Incidences of fatal postoperative pulmonary embolism after prophylaxis with dextran 70 and low-dose heparin: an international multicentre study

The usage and outcomes of dextran in the treatment of acute deep venous thrombosis

OBJECTIVES

In this study, we retrospectively compared the outcomes of patients with acute deep vein thrombosis treated with dextran 40 infusion and unfractionated heparin with those of patients treated with unfractionated heparin alone.

METHODS

We evaluated 104 patients with the diagnosis of acute deep vein thrombosis. The pain complaints of the patients at the time of admission and the pain complaints in the calf with dorsiflexion of the foot were evaluated with the visual analogue pain scale, and the calf diameter of affected limbs was measured. Fifty five patients had dextran 40 infusion and unfractionated heparin treatment concomitantly (Group HD), while 49 patients had unfractionated heparin treatment (Group H). Heparin dose was adjusted to obtain 1.5- to 2.5-fold of normal activated partial thromboplastin time in both groups. Oral anticoagulant, warfarin sodium, was administered in the first day and resumed. Unfractionated heparin infusion therapy was resumed until international normalized ratio values of 2-2.5 were obtained. Dextran 40 infusion therapy was administered for 3 days. Calf diameters, current pain, and calf pain at foot dorsiflexion were recorded at 48 h and 72 h. 65 patients were distal, and 39 patients were proximal and popliteal acute DVT. None of the patients had phlegmasia. All were acute DVT.

RESULTS

At 48 and 72 h of therapy, it was determined that the decrease of the calf diameter and the pain were more significant both at 48th and 72nd hours in the Group HD. The calf circumference change, especially at 72 h, was 2.58 ± 0.39 cm in the group receiving heparin + dextran, while it was 1.76 ± 0.56 cm in the group receiving only heparin. (p = 0.000). While there were only 1.24 ± 1.02 people in the group that received dextran at 72 h, leg pain persisted in 3.35 ± 1.11 people in the other group. (p = 0.000). Evaluation was made only with calf vein diameter measurement. When patients with Homan's sign were evaluated for their calf pain at foot dorsiflexion; both groups had decreased pain at 48th and 72nd hours.

CONCLUSION

In this study, we observed that the use of dextran 40 infusion therapy concomitantly with unfractionated heparin accelerates recovery substantially and decreases patient complaints significantly in early stages. In particular, reduction in leg pain and calf circumference reduction were more adequate in the dextran group. The early decrease in the calf circumference will have clinical consequences such as less heparin intake, earlier return to normal life, and a decrease in the total cost of treatment. Since the antithrombotic and anticoagulant effects of dextran are well known, we think that its use in this treatment as well as venous thromboembolism prophylaxis should be discussed.

Efficacy of Dextran Solutions in Vascular Surgery

The purpose of this paper is to discuss the role and efficacy of dextran in vascular procedures using evidence-based data from the review of surgical literature. A MEDLINE search using “dextran,” “vascular surgery,” and “antiplatelet therapy” as keywords was performed for English-language articles. Further references were obtained through cross-referencing the bibliography cited in each work. Dextran is commonly used in carotid endarterectomy (CEA) patients where the embolic rate is reduced by 46%, resulting in fewer procedure-related strokes. As a prophylactic agent against thrombosis, multiple randomized studies have reported its benefit over other antithrombotic medications. Dextran is also particularly useful in “difficult” infragenicular lower extremity bypasses where artificial grafts (such as polytetrafluoroethylene [PTFE] or umbilical vein) are used in the setting of poor outflow vessels, or those with composite grafts and small-caliber venous conduits. Distal bypasses with adjunctive procedures (eg, arteriovenous fistula or anastomotic cuffs) also have a better outcome with the addition of dextran. Dextran has numerous important implications in vascular surgery, in particular with CEA patients or “difficult” infragenicular bypasses. Its effectiveness with endovascular stents remains unknown.

Timing the First Postoperative Dose of Anticoagulants: Lessons Learned From Clinical Trials

The non-vitamin K antagonist oral anticoagulants (NOACs), rivaroxaban, apixaban, and dabigatran, have been shown in phase 3 trials to be effective for thromboprophylaxis in patients undergoing elective hip or knee arthroplasty. Results from prior studies suggested that the safety of anticoagulants in such patients was improved if the first postoperative dose was delayed for at least 6 h after surgery. The timing of the first postoperative dose of the NOACs tested in phase 2 studies differed among the three NOACs: dabigatran was started 1 to 4 h postoperatively, whereas rivaroxaban and apixaban were started at least 6 and 12 h, postoperatively, respectively. Our review of the timing of initiation of thromboprophylaxis in randomized trials provides three related lessons. First, clinical trials performed before the NOACs were evaluated demonstrated that delaying the first dose of prophylactic anticoagulation until after major surgery is effective and safe. Second, the optimal timing of the first dose of prophylactic anticoagulation after surgery depends on the dose that is selected. Third, the results of the phase 3 trials with NOACs for thromboprophylaxis support the concept that acceptable efficacy and safety can be achieved when the appropriate first postoperative dose of anticoagulant is delayed for at least 6 h after surgery.

Pulmonary embolism in the elderly

The elderly are at increased risk for pulmonary embolism because of both the conditions common to this age group, and the immobility that often accompanies them. Whether aging alone represents a hypercoagulable state is unclear. The incidence of pulmonary embolism rises with age, however, as does pulmonary embolism mortality. The diagnosis of pulmonary embolism is difficult and frequently missed because elderly patients and their physicians may attribute nonspecific symptoms to underlying cardiopulmonary disease or to age itself. Routine laboratory examinations are also nonspecific. Lower extremity studies to diagnose DVT should always be pursued because a positive study results in identical treatment, without the need for further testing. D-dimer concentrations are useful when low, but are commonly elevated in the elderly because of other comorbid conditions. Lung scanning remains the most common initial study to diagnose pulmonary embolism, although spiral CT is as sensitive and specific. Pulmonary angiography should always be considered when the initial studies are nondiagnostic and clinical suspicion is high, and this test is well tolerated in the elderly. The role of newer diagnostic techniques, such as MR imaging, cannot be determined until well-designed outcomes trials are completed. Prophylaxis with appropriate pharmacologic agents or mechanical measures should be administered not only to patients undergoing hip or knee reconstruction surgery, but to all bed-ridden elderly medical and general surgery patients. Treatment for pulmonary embolism with anticoagulation reduces the mortality rate and should be administered in all elderly patients without contraindications. In addition, thrombolysis should be considered for all hemodynamically unstable patients with pulmonary embolism, regardless of age. Vena caval filters are warranted when anticoagulation is contraindicated, although evidence of the long-term benefit of these devices is lacking. At present, pulmonary embolism is underdiagnosed and undertreated in the elderly. By heightening awareness of this diagnosis and its appropriate management in this age group, considerable morbidity and mortality may be avoided.

Incidence of deep venous thrombosis and pulmonary embolism in otolaryngology-head and neck surgery

OBJECTIVE

Postoperative deep venous thrombosis and pulmonary embolus are major causes of morbidity and mortality in patients undergoing surgical procedures. In contrast to other surgical fields, the incidence of these life-threatening conditions has not been studied in our specialty. The purposes of this study were to elucidate the incidence of deep venous thrombosis and pulmonary embolus in patients after otolaryngologic operations and to identify specific risk factors that may contribute to the development of these conditions.

METHODS

A retrospective analysis was done of 12,805 total operations on adults done by the Department of Otolaryngology at our institution from January 1987 to December 1994 to determine the number of patients in whom postoperative deep venous thrombosis and pulmonary embolus developed. Patients in whom a postoperative thromboembolic event developed after an otolaryngologic surgical procedure were identified by the medical records department with use of an abstracting database. This search cross-referenced disease-specific codes for otolaryngologic procedures with the codes for deep venous thrombosis and pulmonary embolus to identify the 34 patients in this report. Results (rounded to the nearest decimal point) were then categorized according to the different subspecialties within otolaryngology, and appropriate statistical analysis tests were performed on the resulting data.

RESULTS

Thirty-four patients with postoperative deep vein thrombosis were identified during the study period, for an overall incidence of 0.3%. Of these 34 patients, 24 also had a pulmonary embolus for an overall incidence of 0.2%. The incidence of deep venous thrombosis (and pulmonary embolus) in the subspecialties was as follows: head and neck surgery, 0.6% (0.4%); otology/neurotology, 0.3% (0.2%); head and neck trauma and plastic surgery, 0.1% (0.1%); and general otolaryngology, 0.1% (0.04%). Only the patient's age and the presence or absence of pneumatic compression devices were identified as independent risk factors for the development of a thromboembolic event.

CONCLUSIONS

Postoperative pulmonary embolus is a rare occurrence in the field of otolaryngology-head and neck surgery. When it does occur, it causes significant morbidity and increases the cost of care for that patient. We discuss our approach to categorizing patients into low-, intermediate-, and high-risk groups, as well as prophylaxis against pulmonary embolus.

Epidemiology, risk factors and prophylaxis of venous thrombo-embolism in obstetrics and gynaecology

Venous thrombo-embolism remains a major cause of mortality and morbidity following gynaecological surgery and in association with pregnancy and delivery. Specific risk factors can be identified pre-operatively and before or during pregnancy and delivery. Clinicians and units should develop guidelines for risk assessment and the implementation of specific thromboprophylactic measures in patients considered to have significant risk. The main prophylactic techniques are unfractionated and low-molecular-weight heparins and physical methods such as graduated elastic compression stockings. It should be noted that there are particular concerns with regard to the use of pharmacological thromboprophylaxis with both heparin and warfarin in pregnancy. Unfractionated heparin is associated with osteoporotic problems, allergy and heparin-induced thrombocytopenia which can cause significant thrombotic problems. Warfarin is associated with teratogenesis and the risk of bleeding in mother and fetus. Clearly, where antenatal thromboprophylaxis is to be used, the risk of the anticoagulants employed must be weighed against the potential benefits. Such assessment might be best done prior to pregnancy in order that the patient can enter pregnancy with a clear view of the potential hazards and benefits. Low-molecular-weight heparins are being increasingly used in pregnancy but it is unclear to what extent they are safer than unfractionated heparins. However, they do appear to have substantially less risk of heparin-induced thrombocytopenia and possibly less risk of heparin-induced osteoporosis. Increasingly, thrombophilia is recognized as underlying many thrombotic problems, particularly in young women, and when the events occur in association with pregnancy. In view of the complexity in the management of such patients, it is important that they be referred to a unit with specific expertise in the management of thrombophilia.

Femoral vein stasis during laparoscopic cholecystectomy: effects of graded elastic compression leg bandages in preventing thrombus formation

Venous stasis of the legs during laparoscopic cholecystectomy was compared between patients without graded compression leg bandages (Group 1; n = 12) and patients with such bandages (Group 2; n = 12) by measuring mean blood flow velocity and cross-sectional area of the femoral vein using a color Doppler ultrasonography. In Group 1, when velocity and area were measured in the supine position, a significant decrease in velocity (p < .05) and a significant increase in area (p < .05) occurred after abdominal insufflation to 10 mm Hg. These changes were greater during abdominal insufflation in the reverse Trendelenburg position than during abdominal insufflation in the supine position. In Group 2, flow velocity was significantly higher (p < .05) before abdominal insufflation as compared with Group 1. After abdominal insufflation to 10 mm Hg and a postural change, velocity significantly decreased (p < .05) and area significantly increased (p < .05) in Group 2, similar to the results in Group 1. During abdominal insufflation at 5 mm Hg or lower, the use of the graded compression bandage was found to be useful for preventing femoral vein stasis. During abdominal insufflation at 10 mm Hg or in the reverse Trendelenburg position, the bandage did not prevent femoral vein stasis.

Thromboembolic disease and thromboprophylaxis in oral and maxillofacial surgery: experience and practice

OBJECTIVE

(i) To determine the incidence of thromboembolic disease (TED) in major maxillofacial surgery and in particular deep vein thrombosis (DVT) and pulmonary embolism (PE). (ii) To determine current thromboprophylactic practice in the specialty.

DESIGN

Retrospective survey by questionnaire of five year experience and current practice in UK maxillofacial surgical units.

SUBJECTS

The patients of 130 consultants carrying out major maxillofacial surgery.

MAIN OUTCOME MEASURES

(i) The number of cases of fatal and non-fatal PE and the number of diagnosed cases of DVT not progressing to PE. (ii) The frequency of use of mechanical and pharmacological thromboprophylactic measures.

RESULTS

(i) There was a 79% return of questionnaires and from these were reported 60 cases of PE of which 14 were fatal with 64 cases of DVT not progressing to PE. Of the PE group almost 60% followed operations for orocervical malignancy while 25% were related to maxillofacial trauma. 64% of respondents had encountered no episodes of perioperative DVT and 68% no cases of PE. (ii) Mechanical thromboprophylactic measures included the use by 76% of respondents of a graduated compression garment, ripple mattress by 47% and intermittent inter-operative calf pressure by 38.5%. Of pharmacological agents 45% used low dose heparin, 14.5% a dextran infusion and 6% an antiplatelet agent. 58.3% gave advice about smoking and 37.5% recommended temporary discontinuation of the contraceptive pill.

CONCLUSIONS

The incidence of DVT and PE in major maxillofacial surgery is low. Nevertheless it is recommended that there is rigid compliance with the recommendations for surgery in general from the thromboembolic risk factors consensus group (THRIFT) and from similar groups in Europe and the USA.

Lower-extremity venous stasis during laparoscopic cholecystectomy as assessed using color Doppler ultrasound

Lower-extremity venous stasis during laparoscopic cholecystectomy was evaluated in 16 patients by monitoring the blood velocity in the femoral vein and the femoral vein size (cross-sectional area) using color Doppler ultrasonography. The blood velocity in the femoral vein decreased significantly after the start of 10-mmHg abdominal insufflation in the supine position. When the patients were placed in a reverse Trendelenburg position during 10-mmHg insufflation, blood velocity in the femoral vein further decreased. However, velocity returned to the baseline after deflation. The cross-sectional area of the femoral vein was significantly elevated after the start of 10 mm Hg insufflation in the supine position. When patients were placed in the reverse Trendelenburg position during 10-mmHg insufflation, this parameter was further elevated, but returned to the baseline soon after deflation. These results indicate that femoral vein stasis during laparoscopic cholecystectomy can be minimized by reducing the pressure of abdominal insufflation and avoiding elevation of the patient's head as much as possible.

Venous thromboembolism in neurosurgery and neurology patients: a review

Thromboembolism is a common problem in neurosurgery and neurology patients. Within this diverse population are subpopulations of patients with varying degrees of thromboembolic risk: low, moderate, and high. Patients at substantial risk for deep vein thrombosis and pulmonary embolism include those with spinal cord injury, brain tumor, subarachnoid hemorrhage, head trauma, stroke, and patients undergoing a neurosurgical operation. There are prophylactic strategies that can be applied to these various risk groups that will dramatically reduce the incidence of thromboembolism. The risk of pulmonary embolism or fatal pulmonary embolism typically exceeds the risk of severe or fatal bleeding from adequate prophylaxis, and these techniques should be applied on a routine basis. To adequately care for patients with deep venous thrombosis and pulmonary embolism, the physician requires a thorough understanding of the methods of diagnosis, the pharmacokinetics of heparin and warfarin, and a knowledge of their role in the treatment strategies that have proven efficacy and safety. In addition, an awareness of the low molecular weight heparins and heparinoids is becoming essential. These new agents have a potentially promising role in both the prophylaxis and treatment of patients with neurological disease. The principles concerning the prophylaxis, diagnosis, and clinical management of venous thromboembolic disease in neurosurgery and neurology patients are dealt with in this review.

Prophylaxis of venous thromboembolism in brain tumor patients

Thromboembolism is a common problem in patients with brain tumors. Within this population are subpopulations of patients at varying but substantial risk for deep vein thrombosis and pulmonary embolism. Prophylactic strategies can be applied to these various risk groups that will dramatically reduce the incidence of thromboembolism, and these should be applied on a routine basis. The standard prophylactic methods for thromboembolic prophylaxis include mechanical devices (e.g., graduated leg stockings; external pneumatic calf compression) and pharmacological agents (e.g., low dose heparin). In addition, a basic knowledge of low molecular weight heparins and heparinoids is essential because these new agents have a potentially promising role in the prophylaxis of neurological disease in certain patients. The principles concerning the prophylaxis of venous thromboembolic disease in patients with brain tumors are addressed in this review.

Safety of enoxaparin and dextran-70 in the prevention of venous thromboembolism in digestive surgery. A play-the-winner-designed study

A total of 327 patients were included in a play-the-winner (PTW)-designed study comparing the safety of prophylaxis with enoxaparin and dextran-70 in patients undergoing digestive surgery. In a PTW-designed study the treatment of any next patient will depend on the outcome of the previous one. If successful, the next patient will receive the same treatment. Excessive bleeding, on the basis of specified criteria, severe adverse effects, or occurrence of clinically detected venous thromboembolism was classified as failure. The PTW design allocates most patients to the superior treatment. In this study 200 patients were given enoxaparin and 127 dextran-70. The success rate was 83% in the enoxaparin group and 74.8% in the dextran-70 group (p = 0.05). The survival analysis of 'Number of patients before change in treatment' shows a significant difference in favour of enoxaparin (p = 0.05). Enoxaparin seems to be superior to dextran-70 as a prophylaxis in digestive surgery. The PTW model is a suitable design in such studies.

Anticoagulants in pregnancy

Pregnancy is associated with a prethrombotic state. Pulmonary embolism is the major cause of maternal mortality. Anticoagulant prophylaxis and therapy are therefore commonplace in pregnant women. Those with inherited and acquired thrombophilic conditions are at increased risk and special considerations arise in management. Heparin has recently become the favoured anticoagulant drug in pregnancy. Its use carries risks of osteopaenia and thrombocytopaenia, as well as haemorrhage, in the mother. Warfarin is teratogenic and may also cause haemorrhagic complications in mother and fetus. Few clinical trial data exists for guidance on optimal anticoagulant regimes during pregnancy and the puerperium and details of management will depend upon the personal preferences of patient and clinician, after due consideration of the perceived risks and benefits in the individual clinical situation.

Pharmacology and physiology of colloids

The importance of an adequate circulating volume in the critically ill is well established. Plasma, albumin, synthetic colloids and crystalloids may all be used for volume expansion but the first two are expensive and crystalloids have to be given in much larger volumes than colloids to achieve the same effect. Synthetic colloids provide a cheaper, safe, effective alternative. There are three classes of synthetic colloid; dextrans, gelatins and hydroxyethyl starches; each is available in several formulations with different properties which affect their initial plasma expanding effects, retention in the circulation and side-effects. There is no ideal colloid but those with low molecular weights such as gelatins are more suitable for rapid, short term volume expansion whilst in states of capillary leak where longer term effects are required hydroxyethyl starches are more effective. Dextrans are as effective as the alternatives but produce more side-effects and the need to pre-treat with hapten-dextran renders them unwieldy in use. Albumin is as persistent as hydroxyethyl starch in the healthy circulation but is retained less well in states of capillary leak. It has no significant advantages over starches and is much more expensive.

Prolonged barbiturate therapy in a patient with closed head injury and jugular venous thrombosis

The case of a patient who sustained a severe closed head injury complicated by jugular venous thrombosis is presented. Early problems with intracranial pressure were related to bifrontal intracerebral contusions. Jugular vein thrombosis became manifest clinically late in the patient's course and was verified by Doppler ultrasonography. Late problems with intracranial hypertension were presumed to be due to decreased cerebral outflow secondary to the thrombosis. The patient required 4 weeks of a high-dose regimen of pentobarbital to control his intracranial pressure. This is an exceptionally long period of time for a patient to be in barbiturate coma for a closed head injury and still make a satisfactory recovery. The incidence, etiology, prevention, and treatment of upper extremity and jugular venous thrombosis are discussed. The ramifications of jugular venous thrombosis in neurosurgical patients are discussed.

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.

Risk of and prophylaxis for venous thromboembolism in hospital patients. Thromboembolic Risk Factors (THRIFT) Consensus Group

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Prevention of deep vein thrombosis in patients with hip fractures: low molecular weight heparin versus dextran

A randomized open trial was undertaken to compare the antithrombotic efficacy of a low molecular weight heparin (LMWH; Sandoparin) with that of dextran 70 in patients undergoing surgery for hip fracture. One hundred thirteen patients received LMWH once daily subcutaneously at a fixed dosage while 103 patients received intravenous dextran 70. Postoperative deep vein thrombosis (DVT) was assessed by a diagnostic algorithm using the 125Iodine fibrinogen uptake test as screening and Duplex ultrasonography and/or ascending venography as confirming techniques for suspected DVT. The frequency of DVT was significantly lower in the LMWH group than in the dextran group (15.5 versus 32.6%, p less than 0.005). Proximal DVT was rare in both groups (LMWH: 2%, Dextran: 1%). Only one case of fatal fat pulmonary embolism was observed during the 10 day prophylaxis period in a patient receiving Dextran. Three cases of pulmonary embolism occurred later; one fatal event in the dextran group on day 14, and two cases in the LMWH group (one fatal and one non-fatal event) on day 14 and 17, respectively. There was no major bleeding complication in either group. We conclude that the LMWH we used is safe, was well tolerated, and has a significantly better thromboprophylactic effect than dextran 70.

An autopsy study of pulmonary thromboembolism in Hong Kong Chinese

A retrospective study of autopsied material in the last 15 yrs is documented an increasing incidence of pulmonary thromboembolism (PTE) in Hong Kong Chinese. The incidence of significant PTE increased from 0.58% in the first 5 yr period to 2.08% in recent years. The topographic features and characteristics of these PTE patients are analysed and the factors contributing to the changes are discussed.

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.

Anticoagulants in the prevention of venous thromboembolism

For 50 years, the key to successfully preventing venous thrombosis (VT) or pulmonary embolism (PE) among high-risk patients has been the judicious use of anticoagulants: first through full doses of oral anticoagulants and more recently through low-dose heparin prophylaxis. Low-dose heparin has become the standard of comparison for other preventive methods, since it is relatively safe and simple, its ability to prevent approximately 65% of the subclinical VT found by leg scanning after elective general surgery is well known, and recent meta-analysis of the many pertinent published clinical trials (large and small) strongly suggests a much greater benefit: a 65% reduction in the risk of postoperative death from major PE. In addition, there are trials that have also found low-dose heparin to be effective in general medical patients, although its value in this clinical setting is much less well documented. Although several effective approaches other than low-dose heparin are available, many of these tend to be either more cumbersome (intermittent external leg compression) or probably less powerful (graded pressure elastic stockings). There are situations where low-dose heparin prophylaxis fails, most obviously after orthopaedic surgery where the use of more complex regimens, including adjusted-dose heparin treatment and various schedules of warfarin prophylaxis, becomes appropriate. Recent progress has come from the intensive clinical exploration of various low molecular weight heparin fractions or fragments which appear to be effective after once daily administration to general surgical patients and show great promise of effectiveness and safety after hip surgery. The level of warfarin effect needed for VT prophylaxis has also been reinvestigated, with trials suggesting a need for less warfarin and a lower prothrombin time effect than was previously thought to be appropriate. Given that any attempts to minimize mortality from PE in hospital patients must rely on the widespread and systematic use of simple, safe, and cost-effective preventive methods, it is hoped that these advances will help move anticoagulant prophylaxis further out of the realm of clinical research and into that of common clinical practice.

Prevention of venous thrombosis and pulmonary embolism

Deep vein thrombosis (DVT) leads to hospitalization for up to 600,000 persons each year in the United States. Venous thrombosis in itself may be benign, but the condition can lead to dangerous complications and has a high recurrence rate. Strategies to prevent DVT involve prevention of stasis and reversal of changes in blood coagulability that allow thrombi to form. Pharmacologic agents have been effective in reducing the incidence of DVT and pulmonary embolism. Low-dose subcutaneous heparin is considered a nearly ideal DVT preventative for surgically treated patients. The risk of hemorrhage is the main limitation to routine use of subcutaneous anticoagulants for DVT, but careful patient selection can minimize that risk. After anticoagulant therapy with heparin, generally for 7 to 10 days, oral warfarin is the drug of choice for maintenance anticoagulation to prevent DVT recurrence. Therapy for pulmonary embolism is the same as for DVT--immediate anticoagulation with heparin followed by maintenance with warfarin.

Thrombosis prophylaxis with low molecular weight heparin in total hip replacement

In a randomized prospective trial, the efficacy of low molecular weight heparin (LMWH) (Fragmin) and dextran 70 (Macrodex) in preventing deep vein thrombosis (DVT) in the legs was evaluated in 98 consecutive patients undergoing elective total hip replacement. The patients were randomly allocated to receive either 2500 anti-factor Xa units LMWH twice daily for 7 days, with the first dose given 2 h before surgery; or 500 ml dextran 70 twice during the day of operation, followed by a single infusion of 500 ml on the first and again on the third postoperative day. DVT was assessed by 125I-fibrinogen test for 2 weeks postoperatively, a positive test being followed by phlebography. DVT developed in 22 (45 per cent) of 49 patients receiving dextran 70 and in 10 (20 per cent) of 49 patients in the LMWH group (P less than 0.01). LMWH was thus statistically significantly better than dextran 70 in preventing DVT in the legs. It was not firmly established whether this benefit was also valid in the high ileofemoral region. Two patients with non-fatal pulmonary embolism were found in each group. Per- and postoperative blood loss and blood transfusion requirements were significantly lower in the LMWH group.

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.

Low molecular weight heparin given the evening before surgery compared with conventional low-dose heparin in prevention of thrombosis

A prospective randomized double-blind trial was performed comparing conventional low-dose heparin with a low molecular weight heparin fragment for thromboprophylaxis in elective general abdominal surgical patients. The first dose of the heparin fragment was given the evening before surgery, and further doses were given thereafter every evening. There were 1002 analysable patients, 826 having received correct prophylaxis. Of these 1002 patients, 64 per cent were operated on for malignant disease. A total of 20 patients died, 10 in each group. The frequency of deep vein thrombosis was significantly reduced among patients with correct prophylaxis with the heparin fragment (9.2-5.0 per cent, P = 0.02) [corrected]. The frequency of bleeding was 6.7 per cent among the heparin fragment patients and 2.7 per cent among the patients given conventional heparin (P = 0.01), but all bleeds were of minor degree and there was no difference in the reoperation rate for bleeding, or in the transfusion requirements. Local pain at the injection site was reported significantly less often among patients given the heparin fragment.

Prevention of venous thromboembolism in general surgical patients. Results of meta-analysis

The results of randomized clinical trials evaluating commonly used methods of deep vein thrombosis (DVT) prophylaxis in moderate- and high-risk general surgery patients were pooled to obtain an unbiased estimate of efficacy and risks. Low-dose heparin (LDH), dextran, heparin-dihydroergotamine (HDHE), intermittent pneumatic compression (IPC), and graded elastic stockings significantly reduced the incidence of DVT; aspirin was ineffective. In contrast to other methods, elastic stockings have not been adequately studied to determine their value in reducing DVT in high-risk patients, such as those with malignancy. Only LDH and dextran were studied in numbers of patients sufficient for demonstrating a clear reduction in pulmonary embolism (PE). In comparison studies, LDH was superior to dextran in preventing DVT, but the two agents were equivalent in protecting against PE. Although HDHE was marginally better than LDH in preventing DVT, it appeared to have no advantage in preventing PE--at least in moderate-risk patients. The incidence of major hemorrhage was not increased with any of the prophylactic agents. However, wound hematomas occurred significantly more frequently with LDH, an effect noted in the pooled data from double-blind and open trials. In comparison trials with LDH, both dextran and HDHE had significantly fewer wound hematomas. LDH administered every 8 hours appeared more effective in reducing DVT than LDH administered every 12 hours; the incidence of wound hematomas was equivalent with both regimens.

A prospective 10-year study of the post-thrombotic syndrome in a surgical population

A total of 564 patients undergoing laparotomy entered a prospective 10-year study to determine the influence of postoperative DVT relative to other thrombotic episodes on the subsequent development of post-thrombotic syndrome (PTS). Pre-existing venous thrombotic disease and postoperative thromboses were assessed at the initial hospitalisation. Subsequent thrombotic episodes and signs of PTS have been monitored at biennial review. Thirty-five patients had PTS by the tenth year but it was already present in 16 before the index operation. Twenty-six patients without previous thrombotic episodes developed spontaneous DVT or phlebitis during the 10-year follow-up. New leg ulcers developed in six patients. Although all thrombotic episodes, irrespective of the relation to the index operation, increased the risk of PTS, most PTS occurred in patients without recognised DVT, although most had lesser venous problems prior to operation. PTS should be seen as resulting from the summation of a number of incidents of damage to the leg veins rather than one postoperative incident. Direction of prophylactic effort to patients with pre-existing venous problems may best reduce PTS among patients undergoing abdominal surgery, but will not make a major impact on the total population incidence of PTS.