DOES HEMATOCRIT AFFECT IN-VITRO HEMOLYSIS TEST-RESULTS - PRELIMINARY-STUDY WITH BAYLOR NASA PROTOTYPE AXIAL-FLOW PUMP/

The effect of hematocrit (Ht) on in vitro hemolysis test results (i.e. , index of hemolysis) was evaluated using a Baylor/NASA prototype axia l flow pump. Red blood cell suspensions of six different Ht (5, 10, 15 , 20, 30, 40%; n = 30) were prepared and used for this evaluation. The pump was operated for 60 min under 5 L/min flow conditions, and blood samples were taken every 10 min to measure plasma free hemoglobin lev els. The normalized index of hemolysis (NIH) was calculated using the regression line slope between time and plasma free hemoglobin level, a nd relationships between NIH and Ht or hemoglobin (Hb) were checked. N IH and Ht had a statistically significant (p < 0.0001) correlation wit h a coefficient of fit of 0.976, and NIH and Hb had a statistically si gnificant (p < 0.0001) correlation with a coefficient of fit of 0.976. To reduce the effect of I-It, NIH/Ht was proposed and compared with a modified index of hemolysis (MIH), which was normalized by the Hb lev el of blood. NIH/Ht and MIH had a poor correlation with I-It (coeffici ent of fit, 0.608) and Hb (coefficient of fit, 0.577), respectively. W hen blood that has a wide range of I-It or Hb values is used for in vi tro hemolysis tests, NIH/Ht is suggested for use as an index of hemoly sis to evaluate the hemolysis characteristics of rotary blood pumps be cause MIH has no dimension and it requires Hb values. In contrast, NIH /Ht has a dimension of g/100 L, which is quite understandable, and it does not require measurement of Hb levels of blood; it is therefore co st-effective.