We have RN's asking this every couple of months and don't know whay we tell them what we do. We always get asked how long after a transfusion can we draw a CBC, PTT, Plt count? We usually tell them to wait at least 30 minutes, but an hour would be better for accurate results. We had a nurse today ask us to draw a PTT during a blood transfusion. Does anyone have any referneces that we could show the nurses, etc how and why blood transfuions may affect lab results? We've always told them to wait a little bit after, but have never really been able to show them why. Just looking for a little info to help back us up.

My biggest concern about drawing during transfusions is that here, all transfusions are run with normal saline and some are preceeded/followed with lasix. So, I usually go the one hour after route to eliminate dilution with the fluids that are run with the blood product.

I think all transfusion can influence the blood test.

I read a blurb (years ago) that you can get valid results 5 minutes post-transfusion . . . would make an interesting study. There does not seem to be any reason for NOT drawing during a transfusion except for the bias against it. Once again, I'm from Missouri so I'd like to know why not . . . blood circulates fairly rapidly. I've looked for data on this - no text addresses it, not even Mollison's many versions.

Transfusion/Blood Transfusion does not matter to draw a blood sample, unless it is not drawn from the same IV line or same extremity. I have not seen any word in the literature (Same as David wrote above) .

In the case of an actively bleeding patient, it may be very necessary to draw during infusion of blood products. The doc needs to know whether the patient is gaining or losing ground. It's up to him/her to properly interpret the data the lab provides, which in some cases should include a comment about the patient's transfusion status (1 hour post, 2nd red cell unit running,... whatever is pertinent to the case).

Our standing policy is to hold all routine labs until 1 hour post transfusion, but like AMcCord said, if the doc wants it drawn, he can interpret things the way he wants to. We usually put in a comment, drawn during transfusion.

I ahven't commented on this thread (not least because it is WAY out of my area of expertise), but a thought has been nagging at me, and I would like to ask, what happens in the case of near patient testing, such as the thromboelastograph, when the patient is being tansfused and, come to that, a patient with major, life-threatening haemorrhage, who is being given a transfusion? Surely, these patients are tested for various parameters whilst a transfusion is happening??????????