Red Blood Cell Product Transfusion Equation for Patients > 40 kg
Transfusing more than the minimum number of blood product units necessary to relieve symptoms, or return a
patient to safe range or targeted levels, is not recommended.1,2 (UW Health Low quality evidence, strong
recommendation) Therefore, a calculator was developed in Health Link which suggests the appropriate number of
packed red blood cells (PRBC) units needed to meet the target hematocrit (Hct) or hemoglobin (Hgb) level
using the mathematical logic outlined below. | Contact the Blood Bank with questions or comments.
Reference the UW Health Blood Product Transfusion Guidelines for transfusion indications or appropriate target levels.
Step 1: Obtain current Hct or Hgb value (last value within 24 hours of current encounter).
Step 2: Is the current value > target value?
If no, proceed to Step 3. If yes, no need to transfuse; return to Step 1.
Step 3: Calculate the difference between the current and target values.
(Target Hct – current Hct) = ΔHgb OR (Target Hgb – current Hgb) = ΔHgb
Step 4: Normalize the current patient weight for the average weight of an adult.7
Actual weight (kg) = Blood volume
Step 5: Calculate the number of PRBC units needed to meet the target value.
ΔHgb x Blood volume = Number of PRBC units (rounded to nearest integer)
Step 6: If the number of PRBC units result is < 5 units, transfuse that number of units and return to
Step 1. If result is > 5 units, consider initiation of the UW Health Massive Transfusion Procedure.
CONTACT PHYSICIAN FOR TRANSFUSION CONCERNS.
DISCLAIMER: The decision to transfuse red blood cells should always be dependent on patient presentation and individual
characteristics, degree of severity of anemia, presence and severity of comorbidities, and the clinical judgement of the physician.
1. Hematology ASo. Ten Things Physicians and Patients Should Question. Choosing Wisely 2013; http://www.choosingwisely.org/societies/american-society-of-
2. Carson JL, Grossman BJ, Kleinman S, et al. Red blood cell transfusion: a clinical practice guideline from the AABB*. Ann Intern Med. Jul 2012;157(1):49-58.
3. AABB, Cross AR, Centers AsB, Program ASB. Circular of Information For the Use of Human Blood and Blood Components2013.
4. Becker J, Shaz B. Guidelines for Patient Blood Management and Blood Utilization. Bethesda, Maryland: AABB; 2011.
5. Thurer R, Katz R, Parce P, Precopio T, Popovsky M. By How Much Does a Single Unit Transfusion Increase the Recipient's Hemoglobin?: AABB; 2010.
6. Miller Y, Bachowski G, Benjamin R, et al. Practice Guidelines for Blood Transfusion. A Compilation from Recent Peer-Reviewed Literature. Second ed: American
National Red Cross; 2007.
7. Walpole SC, Prieto-Merino D, Edwards P, Cleland J, Stevens G, Roberts I. The weight of nations: an estimation of adult human biomass. BMC Public Health.
ξ 1 unit of PRBC raises the Hgb concentration of an average-size adult by ~1 g/dL (or HCT ~3%).2-6
ξ All results are rounded up to the nearest integer.
ξ Lab value = last result within 24 hours of current encounter.
ξ Weight = last value entered during current encounter.
Copyright © 201� University of Wisconsin Hospital s and Clinics Authority
Contact: Lee Vermeulen, CCKM @uwhealth.org Last Revised: 06/2016CCKM@uwhealth.org