The total blood volume can be calculated if the red cell volume and the whole blood hematocrit are known.
total blood volume in liters =
= (red cell volume liters) / (0.9 * (venous hematocrit))
where:
• 0.9 is the ratio for [(whole blood hematocrit) / (venous hematocrit)]
total blood volume in liters =
= (plasma volume in liters) * 100 / (100 - (hematocrit as a percent))
Limitations:
• With hematocrits > 55% this method underestimates the TBV.
• If TBV is based on total body water or lean body mass there is no difference between the values for obese and for lean persons
