Uses of heparin

Some limits to evidence-based medicine: a case study from elective orthopaedics

There has been growing interest in recent years in the application of the principles of evidence-based medicine (EBM), although implementation is complex. Scientific, organisational, and behavioural factors all combine to shape clinical behaviour change. Case study based qualitative data are presented which illuminate such processes within one clinical setting (elective orthopaedics), drawn from a larger study. It is suggested that (1) there are alternative models of what constitutes "evidence" in use; (2) scientific knowledge is in part socially constructed; and (3) clinical professionals retain a monopoly of technical knowledge. The implication is that there may be severe obstacles to the rapid or broad implementation of EBM.

Achieving clinical behaviour change: a case of becoming indeterminate

This paper is based on an empirical study of attempts to achieve change in clinical behaviour across a United Kingdom National Health Service (NHS) Health Authority (HA). We suggest that the evidence based medicine (EBM) movement underpinning such attempts is premised upon a highly rationalistic conception of change. Here the generation and implementation of research findings into clinical practice is understood as movement between discrete entities. Drawing upon poststructural philosophy, social studies of science and technology, social anthropology, and gender studies, we challenge such linear perspectives through a more immanent alternative. We conceive of change as movement within indeterminate or ambiguous relationships. We then proceed to discuss the implications of this modality for the management of clinical behaviour change.

Hazards of heparin: allergy, heparin-induced thrombocytopenia and osteoporosis

Heparin is the commonest mode of thromboprophylaxis used in pregnancy. It does not cross the placenta but has potential adverse effects on the mother, of which the most important is heparin-induced osteoporosis. The hazards of heparin, including bleeding, skin reactions, heparin-induced thrombocytopenia and osteoporosis are discussed and the relevant literature reviewed. Low-molecular-weight heparins have certain advantages over standard unfractionated heparins, especially in obstetrics. Their longer half-life and increased bioavailability enable once-daily injections, making them more convenient and acceptable. They are as effective as standard heparin but have a theoretically more favourable side-effect profile, providing less anticoagulant relative to antithrombotic activity. Current evidence suggests a lower incidence of heparin-induced thrombocytopenia. A reduced risk of osteoporosis is suggested but not yet proven. Although thrombo-embolism is currently the leading cause of maternal mortality in the UK, antenatal heparin prophylaxis is not given to all women with previous thrombo-embolism because of continued fears concerning heparin-induced osteoporosis. A protocol is presented with guidelines for different levels of obstetric prophylaxis depending on the perceived level of risk.

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.

Pilot study of low-molecular-weight heparin in the treatment of acute ischemic stroke

BACKGROUND

Our purpose was to assess the feasibility and risk of performing a double-blind placebo-controlled study of low-molecular-weight heparin in the treatment of acute ischemic stroke.

SUMMARY OF REPORT

Fifty-five patients were treated within 48 hours of stroke onset. Pretreatment computed tomography was performed to rule out cerebral hemorrhage. Fraxiparine (6000 IU per day) was given subcutaneously for 7 days. No adverse reaction was encountered during the treatment period. At 3 months, 26 patients were independent, 21 moderately disabled, 4 severely disabled, and 4 dead.

CONCLUSIONS

It would be safe and practical to conduct a clinical trial on the use of Fraxiparine in the treatment of acute ischemic stroke.