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Overview :
Landsfeld et al used an equation for estimating blood loss
in the Bleeding Severity Index.
amount of blood loss in units of blood =
= (number of units transfused) + (((hematocrit initial in
percent) – (hematocrit after in percent)) / 3) – ((estimated surgical blood
loss in mL) / 400)
where:
• The original
equation had the hematocrit divided by 0.03, which would mean that the
hematocrits would be as decimal fractions.
• Dividing the
hematocrit by 3 (preferably 2.941) gives the hemoglobin in g/dL.
• As a rough
rule of thumb, 1 unit of blood will raise the hemoglobin by 1 g/dL.
• The 400
factor is an estimate for the volume of 1 unit whole blood. 1 unit of whole
blood may vary in volume from 405 – 495 ml (AABB Technical Manual).
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Blood Loss in Units
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Degree
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>= 3 units
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severe
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2 to < 3 units
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moderate
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1 to < 2 units
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mild
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where:
• Categories for minimal and massive blood loss could
probably also be defined.
• The hematocrit would be affected by hemoconcentration and
hemodilution.
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