Life-threatening pulmonary embolism is a frequent complication of many medical illnesses and surgical procedures when antecedent venous thrombosis is associated with low-flow states, venous injuries, obesity, prolonged immobilization, hypercoagulability, and the poorly understood effects of certain malignant tumors.
Heparin is generally accepted as the primary therapy for thromboembolic disease. Venous interruption, proximal to the site of venous thrombosis, is usually reserved for patients who have recurrent, documented pulmonary emboli despite well-controlled, adequate heparinization who have a large, life-threatening embolus such that an additional one might be fatal; who cannot be anticoagulated because of potential bleeding problems; or who are developing progressive pulmonary hypertension from repeated emboli.
Superficial femoral ligation has been largely abandoned because of the inability to precisely localize the proximal extent of the process and the likelihood of undetected thrombus in the opposite extremity or deep pelvic veins. Inferior vena caval ligation avoids these uncertainties and is indicated primarily for recurrent small septic emboli usually associated with pelvic infections.
Caval filters (e.g., Greenfield) placed via the jugular vein are the most commonly used today for prophylaxis against recurrent emboli. If these devices are not available, then caval partitioning using a serrated external clip should be considered. Vena caval interruption by partially occlusive serrated clips has the advantage of maintaining caval flow with a minimal increase in downstream venous pressure, arresting all but the smallest thrombi, and minimizing the resultant edema of the lower extremities. The vena cava remains intact, the new channels are uniform in size, and there are no intraluminal sutures for potential thrombosis as in the sieve technique. Alternatively, the use of a Green-field filter may be considered.
Most patients are heparinized when the decision for vena caval interruption is made. Since heparin is usually administered intravenously and its duration of anticoagulation effect is limited, there should be little delay beyond 4 hours after the last injection. Protamine sulfate should be available during the procedure for heparin reversal, but this is rarely needed. These patients may have impaired cardiac function and abnormal ventilation/perfusion of the lung, requiring vigorous cardiac and pulmonary support.
Epidural or general anesthesia is favored. Airway maintenance for increased oxygenation must be anticipated, and a secure intravenous catheter for medications or transfusions is essential.
The patient is supine with the right flank slightly elevated with a pillow or pads under the opposite flank. The operative site should be at the break level of the operating table, as hyperextension may improve the operative exposure. If the patient has been receiving heparin, coagulation parameters should be obtained immediately before operation to ensure that clotting is normal. Both lower extremities should be wrapped firmly with elastic bandages from ankles to groins, and electrodes should be placed to allow electrocardiographic monitoring. The operative site is widely prepped and draped as usual.
The transperitoneal approach is used when concurrent ligation of the gonadal veins is indicated, as in pelvic thrombophlebitis; otherwise, the extraperitoneal method is preferred. This approach is tolerated better and is performed more easily. A transverse incision is made just above the level of the umbilicus (Figure 1). It is carried from the lateral border of the right rectus muscle to midway between the costal margin and the iliac crest at the level of the midaxillary line. The incision must not be placed too low, as proper exposure of the infrarenal vena cava is difficult.
The incision is extended down to the external oblique aponeurosis, which is incised lateral to the border of the rectus muscle. If necessary, the incision is extended laterally to expose more internal oblique. If the tenth and eleventh intercostal nerves are encountered, they are retracted to avoid injury. The internal oblique and transversus muscles are split down to the peritoneum. The ureter is identified and is retracted medially with the peritoneum. The peritoneum is freed posteriorly and medially with blunt dissection to expose the vena cava. Care must be taken not to dissect beneath the psoas muscle, which is in a somewhat anterior position at the depth of the dissection. If difficulty in exposure because of obesity or if ascites is anticipated, the muscles should be incised and the incision extended. The right renal vein and upper right lumbar veins are exposed (Figure 2). Palpation of the aortic bifurcation is a useful point of reference.
Circumferential dissection of the vena cava immediately below the renal vein but above a major lumbar vein allows passage of the ligature and the lower half of the Adams–DeWeese clip around the vessel (Figure 3). The vena cava should be palpated gently to determine whether there is proximal extension of the thrombus to this level. If a thrombus is found, the patient is placed in a reverse Trendelenburg position. The vena cava is temporarily occluded above the clot, and the vein is opened through a purse-string suture. The thrombus may then be removed before completion of the interruption. After its placement, the clip is closed and its ligature is securely tied (Figure 4). Great care should be exercised to avoid tearing or avulsion of the lumbar veins and to apply the clip just below the renal vein; these ensure good collaterals should the lower vena cava become occluded.
Patients who have had multiple small emboli resulting in pulmonary hypertension should have ligature of the vena cava with heavy nonabsorbable sutures instead of partial occlusion with a clip.
After hemostasis is ensured, the patient is returned to an unflexed position, and the incision is closed in layers as usual.
In the event of intraoperative arrhythmia or other overt evidence of a new pulmonary embolus, heparin should be administered soon and continued. Otherwise, heparinization is reinstituted 24 hours after operation. This is indicated to control and limit extension of the distal thrombus as well as to prevent thrombosis at the site of the clip or ligation and to improve collateral flow. Anticoagulation should continue until all pain and tenderness and most of the edema have disappeared in the lower extremities. In general, the patient will receive 7 to 10 days of in-hospital heparinization followed by several months of oral anticoagulant therapy. In the meantime, the legs should be encased in elastic bandages or elastic stockings, which may be necessary for several months.
Any necessary respiratory support and general postoperative care are maintained as after other major operations. Cardiac disease or complications that often accompany thromboembolic phenomena may require special attention and management.