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Lamb DR, Greenfield A, Thangaraju K, Setua S, Eiker G, Wang Q, Vahedi A, Khan MA, Yahya A, Cabrales P, Palmer AF, Buehler PW. The Molecular Size of Bioengineered Oxygen Carriers Determines Tissue Oxygenation in a Hypercholesterolemia Guinea Pig Model of Hemorrhagic Shock and Resuscitation. Mol Pharm 2023; 20:5739-5752. [PMID: 37843033 DOI: 10.1021/acs.molpharmaceut.3c00611] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2023]
Abstract
Polymerized human hemoglobin (PolyhHb) has shown promise in preclinical hemorrhagic shock settings. Different synthetic and purification schemes can control the size of PolyhHbs, yet research is lacking on the impact of polymerized hemoglobin size on tissue oxygenation following hemorrhage and resuscitation in specialized animal models that challenge their resuscitative capabilities. Pre-existing conditions that compromise the vasculature and end organs, such as the liver, may limit the effectiveness of resuscitation and exacerbate the toxicity of these molecules, which is an important but minimally explored therapeutic dimension. In this study, we compared the effective oxygen delivery of intermediate molecular weight PolyhHb (PolyhHb-B3; 500-750 kDa) to high molecular weight PolyhHb (PolyhHb-B4; 750 kDa-0.2 μm) for resuscitative effectiveness in guinea pig models subjected to hemorrhagic shock. We evaluated how the size of PolyhHb impacts hemodynamics and tissue oxygenation in normal guinea pigs and guinea pigs on an atherogenic diet. We observed that while PolyhHb-B3 and -B4 equivalently restore hemodynamic parameters of normal-dieted guinea pigs, high-fat-dieted guinea pigs resuscitated with PolyhHb-B4 have lower mean arterial pressures, impaired tissue oxygenation, and higher plasma lactate levels than those receiving PolyhHb-B3. We characterized the plasma of these animals following resuscitation and found that despite similar oxygen delivery kinetics, circulating PolyhHb-B3 and -B4 demonstrated a size-dependent increase in the plasma viscosity, consistent with impaired perfusion in the PolyhHb-B4 transfusion group. We conclude that intermediate-sized PolyhHbs (such as -B3) are ideal for further research given the effective resuscitation of hemorrhagic shock based on tissue oxygenation in hypercholesterolemic guinea pigs.
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Affiliation(s)
- Derek R Lamb
- Center for Blood Oxygen Transport and Hemostasis, Department of Pediatrics, University of Maryland School of Medicine, HSF III, 670 West Baltimore St., Baltimore, Maryland 21202, United States
| | - Alisyn Greenfield
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, 452 CBEC, 151 West Woodruff Avenue, Columbus, Ohio 43210, United States
| | - Kiruphagaran Thangaraju
- Center for Blood Oxygen Transport and Hemostasis, Department of Pediatrics, University of Maryland School of Medicine, HSF III, 670 West Baltimore St., Baltimore, Maryland 21202, United States
| | - Saini Setua
- Center for Blood Oxygen Transport and Hemostasis, Department of Pediatrics, University of Maryland School of Medicine, HSF III, 670 West Baltimore St., Baltimore, Maryland 21202, United States
| | - Gena Eiker
- Center for Blood Oxygen Transport and Hemostasis, Department of Pediatrics, University of Maryland School of Medicine, HSF III, 670 West Baltimore St., Baltimore, Maryland 21202, United States
| | - Qihong Wang
- Center for Blood Oxygen Transport and Hemostasis, Department of Pediatrics, University of Maryland School of Medicine, HSF III, 670 West Baltimore St., Baltimore, Maryland 21202, United States
| | - Amid Vahedi
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, 452 CBEC, 151 West Woodruff Avenue, Columbus, Ohio 43210, United States
| | - Mohd Asim Khan
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, 452 CBEC, 151 West Woodruff Avenue, Columbus, Ohio 43210, United States
| | - Ahmad Yahya
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, 452 CBEC, 151 West Woodruff Avenue, Columbus, Ohio 43210, United States
| | - Pedro Cabrales
- Department of Bioengineering, University of California, San Diego, La Jolla, California 92093-0412, United States
| | - Andre F Palmer
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, 452 CBEC, 151 West Woodruff Avenue, Columbus, Ohio 43210, United States
| | - Paul W Buehler
- Center for Blood Oxygen Transport and Hemostasis, Department of Pediatrics, University of Maryland School of Medicine, HSF III, 670 West Baltimore St., Baltimore, Maryland 21202, United States
- Department of Pathology, University of Maryland School of Medicine, 10 S Pine St # 700A, Baltimore, Maryland 21201, United States
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Jana S, Kassa T, Wood F, Hicks W, Alayash AI. Changes in hemoglobin oxidation and band 3 during blood storage impact oxygen sensing and mitochondrial bioenergetic pathways in the human pulmonary arterial endothelial cell model. Front Physiol 2023; 14:1278763. [PMID: 37916221 PMCID: PMC10617028 DOI: 10.3389/fphys.2023.1278763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Accepted: 10/02/2023] [Indexed: 11/03/2023] Open
Abstract
Red blood cells (RBCs) undergo metabolic, oxidative, and physiological changes during storage, collectively described as the "storage lesion." The impact of storage on oxygen homeostasis, following transfusion, is not fully understood. We show that RBC storage induces changes in oxygen binding that were linked to changes in oxygen sensing (hypoxia-inducible factor, HIF-1α) mechanisms and mitochondrial respiration in human pulmonary arterial endothelial cells (HPAECs). A decrease in oxygen affinity (P50) to approximately 20 from 30 mmHg was seen at the first week but remained unchanged for up to 42 days. This led to the suppression of HIF-1α in the first 3 weeks due to limited oxygen supplies by RBCs. Furthermore, membrane oxidative damage, band 3 alterations, and subsequent microparticle (MP) formation were also noted. Mass spectrometric analysis revealed the upregulation of transitional endoplasmic reticulum ATPase, essential for clearing ROS-damaged membrane proteins and the protein DDI1 homolog, a proteasomal shuttle chaperone. Band 3 complex proteins and superoxide dismutase were among the downregulated proteins. Mitochondrial oxygen consumption rates measured in HPAECs incubated with RBC-derived MPs (14-day and 42-day) showed a rise in maximal respiration. Intervention strategies that target intracellular hemoglobin (Hb)'s redox transitions and membrane changes may lead to the reestablishment of oxygen homeostasis in old RBCs.
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Affiliation(s)
| | | | | | | | - Abdu I. Alayash
- Laboratory of Biochemistry and Vascular Biology, Center for Biologics Evaluation and Research Food and Drug Administration (FDA), Silver Spring, MD, United States
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Baek JH, Shin HKH, Koo SM, Gao Y, Qu H, Feng X, Xu X, Pinto J, Katneni U, Kimchi-Sarfaty C, Buehler PW. Polyethylene Oxide Molecular Size Determines the Severity of Atypical Thrombotic Microangiopathy in a Guinea Pig Model of Acute Intravenous Exposure. Toxicol Sci 2021; 177:235-247. [PMID: 32579216 DOI: 10.1093/toxsci/kfaa099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In 2017, Opana ER was voluntarily removed from the U.S. market based on concerns that its risks outweighed its therapeutic benefits. The data that supported this conclusion were based on postmarketing evaluation that demonstrated increased intravenous abuse associated outbreaks of HIV, hepatitis C, and uniquely, a thrombotic thrombocytopenic purpura (TTP)-like syndrome. In 2017, the cause was mechanistically linked to intravenous exposure of the high-molecular weight polyethylene oxide (PEO), an excipient component of the drug product. However, it was unknown how differing PEO preparations might alter this response in vivo. Knowing the likelihood of a PEO driven atypical thrombotic microangiopathy with hemolytic uremic syndrome (TMA-HUS), this study was specifically designed with the primary objective focused on understanding the impact of PEO molecular weight on TMA-HUS in a guinea pig model of acute repeat PEO (1, 4, and 7 MDa) dosing. Results from this analysis suggest that repeated dosing with PEO 4 and 7 MDa, but not 1 MDa induced a marked intravascular hemolysis with schistocytes, mild anemia, thrombocytopenia, hemoglobinuria, and kidney injury, consistent with observations of a TMA-HUS-like syndrome. Nonetheless, observations of tissue microthrombi, complement or altered von Willebrand factor involvement were not observed, which would be consistent with a definitive TMA. Further, only 7 MDa PEO dosing was associated with marked renal hypoxia. Taken together, this study defines renal injury risk with PEO formulations >1 MDa that is driven by a robust intravascular hemolysis and potentially, tissue hypoxia.
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Affiliation(s)
- Jin Hyen Baek
- Laboratory of Biochemistry and Vascular Biology, Division of Blood Components and Devices, Office of Blood Research and Review; Center for Drug Evaluation and Review, FDA, Silver Spring, Maryland
| | - Hye Kyung H Shin
- Laboratory of Biochemistry and Vascular Biology, Division of Blood Components and Devices, Office of Blood Research and Review; Center for Drug Evaluation and Review, FDA, Silver Spring, Maryland
| | - Soo Min Koo
- Laboratory of Biochemistry and Vascular Biology, Division of Blood Components and Devices, Office of Blood Research and Review; Center for Drug Evaluation and Review, FDA, Silver Spring, Maryland
| | - Yamei Gao
- Division of Viral Products, Office of Vaccines, Center for Biologics Evaluation and Research (CBER), FDA, Silver Spring, Maryland
| | - Haiou Qu
- Division of Product Quality Research, Office of Testing and Research, Office of Pharmaceutical Quality; Center for Drug Evaluation and Review, FDA, Silver Spring, Maryland
| | - Xin Feng
- Division of Product Quality Research, Office of Testing and Research, Office of Pharmaceutical Quality; Center for Drug Evaluation and Review, FDA, Silver Spring, Maryland
| | - Xiaoming Xu
- Division of Product Quality Research, Office of Testing and Research, Office of Pharmaceutical Quality; Center for Drug Evaluation and Review, FDA, Silver Spring, Maryland
| | - Julia Pinto
- Division of New Drug Product II, Office of New Drug Products, Office of Pharmaceutical Quality, Center for Drug Evaluation and Research (CDER), FDA, Silver Spring Maryland
| | - Upendra Katneni
- Division of Plasma Protein Therapeutics, Office of Tissues and Advanced Therapies, Center for Biologics Evaluation and Research (CBER), FDA, Silver Spring Maryland
| | - Chava Kimchi-Sarfaty
- Division of Plasma Protein Therapeutics, Office of Tissues and Advanced Therapies, Center for Biologics Evaluation and Research (CBER), FDA, Silver Spring Maryland
| | - Paul W Buehler
- Department of Pathology, University of Maryland School of Medicine, Baltimore, Maryland.,The Center for Blood Oxygen Transport and Hemostasis, Department of Pediatrics, University of Maryland School of Medicine, Baltimore, Maryland
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Bertolone L, Shin HK, Stefanoni D, Baek JH, Gao Y, Morrison EJ, Nemkov T, Thomas T, Francis RO, Hod EA, Zimring JC, Yoshida T, Karafin M, Schwartz J, Hudson KE, Spitalnik SL, Buehler PW, D'Alessandro A. ZOOMICS: Comparative Metabolomics of Red Blood Cells From Old World Monkeys and Humans. Front Physiol 2020; 11:593841. [PMID: 33192610 PMCID: PMC7645159 DOI: 10.3389/fphys.2020.593841] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Accepted: 09/29/2020] [Indexed: 12/14/2022] Open
Abstract
As part of the ZOOMICS project, we set out to investigate common and diverging metabolic traits in the blood metabolome across various species by taking advantage of recent developments in high-throughput metabolomics. Here we provide the first comparative metabolomics analysis of fresh and stored human (n = 21, 10 males, 11 females), olive baboon (n = 20), and rhesus macaque (n = 20) red blood cells at baseline and upon 42 days of storage under blood bank conditions. The results indicated similarities and differences across species, which ultimately resulted in a differential propensity to undergo morphological alterations and lyse as a function of the duration of refrigerated storage. Focusing on purine oxidation, carboxylic acid, fatty acid, and arginine metabolism further highlighted species-specific metabolic wiring. For example, through a combination of steady state measurements and 13C615N4-arginine tracing experiments, we report an increase in arginine catabolism into ornithine in humans, suggestive of species-specific arginase 1 activity and nitric oxide synthesis—an observation that may impact the translatability of cardiovascular disease studies carried out in non-human primates (NHPs). Finally, we correlated metabolic measurements to storage-induced morphological alterations via scanning electron microscopy and hemolysis, which were significantly lower in human red cells compared to both NHPs.
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Affiliation(s)
- Lorenzo Bertolone
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver - Anschutz Medical Campus, Aurora, CO, United States
| | - Hye K Shin
- Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, MD, United States
| | - Davide Stefanoni
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver - Anschutz Medical Campus, Aurora, CO, United States
| | - Jin Hyen Baek
- Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, MD, United States
| | - Yamei Gao
- Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, MD, United States
| | - Evan J Morrison
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver - Anschutz Medical Campus, Aurora, CO, United States
| | - Travis Nemkov
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver - Anschutz Medical Campus, Aurora, CO, United States
| | - Tiffany Thomas
- Department of Pathology and Cell Biology, Columbia University, New York, NY, United States
| | - Richard O Francis
- Department of Pathology and Cell Biology, Columbia University, New York, NY, United States
| | - Eldad A Hod
- Department of Pathology and Cell Biology, Columbia University, New York, NY, United States
| | - James C Zimring
- Department of Pathology, University of Virginia, Charloteseville, VA, United States
| | | | - Matthew Karafin
- Blood Center of Wisconsin, Milwaukee, WI, United States.,Department of Pathology and Laboratory Medicine, Milwaukee, WI, United States
| | - Joseph Schwartz
- Department of Pathology and Cell Biology, Columbia University, New York, NY, United States
| | - Krystalyn E Hudson
- Department of Pathology and Cell Biology, Columbia University, New York, NY, United States
| | - Steven L Spitalnik
- Department of Pathology and Cell Biology, Columbia University, New York, NY, United States
| | - Paul W Buehler
- Department of Pathology, University of Maryland School of Medicine, Baltimore, MD, United States.,Department of Pediatrics, Center for Blood Oxygen Transport and Hemostasis, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Angelo D'Alessandro
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver - Anschutz Medical Campus, Aurora, CO, United States.,Division of Hematology, Department of Medicine, University of Colorado Denver - Anschutz Medical Campus, Aurora, CO, United States
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Development of a real-time blood damage monitoring device for cardiopulmonary bypass system using near-infrared spectroscopy. Lasers Med Sci 2020; 36:783-790. [PMID: 32651700 DOI: 10.1007/s10103-020-03094-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Accepted: 06/29/2020] [Indexed: 10/23/2022]
Abstract
The optical properties of hemoglobin could indicate the degree of hemolysis. We aimed to utilize this to develop a real-time blood damage monitoring device for cardiopulmonary bypass (CPB) systems. The real-time blood damage monitoring device comprised a near-infrared spectroscopy optical module with a fiber spectrometer and monitoring platform and computer software developed using LabVIEW 2017. The fiber spectrometer operated at wavelengths of 545, 660, and 940 nm and contained a detector fiber bundle (source-detector distance = 1.0-2.5 cm). CPB operation was simulated using an artificial heart-lung machine with a flow rate of 3, 4, or 5 L/min. Four hundred milliliter of anticoagulated porcine blood was continuously rotated for 4 h. The transmittance, reflectivity, and absorbance of the blood were measured using the optical device at a frequency of 25 Hz and then digitally averaged into 1-s interval. Samples of damaged blood were collected at regular intervals for in vitro hemolysis tests to calculate the normalized index of hemolysis (NIH). All experiments were repeated three times. We prepared 28 blood bags containing 400 ml of anticoagulant. Paired t test was used to examine the test-retest reliability of the differences between the three methods and control samples. Statistical tests revealed significant differences in the mean values between the test and control groups over time (P < 0.01). Relationship was established between the real-time monitoring results and the NIH values. An effective blood damage detection method that combined in vitro hemolysis tests and near-infrared spectroscopy was achieved. The results demonstrate the clinical potential of a real-time, low-cost, and reliable blood damage monitoring device to improve the safety of CPB operation.
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Baek JH, Shin HKH, Gao Y, Buehler PW. Ferroportin inhibition attenuates plasma iron, oxidant stress, and renal injury following red blood cell transfusion in guinea pigs. Transfusion 2020; 60:513-523. [PMID: 32064619 DOI: 10.1111/trf.15720] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Revised: 12/03/2019] [Accepted: 12/18/2019] [Indexed: 12/25/2022]
Abstract
BACKGROUND Red blood cell (RBC) transfusions result in the sequestration and metabolism of storage-damaged RBCs within the spleen and liver. These events are followed by increased plasma iron concentrations that can contribute to oxidant stress and cellular injury. We hypothesized that administration of a ferroportin inhibitor (FPN-INH) immediately after acute RBC exchange transfusion could attenuate posttransfusion circulatory compartment iron exposure, by retaining iron in spleen and hepatic macrophages. STUDY DESIGN AND METHODS Donor guinea pig blood was leukoreduced, and RBCs were preserved at 4°C. Recipient guinea pigs (n = 5/group) were exchange transfused with donor RBCs after refrigerator preservation and dosed intravenously with a small-molecule FPN-INH. Groups included transfusion with vehicle (saline), 5 mg/kg or 25 mg/kg FPN-INH. A time course of RBC morphology, plasma non-transferrin-bound iron (NTBI) and plasma hemoglobin (Hb) were evaluated. End-study spleen, liver, and kidney organ iron levels, as well as renal tissue oxidation and injury, were measured acutely (24-hr after transfusion). RESULTS RBC transfusion increased plasma NTBI, with maximal concentrations occurring 8 hours after transfusion. Posttransfusion iron accumulation resulted in tubule oxidation and acute kidney injury. FPN inhibition increased spleen and liver parenchymal/macrophage iron accumulation, but attenuated plasma NTBI, and subsequent renal tissue oxidation/injury. CONCLUSION In situations of acute RBC transfusion, minimizing circulatory NTBI exposure by FPN inhibition may attenuate organ-specific adverse consequences of iron exposure.
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Affiliation(s)
- Jin Hyen Baek
- Laboratory of Biochemistry and Vascular Biology, Division of Blood Components and Devices, Center of Biologics Evaluation and Research (CBER), FDA, Silver Spring, Maryland, USA
| | - Hye Kyung H Shin
- Laboratory of Biochemistry and Vascular Biology, Division of Blood Components and Devices, Center of Biologics Evaluation and Research (CBER), FDA, Silver Spring, Maryland, USA
| | - Yamei Gao
- Division of Viral Products, Center of Biologics Evaluation and Research (CBER), FDA, Silver Spring, Maryland, USA
| | - Paul W Buehler
- Department of Pathology, Center for Blood Oxygen Transport, Baltimore, Maryland, USA.,Center for Blood Oxygen Transport and Hemostasis, Department of Pediatrics, University of Maryland Baltimore School of Medicine, Baltimore, Maryland, USA
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Baek JH, Buehler PW. Can molecular markers of oxygen homeostasis and the measurement of tissue oxygen be leveraged to optimize red blood cell transfusions? Curr Opin Hematol 2019; 26:453-460. [PMID: 31483333 DOI: 10.1097/moh.0000000000000533] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE OF REVIEW The clinical indication for transfusing red blood cells (RBCs) is to restore or maintain adequate oxygenation of respiring tissue. Oxygen (O2) transport, delivery, and utilization following transfusion are impacted by perfusion, hemoglobin (Hb) allosteric saturation/desaturation, and the concentration of tissue O2. Bioavailable O2 maintains tissue utilization and homeostasis; therefore, measuring imbalances in supply and demand could be valuable to assessing blood quality and transfusion effectiveness. O2 homeostasis is critically intertwined with erythropoietic response in blood loss and anemia and the hormones that modulate iron mobilization and RBC production (e.g., erythropoietin, erythroferrone, and hepcidin) are intriguing markers for the monitoring of transfusion effectiveness in acute and chronic settings. The evaluation of RBC donor unit quality and the determination of RBC transfusion needs are emerging areas for biomarker development and minimally invasive O2 measurements. RECENT FINDINGS Novel methods for assessing circulatory and tissue compartment biomarkers of transfusion effectiveness are suggested. In addition, monitoring of tissue oxygenation by indirect and direct measurements of O2 is available and applied in experimental settings. SUMMARY Herein, we discuss tissue O2 homeostasis, related aspects of erythropoiesis, molecular markers and measurements of tissue oxygenation, all aimed at optimizing transfusion and assessing blood quality.
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Affiliation(s)
- Jin Hyen Baek
- Laboratory of Biochemistry and Vascular Biology, Division of Blood Components and Devices, Center for Biologics Evaluation and Research, US Food and Drug Administration, Silver Spring, Maryland, USA
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Electron paramagnetic resonance oximetry as a novel approach to monitor the effectiveness and quality of red blood cell transfusions. BLOOD TRANSFUSION = TRASFUSIONE DEL SANGUE 2019; 17:296-306. [PMID: 31184583 DOI: 10.2450/2019.0037-19] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Accepted: 04/17/2019] [Indexed: 12/18/2022]
Abstract
BACKGROUND The goal of red blood cell transfusion is to improve tissue oxygenation. Assessment of red blood cell quality and individualised therapeutic needs can be optimised using direct oxygen (O2) measurements to guide treatment. Electron paramagnetic resonance oximetry is capable of accurate, repeatable and minimally invasive measurements of tissue pO2. Here we present preclinical proof-of-concept of the utility of electron paramagnetic resonance oximetry in an experimental setting of acute blood loss, transfusion, and post-transfusion monitoring. MATERIALS AND METHODS Donor rat blood was collected, leucocyte-reduced, and stored at 4 °C in AS-3 for 1, 7 and 14 days. Red blood cell morphology, O2 equilibrium, p50 and Hill numbers from O2 binding and dissociation curves were evaluated in vitro. Recipient rats were bled and maintained at a mean arterial pressure of 30-40 mmHg and hind limb muscle (biceps femoris) pO2 at 25-50% of baseline. Muscle pO2 was monitored continuously over the course of experiments to assess the effectiveness of red blood cell preparations at different stages of blood loss and restoration. RESULTS Red blood cell morphology, O2 equilibrium and p50 values of intra-erythrocyte haemoglobin were significantly altered by refrigerated storage for both 7 and 14 days. Transfusion of red blood cells stored for 7 or 14 days demonstrated an equivalently impaired ability to restore hind limb muscle pO2, consistent with in vitro observations and transfusion with albumin. Red blood cells refrigerated for 1 day demonstrated normal morphology, in vitro oxygenation and in vivo restoration of tissue pO2. DISCUSSION Electron paramagnetic resonance oximetry represents a useful approach to assessing the quality of red blood cells and subsequent transfusion effectiveness.
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