🩸 Maximum Allowable Blood Loss (MABL)
Maximum allowable blood loss (MABL) estimates the intraoperative blood loss a patient can tolerate before the hematocrit falls below an acceptable minimum.
Maximum Allowable Blood Loss (MABL)
Weight (kg)
Population
Initial hematocrit Hct (%)
Acceptable minimum Hct (%)
When to use
Enter weight, population, initial hematocrit, and the acceptable minimum hematocrit; the tool computes estimated blood volume and MABL.
How it works
MABL = EBV × (Hct_initial − Hct_min) / Hct_initial, where EBV = weight × population coefficient (adult male 75, female 65, child 70, infant 80 mL/kg).
Key points
- This formula divides by the initial hematocrit; some references use the mean of initial and minimum Hct in the denominator, yielding a slightly different and usually more conservative estimate (original synthesis · not guideline verbatim).
- MABL is a planning estimate—the actual transfusion decision integrates bleeding rate, comorbidity, ongoing losses, and individual transfusion triggers.
- The acceptable minimum hematocrit must be lower than the initial value; choose it according to the patient's cardiopulmonary reserve and procedure.
References
Decision support for licensed clinicians only; not a substitute for clinical judgement, diagnosis or local protocols.