Why low Hg, Hct, and RBC postop?

[AlmostNurseJ]

I have had multiple patients that have low Hg, Hct, and RBC counts after surgery, but when putting my reason for the patient's abnormal finding, I can't seem to think of anything except for the fact that they are postop. It makes sense that someone who just had surgery would have a low CBC, but why does it happen exactly?

My patient just had a resection of her colon due to diverticulitis.

Her values are as follows:

First number indicates the day after surgery, second value indicates 7 days later

Hg 9.4, 9.3

Hct 28.1, 28.1

RBC 2.93, 2.92

[adamRn79, BSN, RN]

Random comment; where I work, one ortho surgeon has a standing order to transfuse if hgb

[Do-over, ASN, RN]

Random comment; where I work, one ortho surgeon has a standing order to transfuse if hgb

Does the blood bank object?

I've had some docs order transfusions with higher hgb when MI or ACS.