You might be surprised to learn that many of the patients who receive red cell transfusions in the emergency department don’t need them. A Canadian study looking at trends in transfusion practice in the emergency department found that about half of transfusions given were deemed unnecessary.
If we think of a blood transfusion as a “blood transplant” similar to an organ transplant, then the potential complications including transfusion-associated circulatory overload (TACO), transfusion-related lung injury (TRALI), and alloimmunization become, perhaps, a bit more understandable. When you give someone a blood transfusion, you’re changing the patient’s immune system for life. Red cell transfusions should not be thought of as a delivery system for iron! While IV iron has been used for years in hematology clinics across the country, the emergency medicine community has been largely unaware of this sensible alternative.
The literature is full of studies showing that morbidity and mortality outcomes with lower hemoglobin thresholds, such as 7 g/dL for transfusing ICU patients (in the TRICC [Transfusion Requirements in Critical Care] trial), patients in septic shock (in the TRISS [Transfusion Requirements in Septic Shock] trial), and patients with gastrointestinal bleeds, are similar to outcomes with traditional higher hemoglobin thresholds of 9 or 10 g/dL.
The American Association of Blood Banks, in conjunction with the American Board of Internal Medicine’s Choosing Wisely campaign, recognized that physicians were being overzealous with our transfusions. One of its five statements on medication overuse declared, “Don’t transfuse iron deficiency without hemodynamic instability.”
How Low Can You Go?
So how low can a patient’s hemoglobin go? In a remarkable study (for ethical reasons) of healthy subjects, hemoglobin concentrations were reduced from 13.1 g/dL to as low as 5 g/dL by replacing aliquots of blood (450–900 mL) with 5 percent human albumin and/or autologous plasma. The researchers found that systemic oxygen delivery was maintained as assessed by change of O2 and plasma lactate concentration. Holter monitor readings suggested that myocardial ischemia was extraordinarily rare in this resting healthy population. Based on this and similar studies, the American Society of Anesthesiologists recommends against red cell transfusions in young, healthy patients without ongoing blood loss and a hemoglobin level greater than 6.0 g/dL, unless they are symptomatic or hemodynamically unstable.