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Maximum allowable blood loss (ABL) without transfusion
Estimates intraoperative blood loss tolerated before transfusion, corrected for dilution.
Maximum allowable blood loss (ABL) without transfusion
Patient category (average blood volume)
Weight
Starting hematocrit
%
Lowest acceptable hematocrit
%
Complete the fields above to see the result.
When to use
- Anticipating, before or during surgery, how much blood loss can be tolerated before transfusion is likely needed.
Formula
EBV = weight x average blood volume per kg. ABL = EBV x (starting Hct - lowest acceptable Hct) / average Hct, where average Hct = (starting + lowest acceptable)/2.
Pearls and pitfalls
- Corrects for the fact that hematocrit falls progressively as blood is lost and replaced with crystalloid/colloid, unlike the simpler uncorrected formula.
- Treat the transfusion trigger (lowest acceptable Hct/Hb) as an individualized clinical decision, not a fixed number.