palpable ankle pulse should deter thoughts of reconstruction; treatment should be conservative or ablative.
Arterial calcification on plain X-rays is commonly seen in diabetic patients and does not necessarily denote occlusion.
Preliminary treatment planning, informing the choice of en- dovascular or surgical revascularisation, can often be based on clinical examination supported by duplex ultrasound scanning.
When surgery is selected, the optimal siting of graft outflow requires good-quality arteriography, whether departmental or OTA.
The purpose of outflow imaging is to demonstrate the most proximal arterial site that provides unimpeded perfusion of the distal vasculature through disease-free channels.
When arteriograms show that the occlusive process is confined to the distal vascular bed, commencing beyond the popliteal trifurcation, then it is highly likely to involve the pedal arch and its branches, in which case distal bypass is impracticable (Figure 21.1).
A common pattern of treatable occlusion in people with diabetes comprises a diffusely diseased SFA terminating in an occluded popliteal artery, with refilling of crural arteries in mid-calf (Figure 21.2).
In skilled hands, angioplasty can recanalise about 80% of these cases and clinical success, though not necessarily patency, is reported in 69% at 1 year.32 Surgical
(a) (b) (c)
Figure 21.1 The unreconstructable leg; in the presence of distal ischaemic necrosis, a palpable popliteal pulse with arteriographic evidence of an open trifurcation points to occlusion of the pedal arch: (a) the arteriogram demonstrates a patent femoro-popliteal segment in continuity with an open trifurcation; (b) the posterior tibial artery is patent to ankle level; (c) both plantar arteries and the pedal arch are occluded. Bypass reconstruction is not feasible.
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(a) (b) (c) (d)
(e) (f) (g)
Figure 21.2 Collaboration between surgeons and radiologists; this arteriographic sequence demon- strates multi-segmental occlusion suitable for either angioplasty or bypass: (a) femoral bifurcation and outflow; (b) SFA occlusion at adductor level; (c) diseased but patent popliteal artery and trifurcation; (d) posterior tibial artery reconstitution; (e) posterior tibial and plantar continuity; (f) 6 months after failed angioplasty followed by common femoral to posterior tibial bypass using non-reversed long saphenous vein; duplex scan had suggested outflow stenosis; (g) a focal stenosis is shown in the posterior tibial artery at malleolar level. This was successfully dilated with a 4-mm balloon.
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ADJUNCTIVE MEASURES AND MANAGING COMPLICATIONS 259
bypass using vein grafts offers durable patency with an acceptable complication rate.33 Graft inflow should be sited above the commencement of the occlusive process but does not have to be from the CFA. Use of the SFA or the popliteal arteries for the proximal graft anastomosis has been found compatible with long-term graft patency, particularly in the diabetic population.34 Whichever disease-free crural artery is seen to be in continuity with the pedal arch (through collaterals in the case of the peroneal) can be considered a candidate for graft outflow. Vascular grafts should be as short and direct as possible, and the ankle joint should be crossed only if necessary; so the surgeon must be familiar with the approaches to all three arteries in the calf as well as to the pedal arteries.
Technique Systemic anticoagulation is not essential for peripheral vascular reconstruction; neither is it a contraindication.
Prophylaxis against venous thrombosis is advisable, commencing an agent such as enoxaparin 20 mg s.c. daily on admission to hospital.
During the operation, local intra-arterial flushing with a 10 units/ml solution of heparin in Hartmann’s solution delivered through a blunt cannula is sufficient to prevent local intra-arterial thrombosis during vascular clamping.
Longstanding warfarinisation need not be reversed, provided pre-operative international normalised ratio (INR) levels do not exceed 3 and fresh frozen plasma is available, although neuraxial anaesthesia must be avoided in patients with anticoagulation.
Excessive operative bleeding is likely in patients taking both aspirin and clopidogrel and one of these (usually the clopidogrel) should be withdrawn 7 days before surgery.
Following any successful revascularisation for CLI, a degree of post-operative soft tis- sue swelling is normal, partly due to tissue trauma and disturbance of venous and lymphatic drainage but largely through interstitial fluid accumulation, reflecting temporarily increased vascular permeability.
This results from established circulatory adaptation to chronic under- perfusion and is self-correcting over a period of weeks or months.
When revascularisation follows a period of severe ischaemia sufficient to produce muscle paralysis, pain or tenderness, then some degree of post-operative muscle swelling is inevitable, risking the development of compartment pressure syndrome (CPS).
It is preferable to anticipate this and perform prophylactic fasciotomy, hopefully with the minimum of additional incisions, before wound closure.
Grafts should not be left exposed to the air, but cover with viable muscle rather than skin is sufficient.
If post-operative CPS develops unexpectedly, then full compartmental decompression can be achieved with a single lateral calf incision along the line of the fibula, deepened to the bone, followed by splitting of all the attached fascial septa, both anterior and posterior.
Fibular excision confers no additional benefit.
With this technique, it is helpful to insert a loose-running monofilament subcuticular suture, with no initial attempt at skin closure.
This manoeuvre controls retraction of the skin edges and permits delayed skin closure when the swelling subsides, simply by traction on the subcuticular suture, under sedation.
ADJUNCTIVE MEASURES AND MANAGING COMPLICATIONS Intravenous antibiotic therapy should be administered prophylactically to all patients undergo- ing peripheral vascular reconstruction. The choice of agent should take into account the results
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260 PERIPHERAL VASCULAR DISEASE AND RECONSTRUCTION
of swab cultures from any ulcerated or necrotic areas of skin.
Even when the skin is intact, patients should be routinely screened for methicillin-resistant Staphylococcus aureus (MRSA) colonisation prior to admission to hospital.
A standard regimen might comprise flucloxacillin 1 g i.v. and gentamicin 120 mg i.v. on induction of anaesthesia, with a second dose on the first post-operative day.
Prolonged antibiotic courses should not be administered prophylactically; they should be reserved for specific complications and modified according to the results of bacterial culture.
Once graft flow is established at operation, an intra-graft bolus dose of a vasodilator drug such as one of the prostacycline analogues35 or papaverine 30 mg should abolish any tendency to vasospasm.
There is also some support for giving an infusion of Dextran 40, 500 ml over 4 h, once daily for the first day or two, since this reduces platelet aggregation.
None of the above will compensate for technical shortcomings.
Whenever possible skin wounds should be covered with waterproof occlusive dressings for 48, 72 h, by which time they should have become sealed with a fibrin film and can be left uncovered.
Haematomas and fluid collections should be drained promptly, with full sterile precautions, in theatre if necessary.
Graft patency can be checked by regular foot inspection and pulse palpation, but in case of doubt duplex ultrasound imaging is definitive and can also be used to diagnose deep vein thrombosis when swelling seems excessive.
Graft occlusion should be tackled promptly and aggressively by operative re-exploration.
It is vital to seek and rectify the cause of failure, so in addition to thrombectomy (by balloon catheter extraction and graft flushing), methodical checks of inflow, graft and outflow, with the possible assistance of OTA, are essential.
In the interests of minimising pain and reactive swelling, it is advisable to keep patients on bedrest with the leg elevated for the first 48 h.
Care must be taken to protect pressure areas, particularly the heel of the operated leg or the sacrum in patients remaining on epidural analgesia.
Thereafter, supervised mobilisation is desirable, tailored to the patient’s abilities.
When soft tissue necrosis of the calf or foot is extensive, distal bypass and debridement can be combined with tissue reconstruction, using microvascular free grafts, comprising muscle, skin or both.
Such grafts are fragile and insensate, and so they are unsuitable for weight-bearing surfaces.
Initial enthusiasm for this approach in the United Kingdom has been tempered by poor long-term results, but encouraging reports continue to appear.36
RESULTS OF RECONSTRUCTION These are usually presented in life-table format, quoting primary graft patency, primary assisted patency (including successful thrombectomy cases), secondary patency (including cases of successful re-grafting) and limb salvage (amputation avoided, irrespective of graft patency).
When grafts occlude within the first 6 months of operation, before wound healing and collateral development are consolidated, it is likely that critical ischaemia will return and that, in the absence of successful re-grafting, amputation will prove necessary.
After 6 months, graft failure is less likely to precipitate symptoms of recurrent critical ischaemia.
Somewhat surprisingly, the results of infrainguinal bypass procedures in diabetic patients have not been found inferior in terms of patency to those in non-diabetics, irrespective of anatomical level.37 However, the diabetic population is more susceptible to neuroseptic and trophic complications that can precipitate limb loss despite graft flow being maintained.
At 5 years, secondary graft patency rates of 80% and limb salvage rates of 95% have been reported