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Maximum allowable blood loss

last modified on: Fri, 09/22/2017 - 14:09

return to: Pediatric Otolaryngology

see also: Tonsillectomy and Adenoidectomy; Cleft Lip and Palate Protocols  Pediatric Fluid Management

The volume of circulating blood should be estimated prior to taking a newborn to the operating room.  Blood volumes constitute a greater percentage of body mass in preterm neonates in comparison to their full term counterparts.  The estimated blood volumes may be calculated with the following numbers: 


Circulating blood volume

Preterm neonate

90 -100

Full term neonate

80 - 90


70 - 80


70-  75

Obese child

60 - 65


65 - 70


This calculation allows us to estimate the maximum allowable blood loss for a procedure.  This is calculated from the estimated blood volume, the initial hematocrit and the minimal allowable hematocrit.  

In general, a healthy child does not require transfusion unless the hematocrit has fallen to the 20-25 range for an infant, or 20 for a child.  In pre-term infants, transfusion should be performed based on clinical evaluation of the patient.

To calculate the maximum allowable blood loss, the following formula is used:

MABL = EBV  X  (Child's hematocrit - Minimum accepted hematocrit)

                                  Child's hematocrit

Whereas the EBV for a 5 kg infant is: 5 kg x 80 mL/kg = 400 mL

Leaving the equation:  MABL = 400 x (36-25)    =   122 mL


*Of note, a heel stick can be performed at UIHC to obtain a H/H.


  1. Roseff SD, Luban NL, Manno CS:  Guidelines for assessing appropriateness of pediatric transfusion. Transfusion. 2002;42(11):1398.
  2. Strauss RG. How I transfuse red blood cells and platelets to infants with the anemia and thrombocytopenia of prematurity.  Transfusion. 2008;48(2):209