Читать книгу Practical Cardiovascular Medicine - Elias B. Hanna - Страница 49

Anemia may exacerbate myocardial ischemia in patients with CAD or ACS. Yet transfusion, by itself, does not necessarily reverse this ischemia and may be associated with worse clinical outcomes. This is linked to potential prothrombotic (ADP release) and proinflammatory effects of transfusion and to the impaired oxygen-carrying capacity of the transfused red blood cells.¹⁴¹ In addition, while normal red blood cells transport and dispense nitric oxide to the microvasculature, this function is disrupted in transfused red blood cells, which leads to impaired regional vasodilatation. Two analyses have found that transfusion is associated with increased mortality in ACS patients with a hematocrit > 25–27%.^143,144 A randomized trial, REALITY, showed that a restrictive transfusion strategy (transfusion for Hb ≤8 g/dl) is as safe as a more liberal strategy (transfusion for Hb ≤10 g/dl) in patients with MI, most of whom underwent an invasive strategy.¹⁴⁵ Other studies have found a strong association between transfusion and adverse outcomes after PCI, performed for ACS or stable CAD, and after CABG.¹⁴³ Thus, unless the patient is hemodynamically unstable from bleeding, severely tachycardic, or has refractory angina, transfusion should be withheld when hemoglobin is >8 g/dl or hematocrit is >25% (grade I recommendation, ESC).^4,146 For patients who continue to exhibit episodes of angina at rest or mild exertion, a higher transfusion cutoff may be used (9 g/dl). Also, in patients about to undergo PCI, a higher cutoff has generally been used in real-world registries (9 g/dl).¹⁴⁷