Alterations in Erythrocyte Morphology Induced by Blood Pumps

Abstract

A scanning electron microscopy was used after in vitro and in vivo tests to investigate any alterations caused by the peristaltic roller pump in erythrocyte morphology. The electron micrographs of samples were examined as follows: 1) by image analyser; 2) by applying Bessis's classification for the qualitative study of crenated red blood cells (RBCs). The in vitro test was repeated four times using blood from healthy donors. Each basal blood sample was divided into 250 ml portions, each of which was recirculated for 12 minutes at different flow rates. In order to verify any persistent erythrocyte damage caused by the peristaltic pump, 15 minutes after recirculation at 450 ml/min, another sample was prepared using the blood remaining from the last test. A statistically significant direct correlation was found between blood flow (Qb) increase and the percentage of morphologically altered RBCs, when either using an image analyser (r = 0.97; p < 0.05) or Bessis's classification (r = 0.95; p < 0.05). However, neither method showed any statistically significant difference between the percentage of deformed RBCs, determined in the basal sample, or in the percentage found at the end of the 450 ml/min test after standing 15 minutes at room temperature. The in vivo test was carried out on 6 patients over 2 dialysis sessions, which differed only for the Qb: 250 versus 400 ml/min. The two dialysis sessions gave comparable results when using both study methods regarding the presence of deformed RBCs. While Bessis's classification showed a significant drop in the post-dialysis percentage of dysmorphic RBCs compared to the pre-dialysis value, both with a Qb of 250 ml/min and 400 ml/min, no significant change was found with the image analyser. The contradictory results of the two tests can be attributed to the presence of spherocytes and stomatocytes in the in vivo test which on the other hand were absent in the in vitro test and not easily distinguished by the image analyser with the parameter used. Reduction in the number of deformed RBCs after dialysis in the in vivo test can be attributed to improvement in the acidosis, correction of the hydroelectric imbalances and removal of toxic substances as a result of dialysis, thus allowing the echinocytes, spherocytes and stomatocytes to be transformed into discocytes.