Electronic Measurement of Erythrocyte Volume and Volume Heterogeneity in Horses During Erythrocyte Regeneration Associated with Experimental Anemias

Abstract

Anemia was induced in three groups of horses by moderate or severe acute hemorrhage, or by acetyl phenylhydrazine-induced hemolysis (Groups I, II, and III, respectively). Serial hemograms were done on a multichannel automated blood cell counter with histogram capability. Changes in hematocrit, mean cell volume, erythrocyte number, red cell distribution width (RDW), and standard deviation of erythrocyte volume were examined over time. Significant increases in mean cell volume were first detectable by days 17, 20, and 14 and reached maximum by days 43, 41, and 29, in Groups I, II, and III, respectively ( P < 0.05). Increased mean cell volume was interpreted as reflecting accelerated erythrocyte regeneration; however, not all horses with accelerated regeneration had changes in mean cell volume. Estimated erythrocyte production rate correlated poorly with hematocrit nadir and change in mean cell volume ( r = 0.37 and r = 0.36, respectively, P > 0.05). In some horses effective regeneration occurs without development of macrocytosis. Mean cell volume remained increased after other parameters returned to control values, suggesting that mean cell volume values may provide retrospective evidence of altered erythrocyte turnover. Anisocytosis as indicated by significant increases in the standard deviation was greatest during the early part of the regenerative response, reaching maximum values on days 30, 28, and 21 in Groups I, II, and III, respectively, and began to decrease as homogeneous repopulation with macrocytes occurred. Red cell distribution width increased significantly only in severe hemorrhage and hemolysis groups, reaching mean maximum values of 24.3 on day 20 and of 26.4 on day 21 in Groups II and III, respectively ( P < 0.05). Red cell distribution width did not detect increased erythrocyte volume heterogeneity in Group I.