NAPLES, FLA. – Transfusions using cryopreserved red blood cells may be superior to those using standard blood storage techniques, updated analyses of a prospective study showed.
Cryopreservation minimizes the biochemical insult associated with transfusions and also appears to reduce the storage lesion, or the biochemical and structural changes that occur during refrigeration and adversely affect perfusion and oxygen off-loading, Dr. David A. Hampton said at the annual scientific assembly of the Eastern Association for the Surgery of Trauma (EAST).
Cryopreserved red blood cells (CPRBCs), which are Food and Drug Administration approved for a 10-year storage life, had a median shelf life of 588 days vs. just 14 days for standard liquid preserved packed red blood cells (LPRBCs) (P less than .01).
CPRBC transfusions were used by the U.S. Navy during the Vietnam War and extensively in civilian hospitals until the FDA extended the shelf life of LPRBCs from 21 to 42 days. Secondary to concerns of poor screening practices and the rise in hepatitis and HIV in the 1980s, CPRBCs fell out of favor for routine transfusion and are currently used for patients with rare blood types or if liquid stores run out.
Dr. David A. Hampton
Researchers at five U.S. centers, however, are currently investigating the efficacy and clinical outcomes of CPRBC transfusions as compared with LPRBCs, with results expected later this summer, according to Dr. Hampton, a fourth-year surgery resident at Oregon Health and Science University (OHSU), Portland.
"There haven’t been large, robust studies of this issue, but once that’s been done, we hope the paradigm will shift from LPRBCs to an increase in CPRBC usage," he said in an interview. "All of the current studies are quite favorable and support this change."
European investigators have already shown that autologous CPRBC transfusions do not elicit an inflammatory response in healthy controls (Transfusion 2013;53:28-33), while OHSU previously reported that tissue oxygenation is superior in trauma patients receiving cryopreserved rather than standard blood transfusions during the first 3 hours after transfusion (J. Trauma Acute Care Surg. 2013;74:371-6).
The results presented at EAST were based on biochemical analyses performed on the same 57 adult trauma patients with an Injury Severity Score (ISS) of more than 4 randomized to receive 1-2 U of CPRBCs or LPRBCs.
The standard and cryopreserved groups were similar with respect to age (44 years vs. 50 years), male gender (66% vs. 73%), blunt injury mechanism (97% vs. 86%), ISS (26 vs. 17), APACHE II scores (11 for both), and number of units transfused (3.1 vs. 3.6).
The correction of anemia was similar between the CPRBC and LPRBC groups 12 hours post transfusion (hemoglobin level at 24.6 g/dL vs. 24.8 g/dL) and at discharge (26.0 g/dL vs. 25.8 g/dL), Dr. Hampton said.
The CPRBC group, however, had significantly increased concentrations of 2,3-diphosphoglycerate (DPG) (P less than .04), a protein that enhances oxygen delivery and is virtually undetectable in LPRBCs after 3 weeks of storage.
The CPRBC group had significantly lower levels of serum amyloid P (1.8 mg/dL vs. 34 mg/dL; P less than .01) and C-reactive protein (0.16 mg/dL vs. 5 mg/dL; P less than .01). Elevated levels of these proteins can potentiate anticoagulation, making it difficult to dose heparin, which in turn increases bleeding risk, Dr. Hampton explained.
Dr. Levi Procter
CPRBC patients also had significantly lower levels of interleukin-8 (P less than .04) and tumor necrosis factor–alpha (P less than .05). Elevated levels of these proinflammatory cytokines are directly associated with transfusion-related acute lung injury.
Clinical outcomes were mixed in the study, which won the Raymond H. Alexander resident paper competition at the meeting. The cryopreserved group tended to have less acute renal failure (5% vs. 9%), multiple organ failure (9% vs. 12%), and posttransfusion fever (0% vs. 3%), but were twice as likely to experience deep vein thrombosis (32% vs. 15%) and stayed longer in the hospital (16 days vs. 11 days). Respiratory failure occurred in 32% of patients in both groups. None of the differences reached statistical significance, he said.
The results clearly show that cryopreserved RBCs increase 2,3-DPG concentrations, but the oxygen metric of real interest is whether they can increase end-organ oxygen consumption, said Dr. Levi Procter of the University of Kentucky Medical Center, Lexington, who was invited to discuss the study.
He also noted that cryopreserved blood is more expensive than standard refrigerated blood and requires time to thaw, which can be problematic when patients arrive in shock and need an immediate transfusion.
Cryopreserved blood costs about $400 vs. $200 for standard blood, but the differential is negligible given the longer shelf life, Dr. Hampton said. The FDA has approved a 14-day postthaw shelf life, so cryopreserved blood can be thawed and kept on hand in the trauma bay. In a busy level I trauma center, this pre-positioned blood will be used fairly quickly by incoming patients or those within the wards.