Читать книгу Pathy's Principles and Practice of Geriatric Medicine - Группа авторов - Страница 596

A high INR is one of the most critical factors related to the risk of bleeding – hence the importance of maintaining the lowest effective intensity of anticoagulation in the elderly. Several studies have reported a curvilinear relationship between the degree of anticoagulation and the risk of bleeding (Figure 25.1).⁴⁹

Currently, a target INR of 2.5 (2 to 3) is recommended for treatment of VTE and primary and secondary stroke prevention in individuals with non‐valvular AF. Higher‐intensity anticoagulation may be needed under specific circumstances, such as preventing thromboembolism in those with prosthetic heart valves (2.5–3.5) or recurrent thromboembolism.⁵⁰

Figure 25.1 Relationship between the intensity of anticoagulation and the risk of thromboembolism (TE) and bleeding in 1865 patients receiving oral anticoagulants after insertion of St Jude prosthetic heart valves. The single open circle represents 12 patients who received only antiplatelet agents because of contraindications to warfarin therapy. INR = international normalization ratio.

Source: Horstkotte et al.,⁴⁹ ©1993, ICR Publishers.

There is no biomarker that reflects direct anticoagulant biological activity. Fixed doses are given, although, based on studies conducted so far, it is advisable to adjust the dose in different situations, as mentioned above.