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Query: UMLS:C0034065 (pulmonary embolism)
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Scientific knowledge is reliable because it has been built on accurate measurements. Clinical knowledge is not. The science of biometry was started in 1835 by the Belgian astronomer Adolphe Quetelet. In the last fifty years a precise set of rules have been invented for this science. The method is suitable for a wide range of problems in clinical medicine and as the result of its application in recent years a firm foundation has been laid upon which scientific clinical knowledge can be built. Surge-ns, particularly, have been slow to apply biometrical methods to their clinical problems; but a start has now been made. The outcome of a particular type of treatment is determined by a complex set of inter-acting factors. The basis of the appropriate biometrical method is the elimination of all bias in favour of one of the rival techniques being compared. If this precaution is taken the observed results of the trial can be fitted onto Quetelet's distribution graph, and the probability of the observed difference in the results being due to chance, and nothing else, can be measured mathematically. The accuracy of this measurement deteriorates the greater are the number of the patients who can not be found and examined at the end of the trial. To make this point two trials conducted by the author are used. In the trial designed to discover if postoperative deep vein thrombosis and pulmonary embolism could be prevented by electrically stimulating the patients legs during the operation there was no difficulty. All the patients were examined at the end of the trial, because it ended before any of the patients left the hospital. The trial to discover if the primary treatment of varicose veins ought to be by Fegan's sclerotherapy or by operation was the exact opposite. At the end of the first year of the two year trial 15% of the patients could not be traced. The results in these patients, therefore, was unknown. Because of this, elaborate mathematical calculations had to be made to try and reach a reliable conclusion to the trial. The loss of patients before the end of the trial is a very serious practical difficulty which besets all long-term clinical trials.
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PMID:Clinical trials in surgery. 79 Aug 78

The frequency of deep-vein thrombosis (DVT) determined by the 125I-fibrinogen test and confirmed by phlebographic studies, is 20 to 30 % in high-risk patients over the age of forty undergoing major surgery. Comparison of this figure with the incidence of clinically detected thrombosis (5 to 10 %) shows that physical signs are unreliable in the detection of this disease. The ultimate fate of these thrombi is unknown. The majority will probably disappear spontaneously; some will be responsible for the development of a "post-phlebitic syndrome" in the extremities and some will propagate and may produce a fatal pulmonary embolus. Besides the currently used physical methods of prophylaxis, some new pharmalogical techniques for the prevention of postoperative deep-vein thrombosis have been tested and advocated in neighbouring countries. Oral anticoagulants have been used routinely for many years by most Dutch surgeons but have never become very popular in other countries. They need extensive laboratory control and, in spite of this, up to 20 % overdosage bleedings have been recorded. As both the administration of low-dose subcutaneous heparin and IV dextran have been reported to provide effective prophylaxis against deep venous thrombosis, we decided to study and compare their efficacy in a randomized clinical trial in order to assess their practical value in daily surgical practice. 119 adult patients undergoing abdominal surgery have been investigated. They have been devided at random in three groups : a dextran 40 group (n=39), a heparin group (n=39) and a control group (n=41 patients). DVT was diagnosed by the fibrinogen uptake test in 21,9 % patients in the control group in 12,8 % patients in the dextran group, and in 10,2 % patients in the heparin group. For the highrisk patients over the age of 70, the administration of low dose SC heparin, as well as the administration of IV low molecular weight dextran significantly reduced the incidence of postoperative DVT in the lower extremities (p less than 0.05). The dextran 40 and heparin groups were not significantly different. The techniques are simple and do not need laboratory control. No deleterious side effects have been noted. A large-scale multicentre international, clinical trial (4121 patients) recently showed that low-dose heparin prophylaxis not only lowered the incidence of postoperative deep-vein trombosis without severely augmenting the risk of bleeding, but also significantly reduced the frequency of fatal pulmonary embolism in the postoperative period. It is suggested that the administration of low-dose subcutaneous heparin should become a routine prophylactic measure in daily surgical practice.
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PMID:[The case for more active prevention of deep-vein thrombosis after major surgery (author's transl)]. 79 5

In 632 patients efficacy of dihydroergotamine (DHE) in preventing postoperative deep venous thrombosis (DVT) and pulmonary embolism (PE) was tested vs. low-dose heparin (LDH) by means of the 125I-fibrinogen uptake test (RFUT). The incidence rate of DVT dropped from 36% (untreated group) to 17% after LDH, to 13% after DHE, and to 9% after simultaneous prophylaxis with both drugs. In patients with lower risk operations lasting not longer than 2 hs complete prevention of DVT was achieved by combined use of LDH and DHE. PE incidence in repeated lung perfusion scans of patients with positive RFUT was reduced to 4.3-2.6% (treated groups) in comparison to an incidence of 50% in the control group. This means the decrease of PE was overproportional in all treatment groups in comparison to the decrease of DVT incidence. The combined use of LDH and DHE may be considered as the best prophylactic regimen available for lowering postoperative DVT and PE.
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PMID:Prevention of postoperative thromboembolism by various treatments. Controlled clinical trial in 632 patients using 125I-fibrinogen uptake test and lung perfusion scans in patients with deep venous thrombosis. 80 52

Presently available data indicate that low-dose heparin will significantly diminish postoperative deep venous thrombosis and pulmonary embolism in patients over the age of 40 subjected to major elective abdomino-thoracic surgery. The schedule is 5,000 USP units of heparin subcutaneously beginning two hours before operation and continued every twelve hours (10,000 units per day) until the patient is discharged. Whether anticoagulent therapy should be continued after discharge should be decided on an individual basis. Preoperative tests for patients on this regimen should include an hematocrit, prothrombin time, partial thromboplastic time, and a platelet count. They should also not be receiving aspirin or other platelet anti-aggregating agents for five days before operation. The efficacy of this regimen is complemented by the fact that it is well tolerated by the patient and requires no laboratory monitoring. However, it does produce a definite but acceptably low frequency of minor intraoperative and postoperative bleeding. This low-dose regimen has not proved effective in open prostatectomy or major orthopedic operations. Data are not available concerning the drug's safety in patients receiving spinal or epidural anesthesia. Nor is it recommended for operations on the eye, brain or in patients who are experiencing an active thrombotic process. More than five million individuals over the age of 40 undergo major general surgical operations annually in this country. One or two out of each thousand of these patients will die postoperatively from pulmonary embolism. If low dose heparin prophylaxis in 80% effective, then the possibility exists of saving 4,000 to 8,000 lives annually. Such an impact might be realized if physicians are prepared to recommend the low-dose heparin regimen as primary prophylaxis for all hemostatically competent patients over the age of 40 who undergo abdomino-thoracic surgery.
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PMID:Prevention of venous thromboembolism in surgical patients by low-dose heparin: prepared by the Council on Thrombosis of the American Heart Association. 83 57

The effectiveness of low doses of heparin was investigated for the prevention of clinically manifested thromboembolic disease. In the group of 125 patients, who received 5,000 units of subcutaneous heparin two hours before the operation, and postoperatively 15,000 units per day for seven to ten days, deep vein thrombosis was not observed, and in only 1 patient (0.8%) pulmonary embolism was suspected. Of 216 patients from the control group, pulmonary embolism was clinically diagnosed in 4 (1.9%), deep vein thrombosis in 7 (3.4%), and in 2 patients (0.9%) fatal pulmonary embolism was found at autopsy. The difference between total thromboembolic disease of the control group (6.2%) and heparinized group was highly significant (p less than 0.02). Postoperative bleeding was seen two times more often in the heparin group, but bleeding was not severe and was easily controlled.
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PMID:Prevention of venous thromboembolism with low doses of heparin in urologic patients. 84 98

Fibrinolytic therapy was carried out in 59 patients suffering from a total of 60 deep venous thromboses of the iliac segment (n = 24), the femoropopliteal segment (n = 18), the deep calf veins (n = 2), or the subclavian vein (n = 16). 46 patients received streptokinase (SK), 4 were given urokinase (UK), and 10 were treated with streptokinase followed by urokinase (SK + UK). The duration of fibrinolytic therapy was between 19 and 596 hours (x = 166 +/- 111 hrs). Phlebographic examination was used to determine the location of the thrombotic occlusion as well as to evaluate therapeutic results. To assure sufficient anticoagulatory protection during therapy with streptokinase the dose of streptokinase was either reduced by steps of 20,000 U/hr to a minimum of 40,000 U/hr or heparin was added as a continuous infusion. Urokinase was administered with a mean loading dose of 75,000 IU followed by an average maintenance dose of 40,000 IU/hr; it was always given in combination with heparin. When therapeutic success was graded as complete/partial/no recanalisation, the following results were obtained: thrombotic occlusion up to 1 week old 35%/48%/17%; up to 2 weeks old 57%/14%/29%; 3 or 4 weeks old 12%/38%/50%; older than 4 weeks 13%/37%/50%. The two most common side effects were a fall of the hemoglobin and a rise of body temperature. Treatment with SK had to be interrupted for bleeding in two cases. One patient diet after rupture of the liver and of the spleen following development of subcapsular hematoma in these organs, 3 patients survived pulmonary embolism without major long-term impairment. Considering medical and social aspects (preservation of capability for working in young adults) it appears justified to administer fibrinolytic agents up to a thrombus age of 14 days, in some cases even up to a thrombus age of 28 days. Good results in cases of deep vein thrombosis of the lower limbs are often obtained only when fibrinolytic therapy is extended beyond 96 hours. It should be performed in intensive care units only. Follow-up examinations of the venous drainage capacity up to 2 years after fibrinolytic therapy document the good therapeutic effect that is warrented by streptokinase or urokinase induced complete recanalisation.
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PMID:[Fibrinolytic therapy in deep venous thrombosis of the upper and lower extremity]. 84 72

Antithrombin III (AT III) was determined in 290 patients with deep venous thrombosis and/or pulmonary embolism by immunological methods (radial immunodiffusion, Laurell technique) and by biological activity (heparin cofactor activity and anti-Xa activity). Patients with venous thrombosis had a significantly lower AT III concentration, as determined by the immunological methods or biological method (heparin cofactor activity), than normal persons without any history of venous thrombosis. A decreased level of AT III was found in 27 patients. In these patients the immunoreactive antithrombin III was decreased to the same degree as biological activity (heparin cofactor activity or anti-Xa activity). Thirteen out of these 27 patients belonged to 9 families and, hence, congenital AT III deficiency can be assumed in these cases. The aetiology was unknown in the other half. Patients with AT III deficiency are prone to spontaneous and/or recurrent venous thrombosis. A high incidence of pulmonary embolism and particularly, of fatal pulmonary embolism is remarkable. In more than half of the patients the first thrombotic event occurred before the age of 35. The treatment of choice in such patients is with oral anticoagulants of the coumarin group.
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PMID:[Antithrombin III deficiency and tendency to thrombosis (author's transl)]. 85 29

In a randomized, controlled clinical study, dextran-70, warfarin, or low-dose heparin were administered to patients undergoing total hip replacement on one surgical unit in an attempt to prevent deep venous thrombosis and pulmonary embolism. Calf vein thrombosis was detected by the 125I-fibrinogen uptake test. None of the methods prevented calf vein thrombosis (dextran-70, 51%; warfarin, 58-6%; heparin, 52-6%). Pulmonary embolism was completely prevented in patients treated with warfarin but occurred in 4% of patients treated with dextran-70 and 15-5% of those treated with low-dose heparin. The incidence of complications of therapy was small and comparable in each group. It is suggested that calf vein thrombosis is a frequent and in itself a non-serious complication of total hip replacement surgery and that emphasis might be placed more usefully on prevention of pulmonary embolism.
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PMID:A comparative study of dextran-70, warfarin and low-dose heparin for the prophylaxis of thrombo-embolism following total hip replacement. 85 84

A course of small doses of heparin given subcutaneously before and after elective operations has been reported to reduce the incidence of deep venous thrombosis and pulmonary embolism in general surgical patients. To test the safety of mini-dose heparin for neurosurgical patients, mini-dose heparin was used for 150 adult patients undergoing elective neurosurgical procedures. No operative complications were thought to be related to heparin administration. Postoperatively, there were four wound seromas, two hematomas, and one non-fatal pulmonary embolus. Seven patients died postoperatively, of whom five had no evidence of pulmonary embolus. Although no conclusions were drawn as to the effectiveness of mini-dose heparin in preventing deep venous thrombosis or pulmonary emboli, it was believed that the method could be used safely and without fear of increased intracranial or intraspinal bleeding for neurosurgical patients.
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PMID:Safety of mini-dose heparin administration for neurosurgical patients. 86 4

Eight prospective, controlled, randomised studies on the incidence of postoperative thrombosis in gynaecological patients receiving various drugs for prevention of thromboembolism are analysed. In all patients diagnosis had been established by objective means. The rate of thrombosis in patients without drug prophylaxis has been found to vary between 14 and 29%. Infusions of dextran as well as administration of low-dose subcutaneous heparin significantly reduce the incidence of deep vein thrombosis, even as compared to postoperative oral anticoagulation with cumarins. No difference has been found between dextran and oral anticoagulants, when cumarin adminstration was started before operation, nor between dextran and heparin. Aescin did not show any prophylactic effect. High age, severe leg-vein varicosis as well as surgery for malignant disease increase the risk of thrombosis. No significant influence of overweight, previous deep venous thrombosis, epidural anaesthesia or vaginal operation as compared to abdominal approach could be demonstrated. There are no properly controlled, prospective, randomised studies on the incidence of postoperative fatal pulmonary embolism as influenced by drugs in gynaecological surgery.
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PMID:[Prophylaxis of thromboembolic complications in gynecological surgery (author's transl)]. 87 Mar 88


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