Introduction
Bypass surgery is performed to improve arterial blood circulation, to treat traumatic arterial injuries or to treat arterial aneurysms. A bypass graft is where a graft (either the patient's own vein or an artificial conduit) is joined on to an artery both above and below the blockage (or aneurysm) to return blood flow to as normal as possible. Bypass grafts are mainly used for patients who have inadequate blood flow to the peripheral tissues due to atherosclerotic arterial disease. Once arteries are blocked or severely narrowed a critical lack of blood flow to the tissues occurs. This in turn causes pain, ulcers, poor wound healing and even gangrene. Restoration of blood flow is vital to prevent deterioration and the risk of limb loss.
Indications
Arterial bypass surgery is performed to treat blocked or severely narrowed arteries or aneurysms. This occurs most commonly in the lower limb. It is possible to treat many patients with endovascular stenting of peripheral arteries, however this is not always possible, particularly with very extensive disease. Whilst a stent would generally be the first line treatment, if that is not possible then a bypass graft is considered.
Preoperative Instructions
Several investigations will be arranged prior to planning bypass surgery. This would generally include an ultrasound and CT scan of the arteries to assess the degree of disease and targets for the bypass graft. Vein mapping is required to assess the suitability of a vein to use for the bypass. In general, using the patient’s own vein is the best option for a bypass. If a vein is not suitable then an artificial graft will be used instead.
Bypass grafting is a major procedure, and it is therefore important to re-assess the patient’s general fitness for surgery. This would include checks on cardiac, respiratory and kidney function. Other medical issues such as diabetes need to optimised prior to surgery and a plan for managing the diabetic medications is important. Similarly, any blood thinner medications will need to be reviewed.
It is helpful to bring a full list of current medications with you to hospital. Most patients would be admitted the day before surgery. The length of stay does vary a lot depending on a patient’s mobility, general health and indications for surgery. The usual length of stay would be 7 days.
Procedure
The arterial bypass procedure involves 2 main stages. Firstly, identifying and harvesting a suitable vein to be used as the bypass conduit. The preferred vein is the long saphenous vein, which runs along the inside of the leg from the ankle, through the thigh and to the groin. It provides an excellent conduit for bypass grafts.
The second stage is identifying appropriate inflow and outflow targets. For a bypass graft to function, adequate blood flow into the graft is required. The femoral artery (main artery in the groin) is most commonly utilised. The outflow artery varies and depends on the extent and nature of the arterial disease. The outflow is critical for function of the graft, as the blood entering the graft needs to have somewhere to flow otherwise the blood will clot within the graft. The aim is to have flow down to the tissues that have not been receiving an adequate amount of flow.
To allow harvesting of the vein, and exposure of the target arteries, quite a long incision down the inside of the leg is required. The exact length varies and will be explained prior to the surgery. An artificial (prosthetic) vein will be utilised if the vein is unsuitable.
The graft is joined (anastomosed) to the relevant artery by a strong permanent suture. The wounds are then closed with some deeper sutures and then usually a dissolving suture placed in the skin.
Postoperative Instructions
After the bypass surgery most patients will be managed on the surgical ward. Close monitoring of the function of the bypass will be performed. For the first 24 hours, rest in bed is advisable. After that time, gradually increasing mobility with the aid of physiotherapy will occur. The wound dressing will be left intact for 3-4 days.
It is very common to develop leg swelling after bypass surgery. This will gradually improve, but is aided by regular walking, elevating the leg when not walking and the use of gentle compression bandaging. Discharge form hospital will occur once mobility is back to normal, and the wound has healed adequately. A routine follow-up appointment will be scheduled for 2 weeks post discharge. Regular surveillance of the graft with ultrasound will then be arranged.
Risks
Arterial bypass surgery is generally only recommended if a critical lack of blood flow to the leg has occurred. Most complications are related to the long incision however a number of other issues may arise.
Potential complications include:
- Wound breakdown.
- Wound infection.
- Leg swelling – this is normal after bypass surgery, but in some cases it can be excessive. Too much swelling does put more pressure on the wounds, and more aggressive elevation is then required.
- Graft occlusion – if inadequate flow occurs in the graft, it can occlude leading to critical lack of blood flow to the leg. This is uncommon, but a severe complication that may require urgent further surgery. It can occur if the inflow, outflow or conduit is inadequate.
- Cardiac, respiratory or kidney complications – pre-existing issues can be exacerbated by the stress of bypass surgery.
- Deep vein thrombosis.
- Scarring.
- Nerve irritation – nerves in the thigh and calf can be traumatised from the surgery. This can cause a numb or burning sensation. It does generally improve but can take several months to improve.
Treatment Alternatives
Arterial bypass surgery is generally only considered in patients with severe lack of blood flow or critical aneurysms that are a significant risk. Endovascular stenting is generally considered as a first line treatment in these situations, but is not always feasible in which case, the bypass is considered.
Medical treatment is always recommended as part of the management of arterial disease. This includes a regular walking program. Walking can improve blood flow to the leg and may help reduce symptoms. In less severe cases, regular walking may avoid the need for surgical intervention. Optimisation of other medical conditions is also critical. In particular, high blood pressure, high cholesterol and diabetes should all be reviewed.
In some severe situations a bypass graft is not suitable. This may be due to severe disease with no suitable arteries in the leg to bypass to or if there are severe general medical conditions that would make a bypass graft too dangerous. In this situation, major limb amputation or palliative care would need to be considered.
Related Information
Peripheral Artery Balloon Angioplasty
Peripheral artery Stenting
Diabetic Foot Ulcers
Peripheral Arterial Disease
Femoral Aneurysms
Popliteal Aneurysms