The effect of EDTA, heparin and storage on the erythrocyte osmotic fragility, plasma osmolality and haematocrit of adult ostriches (Struthio camelus)

To investigate the effects of two widely used anticoagulants and storage on the in vitro osmotic fragility of erythrocytes, haematocrit (Hct) and plasma osmolality of ostriches, blood was collected by venipuncture from 8 birds (90-110 kg) into vacutainer tubes containing either EDTA (k3) or lithium heparin. The osmotic fragility of the erythrocytes was determined by measuring the release of haemoglobin from blood added to tubes containing serially diluted phosphate buffered saline (PBS, pH 7.4). The Hct was determined by microcentrifugation and osmolality with a cryoscopic osmometer. Blood samples were analysed at 0.5 h, 6 h and 12 h after collection. EDTA increased the erythrocyte osmotic fragility compared to heparin (P<0.01). The initial haemolysis (>5%) occurred at between 0.50% and 0.55% PBS in heparin. In 0.85% PBS the haemolysis of samples collected in EDTA was greater than 30%, whereas in heparin it was <5%. The mean corpuscular fragility was between 0.35 and 0.45% PBS in heparin and 0.85% PBS in EDTA. Maximum haemolysis occurred in 0.35% PBS with EDTA and in 0.20% PBS with heparin. Hct was not significantly affected by storage (P>0.05). However, Hct values were significantly lower in heparin compared to EDTA (P<0.05). For EDTA and heparin, the osmolalities obtained 30 minutes after collection were significantly lower (P<0.05) than after 6 hours and 12 hours. However, there was no significant difference in the osmolality of the plasma 6 hours after collection compared to 12 hours. Plasma in EDTA had a significantly higher (P<0.05) osmolality than that in heparin.