Washing older blood units before transfusion reduces plasma iron and improves outcomes in experimental canine pneumonia

Abstract

In a randomized controlled blinded trial, 2-year-old purpose-bred beagles (n = 24), with Staphylococcus aureus pneumonia, were exchanged-transfused with either 7- or 42-day-old washed or unwashed canine universal donor blood (80 mL/kg in 4 divided doses). Washing red cells (RBC) before transfusion had a significantly different effect on canine survival, multiple organ injury, plasma iron, and cell-free hemoglobin (CFH) levels depending on the age of stored blood (all, P < .05 for interactions). Washing older units of blood improved survival rates, shock score, lung injury, cardiac performance and liver function, and reduced levels of non-transferrin bound iron and plasma labile iron. In contrast, washing fresh blood worsened all these same clinical parameters and increased CFH levels. Our data indicate that transfusion of fresh blood, which results in less hemolysis, CFH, and iron release, is less toxic than transfusion of older blood in critically ill infected subjects. However, washing older blood prevented elevations in plasma circulating iron and improved survival and multiple organ injury in animals with an established pulmonary infection. Our data suggest that fresh blood should not be washed routinely because, in a setting of established infection, washed RBC are prone to release CFH and result in worsened clinical outcomes.

Figure 1

Survival curves. Kaplan-Meier plots throughout the 96-hour study comparing the 4 types of transfused blood are represented. The different types of blood are represented by different line patterns as follows: dashed black line (42-day-old unwashed blood), solid black line (42-day-old washed blood), solid gray line (7-day-old washed blood), and dashed gray line (7-day-old unwashed blood). There is a qualitative interaction between washing and the age of stored blood (P = .03).

Figure 2

Mean (±SE) shock scores and LIS at serial time points. (A-D) The shock score accounts for the level of vasopressor support (norepinephrine) needed to maintain the mean arterial pressure at a preset normal level for canines (mean 80 mm Hg).^,, (A,C) the shock score is plotted through time (x-axis) for animals receiving 42-day-old blood (A) or 7-day-old blood (C). The LIS in a previously published scoring system increases our ability to find the abnormalities in the lungs, which includes mean pulmonary artery pressure, alveolar-arterial oxygen gradient, plateau pressure, O₂ saturation, and respiratory rate.^,, (B,D) The LIS is plotted in the same fashion as the shock score for old and fresh blood. In each of these panels, unwashed blood is represented by a solid line and washed blood by a dashed line. The P value in each panel indicates differences between washed and unwashed blood (**) and the presence of qualitative interactions between age of blood and washing (*).

Figure 3

Mean (±SE) heart rate and SVI at serial time points. This figure uses the same format as Figure 2, except now heart rate (A,C) or SVI (B,D) are plotted on the y-axis. Similarly, P values are denoted by asterisks in each panel and are explained below the figures.

Figure 4

Mean (±SE) levels of NTBI, PLI, and TBI at serial time points. The format is similar to Figure 2, except now plasma levels of NTBI (A,D), PLI (B,E) and TBI (C,F) are plotted on the y-axis. P values are denoted by asterisks and explained below the figures.

Figure 5

Mean (±SE) levels of plasma CFH and plasma haptoglobin at serial time points. The format is similar to Figure 2, except now plasma levels of CFH (A,C) and haptoglobin (B,D) are plotted on the y-axis. P values are denoted by asterisks and explained below the figures.

Figure 6

Hemolysis rate, red blood cells loss, and biochemical changes with washing of canine blood during the 6-week storage period. Serial changes in stored blood components during 6 weeks. Serial values of (I) percent hemolysis rate (calculated by dividing the supernatant hemoglobin levels by the total sample hemoglobin levels and multiplying by 100 minus the hematocrit value); (II) the change in hemolysis rate with washing; (III) red blood cells loss with washing and (IVA-J) biochemical changes with washing of canine blood of 1 through 6 weeks of storage period are shown. Two bags of canine universal donor leukoreduced blood were sampled each week before and after washing. In panels I-III, each dark circle represents an individual bag of ∼250 g of packed red blood cells. In panel IV (A-J) individual mean values (2 bags) of the different biochemical parameters before washing are represented as dark circles and after washing as white circles.

Figure 7

Mean (±SE) levels of NTBI, PLI, and CFH and effect of washing in canine stored blood during 6-week storage period. Mean levels of NTBI (IA), PLI (IB), and CFH (IC) sampled from 3 bags of canine universal donor leukoreduced blood are plotted throughout time of storage. (IID-F) mean levels of NTBI, PLI, and CFH, respectively, are represented before and after washing 3 additional bags of 1-week and 6-week stored blood.