Strauss et al reported equations for estimating the change in plasma volume for a patient by changes in easily measured laboratory values. The authors are from the Cushing VA Hospital in Framingham, Massachusetts.
Parameters:
(1) hemoglobin at baseline in g/dL
(2) hemoglobin at follow-up in g/dL
(3) hematocrit at baseline as a decimal fraction
(4) hematocrit at follow-up as a decimal fraction
(5) total protein at baseline in g/dL
(6) total protein at follow-up in g/dL
percent change in plasma volume = (plasma volume at follow-up) / (plasma volume at baseline) * 100 =
= (hemoglobin at baseline) / (hemoglobin at followup) * (1 - (hematocrit at followup)) / (1 - (hematocrit at baseline)) * 100
percent change in plasma volume = (plasma volume at follow-up) / (plasma volume at baseline) * 100 =
= (total protein at baseline) / (total protein at follow-up) * 100
An assumption is that a change in plasma volume is the explanation for the change in parameters (no bleeding, no acute catabolism, etc).
