How long?

[phouck]

In your institutions, how long do you wait before drawing a CBC or other lab work from a patient that has just received blood? We used to tell them to wait at least an hour, but I cannot find any reference for that time frame. I have been questione about this a whole bunch lately.

Thanks

[L106]

At our institution, it is up to the physician. However, most of our repeat CBC's are ordered for the day after the transfusion (unless the patient is actively bleeding, of course.)

[AMcCord]

I have seen some references which say that ideally you should wait 24-48 hours (see Mollison - Blood Transfusion in Clinical Medicine), but that's not very real world. We try for 1/2 hour after the end of the transfusion if we receive an order that specifies a draw 'after the 2nd unit' (or 1st or whatever). However, if you are talking about a patient who is actively bleeding, the Hgb is a moving target, so an immediate (5 min) draw can be useful to the physician - is he keeping up with the bleed or losing ground. The amount of fluid pushed into your patient will also have an impact on the Hgb level - the Hgb level at 24 hours might be 10% higher than the level you got at 15 - 60 minutes due to fluid dynamics. So, in some cases, our draws are when the doc specifies. The time most commonly specified by our docs is 30 minutes. 5 minutes is common in surgical bleeds, 15 min for active GI bleeds. Many of our post-transfusion draws are simply ordered for next AM.

You might find this article helpful: Equilibration of Hemoglobin Concentration After Transfusion In Medical Inpatients Not Actively Bleeding, Wiesen et al found in the Annals of Internal Medicine 15 august 1994, volume 121, Issue 4, Pages 278-280. Wiesen and company did a small study of their own with patients >18yrs and no recent active bleeding. They determined that Hgb levels measured in this type of patient at 15 minutes, 1 hr, 2 hrs, and 24 hrs were statistically equivalent. (They note small studies done in pediatric patients and neonates which give equivical results or agree with their findings in adults.) They also cite 19 sources, so you might find a study that is more relevant to your patient population.

Edited October 22, 2009 by AMcCord

[LABLAD42]

August 19, 1994

MEASURING HEMOGLOBIN CONCENTRATION AFTER TRANSFUSION.

AS Brett reviewing Wiesen AR et al. Ann Intern Med 1994 Aug 15.

At what point after blood transfusion is it possible to get a reliable measure of the increase in hemoglobin concentration? These researchers tackled this question by measuring hemoglobin concentrations in 39 patients 15 minutes, 1 hour, 2 hours, and 24 hours after the patients received two units of packed red cells. None of the patients had active or recent bleeding.

The mean baseline hemoglobin level was 7.4 g/dl. Fifteen minutes after the transfusion, the mean hemoglobin concentration was 9.4 g/dl, and remained at this level throughout the first 24 hours. Various clinical variables such as body size, recent diuretic use, or duration of transfusion did not influence these results.

AS Brett

Comment

Determination of hemoglobin concentration 15 minutes after transfusion of packed cells accurately reflects the steady-state concentration for the next 24 hours. When a measure of the effect of a transfusion is needed, a single hemoglobin determination shortly afterward is sufficient.

Citation(s):

Wiesen AR et al. Equilibration of hemoglobin concentration after transfusion in medical inpatients not actively bleeding. Ann Intern Med 1994 Aug 15 121 278 280

PubMed abstract (Free)Web of Science

- See more at: http://www.jwatch.org/jw199408190000005/1994/08/19/measuring-hemoglobin-concentration-after#sthash.YLIdWCz2.dpuf

[tbostock]

Minimum of 15 minutes is adequate

[Auntie-D]

Most places I have worked at have said half an hour. One said after their first urine pass as that indicates haemodynamic stability.