Hgb estimation after blood loss

[YorkshireExile]

Not sure where to put this topic, so hope this place is okay. One of our OB/GYN doctors has expressed her concern to me as to what she thinks is an excessive use of blood units by other doctors when there is a major bleed in OT. (Something that I have also been concerned with.) She tells me they estimate that for every litre of blood lost the Hgb will drop by 2g/dl. This seems a bit high to me, and I remember being told a long time ago the expected drop should only be 1-1.5g/dl. I cannot find any literature or references anywhere though to back this up.

Anyone have any thoughts on this? I`m trying to conserve my precious blood stocks!

[Malcolm Needs ☆]

Not sure where to put this topic, so hope this place is okay. One of our OB/GYN doctors has expressed her concern to me as to what she thinks is an excessive use of blood units by other doctors when there is a major bleed in OT. (Something that I have also been concerned with.) She tells me they estimate that for every litre of blood lost the Hgb will drop by 2g/dl. This seems a bit high to me, and I remember being told a long time ago the expected drop should only be 1-1.5g/dl. I cannot find any literature or references anywhere though to back this up.

Anyone have any thoughts on this? I`m trying to conserve my precious blood stocks!

In a way, you are asking an impossible question, as It depends upon the size of the individual and, therefore, their blood volume. It also depends upon how much colloid/crystalloid has been transfused to maintain this blood volume, and in the case of a colloid in particular, the average molecular weight of the preparation, as the lower the molecular weight the quicker the colloid is cleared from the circulation (but the faster liquid is drawn into the circulation from the interstitial spaces) and vice versa.

I would, therefore, thoroughly recommend reading Chapter 2 of Mollison's Blood Transfusion in Clinical Medicine, Harvey G. Klein and David J. Anstee, Blackwell Publication, 11th Edition.

This is not, in my opinion, an easy read (although, again, in my opinion, it is easier to read than some of the earlier editions!), but it does give all sorts of mathematical equations to help estimate blood loss and how much is required to bring the patient back to some kind of normality.

I am certain that other posters will be able to answer your question better than I, but it's a start.

:)

[Lcsmrz]

I vaguely remember a scientific study from years and years ago about estimating blood loss using various methods. The most accurate was the guestimate by the Anesthesiologist looking over the drapes and saying "looks like about xx units to me."

OB/Gyn docs are notoriously frugal with transfusions (even with large bleeds), whereas Internalists dealing with old, frail patients with multiple morbidities seem to be the most liberal. All clinicians can produce literature supporting their transfusion strategies, since there is a distinct lack of censensus among the different specialties.

I've always used 1 g Hgb per unit as a ballpark figure.

[David Saikin]

When I take a unit of red cells from someone (450-500 mL) I expect their Hgb to drop by about 1 gram. These are relatively healthy individuals - either donors or therapeutic bleeds.

[adiescast]

Generally 1 g/dl is the measure for hemoglobin change with a unit of blood, which is actually half a liter. There does need to be a consideration of whether the patient can tolerate the loss without replacement (like they started with a 15 g hemoglobin and now they are at 12 or even 10). Do you have transfusion guidelines in place at your institution?