The effect of storage time of human red cells on intestinal microcirculatory oxygenation in a rat isovolemic exchange model*

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Abstract
To determine whether the storage time of human leukodepleted red blood cell concentrates compromises intestinal microvascular oxygen concentration oxygen (μPo2) during isovolemic exchange transfusion at low hematocrit. Prospective, randomized, controlled study. University research institute laboratory. Male Wistar rats. Intestinal μPo2 was determined by Pd-porphyrin phosphorescence life-time measurements. Rats were brought near to a state of oxygen supply dependency by hemodilution with a pasteurized plasma protein solution to a hematocrit of 14.3 ± 1.1% (n = 24). Subsequently, an isovolemic exchange transfusion with human leukodepleted red blood cells, stored for 2–6 days (fresh, n = 8), 2–3 wks (intermediate, n = 8), or 5–6 wks (old, n = 8), was performed to determine whether intestinal μPo2 would be preserved. Immunologic reactions were avoided by washing the red blood cell concentrates three times before use. Isovolemic exchange with fresh and intermediate red blood cells maintained μPo2 whereas old cells decreased μPo2 with 26%. Subsequent transfusion with red blood cells (hematocrit ∼60%) until reaching a hematocrit of 32.4 ± 2.1 % (n = 24) increased intestinal μPo2 in all three groups to the same extent between 28% and 32%. No changes in red blood cell deformability, as determined by a Laser-assisted Optical Rotational Cell Analyzer, could be demonstrated during 5 wks of storage. This study shows that at low hematocrit, the oxygen-delivering capacity of human red blood cells stored 5–6 wks is reduced compared with fresh cells and red blood cells stored for an intermediate period. Although red blood cells stored for 2–3 wks are completely devoid of 2,3-diphosphoglycerate, their oxygen-delivering capacity to the intestines was the same as fresh red blood cells. Our study showed that red blood cell deformability was preserved during storage, suggesting that other mechanisms may account for the observed decrease in oxygen delivery by red blood cells stored 2–3 wks.