Red blood cell metabolic responses to refrigerated storage, rejuvenation, and frozen storage.

BACKGROUND: Storage of red blood cells (RBCs) under blood bank conditions promotes metabolic modulation within the RBC. This "metabolic storage lesion" may affect the quality and safety of the transfused RBCs. The aim of this study is to determine the metabolic changes in stored RBCs over 42 days of routine storage followed by a US Food and Drug Administration-approved method of rejuvenation, freezing, and preparation for transfusion. STUDY DESIGN AND METHODS: We exploited a mass spectrometry-based metabolomics approach to monitor 42-day-stored citrate phosphate dextrose/AS-1 RBCs (n = 29) that were rejuvenated, glycerolized and frozen, then thawed and deglycerolized, and held for 24 hours at 1 to 6ºC in saline-glucose. RESULTS: Previously reported metabolic alterations were confirmed in 42-day-old RBCs. In this study, in total, 181 (62%) of the biochemical compounds exhibited significant (p ≤ 0.05) change compared with Day 0 values. Rejuvenation restored adenosine triphosphate and 2,3-diphosphoglycerate levels, replenished purine reservoirs, up regulated glycolysis, increased levels of pentose phosphate pathway intermediates, and partially rescued glutathione biosynthesis. Increased levels of lysophospholipid in rejuvenated RBCs suggests the activation of recycling pathways of damaged membrane lipids, in which a total of 167 (57%) biochemical compounds showed significant change compared with Day 42 values. CONCLUSION: Rejuvenation reversed over one-half of the metabolic biochemical compounds evaluated compared with Day 42 values, and the compounds were stable through frozen storage and preparation for transfusion. Rejuvenation promoted significant metabolic reprogramming, including the reactivation of energy-generating and antioxidant pathways (the pentose phosphate pathway and glutathione homeostasis), salvage reactions, cofactor reservoirs, and membrane lipid recycling.

The bioequivalence of frozen plasma prepared from whole blood held overnight at room temperature compared to fresh-frozen plasma prepared within eight hours of collection.

BACKGROUND: Overnight, room temperature hold of whole blood (WB) before leukoreduction and component processing offers significant logistic and cost advantages over WB processed within 8 hours. Plasma prepared from WB held at room temperature overnight (PF24RT24WB) may result in a degradation of plasma coagulation protein activities compared to plasma frozen within 8 hours of collection. In this study, we intended to evaluate the bioequivalence (BE) of PF24RT24WB prepared using a new WB collection, leukoreduction, and storage system compared to fresh-frozen plasma (FFP) after 12 months of frozen storage. STUDY DESIGN AND METHODS: We conducted a three-center, three-arm evaluation of the LEUKOSEP HWB-600-XL test system (Hemerus Medical LLC) compared to the RZ2000 control (Fenwal, Inc.). FFP was prepared from WB held at room temperature more than 6 hours and placed at less than -18 °C by 8 hours for control (n = 60) and test (n = 60) arms. PF24RT24WB (n = 60) was prepared with the test system from WB held at room temperature and then filtered and processed 20 to 24 hours postcollection. Frozen plasma was tested at 3, 6, and 12 months using a comprehensive panel of protein and coagulation factor assays. RESULTS: The test FFP was BE for all coagulation factors and tested proteins at 12 months. As expected, PF24RT24WB had a reduced Factor (F)VIII activity compared to control FFP (87.1%; 90% confidence interval, 79.4%-93.3%) with the lower confidence limit less than 80%. All other factors were within the BE region. CONCLUSION: Leukoreduced FFP and PF24RT24WB prepared using the LEUKOSEP HWB-600-XL system has been shown to be BE to control leukoreduced FFP with an expected decrease in FVIII activity after overnight hold.

Additive solution-7 reduces the red blood cell cold storage lesion.

BACKGROUND: Transfusion of long-stored red blood cells (RBCs) is associated with decreased in vivo RBC recovery, delivery of RBC breakdown products, and increased morbidity and mortality. Reducing the burden of this RBC "storage lesion" is a major challenge in transfusion medicine. Additive solution-7 (AS-7) is a new RBC storage solution designed to improve RBC metabolism by providing phosphate and increasing buffering capacity. STUDY DESIGN AND METHODS: Storage quality in AS-7 was measured in a prospective, randomized, three-center trial using units of whole blood from healthy human subjects whose RBCs were stored for up to 56 days in AS-7 (n = 120) or for 42 days in the control solution AS-1 (n = 60). RESULTS: Hemolysis and shedding of protein-containing microvesicles were significantly reduced in RBCs stored in AS-7 for 42 and 56 days compared with RBCs stored in AS-1. Autologous in vivo recoveries of RBCs stored in AS-7 was 88 ± 5% at 42 days (n = 27) and 82 ± 3% at 56 days (n = 27), exceeding recoveries of RBCs stored in currently used solutions. CONCLUSION: Increasing the phosphate, pH range, and buffer capacity of a RBC storage system allowed RBCs to be stored better and longer than currently approved storage systems. AS-7 ameliorates the long-term storage lesion resulting in significantly increased viability in vitro and in vivo.

Overnight, room temperature hold of whole blood followed by 42-day storage of red blood cells in additive solution-7.

BACKGROUND: Overnight, room temperature hold (ONH) of whole blood before component processing offers several benefits. This study evaluated the storage and in vivo recovery characteristics of ONH red blood cells (RBCs) stored in additive solution-7 (AS-7). STUDY DESIGN AND METHODS: We conducted a three-center, three-arm evaluation of a new blood collection system with AS-7 compared to leukoreduced RBCs processed within 8 hours and stored in AS-1 (control). Whole blood (500 ± 50 mL) from healthy research subjects (n = 240) was held at room temperature 0 to 2 hours, 6 to 8 hours, or ONH (18-24 hr) before component processing and storage at 1 to 6 °C. RBCs were evaluated on Days 42 and 56 with a panel of in vitro assays. Subsets of the AS-7-stored RBCs were evaluated for (51) Cr 24-hour in vivo recovery and long-term survival. RESULTS: Adenosine triphosphate (ATP) levels in ONH RBCs were not different than AS-7 RBCs prepared within 8 hours. ATP was higher in the ONH group on Day 42 than control, and ATP was maintained in all AS-7 groups through Day 56. ONH units had 0.36 ± 0.14% on Day 42 hemolysis (60/60 < 0.8%), and 0.54 ± 0.22% on Day 56 (10/60 > 0.8%, 2/60 > 1%). In vivo recoveries of stored RBCs were not different between the AS-7 arms at 42 days (p = 0.16; 27/27 ONH units > 75%), but the Day 56 ONH was significantly less than ONH on Day 42 (p = 0.008; 7/28 < 75%). CONCLUSIONS: Overnight hold of whole blood at room temperature before component processing meets current regulatory requirements when RBCs are stored up to 42 days in AS-7.

In vitro and in vivo quality of leukoreduced apheresis platelets stored in a new platelet additive solution.

BACKGROUND: Platelets (PLTs) stored in additive solutions (PASs) may reduce the risk of several plasma-associated adverse transfusion reactions such as allergic reactions and potentially transfusion-associated lung injury. The objective of this study was to determine the in vitro characteristics and the in vivo radiolabeled recovery and survival of apheresis PLTs (APs) stored in a new PAS and compare the latter to Food and Drug Administration (FDA) criteria. STUDY DESIGN AND METHODS: Hyperconcentrated APs were collected from healthy subjects in a paired crossover study comparing PAS (35% plasma) and 100% plasma-stored APs (Part 1) up to 7 days and, in Part 2, to determine the in vivo recovery and survival of PAS stored AP at 5 days compared to fresh PLT controls. In vitro and in vivo assays were performed following standard methods. RESULTS: Sixty-six and 25 evaluable subjects successfully completed Parts 1 and 2, respectively. pH for PAS AP was maintained above 6.6 for 5 days of storage. P-selectin values were consistent with published values for commonly transfused PLT products. The PAS in vivo PLT recovery (54.3 ± 8.1%) was 86.7% of the fresh control, and survival (6.4 ± 1.3 days) was 78.0% of the fresh control, both meeting the FDA performance criteria. CONCLUSION: APs stored in PAS with 35% plasma carryover maintained pH over 5 days of storage and met current FDA criteria for radiolabeled recovery and survival. The use of PAS for storage of single-donor PLTs in clinical practice represents an acceptable transfusion product that reduces the volume of plasma associated with PLT transfusion.

Exploratory in vitro study of red blood cell storage containers formulated with an alternative plasticizer.

BACKGROUND: The plasticizer di-2-ethylhexyl phthalate (DEHP) is a common component in medical plastics. There is motivation to replace this component; however, DEHP is necessary to prevent excessive hemolysis in stored red blood cells (RBCs). Our objective is to evaluate a candidate replacement plasticizer (Hexamoll, di-isononyl cyclohexane-1,2-dicarboxylic acid [DINCH], BASF Corp.) compared to DEHP in an in vitro feasibility study. We hypothesize that the candidate will provide at least equivalent protection against hemolysis for RBCs stored for 42 days and periodic mixing of RBCs will add additional protection against hemolysis. STUDY DESIGN AND METHODS: Whole blood was collected into citrate-phosphate-dextrose; combined into pools of 2 ABO identical whole blood units; and divided, leukoreduced, centrifuged, and separated into plasma and RBCs. Additive solution was added, and the RBCs were stored for 42 days at 1 to 6°C. In three parts of this study, split pools were paired as DINCH-polyvinyl chloride (PVC) with weekly mixing versus DINCH-PVC with no mixing, DINCH-PVC mixed versus DEHP-PVC no mix, and DINCH-PVC versus DEHP-PVC with neither mixed. A standard panel of in vitro RBC characteristics was determined on Days 0 and 42. RESULTS: Mixing DINCH-PVC weekly improved Day 42 hemolysis (0.36 ± 0.07% vs.0.56 ± 0.15%, p = 0.002), and mixed DINCH-PVC bags were noninferior to unmixed DEHP-PVC bags (p ≤ 0.05). DINCH-PVC bags stored without weekly mixing were inferior to unmixed DEHP-PVC bags for hemolysis on Day 42, although no individual bag exceeded 0.8% hemolysis. CONCLUSION: Periodic mixing of RBCs stored in DINCH-PVC provides additional protection against hemolysis. Unmixed DINCH-PVC bags were inferior to DEHP-PVC bags for prevention of hemolysis, but remain a candidate for replacement DEHP in RBC storage bags.

Validation of a microbial detection system for use with ACD-A platelets with PAS III platelet additive solution.

BACKGROUND: The BacT/ALERT microbial detection system (BTA) is used for testing leukoreduced apheresis platelets (LR-AP) in plasma. Platelet additive solutions (PASs) such as InterSol (PAS III) may be used to reduce the amount of plasma transfused in LR-AP. This study evaluated the performance of the two-bottle BTA testing scheme in the recovery of seeded microorganisms from LR-AP in InterSol-plasma compared to a reference plate culture method. STUDY DESIGN AND METHODS: Hyperconcentrated, double LR-AP were collected from healthy donors; InterSol was added (65% Intersol:35% plasma), equally divided into two containers, and then inoculated with an isolate of 1 of 10 clinically relevant index organisms at two levels. Aerobic (BPA) and anaerobic (BPN) BTA bottles were inoculated with 4 mL each of the inoculated LR-AP, and blood agar plates (BAPs) for aerobic and anaerobic culture (0.5 mL each). RESULTS: Zero false-positives from 103 bottle pairs were observed. All 400 two-bottle BTA tests were positive within 24 hours, except for Propionibacterium acnes (maximum time-to-detection of 86.4 hr) and 13 of 20 pairs of Streptococcus viridans (maximum time-to-detection of 31.7 hr). Thirteen of 400 BAP two-plate tests were negative for starting bacterial concentrations of 10 colony-forming units (CFUs)/mL or less. At 40 CFUs/mL or less, BTA was 100% positive while BAP was 94% positive. CONCLUSION: Seeded organism recovery was superior in the two-bottle BTA test system compared to the two-plate BAP system using InterSol platelets (PLTs). This performance is comparable to previously published results for PLTs in plasma. The use of InterSol does not appear to have a detrimental effect on the performance of the two-bottle BTA system.

Bacterial growth kinetics in ACD-A apheresis platelets: comparison of plasma and PAS III storage.

BACKGROUND: Our objective was to determine the growth kinetics of bacteria in leukoreduced apheresis platelets (LR-AP) in a platelet (PLT) additive solution (PAS; InterSol, Fenwal, Inc.) compared to LR-AP stored in plasma. STUDY DESIGN AND METHODS: Hyperconcentrated, double-dose LR-AP were collected from healthy donors with a separator (AMICUS, Fenwal, Inc.). LR-AP were evenly divided, InterSol was added to half (65% InterSol:35% plasma [PAS]), and PLTs in autologous plasma were used for a paired control (PL). Bacteria were inoculated into each LR-AP PAS/PL pair (0.5-1.6 colony-forming units [CFUs]/mL), and bacterial growth was followed for up to 7 days. Time to the end of the lag phase, doubling times, maximum concentration (conc-max), and time to maximum concentration (time-max) were estimated. RESULTS: Streptococcus viridans did not grow to detectable levels in either PAS or PL units. The other bacteria had no significant overall difference in the conc-max (p = 0.47) or time-max (p = 0.7) between PL and PAS LR-AP; PL had a 0.14 hours faster doubling rate (p = 0.023); and PAS had a 4.7 hours shorter lag time (p = 0.016). CONCLUSION: We observed that five index organisms will grow in LR-AP stored in a 35%:65% ratio of plasma to InterSol where initial bacterial concentrations are 0.5 to 1.6 CFUs/mL. The more rapid initiation of log-phase growth for bacteria within a PAS storage environment resulted in a bacterial concentration up to 4 logs higher in the PAS units compared to the plasma units at 24 hours, but with no difference in the conc-max. This may present an early bacterial detection advantage for PAS-stored PLTs.

Automated collection of double red blood cell units with a variable-volume separation chamber.

BACKGROUND: Automated collection of blood components offers multiple advantages and has prompted development of portable devices. This study sought to document the biochemical and hematologic properties and in vivo recovery of red cells (RBCs) collected via a new device that employed a variable-volume centrifugal separation chamber. STUDY DESIGN AND METHODS: Normal subjects (n = 153) donated 2 units of RBCs via an automated blood collection system (Cymbal, Haemonetics). Procedures were conducted with wall outlet power (n = 49) or the device's battery source (n = 104). Units were collected with or without leukoreduction filtration and were stored in AS-3 for 42 days. The units were assessed via standard biochemical and hematologic tests before and after storage, and 24 leukoreduced (LR) and 24 non-LR RBCs were radiolabeled on Day 42 with Na(2)(51)CrO(4) for autologous return to determine recovery at 24 hours with concomitant determination of RBC volume via infusion of (99m)Tc-labeled fresh RBCs. RESULTS: Two standard RBC units (targeted to contain 180 mL of RBCs plus 100 mL of AS-3) could be collected in 35.7 +/- 2.0 minutes (n = 30) or 40.3 +/- 2.7 minutes for LR RBCs (n = 92). An additional 31 collections were conducted successfully with intentional filter bypassing. RBC units contained 104 +/- 4.1 percent of their targeted volumes (170-204 mL of RBCs), and LR RBCs contained 92 percent of non-LR RBCs' hemoglobin. All LR RBCs contained less than 1 x 10(6) white blood cells. Mean hemolysis was below 0.8 percent (Day 42) for all configurations. Adenosine triphosphate was well preserved. Mean recovery was 82 +/- 4.9 percent for RBCs and 84 +/- 7.0 percent for LR RBCs. CONCLUSIONS: The Cymbal device provided quick and efficient collection of 2 RBC units with properties meeting regulatory requirements and consistent with good clinical utility.

In vitro and in vivo evaluation of LEUKOSEP HRC-600-C leukoreduction filtration system for red cells.

BACKGROUND: Documentation of the benefits of leukoreduction has led to the increased use of this technique and the need for development of efficient and effective techniques for its accomplishment. This study investigated the in vitro properties and in vivo autologous radiolabeled recovery of leukoreduced red cells (RBCs) produced through a leukoreduction filtration system for RBCs (LEUKOSEP HRC-600-C, Hemerus Medical). STUDY DESIGN AND METHODS: Normal subjects donated 36 units of RBCs that were leukoreduced on Days 0, 3, or 5 through a "hands-off" technique. Biochemical studies were performed before and after filtration and at the end of 42 days of storage. Units leukoreduced on Days 0 or 5 were held until Day 42 and used for autologous radiolabeled return to determine recovery with 51Cr single-label radiolabeling techniques. RESULTS: Leukoreduction filtration was accomplished in 16.3 +/- 2 minutes on Day 0 at room temperature or 27 to 30 minutes on Days 3 or 5 after refrigeration. Leukoreduction efficiency was 4.6 +/- 0.6 log with a median residual white blood cell (WBC) content of fewer than 3.3 x 10(4) WBCs per unit. RBC recovery was 90 +/- 2 percent. Hemolysis was 0.34 +/- 0.16 percent at the end of 42 days of storage. The in vivo recovery of radiolabeled RBCs 24 hours after autologous return was 80.6 +/- 4.5 percent for RBC units leukoreduced on Days 0 and 5 combined. CONCLUSION: The LEUKOSEP HRC-600-C WBC reduction filtration system produced leukoreduced RBCs efficiently and effectively with acceptable poststorage biochemical measures and posttransfusion recovery after 42 days of storage.

Efficacy of apheresis platelets treated with riboflavin and ultraviolet light for pathogen reduction.

BACKGROUND: Pathogen reduction technologies for platelet (PLT) components offer a means to address continued viral transmission risks and imperfect bacterial detection systems. The efficacy of apheresis PLTs treated with riboflavin (vitamin B2) plus ultraviolet (UV) light (Mirasol, Navigant Biotechnologies) was investigated in a single-blind, crossover study in comparison to untreated PLTs. STUDY DESIGN AND METHODS: Normal subjects (n = 24) donated PLTs by apheresis on two occasions at least 2 weeks apart. Units were randomized to control or test arms, the latter receiving the addition of 28 mL of 500 micromol per L B2 and exposure to 6.2 J per mL UV light. PLTs were stored for 5 days with biochemical and hematologic analyses performed before and after illumination on Day 0 and at the end of storage. An aliquot of each unit was radiolabeled and returned to determine recovery and survival. RESULTS: The PLT content of treated units was maintained from Day 0 (4.1 x 10(11) +/- 0.4 x 10(11)) to Day 5 (4.0 x 10(11) +/- 0.4 x 10(11)). Treatment with B2 plus UV light was associated with an increase in lactate production with concomitant increases in glucose consumption. pH (control, 7.38 +/- 0.07; test, 7.02 +/- 0.10) was well maintained throughout storage. Recovery of treated PLTs (50.0 +/- 18.9%) was reduced from that of control PLTs (66.5 +/- 13.4%); survival was similarly shortened (104 +/- 26 hr vs. 142 +/- 26 h; p < 0.001). CONCLUSIONS: PLTs treated with B2 plus UV light demonstrate some alterations in in vitro measures but retain in vitro and in vivo capabilities similar to pathogen-reduced and licensed PLT components that have been shown to have useful clinical applicability. The recovery, survival, and metabolic properties of Mirasol PLTs should provide sufficient hemostatic support in thrombocytopenia to justify patient clinical trials.

Further evaluation of a new standard of efficacy for stored platelets.

BACKGROUND: The proposal to assess the viability capabilities of platelets (PLTs) collected, treated, or stored in a developmental system against "fresh" PLTs from the same subject poses several important methodologic issues pertaining to the timing and manner of the collecting and separating the fresh PLTs. This study extended the previous validation of this method of comparing fresh and stored PLTs, applying it to an assessment of apheresis PLTs stored for 7 days with a newly standardized radiolabeling protocol. STUDY DESIGN AND METHODS: Eighteen normal subjects donated 1 unit of leukoreduced PLTs, pheresed with a standard, approved system. They received an aliquot radiolabeled with 51Cr on Day 7 simultaneously with 111In-labeled fresh PLTs that had been separated by a manual method. Recovery and survival were compared to determine whether the stored PLTs were not inferior to the criterion of 67 percent of recovery and 50 percent of survival of fresh PLTs. Separate studies were undertaken to document the similarity of recovery and survival with 51Cr and 111In radiolabeling in PLTs stored to 8 days and to determine the importance of correcting the radioactivity in timed samples for the activity remaining in blood beyond the life span of the retransfused PLTs. RESULTS: PLTs stored for 7 days demonstrated 88.7 +/- 35.2 percent of the recovery and 89.9 +/- 21.2 percent of the survival of PLTs collected via a nonproprietary, manual system and thus met the comparative criterion. In a separate study (n = 12), labeling Day 8 PLTs with 51Cr or 111In resulted in recoveries and survivals that were not different. Radiolabel eluted from labeled PLTs in vitro was taken up by cellular blood elements in a reuptake incubation. CONCLUSION: Apheresis PLTs stored for 7 days met the criterion proposed for comparison with fresh PLTs. This analytic approach is feasible with PLTs collected and prepared via a manual method. A standardized protocol for radiolabeling PLTs with 51Cr and 111In and analyzing the results in a standardized fashion was employed successfully, with the two radioisotopes yielding similar results. The importance of correcting for residual activity after disappearance of injected cells was noted.

Preliminary validation of a new standard of efficacy for stored platelets.

BACKGROUND: Platelet preparation and storage systems, unlike those for RBC, lack an objective, absolute performance criterion to determine acceptability. Recently, a criterion based on paired comparison with the radiolabeled recovery and survival of "fresh" platelets has been proposed, namely, recovery = two-thirds and survival = half of "fresh" platelets. STUDY DESIGN AND METHODS: Eleven normal subjects donated a unit of leukoreduced apheresis platelets using a standard, approved system. They received an aliquot radiolabeled with 111In or 51Cr (random selection) 4 to 20 hours after donation and, using the other radioisotope, on Day 5 of storage. The recovery was calculated based on the injectate radioactivity. The survival was determined using the multiple-hit model. The area under the platelet survival curve was calculated using the COST program. RESULTS: Reinfusion of platelets less than 20 hours after collection resulted in a recovery of 74.7 +/- 12.3 percent and a survival time of 7.5 +/- 1.1 days. Reinfusion on Day 5 resulted in a recovery of 58.2 +/- 12.0 percent and a survival time of 6.9 +/- 1.4 days, values that were 77.9 +/- 9.5 percent and 91.8 +/- 16.1 percent of the observation using "fresh" platelets, respectively. The area under the curve using Day 5 platelets was 67.8 +/- 11.5 percent of that using "fresh" platelets. CONCLUSION: The proposed criterion for objective evaluation of platelet preparation and storage systems appears applicable to a commonly accepted approach, leukoreduced apheresis platelets stored in plasma for 5 days, and merits evaluation using other collection, treatment, and storage systems.

Seven-day storage of single-donor platelets: recovery and survival in an autologous transfusion study.

BACKGROUND: Bacterial screening may effectively reduce the morbidity and mortality risk associated with extended storage of platelets. Platelet viability then becomes the primary determinant of acceptable storage time. This study evaluates the effectiveness of platelets stored in plasma for 7 days. STUDY DESIGN AND METHODS: WBC-reduced, single-donor platelets (n = 24) were collected and stored by standard methods at two sites. Standard in vitro platelet biochemical and functional parameters were monitored over the storage period. On Days 5 and 7 of storage, platelets were alternately labeled with 51Cr and (111)In and returned to the subject, and recovery and survival were determined. RESULTS: Component pH(22 degrees C) was maintained in the range 6.2 to 7.61 through 7 days and did not detrimentally affect either in vitro or in vivo outcomes. In vitro platelet characteristics were adequately maintained over 7 days. Day 5 platelets had better recovery (63.0 +/- 4.36 vs. 53.9 +/- 4.36%, p < 0.0001) and survival (161 +/- 8.1 vs. 133 +/- 8.1 hr, p = 0.006) than Day 7 platelets adjusting for radioisotope, center, and donor effects. CONCLUSION: Although declines in recovery and survival were noted, these are less than used previously to gain licensure of 7-day storage and are unlikely to be clinically significant. Extension of storage to 7 days could be implemented with bacterial screening methods to select out contaminated components without a significant effect on the platelet efficacy compared to 5-day components.

Production of pathogen-inactivated RBC concentrates using PEN110 chemistry: a Phase I clinical study.

BACKGROUND: Despite extensive reductions in risk, donor selection and testing cannot eliminate pathogen transmission. The objective of this study was to evaluate clinically the viability of pathogen-inactivated RBCs. STUDY DESIGN AND METHODS: Twelve healthy subjects each donated two units of blood that were handled as additive system control units or were inactivated using the PEN110 process (INACTINE, V.I. Technologies) in randomized order. PEN110, which inactivates pathogens by reacting with nucleic acid bases, was incubated with RBCs for 6 hours, followed by washing and quenching with sodium thiosulfate. Radiolabeled RBC recovery and survival determinations were undertaken after 28 days of storage; biochemical and hematologic variables were assessed over 42 days. RESULTS: After 28 days, treated units had a 24-hour double-label ((51)Cr/(99m)Tc) recovery (85.0 +/- 5.0%) that was indistinguishable from control units (85.9 +/- 2.7%); the times required for reduction of radioactivity of labeled cells to half the Day 1 activity (T(50)) were similar for both groups (treated, 31.9 +/- 8.2 days; control, 32.9 +/- 3.3 days). No deleterious effects of PEN110 treatment were found on RBC antigens tested. Treatment reduced 2,3-DPG levels by half and slightly lowered pH levels. Throughout the 42-day storage period, treated RBCs had a lower level of lactate production and a trend toward lower glucose consumption. Hemolysis remained below 1 percent; supernatant potassium and ATP levels were lower than those seen in control RBCs. CONCLUSION: PEN110-treated RBCs stored for 28 days meet all critical requirements for therapeutically useful units.