The anastomosis itself is usually accomplished by a continuous suture of fine, nonabsorbable suture material on atraumatic needles. Two angle sutures of 00000 arterial synthetic material are placed with knots tied on the outside (Figure 14). Both the portal vein and the inferior vena cava are very fragile. It is therefore necessary to use the utmost caution during the suturing process to avoid trauma to these vein walls. This caution should apply not only to the surgeon doing the actual suturing but equally, if not more, to the assistant holding the clamps. A very slight shearing force created by shifting the vascular clamps in relation to each other may easily disrupt a partly completed anastomosis. Leaks from the anastomotic site, particularly along the left side of the anastomosis, may be difficult to expose for subsequent resuturing. The anastomosis is completed (Figures 15 and 16) and the occluding clamps are released one at a time to check the adequacy of the suture line. Although the portal vein represents the high-pressure system in this anastomosis, it is usually convenient to release one of the portal clamps first, since these are normally easier to reapply if hemostasis is not satisfactory. After all clamps are released, it is frequently possible to detect the functioning of the shunt by visible turbulence in the vena cava. Palpation of the opening between the two veins by invaginating the anterior wall of the portal vein can also be used to verify the patency of the anastomosis. Repeat measurement of pressure in the portal system will normally show that it has been reduced to about half of its preoperative level.
The completed end-to-side anastomosis is illustrated (Figure 17). This is usually accomplished by dividing the portal vein as close as possible to the liver hilum. It is important not to leave the proximal stump of the portal vein too short, since this is a large vein and under considerable pressure. One should leave room for a double ligature, the second being a transfixation suture ligature with several millimeters of vein cuff to assure adequate control of the hepatic side of the portal vein (Figure 18). A longer stump of portal vein is retained if a double end-to-side shunt is indicated (Figure 19). A noncrushing vascular clamp is placed on the portal vein as close to the pancreas as possible to leave the maximum amount of portal vein free for the anastomosis (Figure 19). Again, the appropriate side on the inferior vena cava is selected, excluded by a partially occluding vascular clamp, and an ellipse of vein wall is excised. A single-layer continuous anastomosis of arterial synthetic suture is accomplished as described for side-to-side anastomosis (Figure 20). Although this is an easier anastomosis to accomplish, the same precautions apply here concerning the fragility of the vein walls. After the anastomosis has been completed, the clamps are removed individually. If hemostasis is satisfactory, the procedure is concluded as described above.
The incision is closed in layers (Figures 21 and 22). Drainage of the right upper quadrant is ordinarily not required unless there has been unusual trauma to the liver, pancreas, or biliary system. Retention suturing may be useful.
In the immediate postoperative period it is important to prevent hypoxia; therefore, routine administration of oxygen is recommended for the first 24 to 48 hours. Central venous pressure combined with serial hematocrits should be monitored to assure maintenance of an adequate blood volume.
Because this type of shunt has the highest incidence of hepatic coma, postoperative efforts to decrease protein catabolism should be continuous. During the period of no oral intake, the patient should be given a minimum of 200 g of carbohydrate per day to prevent the undue breakdown of protein. When oral intake is resumed, protein should be restricted initially to 30 g per day. If tolerated, gradual increments, usually 10 g every other day, may be instituted until a level of 50 to 75 g of protein is reached. Tolerance of this nitrogen load may be checked with fasting and 2-hour postprandial blood ammonia levels. If signs of hepatic insufficiency develop, protein in-take should be further restricted and intestinal antibiotics administered.
The prothrombin activity must be monitored and supplemental vitamin K given as indicated. Continued administration of multiple vitamin preparations is also useful.
Ascites may be a distressing if not a dangerous problem postoperatively. Careful monitoring of both fluid and sodium intake may prevent or minimize this complication. If ascites develops, it is best managed by severe sodium restriction combined with diuretics.
The increased incidence of peptic ulceration following portacaval shunt should be remembered and appropriate (low-sodium) antacid therapy and proton pump inhibitors be given.