal arterial bypass: after revascularization (ideally using a venous conduit as previously described) compartmental fasciotomies should be performed to prevent reperfusion-associated oedema leading to a compartment syndrome. Muscle condition can also be inspected. Primary amputation is performed when the leg is not viable. Skin matting muscle tenderness with sensory and motor loss all suggest lack of viability. The risks of revascularizing a non-viable limb include reperfusion-associated arrhythmias, hyperkalaemia and rhabdomyolysis, and are associated with a high mortality.
Intra-arterial thrombolysis: direct intra-arterial infusion of tissue plasminogen activator is used to dissolve acute thrombus and
a
FURTHER READING Beard J D, Gaines P A (Editors). A companion to specialist surgical practice: vascular and endovascular surgery. 2nd edition. London: W B Saunders, 2001. Earnshaw J, Murie J (Editors). The evidence for vascular surgery. London: TFM, 1999.
b
Subintimal percutaneous angioplasty. a Before the procedure (arrow). b After the procedure (arrow). 3
SURGERY 22:12
334
© 2004 The Medicine Publishing Company Ltd