Low Molecular Weight Heparin for Thromboprophylaxis during Caesarean Section

Abstract

Normal pregnancy is associated with an increased risk of thromboembolic disease [ 1 Bonnar J. Management of venous thrombosis in pregnancy and the puerperium. in: Poller L. Thomson J.J. Thrombosis and Its Management. Churchill Livingstone, London, Edinburgh, New York1993: 47-63 Google Scholar ]. Patients with a personal or family history of pulmonary embolism or venous thrombosis have a high risk of thromboembolic event during pregnancy. Women who are obese, greater than 35 years of age, and require delivery by caesarean section are at increased risk and prophylaxis with heparin is therefore recommended [ 2 Royal College of Obstetricians and Gynaecology. Report on RCOG working party on prophylaxis against thromboembolism in gynaecology and obstetrics (1995). Google Scholar , 3 Lowe G.D.O. Greer I.A. Cooke T.G. Dewar E.P. Evans M.J. Forbes C.D. Risk of and prophylaxis for venous thromboembolism in hospital patients. Thromboembolic risk factors THRIFT consensus group. Br Med J. 1992; 305: 567-574 Crossref PubMed Google Scholar ]. Unfractionated heparin (UH) is generally used for thrombosis prophylaxis and treatment. In recent years several low molecular weight heparins (LMWH) have been developed with increased bioavailability and longer effect duration than standard heparin [ 4 Lane D.A. Macgregor I.R. Michalski R. Kakkar V.V. Anticoagulant activity of four unfractionated and four fractionated heparins. Thromb Res. 1978; 12: 257-271 Abstract Full Text PDF PubMed Scopus (82) Google Scholar ]. These LMWHs have also reduced haemorrhagic and osteoporotic side effects [ 4 Lane D.A. Macgregor I.R. Michalski R. Kakkar V.V. Anticoagulant activity of four unfractionated and four fractionated heparins. Thromb Res. 1978; 12: 257-271 Abstract Full Text PDF PubMed Scopus (82) Google Scholar ]. Enoxaparin is an LMWH of mean molecular weight of 4,500 daltons. A study of 69 pregnant women at high risk of thromboembolism showed that 40 mg of enoxaparin was required for prophylaxis during pregnancy [ 5 Nelson-Piercy C. Letsky E.A. de Swiet M. Low-molecular-weight heparin for obstetric prophylaxis Experience of sixty nine pregnancies in sixty-one women at high risk. Am J Obstet Gynecol. 1997; 176: 1062-1068 Abstract Full Text Full Text PDF PubMed Scopus (273) Google Scholar ]. A recent Food and Drug Administration report has raised concerns regarding the appropriate dose and safety of LMWHs in patients undergoing regional anaesthesia [ 6 Food and Drug Administration (FDA). Reports of epidural or spinal haematomas with concurrent use of low molecular weight heparin and spinal/epidural anaesthesia or spinal puncture (Dec. 1997). Google Scholar ]. Insufficient information exists on the appropriate dose of LMWH for women undergoing elective caesarean section and on the optimum time for needle insertion and catheter removal in patients receiving spinal or epidural anaesthesia. Levels of anti-Xa activity following enoxaparin injection provide an indication of the effects and possible risks of LMWH use during caesarean section. In this study, we investigated anti-Xa levels during caesarean section in women at moderate risk of thromboembolism who received enoxaparin 20 mg/day. In addition a 24-hour pharmacological and haematological profile of enoxaparin was investigated.