Your patient presents with dizziness and a hemoglobin of 7.2. You give them 2 units of packed red blood cells. Now the question is, how do you assess how well that transfusion worked?
For every person you ask, you will get a different answer about when to check a post-transfusion H/H. One hour…two hours…twenty-four hours…
This Journal Watch from 1994 reports no difference whether H/H is measured at 15 minutes or 24 hours. That being said, there is an even older opinion in the heme path community that 24 hours is considered a good amount of time to allow for fluid shifts and false elevations of lab values.
I personally use 6 hours since that’s what I’ve been taught at my training institutions. The time very well may vary for you. But as you can see, it’s possible to justify most times.