Key Feature 1: Assess the risk of decompensation of anemic patients (ex: volume status, the presence of congestive heart failure [CHF], angina, or other disease states) to decide if prompt transfusion or volume replacement is necessary.
Skill: Clinical Reasoning, Selectivity
Phase: Diagnosis, Treatment
Anemia is common problem. And sometimes it can take a bit of time to figure out what the exact cause is. Most of the time, at least in primary care, anemia is mild and we have time to figure out the etiology to try to deal with the underlying reason for the problem. But in the hospital setting, it becomes not uncommon to manage patients with significant anemia and who may or may not warrant a blood transfusion.
According to the UpToDate article, Use of blood products in the critically ill (2017), indications for the transfusion of packed red blood cells include:
In practice, as a person who generally is not working in critical care settings, I tend to rely on the <70 threshold for deciding on whether or not to order a blood transfusion. But it is important to keep in mind that some patients will have less of a reserve to cope with a decreased supply of oxygen, and these patients may warrant a blood transfusion at a higher threshold than the <70 g/L rule of thumb. In the patient with angina for example, they are exhibiting a sign that they have inadequate oxygen delivery to their heart muscle, and if there is a full on acute MI happening and associated anemia, they certainly warrant a blood transfusion as their heart is already starving of oxygen.
It is also important to consider volume status*, and whether the patient is hypovolemic or hypervolemic. In a patient who is volume deplete but not anemic (essentially dehydrated), we would normally just replace their fluid needs with a crystalloid solution such as normal saline. But in a patient who is volume deplete and more than mildly anemic, they need a blood transfusion; infusion of a crystalloid solution may help keep their body tissue perfused, but it would not increase the oxygen carrying concentration of their blood (and in fact would contribute to decreasing it), and so they really need red blood cells to rectify the problem. On the other hand, in a patient who is hypervolemic and anemic, they may appear more anemic than they otherwise would be if their blood volume wasn't so expanded, and they are also at risk of transfusion-associated circulatory overload (TACO). If a transfusion is necessary in such a patient, I suppose it would be prudent to both reduce circulatory volume and replace red blood cells, but this would be far beyond my level of comfort. I would certainly consult a critical care specialist or a physician who is trained in the management of decompensation of the disease process responsible for the volume overload, such as a cardiologist in the setting of congestive heart failure and/or a nephrologist if a patient has comorbid kidney failure.
One other point that I think is important to mention here is that it is always stressed that patients need to provide consent when it comes to receiving blood products (unless there is implied consent as in an emergency situation). It is interesting to me that this is stressed, as really, we should be gathering consent any time we are about to start an intervention. But I suppose this is particularly stressed because there is a small risk of some very serious consequences. The general risks to outline to a patient regarding blood transfusion when obtaining informed consent include:
*I perform a volume assessment as part of my cardiovascular exam (I like to think of it in two parts, the first half being the precordial exam, and the second being my assessment of volume status). Importantly, each sign by itself may be an indicator of more than volume status (ex: tachycardia in the setting of significant pain), but it is the composite picture that matters. The signs I look for to assess volume status are as follows:
** To calculate the mean arterial pressure (MAP) = diastolic BP added to (0.3 x the pulse pressure, where the pulse pressure = the systolic BP - the diastolic BP)