Each year approximately 100 million units of blood are transfused worldwide. Current regulations allow RBCs to be stored in approved solutions for up to five or six weeks. Regulatory agencies use cell survival studies and in vitro markers of hemolysis, rather than measures of oxygen delivery, to establish the maximal duration of blood storage. During storage, RBCs undergo cumulative structural, biochemical, and enzymatic changes that collectively might impair the ability of erythrocytes to deliver oxygen to tissues and contribute to adverse patient outcomes.
Study design and Methods: We conducted a prospective, randomized, controlled, clinical trial comparing short-storage versus longer-storage RBCs for tissue oxygen delivery as measured by reduction in blood lactate levels in severe anemia. We studied 290 patients presenting to a university hospital urgent care facility with a hemoglobin ≤5g/dL and lactate ≥5mM. Patients were children, age 6 to 60 months, whose lactic acidosis was due to severe anemia and who did not have shock, trauma, impaired cardiac function, refractory hypoxia, need for pressors, liver disease or tissue injury. Subjects were randomly assigned to receive leukoreduced RBCs stored 1-10 days (n=145) versus 25-35 days (n=145). All patients received 10mL/kg of RBCs during hours 0-2; and, if indicated per protocol, an additional 10mL/kg during hours 4-6. The study was conducted in Kampala, Uganda and registered as #NCT01586923 at clinicaltrials.gov.
Results: Hour 0 was the start of transfusion.We measured blood lactate levels at time 0, 2, 4, 6, 8 and 24 hours following transfusion. The primary outcome was the proportion of patients achieving a lactate ≤3mM at 8 hours. Other measures included cerebral tissue oxygen saturation measured non-invasively, clinical and laboratory changes following transfusion, survival, and 30-day follow-up. At presentation, the mean hemoglobin was 3.7 ±1.3g/dL and mean lactate was 9.3 ±3.4mM. RBC storage averaged 7.8 ±2.1 days in the shorter-storage arm and 31.6 ±2.8 days in the longer-storage arm without overlap. See Fig 1A. The proportion achieving a lactate ≤3mM at 8 hours was 0.58 (95% CI, 0.49-0.66, shorter-storage) versus 0.61 (95% CI, 0.52-0.69, longer-storage), p=0.72, a result meeting the pre-specified margin of non-inferiority. Mean lactate levels were not statistically different between the two arms at 2, 4, 6, 8 or 24 hours. See Fig 1B. Kaplan-Meier analysis and global non-linear regression revealed no difference in lactate clearance between the shorter-storage and longer-storage groups. Clinical assessment, serial measurements of hemoglobin concentration, cerebral tissue oxygen saturation, and electrolyte abnormalities improved to the same degree in the two groups following transfusion. Adverse events, survival, and 30-day recovery were not significantly different between the two groups. Pre-specified sub-group analysis among patients receiving 20mL/kg of RBCs revealed no significant differences in outcomes. Given the severity of anemia, transfusions represented 60% to 90% of the patients' pre-transfusion red cell mass.
Conclusion and Relevance: This is the first major randomized trial specifically testing whether prolonged storage RBCs deliver oxygen as well as short-storage RBCs. We tested the two extremes of blood storage duration and found that longer-storage RBCs were not inferior to shorter-storage RBCs for oxygen delivery as measured by reduction of elevated blood lactate levels, improved cerebral oxygen saturation, clinical outcomes, laboratory results, or adverse events. The results carry relevance for health policy decisions regarding the acceptable duration of RBC storage worldwide.
No relevant conflicts of interest to declare.
Asterisk with author names denotes non-ASH members.
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