Thromboembolic disease

Prophylaxis of Postoperative Deep Venous Thrombosis and Pulmonary Embolism

Many attempts have and are being made to discover the etiology of postoperative deep venous thrombosis in an attempt to determine how it can be prevented in order to save patients’ lives from massive fatal pulmo­nary embolism following successful surgical operative procedures. Some progress has been made in the last three decades, since deaths from this dreaded complication have diminished. It has never been proved that there are changes in the blood clotting mechanism that might be a cause of the condition, but the use of anticoagulants, especially of the warfarin group, in adequate amounts does have a beneficial eflFect in controlling the condi­tion when administered in the early stages of the disease. Its value as a routine prophylactic measure in all patients has not proved to be a pan­acea. Also, anticoagulation does carry some risk in the postoperative pa­tient because of the danger of hemorrhage. In elderly patients, who are the patients most frequently afflicted with thromboembolism, it may cause bleeding from unsuspected lesions. It is recommended, however, that any patient who has had a previous episode of deep venous thrombosis, with or without pulmonary embolism, and who requires further surgery be given the protection of postoperative anticoagulation provided by Coumadin therapy. The use of elastic stockings during the postoperative period has some advocates, but it is doubtful that they are of much value, and serious ischemic lesions of the feet have developed from their use in elderly patients.

There seems little question that early ambulation has contributed more to the prevention of thromboembolic disease in postoperative pa­tients than any other form of therapy. It is well known that deep venous thrombosis rarely develops in an individual who is able to be up and walk­ing about. This is confirmatory evidence that in the vast majority of pa­tients the condition begins in the lower extremities and that most frequently it first involves the deep veins of the calf muscles. These facts have been known and reported for many years, first by the pathologists in the last century and later by surgeons.

Elevation of the foot of the bed to favor drainage of blood from the lower limbs is one of the more common so-called prophylactic measures that was recommended many years ago and is still adhered to by some. Other measures such as passive leg exercises and bicycle exercises with the legs elevated have proved to be of little or no value; one reason is that they usually require the assistance of someone at the bedside. This is dif­ficult to provide today and, as a result, exercises are done too infrequently to be of any special value. Furthermore, they do not contract the calf muscles sufficiently actively to push blood along and to prevent it from

stagnating. Fortunately the use of tight abdominal bandages and binders around the abdomen, which contribute to venous stasis in the lower limbs, has been discontinued.

There seems little question that stagnation of the blood in the veins of the lower extremities is an important etiological factor of deep venous thrombosis. This is increased in the elderly patient, in part because with increasing age the caliber of the deep veins of the lower extremities gradu­ally becomes greater so that the blood flows through them at a slower rate. Another contributing factor in the elderly is the degenerative changes that develop in the, venous endothelium as a result of phlebosclerosis, which can act as a nidus for thrombus formation, especially in the presence of a sluggish blood flow. With this rather simple plausible explanation of the cause of deep venous thrombosis, it seems obvious that some form of treatment should be instituted that will stimulate the flow of blood through the veins of the lower extremity and prevent it from stagnating. Without question this is what early ambulation does, since it has definitely reduced the incidence of the disease. Fortunately it is so generally practiced today that most postoperative patients are ambulating several times a day begin­ning usually on the first postoperative day. It is advised that the time out of bed be spent walking rather than sitting in a chair for an indefinite period of time, since sitting tends to favor stagnation and thrombosis of the blood in the lower extremities.

Unfortunately following some of the major vascular operative proce­dures this practice cannot be carried out the first postoperative day, so it is necessary to utilize some other method of ambulation while the patient is still in bed (see Plate 44). It is necessary to emphasize again and again that the postoperative care, especially in these patients, should include daily examination of the calf muscles to detect at the earliest possible time any evidence of tenderness which might indicate the presence of an early deep venous thrombosis. The development in a postoperative patient of a con­comitant rise in temperature, pulse and respiration, irrespective of any positive signs of phlebitis in the extremities, should make one suspect the presence of deep venous thrombosis with a small nonfatal pulmonary embolism. Since most fatal pulmonary emboli are preceded by a small warning embolus, it is recommended that measures be taken to prevent the development of additional emboli, preferably by bilateral superficial fe­moral vein interruption followed by anticoagulant therapy with Coumadin for a period of at least two weeks. This method of therapy is also recom­mended if a definite diagnosis of deep thrombophlebitis limited to the calf veins is made even without preliminary pulmonary embolism. To wait after the diagnosis of an early localized deep phlebitis in the calf has been made until a patient develops an iliofemoral thrombophlebitis or a pulmo­nary embolus before carrying out definitive treatment shows a serious lack of judgment, since an inferior vena cava interruption may be necessary if the patient has not already succumbed to a massive pulmonary embolus.

A number of patients who have had massive pulmonary emboli have been saved by an emergency pulmonary artery embolectomy utilizing a cardiopulmonary bypass. Despite these successes, there are still patients who die so quickly from complete occlusion of the pulmonary artery that they cannot be moved to the operating room in time to perform this operation. It seems, therefore, that the prevention of deep venous thrombosis is the goal that we should aspire to. With more attention given postopera­tively to the lower extremities and to the use of the available prophylactic measures, the incidence of this dreaded complication can be greatly reduced.

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