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SELECT ERYTHROCYTE CHARACTERISTICS IN PREVIOUSLY FROZEN WHOLE BLOOD ARE DIFFERENT FROM IMMEDIATE ANALYSIS

Abstract

Immediate analysis of blood samples is optimal for the best representation of in vivo measurements. However, this is not always possible, and the extent to which freezing whole blood affects measurement parameters is not well understood. PURPOSE: To investigate if blood parameters are preserved when samples are frozen rather than analyzed immediately with and without the addition of a cryoprotectant. METHODS: Venous blood was analyzed immediately and divided into samples stored at ~9ºC or -70ºC. Samples stored at ~9ºC, and samples stored at -70ºC, once thawed, were analyzed immediately, and on days 1, 2, 5, and 10 post-draw or postthaw, respectively. In addition, some samples were analyzed on days 16 and 88 post-draw or post-thaw. Hemoglobin concentration (tHb), oxyhemoglobin (HbO2), carboxyhemoglobin (HbCO), methemoglobin (MetHb), and oxygen content (O2ct) were measured in sextuplicate using an OSM3 hemoximeter. Hematocrit (Hct) was measured in triplicate using microcentrifugation. In a separate group of samples, two cryoprotectants, dimethyl sulfoxide (DMSO) and glycerol, were added at concentrations of 1%, 2%, 15%, and 50% and Hct was measured. RESULTS: A significant main effect of time was observed in tHb (β = 0.006, p = 0.025), HbO2 (β = -0.344, p < .001), HbCO (β = 0.025, p < .001), MetHb (β = 0.388, p < .001), and O2ct (β = -0.081, p < .001). A significant main effect of condition was observed in all parameters (∆tHb = -1.379, ∆HbCO = 0.389, ∆MetHb = -4.52, ∆O2ct = -1.452; p < .001), excluding HbO2 and Hct. A significant interaction was observed in all parameters (coeff: tHb [0.017], HbO2 [0.227], HbCO [-0.021], MetHb [- 0.169], O2ct [0.077]; p < .001), excluding Hct. We were unable to measure Hct because samples did not separate with microcentrifugation post-thaw. At cryoprotectant concentrations of 15% and 50%, some separation for Hct was observed, more so with glycerol than DMSO. CONCLUSION: Whether samples were frozen or not, stability was only observed in Hct stored at ~9ºC. Differences in post-thaw data suggest that freezing whole blood does not provide an optimal representation of in vivo measurements. Additionally, while cryoprotectant use for preservation of Hct may be possible, its use may not be viable for blood parameter analysis. Thus, further investigations are needed to develop alternative storage methods.

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