9. PRINCIPLES OF BASIC VASCULAR SURGERY

Vessel handling

Blood vessels are far less forgiving than other tissues commonly handled in general surgical practice. The vessel wall is made up of three layers, all of which are delicate and easy to traumatise. This is even more the case when the vessel is diseased. As a rule, the vessel wall should never be grasped between forceps. During dissection, the surgeon should endeavour to 'dissect the vessel off the patient'. If touching the vessel is truly unavoidable, only grasp the adventitia and, even then, only lightly. Often the closed forceps can be used to deflect the vessel or traction on a suture or neighbouring structure can afford the exposure required.

After circumferential vessel dissection, to obtain control of the vessel, slings are carefully placed. This should be done using a right-angled forcep, but resist the temptation to push the instrument through remaining tissue on the invisible surface of the vessel. The tangible resistance is often due to the presence of a significant branch artery or venous tributary and it is all too easy to avulse these by the clumsy use of the right-angled forceps. When this situation arises, patiently return to scissor dissection until all intervening tissue is cleared. Traditionally, right-angled forceps are passed around arteries in a direction away from the neighbouring vein to minimise the risk of venous trauma.

Vascular clamps are potentially dangerous. They should be applied with care and only as tight as is necessary to arrest blood flow. Try to place clamps to aid the subsequent procedure rather than hinder it. Select a clamp of appropriate size and strength for the vessel being treated.

Vascular sutures and needles

Vascular sutures are non-absorbable and monofilament. They pass smoothly through the vessel wall causing minimal disruption to the component layers. The size of suture used will depend largely on the size of vessel in question and the extent of disease. Generally speaking, 2/0 and 3/0 sutures are used for the aorta, 3/0 and 4/0 for the iliac arteries, 5/0 and 6/0 for the femoral and popliteal arteries and 7/0 for the crural and brachial arteries. For the direct suture of veins, size again relates to vessel calibre, although often, relatively smaller sutures will be used due to the relatively thin venous wall.

The needles used in vascular surgery are curved but not semi-circular. This configuration ensures that when they are used correctly and enter the vessel wall perpendicular to its longitudinal and transverse axes, the smallest needle hole is created. Often, so-called 'calcium cutting' or specially-strengthened needles are needed to traverse calcified arterial wall.

Suture technique

The needle should be mounted on the needle-holder approximately one-third to half-way along its length from the point. Try to create an 'open' angle between the needle and holder. This approach allows for the maximum possible manoeuverability for the operator. As a rule, sutures should be passed from within the vessel lumen outwards. This guarantees that the intima is tacked down and cannot be raised as a flap after blood flow is restored. This latter event is disastrous as vessel occlusion and thrombosis can occur. The object of all vascular suture lines is to create an everted anastomosis with even tension that is completely haemostatic. In order to minimise damage to the vessel wall during suturing and to guarantee precise suture placement, it is recommended that the suture is passed through the vessel wall by a number of short pushes of the needle. Do not grasp the needle by its point after it has passed through the vessel, as this will blunt it and compromise the safe performance of the remainder of the anastomosis. Avoid ripping the needle through the vessel wall as this leads to the creation of slits instead of needle holes. These will inevitably leak and cause you problems.

When tying knots with vascular sutures, it is important to have all vessels clamped to avoid the knot being tied loose. A useful tip for snugging down the first throw is to tie a double throw or to tie the first two throws as a 'granny knot' followed by carefully squared reef knots. Six to eight throws in total should ensure against knot slippage.