Abstract
Experimental: Two anticoagulants were tested, K2-EDTA and lithium-heparin. Blood was collected in both glass and plastic tubes using EDTA and in glass tubes only when lithium-heparin was used in two forms: dry and in a dilute saline sample. EDTA anticoagulated blood samples collected in plastic tubes were stored at 4°C, room temperature and 37°C. Immediately after the venepuncture and 1, 2, 6 and 24 hours later the following tests were carried out: whole blood filtration (Reid et al., 1976) using Nuclepore Hemafil filters, blood and plasma viscosity at low and high shear rates (Contraves LS 30 and Brookfield LVT viscometers), blood cell counts, red cell indices (Coulter counter S plus) and hematocrit. The morphology of erythrocytes was studied by means of Scanning Electron Microscopy (SEM) .The specimens of red cells were obtained from the same samples that underwent rheological tests. Results: Using heparin as an anticoagulant, whole blood filtration was severely impaired or blocked and blood viscosity and hematocrit were higher than they were using EDTA. The rheological properties of blood were altered by the storage, even after 1 hour, and the alteration became progressively greater as a function of time. SEM observations contributed to clarifying the effect of anticoagulants and storage conditions on the rheological properties of blood showing several changes of red blood cell morphology.
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