The sequence in which the sutures are placed may vary, but the same technique is used for each individual suture. For end-to-end anastomosis, a suture is inserted at each end of the opening. The back wall is then sutured, followed by the front wall. For end-to-side anastomosis, the triangulation technique classically described by Carrel is stan-dard.
The technique involves the insertion of three key sutures at equal distances around the circumference of the line of the anastomosis, the intervening gaps being filled in with additional sutures. The first two of the key sutures are inserted 120° apart, and the additional sutures inserted between.
The vessels are turned over, and the third key suture is placed in the middle of the back wall equidistant from the first two. The intervening gaps are then closed. The distance between indi-vidual sutures should be such that the vessel ends are completely apposed leaving no holes between, through which blood can escape. The sequence in which the vessels are anasto- mosed is to some extent a matter of personal preference, and is often dictated by the circumstances in the individual case.
If one ves-sel lies deep to the other, the deeper anastomosis should be completed first. In carrying out vessel anastomoses, a problem which the surgeon faces is what to do with the needle while the instrumental tying of each suture is being carried out. It is essential that it should be kept visible in the field, ready to be picked up when the ends of the completed knot are cut. A solution is to insert its tip into the gauze swab usually in the field , present to soak up excess irrigation fluid. When both anastomoses, arterial and venous, are completed the circulation is restored by removing the microclamps, starting with the clamp distal to the venous anastomosis, working back against the direction of flow, and finishing with the clamp proximal to the arterial anasto-mosis.
The clamp distal to any anastomosis in the direction of flow should always be removedfirst, other» wise the build-up of pressure is liable to result in leakage of blood from the anastomosis, and thrombosis may result. When the clamps are opened, and blood passes across the anastomosis there may be a little bleeding from between sutures, but this subsides quickly. An obvious source of leakage calls for additional sutures.
It may take a few moments for the flap to become pink, and the first sign of circulation is often filling of the vein. At first, flow may be sluggish, but it usually picks up quickly. A bounding, pulsatile artery, a pink flap, and a full vein are signs of a healthy, satisfactory circulation. If this is not rapidly forthcoming, the cause must be sought.
Arterial spasm can be corrected by topical application of a dilating agent such as local anaesthetic or papaverine, but if this fails it is better to take down or resect the anastomosis and refashion it. Expectant management merely postpones the inevitable. The same applies to venous problems.
Test for patency
If doubt exists, patency can be tested by occlud-ing the vessel distal to the anastomosis with two microforceps placed side by side. Blood is milked distally by the distal forceps leaving an empty portion of vessel.
The proximal forceps are opened and, if the empty portion fills, it means that the anastomosis is patent. With the anastomoses complete and function-ing, the vessels usually take up a ‘natural posi-tion’ in which they curve or loop gently, but the surgeon must also see that there is no kinking or compression. The final step in the procedure is the insertion of a drain under the flap.
If suction drainage is being used it should be applied at a distance from the site of the anastomosis, prefer-ably fixed in position by using a transfixing suture through drain and skin.