Whole blood and plasma water in health and disease: longitudinal and transverse observations and correlations with several different hematological and clinicochemical parameters

Abstract

In a healthy reference population, hemoglobin (Hgb) and hematocrit (Hct) have been proposed as surrogate markers for whole blood water (WBW). We have extended this study under different physiological and pathological conditions in two longitudinal series, viz. (1) acute hyper- and hypohydration experiments in a healthy individual and (2) three athletes running 5 km each, and in three transverse series, viz. (3) a young reference population ( n = 97, 49 females), (4) an old reference population ( n = 37, nine females) consisting of inhabitants of a nursing home and (5) cardiac, hematological and renal patients including severe anaemia, polycythaemia and abnormal protein levels ( n = 50, 25 females) with suspected hydration disturbances. The only sex difference found was a lower WBW in males in the young reference group. The percentage change of PW was less than that of WBW. In all five groups together ( n = 293) WBW correlated closely ( P < 0.0001) with Hgb and Hct (both r = − 0.95) and with erythrocyte count ( r = − 0.85), whereas PW correlated with total protein (Tprot) ( r = − 0.84). In the longitudinally studied groups (1) and (2) WBW also correlated ( P < 0.0001) with cholesterol, Ca, Tprot, albumin, platelets, globulin and white blood cells ( r ± 0.98−0.37), while PW correlated ( P < 0.0001) not only with the same clinicochemical parameters but also with Hct, Hgb and red blood cells ( r ± 0.98−0.44). The homeostasis of PW is more narrowly regulated than that of WBW. Hgb, Hct and erythrocyte count reflect WBW and Tprot reflects PW also under disease conditions. WBW (mass%) can be calculated from Hgb and Hct using the formulae:− 0.09 × Hgb (g/l) + 91.7 and − 28.6 × Hct (v/v) + 91.8 and PW (mass%) from Tprot using the formula: − 0.09 × Tprot (g/l) + 97.6. Other correlations were observed only in a longitudinal setting and presumably are due to concentration and dilution.