MECHANICAL WHITE BLOOD-CELL DAMAGE IN ROTARY BLOOD PUMPS

Mechanical trauma of white blood cells (WBC) due to the operation of a rotary blood pump was examined, using a simple method of trypan blue dye exclusion test for a cell viability measurement. The degree of WBC trauma was investigated using a roller pump (RP) and 3 commercially a vailable centrifugal pumps (Bio-Medicus [BP], Capiox [CP], Nikkiso [NK ]), and compared with the red blood cell (RBC) trauma. Each pump was o perated 3 times at a flow rate of 5 L/min against the total pressure h ead of 350 mm Hg for 6 h in a mock circuit viith 400 ml of fresh bovin e blood. Blood was sampled at 2 h intervals measuring plasma free hemo globin concentration and the percentage of damaged WBC in the trypan b lue dye exclusion test. Each pump demonstrated a linear increase in th e degree of WBC trauma, and there were differences among the tested pu mps (RP > BP > CP > NK). These findings were similar to those of the f ree hemoglobin measurements. To compare the degree of RBC and WBC trau ma, the probability (gamma,omega) of RBC and WBC to be damaged was cal culated, respectively. gamma = Delta D-RBC/Delta N, omega = Delta D-WB C/Delta N where D-RBC and D-WBC are the ratios of the damaged RBC and WBC, respectively, and N is the passing number defined as Qt/V (Q, flo w rate; t, time; V, circulating volume). The data of this study demons trated that the omega value was approximately 20 times or more greater than the gamma equally in all the tested pumps. This suggests that a WBC is more vulnerable to mechanical damage by a rotary blood pump tha n a RBC.