The value of adding impedance plethysmography to 125I-fibrinogen leg scanning for the detection of deep vein thrombosis in high risk surgical patients: a comparative study between patients undergoing general surgery and hip surgery

Low-molecular-weight heparinoid orgaran is more effective than aspirin in the prevention of venous thromboembolism after surgery for hip fracture

BACKGROUND

The study objective was to determine the relative efficacy and safety of a low-molecular-weight heparinoid (Orgaran) compared with aspirin for the prevention of postoperative venous thromboembolism in patients undergoing surgery for fractured hips. A double-blind, randomized, controlled trial was used to study 251 consecutive eligible and consenting patients undergoing surgery for hip fracture in seven participating hospitals.

METHODS AND RESULTS

Patients received either fixed-dose Orgaran by subcutaneous injection every 12 hours in a dose of 750 anti-Factor Xa units or aspirin 100 mg orally twice daily; both regimens were started 12 to 24 hours after surgery and continued for 14 days or until discharge, if sooner. All patients had postoperative 125I-fibrinogen leg scanning and impedance plethysmography. If the results of one or both tests were positive, then venography was performed. Otherwise, venography was done at day 14, or sooner if the patient was ready for discharge. Pulmonary embolism in symptomatic patients was diagnosed on the basis of a high probability perfusion/ventilation lung scan, a positive angiogram, or a clinically significant embolism detected at autopsy. Evaluable venograms were obtained in 90 of the 125 patients randomly assigned to receive Orgaran and in 87 of the 126 patients assigned to receive aspirin. Venous thromboembolism was detected in 25 (27.8%) patients in the Orgaran group and in 39 (44.3%) patients in the aspirin group. Thus, there was a relative risk reduction of 37% with Orgaran (P=.028; 95% confidence interval, 3.7% to 59.7%). Six (6.8%) of 88 patients in the Orgaran group and 12 (14.3%) of 84 patients in the aspirin group developed proximal deep vein thrombosis or pulmonary embolism, a relative risk reduction of 52% with Orgaran (P=.137; 95% confidence interval, -30.7% to 84.6%). Hemorrhagic complications occurred in 2 (1.6%) patients given Orgaran and 8 (6.4%) patients given aspirin (P=.10). There was one major bleed in the Orgaran group compared with four in the aspirin group.

CONCLUSIONS

This study demonstrates that Orgaran is significantly more efficacious than aspirin in preventing postoperative venous thromboembolism in patients undergoing surgery for fractured hips, with no evidence of any increase in hemorrhagic complications.

Efficacy of a postoperative regimen of enoxaparin in deep vein thrombosis prophylaxis

Venous thromboembolism is a common complication in patients undergoing elective hip replacement, in whom the incidence of calf vein thrombosis is 40% to 60%; proximal vein thrombosis, 20%; and fatal pulmonary embolism, 1% to 2% when prophylaxis is not used. A double-blind, randomized trial comparing low-molecular-weight heparin (enoxaparin) with placebo for the prevention of venous thrombosis in patients undergoing elective hip surgery was carried out. Prophylactic treatment with a fixed dose was begun postoperatively and continued for 14 days. Fifty patients in each treatment group underwent surveillance with 125I-fibrinogen leg scanning and impedance plethysmography. In the first 24 patients, venography was performed only if their surveillance test was positive. Venography was requested in the remaining 76 patients even if the screening tests were negative; in this latter group, venous thrombosis occurred in 4 patients (10.8%) given enoxaparin and 20 patients (51.3%) given placebo (p = 0.0002). The corresponding rates for proximal vein thrombosis were 5.4% and 23.1%, respectively (p = 0.029). In the entire group of 100 patients, venous thrombosis occurred in 12% of those given enoxaparin and 42% of those given placebo (p = 0.0007). The corresponding rates for proximal vein thrombi were 4% and 20%, respectively (p = 0.014). The observed hemorrhagic rate was 5% in each treatment group. The results of this study show that prophylaxis with fixed-dose enoxaparin is effective and safe for patients undergoing elective hip replacement.

Prospective randomized trial of sequential compression devices vs low-dose warfarin for deep venous thrombosis prophylaxis in total hip arthroplasty

A prospective randomized trial compared the effectiveness of low-dose warfarin (LDW) to sequential compression devices (SCD) for deep venous thrombosis (DVT) prophylaxis in 95 patients after total hip arthroplasty (THA). Patients were 39 years of age or older, with no history of previous venous disease. Bilateral lower-extremity venography was used for thrombi detection. Venous thrombi occurred in 12 patients (all calf) on LDW (26.6%) and 3 patients with SCDs (one calf, two thigh) (6.0%). The incidence of DVT was significantly higher in the LDW group (P less than .006). In this study of average-risk patients, the use of SCDs significantly outperformed LDW as a prophylactic agent. However, the thrombi that did occur with SCDs were more critical.

Diagnosis of deep vein thrombosis

A wide range of clinical symptoms and signs are observed with venous thrombosis. Nonetheless, clinical diagnosis has been found to be unreliable and accurate diagnostic methods must be used before potent therapy such as anticoagulation is instituted, since the complications of treatment themselves can be life-threatening. Phlebography is still the basic reference for evaluation of deep venous disease. While it is felt to be the most accurate, there are still limitations relative to difficulty in separating acute from chronic disease, and in obtaining adequate contrast in certain veins such as calf muscles and in the larger intraabdominal veins. Moreover, it is an uncomfortable invasive test, not without complications of its own. The 125I-fibrinogen uptake test is an excellent test for screening for forming thrombi. The sensitivity of this test is high, particularly in the detection of small calf vein thrombi. The primary drawbacks of this technique are that it is falsely positive in cases where there has been bleeding, inflammation, gross edema, arthritis, or leg ulceration. It is not accurate above mid-thigh because of the high blood flow at the level of the groin and pelvis. Radioactive labeled plasmin which will adhere to the surface of recently formed thrombi can also be used for diagnosis. The limitations are a very short half-life of the radioactive label so that repeated investigation of a patient cannot be performed unless new injections are given. The diagnostic accuracy is comparable to that of radioactive labeled fibrinogen and has the same advantages and disadvantages. Plethysmographic techniques have been used with various modifications.(ABSTRACT TRUNCATED AT 250 WORDS)

Deep venous thrombosis: an overview

The patients at high risk of deep venous thrombosis are defined. Factors in the formation of intravenous thrombi are described. The roles of endothelium, formed elements, clotting factors, and their interrelationships are correlated. Diagnostic modalities and their application are described, and the commonly used medical and surgical therapies are specifically outlined.

Double-blind randomised trial of Org 10172 low-molecular-weight heparinoid in prevention of deep-vein thrombosis in thrombotic stroke

In a double-blind, randomised trial Org 10172 low-molecular-weight (LMW) heparinoid was compared with placebo in the prevention of deep-vein thrombosis in patients with acute thrombotic stroke. Prophylaxis was started within 7 days of the onset of stroke with a loading dose of 1000 anti-factor-Xa units intravenously followed by a fixed dose of 750 anti-factor-Xa units twice a day subcutaneously; it was continued for 14 days or until hospital discharge, if earlier. 50 patients were randomised to receive Org 10172 and 25 to receive placebo. All patients underwent surveillance with I125-fibrinogen leg scanning and impedance plethysmography. Venography was carried out if either test became positive. Venous thrombosis occurred in 2 of 50 patients (4.0%) given Org 10172 and 7 of 25 patients (28.0%) given placebo (p = 0.005); the corresponding rates of proximal-vein thrombosis were 0% and 16%, respectively (p = 0.01). There was one major haemorrhage in the Org 10172 group and one minor bleed in the placebo group.

Epidemiology and pathogenesis of venous thrombosis

Venous thrombi are intravascular deposits composed predominantly of fibrin and red blood cells with a variable platelet and leukocyte component. They frequently arise in large venous sinuses in the calf, in valve cusp pockets either in the deep veins of the calf or thigh or in venous segments that have been exposed to direct trauma. Venous thrombosis can be produced experimentally by a combination of stasis and systemic hypercoagulability or by stasis and endothelial damage. Thrombosis is augmented if the fibrinolytic mechanism is inhibited or defective. A number of clinical conditions and laboratory abnormalities are associated with and predispose to venous thrombosis and, in many of these, it is possible to identify one or more of the thrombogenic factors discussed. Venous thromboembolism (venous thrombosis and pulmonary embolism) is a serious and potentially fatal disorder that usually complicates the course of sick hospitalized patients, but occasionally affects ambulant and otherwise healthy individuals. Screening studies with iodine-125 fibrinogen leg scanning, impedance plethysmography and perfusion lung scanning have shown that the majority of venous thrombi and pulmonary emboli that occur in hospitalized patients are small and asymptomatic, and it is likely that most are clinically insignificant. In bedridden patients, most thrombi commence in the calf and are asymptomatic. When a calf vein thrombus extends into the proximal venous segment, the risk of clinically significant pulmonary embolism increases. Less is known about the incidence and clinical significance in a nonhospital population; although asymptomatic disease occurs, its frequency is unknown. In contrast to the patients with asymptomatic venous thrombosis, symptomatic patients with venous thrombosis usually have large occulsive thrombi localized in their proximal veins.

A randomized controlled trial of a low-molecular-weight heparin (enoxaparin) to prevent deep-vein thrombosis in patients undergoing elective hip surgery

There is experimental evidence that low-molecular-weight fractions of heparin are as effective as the standard form but cause less bleeding. We therefore performed a double-blind, randomized trial comparing PK10169 low-molecular-weight heparin with placebo for the prevention of venous thrombosis in patients undergoing elective hip surgery. Prophylactic treatment with a fixed dose was begun postoperatively and continued for 14 days. Fifty patients in each treatment group underwent surveillance with [125I]fibrinogen leg scanning and impedance plethysmography. In the first 24 patients, venography was performed only if either surveillance test was positive. Because the rate of venous thrombosis detected in those patients was unexpectedly low, venography was requested in the remaining 76 patients, even if the screening tests were negative. In this latter group, venous thrombosis occurred in 4 patients (10.8 percent) given PK10169 heparin and 20 patients (51.3 percent) given placebo (P = 0.0002); the corresponding rates for proximal-vein thrombosis were 5.4 percent and 23.1 percent, respectively (P = 0.029). In the entire group of 100 patients, venous thrombosis occurred in 12 percent of those given PK10169 heparin and 42 percent of those given placebo (P = 0.0007), and the corresponding rates for proximalvein thrombi were 4 percent and 20 percent, respectively (P = 0.014). The observed hemorrhagic rate was 4 percent in each treatment group. We conclude that prophylaxis with fixed-dose PK10169 heparin is effective and safe for patients undergoing elective hip replacement.

An evaluation of suloctidil in the prevention of deep vein thrombosis in neurosurgical patients

Suloctidil (200 mg t.i.d.) was compared with placebo in a randomized, double-blind trial to assess its value in preventing deep venous thrombosis (DVT) in high-risk neurosurgical patients, comprising 136 patients with brain or spinal tumour, head or spinal injury, or subarachnoid or intracranial hemorrhage. 125I fibrinogen leg scanning and impedance plethysmography were performed for up to 14 days to detect DVT. The two groups were also evenly balanced for DVT risk factors. Seventeen of 68 patients (25%) (95% confidence interval, 15-35%) treated with suloctidil and 12 of 68 patients (21%) (95% confidence interval, 11-32%) treated with placebo developed deep venous thrombosis. This observed difference in outcomes is not statistically significant (X2 = 1.096; p = 0.30). The estimated 95% confidence interval for the true difference in the incidence of DVT between suloctidil-treated and placebo-treated patients ranges from an 11% benefit in favour of suloctidil to an 18% benefit in favour of placebo. Major deep vein thrombosis occurred in two patients on suloctidil and three patients in the placebo group; there were no fatal pulmonary emboli during the 14-day study period, during which time four patients in each group died of non-thromboembolic complications. There was no observed difference in hemorrhagic complications. Long-term outcomes at three-months follow-up were similar between the two treatment groups. It is concluded that there is no real evidence that suloctidil (200 mg t.i.d.) is an effective regimen for the prevention of DVT in high-risk neurosurgical patients.

Plasma betathromboglobulin and serum fragment E in acute partial stroke

Plasma betathromboglobulin (BTG) and serum fragment E (FgE) were measured serially by radioimmunoassay for 7 d in 67 patients admitted with acute partial stroke. Twelve patients progressed within 7 d of admission. Plasma BTG was not different from normal in patients with acute partial stroke and did not increase significantly with stroke progression. Serum FgE was elevated in patients with acute partial stroke compared with normal values, and was significantly higher in patients who progressed compared with those who remained stable. The results indicate that fibrin formation may be more important in the process of stroke progression than activation of platelets.