Bentley and Lewis estimated red cell mass from hematocrit and body weight.



(1) venous hematocrit as a decimal fraction

(2) body weight in kilograms


estimated red cell volume in mL per kg =

= 6.293 * EXP^(3.39 * (venous hematocrit))


estimated red cell volume in mL =

= (estimated volume in mL per kg) * (body weight in kilograms)



• The use of actual vs ideal vs lean body weight vs fat free mass would impact the estimate. Fat is not very vascular. Lean or Ideal body weight might be a good choice.

• The specific gravity of RBC is 1.094 g/mL (see above).

• In Fairbanks the equation is reported with base 10 instead of EXP, but this gives poor results.


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