Electrical impedance alterations of red blood cells during storage

The electrical impedance of blood is determined mainly by the resistance of the plasma (Rp), resistance of the red cell interior fluid (Ri), and capacitance of the cell membranes (Cm). These parameters were measured on 10 stored blood samples consecutively during 4 or 5 weeks of storage at 4 degrees C, once every week. Compared to the values of fresh samples, a statistically significant decrease in Rp was found mainly during the first week of storage, Ri did not decrease significantly until after 3 weeks, whereas Cm decreased progressively with time. These alterations can be explained by known red cell lesions during storage. The results indicate that electrical impedance measurements might be useful for monitoring red cell ageing and assessing the quality of stored red blood cells.