Risk factors for bleeding during anticoagulation

Abstract

Heparin: Conventional heparin at therapeutic doses increases risk of haemorrhage. Length of treatment with heparin appears to be an important determinant of cumulative risk of bleeding, with less conclusive evidence to support the effects of higher daily doses or greater prolongation of the APTT. Continuous intravenous infusion and intermittent subcutaneous injection are likely to be equally safe methods of administration. Recent trauma, liver dysfunction and cerebrovascular disease (in the case of intracranial bleeding) are recognized risk factors for major or life-threatening haemorrhage. The presence of other serious underlying illnesses as well as combination with other antithrombotic agents increases bleeding risk. Elderly patients seem to be at increased haemorrhagic risk compared with younger patients but, conversely, may have more to gain from therapy. Warfarin: Bleeding risk is increased by either inpatient or outpatient warfarin therapy. There is some evidence that bleeding risk is greater for inpatients, but that the risk of bleeding is less for patients treated with warfarin than for those on heparin. Whether this is related to patient characteristics or a greater prohaemorrhagic effect of heparin compared to warfarin is unclear. Cumulative bleeding rates increase with the duration of warfarin therapy, although risks are probably greatest during the initiation of treatment. There is good evidence that haemorrhagic risk is influenced by the intensity of anticoagulation, the additional use of aspirin and the nature of the presenting and associated disorders. Previous stroke or gastrointestinal bleeding increase bleeding risk, as do the presence of other serious illnesses. Lesions in the gastrointestinal and genitourinary tracts are responsible for a large proportion of bleeding, which therefore warrant investigation. The relationship between factors such as age, hypertension and bleeding risk is unclear through the nature of the studies; increasing age and hypertension may be useful markers, both of risk of bleeding and risk of thromboembolism.