amount of blood loss in units =
= (number of units transfused) + (((initial hematocrit in percent) – (final hematocrit in percent)) / 3) – ((estimated blood loss during surgery) / 400)
where:
• This is implemented in the chapter on transfusion medicine.
• The equation has hematocrit divided by 0.03, with the hematocrit reported as a decimal fraction.
• Dividing hematocrit by 3 (actually 2.941) gives hemoglobin. A rough rule of thumb is that a change 1 g/dL of hemoglobin reflects a comparable change of 1 unit of blood.
• The 400 indicates the volume in mL of a unit of whole blood (actually 405 to 495).
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Amount of Blood Loss
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Grade
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< 1 unit
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minimal
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1 to < 2 units
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mild
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2 to < 3 units
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moderate
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>= 3 units
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severe
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Rate of Bleeding
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Type
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< 3 days
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acute
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3 – 7 days
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subacute
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> 7 days
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chronic
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Consequences of bleeding:
(1) fatal: results in the death of the patient
(2) life-threatening:
(a) causes serious, permanent injury such as myocardial infarction or stroke
(b) requires re-operation to control
(3) potentially life-threatening: 2 or 3 of the following
(a) severe blood loss
(b) hypotension: >=20% fall in systolic pressure to <= 90 mm Hg
(c) critical anemia: >= 20% fall in hematocrit to <= 20%
Major blood loss:
(1) fatal
(2) life-threatening or potentially life-threatening
(3) acute or subacute bleeding requiring reoperation
(4) acute or subacute bleeding with moderate or severe blood loss
Minor blood loss:
(1) acute or subacute non-major internal bleeding
(2) chronic moderate blood loss with loss >= 1 unit per week and transfused >= 2 units of blood
(3) chronic moderate blood loss with change in hematocrit >= 20% and transfused >= 2 units of blood
(4) chronic moderate blood loss with blood loss >= 1 unit per week, a change in hematocrit >= 20%, not transfused >= 2 units, and discharged with hematocrit <= 30%
Everything else is classed as "none", but I would think "minimal" would be more appropriate.
