This document provides information on calculating estimated blood volume and allowable blood loss for patients. It discusses that estimated blood volume is calculated as body weight in kg multiplied by average blood volume per kg for a person's age and sex. Allowable blood loss is calculated as estimated blood volume multiplied by the difference between initial and minimum acceptable hemoglobin levels, divided by the initial hemoglobin level. The document also discusses guidelines for replacing blood loss with fluids or transfusions to maintain appropriate hemoglobin and hematocrit levels.

1. By
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2. Maximum ABL calculation
• Definition
• EBV calculation: body wt (kg) x average blood volume (ml/kg)
• ABL= [EBV x (Hi-Hf)]/Hi
• Where:
• EBV=Estimated Blood Volume
• Hi= initial hemoglobin
• Hf= final hemoglobin

3. Average blood volumes
 Premature Neonates 95 mL/kg
 Full Term Neonates 85 mL/kg
 Infants 80 mL/kg
 Adult Men 75 mL/kg
 Adult Women 65 mL/kg
Normal Hct Values
 Men 42-52%
 Women 37-47%
• If the patient is obese, using the IBW or ABW will give more accuracy than an actual weight.

4. • Example
Question: Before surgery is to take place, what is the estimated blood volume (EBV)
of a female patient weighing 50 kg? Also, what is the allowable blood loss (ABL) of
this patient if her Hct is 45?
In the example above, EBV = 50kg x 65 (adult woman’s blood volume) = 3250 The
initial Hct (Hi) = 45%, her current Hct The final lowest acceptable Hct (Hf) = 30%
(What ever cut off is used clinically to decide how low the individual’s Hct will be
allowed to drop. Thirty percent is used in this calculator but in reality this will vary
from case to case.) So the example would look like this:
• (3250 x (45 – 30))/45 = 1083 Using this rough estimate, the patient in this example
could loose 1083 mL of blood without needing a transfusion.

5. Replacing Blood Loss
Ideally, blood loss should be replaced with crystalloid or colloid solutions to
maintain intravascular volume (normovolemia) until the danger of anemia
outweighs the risks of transfusion.
 At that point, further blood loss is replaced with transfusions of red blood cells to
maintain hemoglobin concentration (or hematocrit) at that level.
 For most patients, that point corresponds to a hemoglobin between 7 and 10 g/dL
(or a hematocrit of 21-30%).
 Below a hemoglobin concentration of 7 g/dL, the resting cardiac output has to
increase greatly to maintain normal oxygen delivery”

6. Estimating blood loss
• Dry sponges
4×4 hold ~ 10 mL blood
Ray-techs ~ 10-20 mL blood
Lap sponges ~ 50-100 mL blood

7. Pediatric cases should have sponges & gauze weighed for blood loss
Blood loss replacement
• Replace 1 mL blood with:
i. 3 mL crystalloid (i.e. NS, Dextrose, LR)
ii. 1 mL colloid (i.e. albumin**, Hespan®, Dextran®)
iii. 1 mL whole blood
iv. 1 mL PRBC