FAQs
Is There a Hemoglobin Level that Should Trigger a Red Cell Transfusion?
The discussion on this topic could be a very long one, and there is a lot that I could say about it, but let's start by saying this: In my opinion, and in that of most transfusion medicine physicians, there really is not a particular threshold hemoglobin or hematocrit at which you can say "OK, that's it. This patient definitely needs a transfusion."
If you have been around transfusion services or operating rooms for very long, you know that in the eyes of some clinicians, a hemoglobin level of 10 g/dl (corresponding to a hematocrit of 30%) has traditionally served as the "threshold" for transfusion of red cells. In other words, "if the patient's hemoglobin is below 10, doggone it, get it above 10!" What many don't realize is that this value came from some papers published by Mayo Clinic physicians just after World War II (yep, over 50 years ago!) that suggested that people in that era with hemoglobin levels between 8 and 10 g/dL did better after surgery. From that "ancient literature," we ended up with the general, widely held feeling that 10 was the "trigger" hemoglobin for red cell transfusion!
Unfortunately, many clinicians learned the basics of transfusion medicine in exactly the wrong way: From a tired resident, fellow student or intern, or even worse, from an attending who was taught the wrong way himself! It's really not too hard to understand how the 10 g/dl "trigger" came into common usage and acceptance. The truth, though, is more complicated.
Currently, consensus guideline and practice parameter papers have come from all specialties containing variations on the same theme: The 10 g/dl "trigger" is obsolete! Rather, the preferred method of deciding whether or not to transfuse is to evaluate each patient on a case-by-case basis, taking into account the medical (especially cardiac and pulmonary) history, ability to compensate for a lower hemoglobin, medication history (beta blockers limit compensatory tachycardia in anemia, for example), and rate of hemoglobin decline to decide on the utility of a transfusion. Studies have clearly shown that many people can tolerate lower hemoglobin levels than we used to think they could, especially if they have proper compensatory mechanisms (ability to increase cardiac output, etc.).
So what this comes down to is a basic consensus across specialties: Patients with a hemoglobin over 10 g/dl rarely need a red cell transfusion, those with a hemoglobin below 6 usually need a transfusion, and those in between may or may not need a transfusion.
So, the bottom line is simply this: automatic thresholds are simply inappropriate when applied "across the board." A better strategy is to assess each patient and decide what this patient's threshold is, based on clinical and laboratory findings, as well as patient history.
As you can imagine, the reason that the above advice is not followed very often is that it is, quite honestly, much more difficult to evaluate every aspect of a person's response to anemia prior to making a transfusion decision than it is to just look at a lab value! Just because something is more difficult, however, does not make it wrong. The patient on the other end of the transfusion decision deserves a full evaluation and not a quick glance at a lab value before being given a bag of someone else's blood!