Decreased erythrocyte deformability after transfusion and the effects of erythrocyte storage duration

Abstract

Background: Erythrocyte cell membranes undergo morphologic changes during storage, but it is unclear whether these changes are reversible. We assessed erythrocyte cell membrane deformability in patients before and after transfusion to determine the effects of storage duration and whether changes in deformability are reversible after transfusion.

Methods: Sixteen patients undergoing posterior spinal fusion surgery were studied. Erythrocyte deformability was compared between those who required moderate transfusion (≥ 5 units erythrocytes) and those who received minimal transfusion (0-4 units erythrocytes). Deformability was measured in samples drawn directly from the blood storage bags before transfusion and in samples drawn from patients before and after transfusion (over 3 postoperative days). In samples taken from the blood storage bags, we compared deformability of erythrocytes stored for a long duration (≥ 21 days), those stored for a shorter duration (<21 days), and cell-salvaged erythrocytes. Deformability was assessed quantitatively using the elongation index (EI) measured by ektacytometry, a method that determines the ability for the cell to elongate when exposed to shear stress.

Results: Erythrocyte deformability was significantly decreased from the preoperative baseline in patients after moderate transfusion (EI decreased by 12% ± 4% to 20% ± 6%; P = 0.03) but not after minimal transfusion (EI decreased by 3% ± 1% to 4% ± 1%; P = 0.68). These changes did not reverse over 3 postoperative days. Deformability was significantly less in erythrocytes stored for ≥ 21 days (EI = 0.28 ± 0.02) than in those stored for <21 days (EI = 0.33 ± 0.02; P = 0.001) or those drawn from patients preoperatively (EI = 0.33 ± 0.02; P = 0.001). Cell-salvaged erythrocytes had intermediate deformability (EI = 0.30 ± 0.03) that was greater than that of erythrocytes stored ≥ 21 days (P = 0.047), but less than that of erythrocytes stored <21 days (P = 0.03).

Conclusions: The findings demonstrate that increased duration of erythrocyte storage is associated with decreased cell membrane deformability and that these changes are not readily reversible after transfusion.

Fig. 1

Representative curves plotting the elongation index (EI) at increasing levels of shear stress as measured by ektacytometry. Erythrocytes with a greater EI are more deformable and thereby can transition from the normally round-shaped cell to an elongated, elliptical-shaped cell when subjected to shear stress.

Fig. 2

Erythrocytes drawn from patients who underwent moderate blood transfusion (≥5 units) exhibited a greater decrease in elongation index (EI) (loss of deformability) compared to erythrocytes drawn from patients who underwent minimal transfusion (0–3 blood units). The EI was significantly lower at the end of surgery than at the preoperative baseline (P = 0.03), and this decreased deformability persisted through postoperative day (POD) 3. The small decrease in deformability from baseline in the minimal transfusion group over the 3-day period was not significant. Overall, the differences between and within groups were statistically significant (P = 0.008). *Significantly different from preoperative patient blood and minimal transfusion group.

Fig. 3

Comparison of erythrocyte elongation index (EI) in blood drawn preoperatively (preop), in cell salvage blood, and in allogeneic blood units stored for ≥21 days or <21 days. A greater EI indicates a more deformable erythrocyte cell membrane. The differences among the four groups were significant (P = 0.008). Deformability for erythrocytes stored for the longer duration (≥21 days) was significantly less than that for erythrocytes stored <21 days (P = 0.001) and erythrocytes drawn from patients preoperatively (P = 0.001). Deformability for cell salvage erythrocytes was significantly greater than that of erythrocytes stored ≥21 days (P = 0.047) and less than that of both preoperative patient blood (P = 0.01) and blood stored <21 days (P = 0.03). *Significantly less than preoperative patient blood and blood stored <21 days; #significantly less than preoperative patient blood and blood units of <21 day storage duration, and significantly greater than blood units of ≥21 day storage duration.

Fig. 4

Comparison of erythrocyte deformability in preoperative patient blood, blood units stored for a short duration (12–20 days), and blood units stored for a long duration (21–40 days). Loss of deformability as measured by ektacytometry is indicated by a decreased elongation index (EI). Erythrocyte deformability was significantly less in samples drawn from blood units of longer storage duration than in samples drawn from preoperative patient blood or samples drawn from blood units with shorter storage duration. *P = 0.001 compared to preoperative patient blood and blood units stored 12–20 days.