Low molecular weight heparin plus dihydroergotamine for prophylaxis of postoperative deep vein thrombosis

American Society of Hematology 2019 guidelines for management of venous thromboembolism: prevention of venous thromboembolism in surgical hospitalized patients

BACKGROUND

Venous thromboembolism (VTE) is a common source of perioperative morbidity and mortality.

OBJECTIVE

These evidence-based guidelines from the American Society of Hematology (ASH) intend to support decision making about preventing VTE in patients undergoing surgery.

METHODS

ASH formed a multidisciplinary guideline panel balanced to minimize bias from conflicts of interest. The McMaster University GRADE Centre supported the guideline-development process, including performing systematic reviews. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach was used to assess evidence and make recommendations, which were subject to public comment.

RESULTS

The panel agreed on 30 recommendations, including for major surgery in general (n = 8), orthopedic surgery (n = 7), major general surgery (n = 3), major neurosurgical procedures (n = 2), urological surgery (n = 4), cardiac surgery and major vascular surgery (n = 2), major trauma (n = 2), and major gynecological surgery (n = 2).

CONCLUSIONS

For patients undergoing major surgery in general, the panel made conditional recommendations for mechanical prophylaxis over no prophylaxis, for pneumatic compression prophylaxis over graduated compression stockings, and against inferior vena cava filters. In patients undergoing total hip or total knee arthroplasty, conditional recommendations included using either aspirin or anticoagulants, as well as for a direct oral anticoagulant over low-molecular-weight heparin (LMWH). For major general surgery, the panel suggested pharmacological prophylaxis over no prophylaxis, using LMWH or unfractionated heparin. For major neurosurgery, transurethral resection of the prostate, or radical prostatectomy, the panel suggested against pharmacological prophylaxis. For major trauma surgery or major gynecological surgery, the panel suggested pharmacological prophylaxis over no prophylaxis.

Hepatic veins as a site of clot formation following liver resection

Pulmonary embolism occurs more frequently after hepatectomy than previously thought but is infrequently associated with peripheral deep vein thrombosis. In this paper, we report 2 cases of postoperative hepatic vein thrombosis after liver resection. Both patients had undergone major hepatectomy of a non-cirrhotic liver largely exposing the middle hepatic vein. Clots were incidentally found in the middle hepatic vein 4 and 17 d after surgery despite routine systemic thrombo-prophylaxis with low molecular weight heparin. Coagulation of the transition plan in a context of mutation of the prothrombin gene and inflammation induced biloma were the likely predisposing conditions. Clots disappeared following curative anticoagulation. We conclude that thrombosis of hepatic veins may occur after liver resection and is a potential source of pulmonary embolism.

Low-molecular-weight heparin for the prevention of postoperative venous thromboembolism after abdominal surgery: a review

PURPOSE OF REVIEW

To analyze the effect of low-molecular-weight heparin in abdominal surgery, which carries a significant risk of thrombosis, a risk further increased by cancer.

RECENT FINDINGS

Searches in EMBASE and PubMed between 1980 and 2004 were conducted to identify studies of thromboprophylaxis in abdominal surgery patients. Sixteen comparative studies were identified. They showed that low-molecular-weight heparin is as effective as unfractionated heparin in reducing venous thromboembolism and, at appropriate doses, can reduce bleeding complications. In very-high-risk cancer patients, a higher dose of low-molecular-weight heparin may offer increased efficacy without increasing the risk of bleeding. Extending the standard 7-10-day low-molecular-weight heparin prophylaxis period may benefit certain high-risk patient groups.

SUMMARY

Patients undergoing abdominal surgery should be stratified according to thromboembolism risk and given prophylaxis accordingly. Low-molecular-weight heparin is a recommended alternative to unfractionated heparin in moderate- or high-risk patients. In patients with cancer, high doses of low-molecular-weight heparin may offer increased efficacy without increased bleeding, and an extended 4-week period of prophylaxis could be beneficial.

Low molecular weight heparin for the prevention of venous thromboembolism after abdominal surgery

Background

Abdominal surgery carries a significant risk of venous thrombosis, a risk further increased in patients with cancer.

Methods

Embase and Pubmed searches between 1980 and 2003, using the key words ‘heparin,’ ‘surgery,’ ‘abdominal or rectal or colorectal or rectum or colon’ and ‘clinical trial’, were conducted to identify studies of thromboprophylaxis in patients having abdominal surgery.

Results

A total of 16 comparative studies were identified. These show that low molecular weight heparin (LMWH) is as effective as unfractionated heparin (UFH) in reducing venous thromboembolism after abdominal surgery and, at appropriate doses, can reduce bleeding complications. In very high-risk patients, a higher dose of LMWH may offer increased efficacy without increasing bleeding risk. Extending the standard 7–10-day period of prophylaxis may benefit certain high-risk groups; recent data show a significant benefit of 4-week enoxaparin thromboprophylaxis compared with a standard regimen, at no cost to safety.

Conclusion

Patients undergoing abdominal surgery should be stratified according to thromboembolism risk and managed accordingly. LMWH is a recommended alternative to UFH in moderate- or high-risk patients. In patients with cancer, high doses of LMWH may offer increased efficacy without increasing the bleeding risk and an extended 4-week period of prophylaxis appears beneficial.

Meta-analysis of low molecular weight heparin in the prevention of venous thromboembolism in general surgery

BACKGROUND

Low molecular weight heparins (LMWHs) have become routine thromboprophylaxis in general surgery. However, their actual clinical effect, its magnitude relative to that of unfractionated heparin (UFH), and the optimal dose are still debated.

METHODS

A meta-analysis was performed of all available randomized trials in general surgery comparing LMWH with placebo or no treatment, or with UFH.

RESULTS

Comparison versus placebo or no treatment confirmed that the significant reduction in asymptomatic deep vein thrombosis (DVT) obtained with LMWH (n = 513; relative risk (RR) 0.28 (95 per cent confidence interval 0.14-0.54)) was associated with a significant reduction in clinical pulmonary embolism (n = 5456; RR 0.25 (0.08-0.79)) and clinical venous thromboembolism (VTE) (n = 4890; RR 0.29 (0.11-0.73)), and a trend towards a reduction in overall mortality rate. Comparison versus UFH showed a trend in favour of LMWH, with a significant reduction in clinical VTE (P = 0.049), a trend also found for cancer surgery. LMWH at doses below 3400 anti-Xa units seemed to be as effective as, and safer than, UFH, while higher doses yielded slightly superior efficacy but increased haemorrhagic risk, including that of major haemorrhage.

CONCLUSION

Asymptomatic DVT may be regarded as a reliable surrogate endpoint for clinical outcome in studies investigating thromboprophylaxis in general surgery. LMWH seems to be as effective and safe as UFH. Determination of the optimal dose regimen of LMWH for this indication requires further investigation.

A comparative trial of a low molecular weight heparin (enoxaparin) versus standard heparin for the prophylaxis of postoperative deep vein thrombosis in general surgery

BACKGROUND

Various studies have been performed in general surgery patients comparing low molecular weight heparin (LMWH) with standard heparin (SH) for the prevention of postoperative deep vein thrombosis (DVT), revealing contradicting results. Therefore, we have compared the efficacy and safety of a LMWH for the prevention of DVT after major general surgery.

PATIENTS AND METHODS

Patients received either 20 mg LMWH (enoxaparin) once daily, or 5,000 IU SH TID, starting preoperatively in a prospective, randomized, double-blind international multicenter trial. DVT was diagnosed using fibrinogen I 125 leg scanning. Major and minor bleeding were assessed clinically.

RESULTS

A total of 718 patients were randomized to LMWH, and 709 patients to SH. DVT was detected in 58 LMWH-treated patients (8.1%, 95% confidence interval [CI] 6.2% to 10.3%) and in 45 patients allocated to SH (6.3%, 95% CI 4.7% to 8.4%, P > 0.05). Major bleeding complications occurred in 11 LMWH-treated patients (1.5%, 95% CI 0.8% to 2.7%) and in 18 patients to whom standard heparin was administered (2.5%, 95% CI 1.5% to 3.9%, P > 0.05). Four LMWH-treated patients (0.6%) required reoperation for bleeding as compared to 13 patients in the SH group (1.8%, P = 0.03).

CONCLUSION

This LMWH appeared as effective and safe as SH. In view of its more convenient way of administration, this LMWH might be preferred for thromboprophylaxis.

Low-molecular-weight heparin

Low molecular weight heparins (LMWHs) are mixtures of heparin molecules in the range of 3000 to 10,000 daltons. As LMWHs of various manufacturers are all produced differently, they are not comparable to each other and are therefore considered to be individual products with different pharmacologic and clinical properties. All these agents have some common characteristics, however, such as a higher availability after subcutaneous administration and a longer biologic half-life. Numerous clinical trials have demonstrated that LMWHs are highly effective and safe for postsurgical prophylaxis of deep vein thrombosis (DVT); therefore, the LMWHs that are commercially available so far, are mainly approved in this indication. LMWHs are also effective in the prophylaxis of DVT in medical indications, as well as for the treatment of established DVT.

Prophylaxis of postoperative thromboembolism with low molecular weight heparins

To evaluate the thromboprophylactic use of low molecular weight heparins (LMWHs), publications from 27 orthopaedic trials and 35 studies of patients undergoing general or gynaecological surgery were scrutinized and subjected to a partial meta-analysis. In orthopaedic surgery, LMWHs were superior to placebo or dextran and at least as efficient as unfractionated heparin in the prevention of deep vein thrombosis (DVT). Compared with unfractionated heparin, one of the LMWH preparations significantly reduced the total incidence of DVT. The rate of non-fatal pulmonary embolism was 0.49 per cent in patients receiving LMWH and 1.22 per cent in controls. Seven orthopaedic patients (0.15 per cent) died from pulmonary embolism, none of whom received LMWH. In general surgery, the LMWHs were at least as efficient as unfractionated heparin, with a trend towards a lower risk of pulmonary embolism with the former. Compared with unfractionated heparin, LMWHs did not reduce the postoperative mortality rate, nor did they cause haemorrhage. LMWHs provide safe and efficient prophylaxis by administration once daily.

Evaluation of a low molecular weight heparin as an anticoagulant in a model of cardiopulmonary bypass surgery

Heparin, the classically used anticoagulant in cardiopulmonary bypass surgery, has several disadvantages such that alternate anticoagulants are being sought. Previous reports have described questionable safety with the clinical use of low molecular weight (LMW) heparin in cardiac surgery. The dog cardiopulmonary bypass model described herein may provide a useful means to study the pharmacology of new drugs prior to clinical use. Dogs were given a single loading dose of 250 USP units/kg (1.66 mg/kg) of unfractionated heparin (control) or 250 anti-factor Xa units/kg (2.3 mg/kg) LMW heparin and placed on bypass for 60 minutes. Prior to, during, and following bypass blood samples were taken to measure coagulation and hematological parameters. The dogs remained anesthetized for 150 minutes post-bypass. Post-operative blood loss and fibrin deposition in the arterial line filters were measured. Our findings showed there was no significant blood loss (heparin 452 +/- 67 gms; LMW heparin 289 +/- 82 gms) and no significant fibrin deposition (heparin 22 +/- 3 gms; LMW heparin 28 +/- 7 gms) with the LMW heparin. These findings suggest that this LMW heparin should be safe and effective at the studied bolus dose as an anticoagulant for use in cardiopulmonary bypass surgery, and that protamine should be used to reverse the anticoagulant response after surgery.

Low molecular weight versus standard heparin for prevention of venous thromboembolism after major abdominal surgery. The Thromboprophylaxis Collaborative Group

Low-molecular-weight heparin (LMWH) is effective in the prevention of postoperative venous thromboembolism but does it have the safety advantages over standard heparin (SH) that have been claimed? In a multicentre randomised trial in 3809 patients undergoing major abdominal surgery (1894 LMWH, 1915 SH) heparin was given preoperatively and continued for at least 5 postoperative days. Patients were assessed in the postoperative period and were followed up for at least 4 weeks, the emphasis being on safety. Major bleeding events occurred in 69 (3.6%) patients in the LMWH group and 91 (4.8%) patients in the SH group (relative risk 0.77, 95% confidence interval 0.56-1.04; p = 0.10). 93 indices of major bleeding were observed in the 69 LMWH patients and 141 in the SH patients. (p = 0.058). Severe bleeding was less frequent in the LMWH group (1.0% vs 1.9%; p = 0.02), as was wound haematoma (1.4% vs 2.7%; p = 0.007). Bleeding episodes with LMWH were less likely to lead to further surgery to evacuate a haematoma or to control bleeding, and injection site bruising was also less common in the LMWH group. No significant differences were found in the efficacy of the two agents. Perioperative death rates were 3.3% in the LMWH group and 2.5% in the SH group; pulmonary emboli were detected in 0.7% and 0.7%; and deep-vein thrombosis was diagnosed in 0.6% of patients in each group. Follow-up was done on 91% of 3699 evaluable patients. There were 19 further deaths (10 LMWH, 9 SH group) and 25 patients with thromboembolic complications (15 and 10). Of the 3 patients with fatal pulmonary emboli during follow-up 2 had received LMWH and 1 SH. The two drugs were of similar efficacy. The primary end point, the frequency of major bleeding, showed a 23% reduction in the LMWH group, but this difference was not significant. The secondary safety end points revealed that LMWH was significantly better than SH. Fatal pulmonary embolism occurs rarely (0.09%) following discharge from hospital so the cost benefit ratio would not justify prolonged prophylaxis in this setting.

Prevention of deep vein thrombosis in neurosurgical patients: a prospective double-blind comparison of two prophylactic regimen

In a prospective, randomized, double-blind investigation of anticoagulant agents for prevention of deep vein thrombosis in patients undergoing operations at the lumbar-vertebral disc, 179 patients were randomly allocated to two groups. 87 patients received a fixed combination of low-molecular weight heparin 1,500 U-aPTT plus dihydroergotamine 0.5 mg (LMWH/DHE) once a day and additionally one injection of placebo per day, 92 patients received a fixed combination of sodium heparin 5,000 U plus dihydroergotamine 0.5 mg (HDHE) twice a day. Treatment was initiated two hours preoperatively in both groups and continued for at least seven days. Deep vein thrombosis (DVT), detected by the 125Iodine-labelled fibrinogen uptake-test, occurred in four patients treated with LMWH/DHE and in three patients with HDHE. In all seven patients phlebography was performed, confirming the diagnosis of DVT in one patient of the LMWH/DHE group and in two patients of the HDHE group, only. No increased bleeding was found in either group. Especially no neurological complications caused by epidural bleeding were observed. We therefore recommended to treat routineously all patients undergoing operations at the vertebral disc with antithrombotic agents. The advantages of the once daily regimen with low-molecular weight heparin include better patients' acceptance and less nursing time.

Low molecular weight heparin in prevention of perioperative thrombosis

OBJECTIVE

To determine whether prophylactic treatment with low molecular weight heparin reduces the incidence of thrombosis in patients who have had general or orthopaedic surgery.

DESIGN

Meta-analysis of results from 52 randomised, controlled clinical studies (29 in general surgery and 23 in orthopaedic surgery) in which low molecular weight heparin was compared with placebo, dextran, or unfractionated heparin.

SUBJECTS

Patients who had had general or orthopaedic surgery.

INTERVENTION

Once daily injection of a low molecular weight heparin compared with placebo, dextran, or unfractionated heparin.

MAIN OUTCOME MEASURES

Incidence of deep venous thrombosis, pulmonary embolism, major haemorrhages, and death.

RESULTS

The results confirm that low molecular weight heparins are more efficacious for the prophylactic treatment of deep venous thrombosis than placebo (common odds ratio 0.31, 95% confidence interval 0.22 to 0.43; p < 0.001) and dextran (0.44, 0.30 to 0.65; p < 0.001). The results suggest that low molecular weight heparins are also more efficacious than unfractionated heparin (0.85, 0.74 to 0.97; p = 0.02), with no significant difference in the incidence of major haemorrhages (1.06, 0.93 to 1.20; p = 0.62).

CONCLUSIONS

Low molecular weight heparins seem to have a higher benefit to risk ratio than unfractionated heparin in preventing perioperative thrombosis. However, it remains to be shown in a suitably powered clinical trial whether low molecular weight heparin reduces the risk of fatal pulmonary embolism compared with heparin.

Low-molecular-weight heparin versus standard heparin in general and orthopaedic surgery: a meta-analysis

Low-molecular-weight heparins (LMWHs) have theoretical advantages over standard heparin as postoperative thromboprophylactic agents. We conducted a meta-analysis of studies reported between 1984 and April, 1991, in which LMWHs were compared with standard heparin for postoperative prophylaxis. We included only randomised studies (reported in English, French, or German) in which investigators compared currently recommended doses of the agents and used adequate screening techniques for deep vein thrombosis. For all surgical studies the relative risk (LMWH versus standard heparin) for deep vein thrombosis was 0.74 (95% Cl 0.65-0.86), for pulmonary embolism 0.43 (95% Cl 0.26-0.72), and for major bleeding 0.98 (95% Cl 0.69-1.40). Comparable relative risks were observed for the general and orthopaedic surgery studies separately. When the analysis for the general surgery studies was limited to those of strong methodology, assessed by eight criteria defined in advance, the benefit/risk ratio was less favourable--relative risk for deep vein thrombosis 0.91 (95% Cl 0.68-1.23), for major bleeding 1.32 (95% Cl 0.69-2.56). There is at present no convincing evidence that in general surgery patients LMWHs, compared with standard heparin, generate a clinically important improvement in the benefit to risk ratio. However, LMWHs may be preferable for orthopaedic surgery patients, in view of the larger absolute risk reduction for venous thrombosis.

[Different effectiveness of two preparations of low molecular weight heparin in patients with elective hip joint replacement]

In an open randomised trial 3 regimen of prophylaxis for deep vein thrombosis were compared in 105 patients undergoing elective hip arthroplasty. One part of the patients received one injection daily of a low molecular weight heparin, another part was treated with one injection of a combination containing a different type of low molecular weight heparin + dihydroergotamine per day and a third part of the patients received 3 applications of 5000 IU unfractionated heparin per day. The frequency of DVT determined by the 125iodine-labelled fibrinogen uptake test and phlebography was 22.9% in patients receiving the combination and 50.0% in those receiving the low-molecular weight heparin alone. The difference was statistically significant with 2 p = 0.03. The incidence of DVT in patients receiving unfractionated heparin was 30.6%. No difference in the development of bleeding complications was found between the three treatment groups.

Prophylaxis of venous thromboembolism

The objective of prophylaxis in venous thromboembolism is, first, to prevent fatal pulmonary embolism and, second, to reduce the morbidity associated with deep vein thrombosis (DVT) and the postphlebitic limb. This should now be standard practice for most patients over 40 years of age undergoing major surgery and for younger patients with a history of venous thromboembolism. Particularly high-risk groups include patients over 60 years of age undergoing major surgery, those with malignancy, and those requiring hip operations. Low-dose subcutaneous heparin 5,000 IU commencing 2 hours preoperatively and continuing 12 hourly until the patient is fully mobile is unequivocally effective in preventing DVT in medical and surgical patients and, most importantly, significantly reduces the incidence of fatal postoperative pulmonary embolism and total mortality. Such prophylaxis, in the presence of established DVT, also limits proximal clot propagation, which is the precursor of major pulmonary embolism. Low-dose heparin prophylaxis is associated with a small risk of bleeding complications, evidenced mostly by an increased frequency of wound hematoma rather than major clinical hemorrhage. Low molecular weight heparin fragments (e.g., Fragmin, Choay, Enoxaparine) are emerging as useful alternative agents, having the advantage of once daily administration and yet providing similar efficacy in the prevention of DVT. Mechanical methods of prevention which counteract venous stasis, such as graduated elastic compression stockings, are also useful in protecting against DVT but have not been shown to prevent fatal postoperative pulmonary embolism. They are recommended particularly for patients in whom heparin prophylaxis is best avoided (e.g., neurosurgery) and possibly in combination with heparin in very high-risk patients.

Randomized controlled study of heparin and low molecular weight heparin for prevention of deep-vein thrombosis in medical patients

166 patients aged 40-80 years were included in a controlled, randomized, double-blind study to determine the efficacy and safety of a single daily injection of a low molecular weight (LMW) heparin for prevention of deep-vein thrombosis compared to low dose conventional heparin. Patients received 1 x 1.500 aPTT units of a LMW heparin fraction (plus 2 x placebo injection) or 3 x 5.000 IU of an unfractionated heparin. During 10 days of treatment, patients underwent repeated clinical investigation, serial impedance plethysmography, and Doppler sonography for detection of thrombosis of the lower limbs. Combined application of these methods revealed evidence of thrombosis in 4.5% of patients on unfractionated heparin and 3.6% of patients on LMW heparin. Subcutaneous hematomas were significantly smaller in diameter upon treatment with LMW heparin (p less than 0.001). Antithrombin III levels were significantly higher at the end of the observation period in the LMW heparin group (p less than 0.005). Thrombocyte count, transaminases, creatinine, and haemoglobin did not change in either group. The results indicate that LMW heparin administered by a single s.c. dose daily may be as effective as low dose heparin in prevention of deep venous thrombosis in medical inpatients.

Prophylaxis of thromboembolism in general surgery: comparison between standard heparin and Fragmin

In a double blind randomized trial on 250 patients undergoing elective abdominal surgery the effect of Fragmin was compared with heparin. Patients over 40 years of age except appendectomy and herniotomy were included. The dose of heparin was 5,000 IU b.i.d. whilst Fragmin was given in a dose of 2,500 U once per day and the second injection was a placebo. Prophylaxis started 2 h preoperatively and was maintained for 7 days. The fibrinogen uptake test was used as a screening method for thrombosis which was confirmed by phlebography. 124 patients were in the heparin group and 126 in the Fragmin group. Comparability between groups was found in: age, sex, Broca index, amount and type of risk factors, type of surgery. Thromboembolism was found in 10 cases in each group. Blood transfusions on the postoperative days 1 to 6 were required in 2 Fragmin and in 12 heparin patients. The total amount of blood given during that time was 6 units in the Fragmin and 37 units in the heparin group. These differences were significant.

Clinical experience with low molecular weight heparins

Low molecular weight heparins (LMWHs) have been prepared by means of different fragmentation or fractionation procedures with the aim of obtaining a more effective and/or safer antithrombotic agent than standard heparin (SH). LMWHs resulting from different production procedures are structurally heterogeneous; this could account for the different efficacy and safety observed clinically. Many clinical trials have been carried out on the prevention of deep-vein thrombosis (DVT) and pulmonary embolism in patients undergoing major abdominal or orthopedic surgery, hemodialysis or affected by non-hemorrhagic stroke. When given once daily, LMWHs are at least as effective in all indications as SH given twice or three times daily and some of them resulted even more effective than SH in general and in orthopedic surgery. The role of LMWHs in the treatment of DVT and their superiority over SH in terms of bleeding remain to be established.

Fixed combinations of low-molecular weight or unfractionated heparin plus dihydroergotamine in the prevention of postoperative deep vein thrombosis

A prospective, double-blind, randomized, controlled clinical trial compared the efficacy and safety of fixed combinations of low-molecular weight heparin or standard unfractionated heparin plus dihydroergotamine mesylate in the prevention of deep vein thrombosis in high-risk patients undergoing elective major abdominal surgery. Two hundred patients, with a mean age of 66.6 years and almost half with malignancy, were allocated to receive either 5,000 IU unfractionated heparin plus 0.5 mg dihydroergotamine mesylate twice daily or 1,500 IU low-molecular weight heparin plus 0.5 mg dihydroergotamine mesylate once daily together with one placebo injection per day. Treatment was commenced 2 hours preoperatively and continued for at least 7 days. The incidence of deep vein thrombosis, determined by radiolabelled fibrinogen uptake and phlebography, was 11 percent in the unfractionated heparin plus dihydroergotamine mesylate group and 11.4 percent in the low-molecular weight heparin and dihydroergotamine mesylate group. Neither these figures nor those for major proximal thrombi proved significantly different. Of the four parameters used to assess hemorrhagic complications, only the decrease in postoperative hemoglobin levels in the low-molecular weight and dihydroergotamine mesylate group reached statistical significance. These results indicate that once-daily prophylaxis with a combination of low-molecular weight heparin and dihydroergotamine is safe, effective, and convenient in high-risk patients undergoing major abdominal surgery.

Prevention of thromboembolism in hip-fracture patients. Comparison of low-dose heparin and low-molecular-weight heparin combined with dihydroergotamine

In a prospective, double-blind, controlled study, we compared the antithrombotic efficacy of low-dose heparin with dihydroergotamine (A), low-molecular-weight heparin with dihydroergotamine (B), and placebo (C). Two hundred and thirteen patients surgically treated for fractures of the hip were randomly divided into three groups. One hundred and sixty-one patients were analyzed. All thrombi were verified by ascending phlebography. Nine patients died within 1 month after operation. A and B proved to be equally safe but failed to provide any protection against deep-vein thrombosis, although B showed a tendency to reduce the incidence. Mortality within 1 month of operation was unaffected by the type of prophylaxis.

A prospective randomized trial of low molecular weight heparin-DHE and conventional heparin-DHE (with acenocoumarol) in patients undergoing gynaecological surgery

The antithromboembolic efficacy of once a day low molecular weight heparin in fixed combination with dihydroergotamine (LMWH-DHE) was compared with conventional heparin-DHE in combination with Acenocoumarol (heparin-DHE/A) in 191 patients undergoing gynaecological surgery. LMWH-DHE proved equally effective in preventing thromboembolic complications, with a similar incidence of postoperative bleeding and side effects. Deep vein thrombosis occurred once in each group and one non-fatal pulmonary embolism occurred in the LMWH-DHE group. The main advantage of LMWH-DHE was significantly better patient acceptance of the single daily subcutaneous injection as compared with the two injections of conventional heparin-DHE (P = 0.02). On the other hand, LMWH-DHE was associated with significantly increased incidence of intraoperative bleeding (P less than 0.02). The bleeding did not, however, cause any clinical problems. Discontinuation of therapy due to bleeding or pain at the site of injection occurred three times in each group. We consider the use of LMWH-DHE to be an attractive, economic and safe method of thromboembolic prophylaxis.

Comparison of a low molecular weight heparin and unfractionated heparin for the prevention of deep vein thrombosis in patients undergoing abdominal surgery. The European Fraxiparin Study (EFS) Group

In a prospective, randomized multicentre trial the efficacy and safety of the low molecular weight heparin (LMWH) fraction Fraxiparin and unfractionated calcium heparin (Calciparin) were compared for the prevention of postoperative deep vein thrombosis. Of 1909 patients included in the trial 1896 underwent abdominal surgery and received either one daily subcutaneous injection of 7500 anti-Xa units Fraxiparin or 5000 units calcium heparin three times a day subcutaneously. Elastic compression stockings were worn by both groups of patients in the postoperative period. Before randomization the patients were stratified in two subgroups with or without malignant disease. To assess the rate of deep vein thrombosis (DVT), 125I-labelled fibrinogen leg scanning was performed daily for 7 postoperative days. Positive results were confirmed by phlebography whenever possible. Venous thrombosis occurred in 27 of 960 patients (2.8 per cent) given Fraxiparin and in 42 of 936 patients (4.5 per cent) given calcium heparin (P = 0.034). The rates of proximal vein thrombosis were 0.4 per cent (4 patients) and 1.4 per cent (13 patients) respectively (P less than 0.05). Pulmonary embolism occurred in 2 of 960 patients (0.2 per cent) treated with Fraxiparin and in 5 of 936 patients (0.5 per cent) treated with calcium heparin. The two treatments were equally well tolerated. Intra- and postoperative blood loss, the number of wound haematomas as well as frequency and volume of transfusions were similar in both groups. The present trial demonstrates that a single daily subcutaneous injection of Fraxiparin is more effective than the established low dose subcutaneous heparin prophylaxis with 5000 units three times per day in preventing postoperative DVT after abdominal surgery in patients wearing compression stockings.

Heparin/dihydroergotamine for venous thrombosis prophylaxis: comparison of low-dose heparin and low molecular weight heparin in hip surgery

In a prospective, double-blind controlled study we have compared the prophylactic efficacy against deep vein thrombosis of low-dose heparin + dihydroergotamine (A), low molecular weight heparin + dihydroergotamine (B) and placebo (C). A total of three hundred and fifty-six patients undergoing total hip replacement were randomized into three groups and 316 patients were analysed. All thrombi were verified by ascending phlebography. One-third of the patients developed deep vein thrombosis in group A and B, differing significantly from group C. The operative blood loss in group B was higher than that in groups A and C. However, the number of patients transfused and their transfusion requirements did not differ. Severe bleeding occurred in one patient in each group. No deaths were registered during the study. Our study indicates that prophylactic treatment against postoperative deep vein thrombosis with low molecular weight heparin + dihydroergotamine once daily is as effective and safe as conventional low-dose heparin + dihydroergotamine twice daily in patients undergoing total hip replacement. The once-daily regimen has the advantage of better patient acceptance and less nursing time.

Clinical studies with low-molecular-weight heparin(oid)s: an interim analysis

In this review an interim analysis was made of all clinical studies performed with low-molecular-weight heparin(oid)s (LMWH) up to January 1987. Thus far, many experimental studies on LMWH show these substances to have an increased benefit/risk ratio concerning efficacy and bleeding as compared to standard heparin. In man, this increased ratio was verified in some small open studies. However, until the present day, controversy still exists. Some of the difficulties in assessing the results of different investigations include the existence of various kinds of LMWH and the lack of a consensus as to the unitage in which they are expressed. Furthermore, no international agreement exists as to the test measuring dosage/effect and its standard. In the following review all published clinical studies were analyzed for patient groups. Important issues concerning controversy with regard to efficacy, bleeding risk, diagnosis, and testing are discussed. In general, it may be concluded that LMWH have an antithrombotic potential comparable to that of heparin, and that the benefit/risk ratio i.e., decreased bleeding potential when compared to standard heparin, as found in animal experiments, has not been clearly demonstrated in man.