Hemoglobin-based Oxygen Carriers Research Articles

Polydopamine-based surface modification of hemoglobin particles for stability enhancement of oxygen carriers

Templated assembly techniques have been extensively used to develop various types of hemoglobin (Hb) loaded particles with improved performance. However, several instability issues must still be solved, including Hb exposure, enhanced Hb auto-oxidation, and the relatively weak binding of Hb to cross-linkers. Herein, to meet the stability requirements for novel hemoglobin-based oxygen carriers (HBOCs), hemoglobin-polydopamine particles (Hb-PDA) were fabricated using a mild process that combines the co-precipitation of Hb and an inorganic template with the spontaneous adhesion of PDA. The Hb-PDA showed uniform size distribution, chemical integrity of both Hb and PDA, high biocompatibility, and robust oxygen delivery. Our results demonstrated that the use of polydopamine as a biocompatible coating material reduced Hb leakage from the particles under both static and flow conditions, thus mitigating the toxicity associated with free Hb and strengthening the stability of Hb particles. In addition, Hb-PDA reduced HUVEC (Human Umbilical Vein Cells) oxidative injury and scavenged 85% of the available hydroxyl radicals, exhibiting its potential to act as an antioxidant for encapsulated Hb. Hb-PDA therefore shows significant promise as a cell-like structurally and functionally stable HBOCs.

Microvascular and Systemic Impact of Resuscitation with PEGylated Carboxyhemoglobin-Based Oxygen Carrier or Hetastarch in a Rat Model of Transient Hemorrhagic Shock.

Hemorrhage is the leading cause of preventable, traumatic death. Currently, prehospital resuscitation fluids provide preload but not oxygen-carrying capacity-a critical blood function that mitigates microvascular ischemia and tissue hypoxia during hemorrhagic shock. Solutions containing polymerized hemoglobin have been associated with vasoactive and hypertensive events. A novel hemoglobin-based oxygen carrier, modified with PEGylation and CO moieties (PEG-COHb), may overcome these limitations. To evaluate the systemic and microcirculatory effects of PEG-COHb as compared with the 6% hetastarch in a rat model of hemorrhagic shock. Male Sprague Dawley rats (N = 20) were subjected to severe, controlled, hemorrhagic shock. Animals were randomized to 20% estimated blood-volume resuscitation with either 6% hetastarch or PEG-COHb. Continuous, invasive, cardiovascular measurements, and arterial blood gases were measured. Microcirculatory measurements of interstitial oxygenation (PISFO2) and vasoactivity helped model oxygen delivery in the spinotrapezius muscle using intravital and phosphorescence quenching microscopy. Hemorrhage reduced mean arterial pressure (MAP), arteriolar diameter, and PISFO2, and increased lactate 10-fold in both groups. Resuscitation with both PEG-COHb and hetastarch improved cardiovascular parameters. However, PEG-COHb treatment resulted in higher MAP (P < 0.001), improved PISFO2 (14 [PEG-COHb] vs. 5 [hetastarch] mmHg; P < 0.0001), lower lactate post-resuscitation (P < 0.01), and extended survival from 90 to 142 min (P < 0.001) as compared with the hetastarch group. PEG-COHb improved MAP PISFO2, lactate, and survival time as compared with 6% hetastarch resuscitation. Importantly, hypertension and vasoactivity were not detected in response to PEG-COHb resuscitation supporting further investigation of this resuscitation strategy.

Renal Protection Against Ischemia Reperfusion Injury: Hemoglobin-based Oxygen Carrier-201 Versus Blood as an Oxygen Carrier in Ex Vivo Subnormothermic Machine Perfusion.

The optimal method of oxygen delivery to donor kidneys during ex vivo machine perfusion has not been established. We have recently reported the beneficial effects of subnormothermic (22°C) blood perfusion in the preservation of porcine donation after circulatory death kidneys. Since using blood as a clinical perfusate has limitations, including matching availability and potential presence of pathogen, we sought to assess hemoglobin-based oxygen carrier (HBOC-201) in oxygen delivery to the kidney for renal protection. Pig kidneys (n = 5) were procured after 30 minutes of warm in situ ischemia by cross-clamping the renal arteries. Organs were flushed with histidine tryptophan ketoglutarate solution and subjected to static cold storage or pulsatile perfusion with an RM3 pump at 22°C for 4 hours with HBOC-201 and blood. Thereafter, kidneys were reperfused with normothermic (37°C) oxygenated blood for 4 hours. Blood and urine were subjected to biochemical analysis. Total urine output, urinary protein, albumin/creatinine ratio, flow rate, resistance were measured. Acute tubular necrosis, apoptosis, urinary kidney damage markers, neutrophil gelatinase-associated lipocalin 1, and interleukin 6 were also assessed. HBOC-201 achieved tissues oxygen saturation equivalent to blood. Furthermore, upon reperfusion, HBOC-201 treated kidneys had similar renal blood flow and function compared with blood-treated kidneys. Histologically, HBOC-201 and blood-perfused kidneys had vastly reduced acute tubular necrosis scores and degrees of terminal deoxynucleotidyl transferase 2'-deoxyuridine, 5'-triphosphate nick end labeling staining versus kidneys treated with cold storage. Urinary damage markers and IL6 levels were similarly reduced by both blood and HBOC-201. HBOC-201 is an excellent alternative to blood as an oxygen-carrying molecule in an ex vivo subnormothermic machine perfusion platform in kidneys.

Rational Mutagenesis to Engineer Heme Stability in Recombinant Human Hemoglobin to Design Potential Hemoglobin Based Oxygen Carrier

Certain life-saving medical conditions like surgery, war wound and trauma necessitate blood transfusions. The transfusion process is associated with several risks and side effects. Heterologous expression of human hemoglobin for developing HBOCs seems to be an alternative to blood transfusion. However, such hemoglobins suffer quite a few disadvantages as described in Varnado et al. A major problem that prevents wider use of HBOCs is the dissociation of “heme” from its protein matrix. The released heme causes serious renal cytotoxicity which needs to be minimized. We successfully engineered heme stability into myoglobin by covalent linkage with a side chain from the apoprotein mimicking a cyanobacterial globin.Efforts are on in translating the heme stability in human hemoglobin. Based on rational mutagenesis, we were indeed able to engineer heme stability to an extent into recombinant human hemoglobin. Specific mutations in the α- and β- chains individually caused significant increase (∼3-4 fold) in the hemin retention. These mutations did not show any major influence on the structural stability and heme coordination of the protein. Moreover, engineered rHb mutants exhibited autooxidation rates similar to the wild type protein. Such preliminary success in engineering heme stability holds promise for the production of stable recombinant HBOCs.

Synthesis and characterisation of aqueous haemoglobin-based microcapsules coated by genipin-cross-linked albumin

Bovine serum albumin (BSA)-coated haemoglobin (Hb)-microcapsules prepared by co-precipitation of Hb and MnCO3 may present an alternative type of artificial blood substitute. Prepared microcapsules were analysed by Scanning electron microscopy (SEM) and Respirometry, cytotoxicity was evaluated by addition of microcapsules to murine fibroblast-derived cell line L929 (American Type Culture Collection, NCTC clone 929 of strain L). The capsules come along with a mean diameter of approximately 0.6 μm and a mean volume of 1.13 × 10−19 L, thus an average human red blood cell with a volume of 9 × 10−14 L is about 800,000 times bigger. Hb-microcapsules are fully regenerable by ascorbic acid and maintain oxygen affinity because oxygen is able to pass the BSA wall of the capsules and thereby binding to the ferrous iron of the haemoglobin entity. Therefore, these microcapsules present a suitable type of potential artificial haemoglobin-based oxygen carrier (HbOC).

Ex-Vivo Normothermic Limb Perfusion With a Hemoglobin-Based Oxygen Carrier Perfusate.

Ex-vivo normothermic limb perfusion (EVNLP) has been proven to preserve limb viability better than standard cold storage. Perfusates containing packed red blood cells (pRBC) improve outcomes when compared to acellular perfusates. Limitations of pRBC-based perfusion include limited availability, need for cross match, mechanical hemolysis, and activation of pro-inflammatory proteins. Hemoglobin-based oxygen carrier (HBOC)-201 (Hemopure) is a solution of polymerized bovine hemoglobin, characterized by low immunogenicity, no risk of hemolytic reaction, and enhanced convective and diffusive oxygen delivery. This is a preliminary study on the feasibility of EVNLP using HBOC-201 as an oxygen carrier. Three porcine forelimb perfusions were performed using an established EVNLP model and an HBOC-201-based perfusate. The perfusion circuit included a roller pump, oxygenator, heat exchanger, and reservoir. Electrolytes, limb temperature, weight, compartment pressure, nerve conduction, and perfusion indicated by indocyanine green angiography and infra-red thermography were monitored. Histological evaluation was performed with hematoxylin and eosin and electron microscopy. Three limbs were perfused for 21.3±2.1hours. Muscle contractility was preserved for 10.6±2.4hours. Better preservation of the mitochondrial ultrastructure was evident at 12hours in contrast to crystallization and destruction features in the cold-storage controls. An HBOC-201-EVNLP produced outcomes similar to RBC-EVNLP with preservation of muscle contractility and mitochondrial structure.

Protective effects of HBOC on pulmonary vascular leakage after haemorrhagic shock and the underlying mechanisms

Volume resuscitation is an important early treatment for haemorrhagic shock. Haemoglobin-based oxygen carrier (HBOC) can expand the volume and provide oxygen for tissues. Vascular leakage is common complication in the process of haemorrhagic shock and resuscitation. The aim of this study was to observe the effects of HBOC (a bovine-derived, cross-linked tetramer haemoglobin oxygen-carrying solution, 0.5 g/L) on vascular leakage in rats after haemorrhagic shock. A haemorrhagic shock rat model and hypoxic vascular endothelial cells (VECs) were used. The role of intercellular junctions and endothelial glycocalyx in the protective effects of HBOC and the relationship with mitochondrial function were analysed. After haemorrhagic shock, the pulmonary vascular permeability to FITC-BSA, Evans Blue was increased, endothelial glycocalyx was destroyed and the expression of intercellular junction proteins was decreased. After haemorrhagic shock, a small volume of HBOC solution (6 ml/kg) protected pulmonary vascular permeability, increased structural thickness of endothelial glycocalyx, the levels of its components and increased expression levels of the intercellular junction proteins ZO-1, VE-cadherin and occludin. Moreover, HBOC significantly increased oxygen delivery and consumption in rats, improved VEC mitochondrial function and structure. In conclusion, HBOC mitigates endothelial leakage by protecting endothelial glycocalyx and intercellular junctions through improving mitochondrial function and tissue oxygen delivery.

Increased and safe utilization of high-risk donor livers for transplantation after ex situ resuscitation and assessment using sequential hypo- and normothermic machine perfusion

Background: Despite persistent donor organ shortage, a high number of donor livers is currently not used for transplantation. We aimed to increase the number of transplantable livers by resuscitating and assessing hepatobiliary viability of initially declined high-risk livers using a protocol of end-ischemic sequential ex situ hypothermic and normothermic machine perfusion. Method: In this prospective clinical trial, all nationwide declined livers were eligible for inclusion (Netherlands Trial Registry NTR5972). The protocol consisted of one hour hypothermic oxygenated perfusion (10°C) for resuscitation, one hour of controlled oxygenated rewarming, and subsequent normothermic machine perfusion (NMP) for viability testing. A perfusion fluid containing a hemoglobin-based oxygen carrier was used for all temperature phases. During the first 150 min of NMP, viability of liver and biliary tree was assessed, using the following criteria: perfusate lactate <1.7mmol/L, pH 7.35-7.45, cumulative bile production >10mL and biliary pH>7.45. Livers meeting these criteria were secondary accepted for transplantation. All recipients gave written informed consent. Primary endpoint was safety and feasibility, as reflected by a 3-months graft survival rate of at least 80%. Results: Between August 2017 and October 2018, 16 livers underwent machine perfusion after an average of 288 (241-480) min of static cold preservation. All livers were derived from donation after circulatory death donors, with a median age of 63 (range 42-82) years. During NMP, all livers cleared lactate and produced sufficient bile volume, but in 5 cases biliary pH remained <7.45. The 11 (69%) livers that met all viability criteria were successfully transplanted, increasing the number of deceased donor liver transplants by 20%. Patient and with graft survival at 3 months was 100%. Conclusion: Sequential hypo- and normothermic machine perfusion enabled resuscitation and selection of initially declined high-risk donor livers. This method offered a valuable tool to safely increase the number of transplantable livers by 20%.

Systemic and microvascular comparison of Lactated Ringer’s solution, VIR-HBOC, and alpha-alpha crosslinked haemoglobin-based oxygen carrier in a rat 10% topload model

Medical support for traumatic haemorrhage is lacking for far-forward combat units. VIR-HBOC (haemoglobin-based oxygen carrier) is a novel biological therapeutic under development as a field-stable resuscitation fluid. HBOCs have a long history of complications, chief among them is vasoconstrictive hypertension, which must be resolved before efficacy testing. As such, VIR-HBOC was compared against Lactated Ringers (LRS; vehicle) and a cross-linked haemoglobin (ααHb; a known vasoactive HBOC) in a rat topload model. Twenty-three male, Sprague Dawley rats were randomly assigned to receive a 10% infusion (estimated total blood volume) of one test article while normotensive and under anaesthesia. Cardiovascular, blood chemistry and oximetry, microvascular arteriolar diameters, and interstitial tissue oxygenation parameters were measured. Circulatory half-life was calculated by plasma total haemoglobin. Treatment with ααHb caused immediate increases in mean arterial pressure compared to LRS and VIR-HBOC groups, and corresponding arteriolar vasoconstriction (p < .05), which did not occur for LRS or VIR-HBOC. Circulatory half-lives for VIR-HBOC and ααHb were calculated as 340 and 157 min, respectively. This first report of VIR-HBOC showed no evidence of a hypertensive or vasoactive effect. It was well-tolerated over the eight-hour time course of this topload model, which warrants further investigation in studies of haemorrhagic shock.

Engineering hemoglobin to enable homogenous PEGylation without modifying protein functionality.

In order to infuse hemoglobin into the vasculature as an oxygen therapeutic or blood substitute, it is necessary to increase the size of the molecule to enhance vascular retention. This aim can be achieved by PEGylation. However, using non-specific conjugation methods creates heterogenous mixtures and alters protein function. Site-specific PEGylation at the naturally reactive thiol on human hemoglobin (βCys93) alters hemoglobin oxygen binding affinity and increases its autooxidation rate. In order to avoid this issue, new reactive thiol residues were therefore engineered at sites distant to the heme group and the α/β dimer/dimer interface. The two mutants were βCys93Ala/αAla19Cys and βCys93Ala/βAla13Cys. Gel electrophoresis, size exclusion chromatography and mass spectrometry revealed efficient PEGylation at both αAla19Cys and βAla13Cys, with over 80% of the thiols PEGylated in the case of αAla19Cys. For both mutants there was no significant effect on the oxygen affinity or the cooperativity of oxygen binding. PEGylation at αAla19Cys had the additional benefit of decreasing the rates of autoxidation and heme release, properties that have been considered contributory factors to the adverse clinical side effects exhibited by previous hemoglobin based oxygen carriers. PEGylation at αAla19Cys may therefore be a useful component of future clinical products.

Alternatives to Transfusion

We discuss two main categories of blood substitutes: perfluorocarbons and hemoglobin-based oxygen carriers. We provide a review of the notable products developed in both categories and include their attributes as well as their setbacks. We contribute a case report tothe growing literature of the successful use of Sanguinate. We find that artificial oxygen carriers are an attractive field of research because of the practical limitations and the multitude of potential complications that surround human blood transfusions.

Transfusion support and alternatives for Jehovah's Witness patients.

Jehovah's Witness patients with critical anemia or undergoing major surgery are challenging for healthcare providers to manage, as most will decline transfusion of whole blood and its main components. Recent advances in our understanding of hemostatic agents, alternative hemoglobin-based oxygen carriers, and patient blood management have culminated in a complex array of options to manage critical anemia and bleeding in this patient population. Refusal of blood products in the setting of critical anemia is associated with significant risk of morbidity and mortality. With implementation of patient blood management measures, targeted treatment of anemia and coagulopathy has reduced the need for transfusions. Likewise, increased clinical experience with hemoglobin-based oxygen carriers in Jehovah's Witnesses with critical anemia has provided new insights into their potential benefits and pitfalls. Options and alternatives to manage the Jehovah's Witness patient in the perioperative setting or in the setting of critical anemia will be reviewed.

The impact on the bioenergetic status and oxidative-mediated tissue injury of a combined protocol of hypothermic and normothermic machine perfusion using an acellular haemoglobin-based oxygen carrier: The cold-to-warm machine perfusion of the liver.

IntroductionThe combination of hypothermic and normothermic machine perfusion (HMP+NMP) of the liver provides individual benefits of both techniques, improving the rescue of marginal organs. The aim of this study was to investigate the effect on the bioenergetic status and the oxidative-mediated tissue injury of an uninterrupted combined protocol of HMP+NMP using a single haemoglobin-based oxygen carrier (HBOC)-based perfusate.MethodsTen discarded human donor livers had either 2 hours of dual hypothermic oxygenated perfusion (D-HOPE) with sequential controlled rewarming (COR) and then NMP using the HBOC-based perfusate uninterruptedly (cold-to-warm group); or 2 hours of hypothermic oxygenated perfusion (HOPE) with an oxygen carrier-free perfusate, followed by perfusate exchange and then NMP with an HBOC-based perfusate. Markers of liver function, tissue adenosine triphosphate (ATP) levels and tissue injury were systematically assessed.ResultsThe hypothermic phase downregulated mitochondrial respiration and increased ATP levels in both groups. The cold-to-warm group presented higher arterial vascular resistance during rewarming/NMP (p = 0.03) with a trend of lower arterial flow (p = 0.09). At the end of NMP tissue expression of markers of reactive oxygen species production, oxidative injury and inflammation were comparable between the groups.ConclusionThe uninterrupted combined protocol of HMP+NMP using an HBOC-based perfusate—cold-to-warm MP—mitigated the oxidative-mediated tissue injury and enhanced hepatic energy stores, similarly to an interrupted combined protocol; however, it simplified the logistics of this combination and may favour its clinical applicability.

Reassessment of the Need for an Oxygen Carrier for the Treatment of Traumatic Hemorrhage When Blood is not an Option.

Approximately 10 years ago, the development of hemoglobin-based oxygen carriers (HBOCs) was largely stalled after two large phase 3 clinical trials failed to achieve licensure primarily because the safety profile was viewed as unsatisfactory when HBOCs were compared with red cells. Concerns were also raised that HBOCs, as a class, had inherent toxicities. Since then, clinical experience with HBOCs in expanded access programs and under licensure in South Africa has demonstrated that HBOCs can be used safely and effectively. In recent years, clinical studies have demonstrated that prehospital blood transfusion improves survival in severely injured patients with hemorrhage, especially when transport times are longer than 20 to 30 min. Yet, logistical constraints still limit use of blood products in the prehospital setting. As the urgent need for oxygen-carrying capacity for trauma patients for whom red cells are not available is becoming much more apparent, it is imperative that we reexamine the possibility of using HBOCs when red blood cell transfusion is not an option.

Hemoglobin-based Oxygen Carriers (HBOC)-What the Next Generation Holds: When Red Blood Cells are not an Option.

∗Combat Casualty Care Research Program, United States Army Medical Research and Materiel Command, Fort Detrick, Maryland †United States Army Institute of Surgical Research, JBSA-Fort Sam Houston, Houston, Texas ‡University of California, San Francisco, California E-mail: [email protected] The authors report no conflicts of interest.

Hemoglobin-based Oxygen Carriers: Current State-of-the-art and Novel Molecules.

In blood, the primary role of red blood cells (RBCs) is to transport oxygen via highly regulated mechanisms involving hemoglobin (Hb). Hb is a tetrameric porphyrin protein comprising of two α- and two β-polypeptide chains, each containing an iron-containing heme group capable of binding one oxygen molecule. In military as well as civilian traumatic exsanguinating hemorrhage, rapid loss of RBCs can lead to suboptimal tissue oxygenation and subsequent morbidity and mortality. In such cases, transfusion of whole blood or RBCs can significantly improve survival. However, blood products including RBCs present issues of limited availability and portability, need for type matching, pathogenic contamination risks, and short shelf-life, causing substantial logistical barriers to their prehospital use in austere battlefield and remote civilian conditions. While robust research is being directed to resolve these issues, parallel research efforts have emerged toward bioengineering of semisynthetic and synthetic surrogates of RBCs, using various cross-linked, polymeric, and encapsulated forms of Hb. These Hb-based oxygen carriers (HBOCs) can potentially provide therapeutic oxygenation when blood or RBCs are not available. Several of these HBOCs have undergone rigorous preclinical and clinical evaluation, but have not yet received clinical approval in the USA for human use. While these designs are being optimized for clinical translations, several new HBOC designs and molecules have been reported in recent years, with unique properties. The current article will provide a comprehensive review of such HBOC designs, including current state-of-the-art and novel molecules in development, along with a critical discussion of successes and challenges in this field.

Current Challenges in the Development of Acellular Hemoglobin Oxygen Carriers by Protein Engineering.

This article reviews the key biochemical mechanisms that govern O2 transport, NO scavenging, and oxidative degradation of acellular hemoglobin (Hb) and how these ideas have been used to try to develop strategies to engineer safer and more effective hemoglobin-based oxygen carriers (HBOCs). Significant toxicities due to acellular Hb have been observed after the administration of HBOCs or after the lysis of red cells, and include rapid clearance and kidney damage due to dissociation into dimers, haptoglobin binding, and macrophage activation; early O2 release leading to decreased tissue perfusion in capillary beds; interference with endothelial and smooth muscle signaling due to nitric oxide (NO) scavenging; autooxidization of heme iron followed by production of reactive oxygen species; and iron overload symptoms due to hemin loss, globin denaturation, iron accumulation, and further inflammation. Protein engineering can be used to mitigate some of these side effects, but requires an in-depth mechanistic understanding of the biochemical and biophysical features of Hb that regulate quaternary structure, O2 affinity, NO dioxygenation, and resistance to oxidation, hemin loss, and unfolding.

Users Guide to Pitfalls and Lessons Learned About HBOC-201 During Clinical Trials, Expanded Access, and Clinical Use in 1,701 Patients.

Lessons learned during 1,701 clinical uses of HBOC-201, a polymerized bovine hemoglobin-based oxygen carrier (HBOC), were identified to provide management lessons and training material for future clinical trials and use. HBOC-201 contains 13 g/dL hemoglobin (Hb), is iso-oncotic, stable at 2°C to 30°C with shelf-life of 3 years, requires no cross-matching with half-life of 19 h, and plasma volume distribution. Adverse effects include increased blood pressure, oliguria, gastrointestinal (GI) symptoms, yellow skin and scleral discoloration, decreased pulse oximetry measurements, and transient increases in methemoglobin, hepatic, and pancreatic enzymes. There was no cardiotoxicity. Elevations in blood pressure were transient and were managed with vasodilators. Oliguria was of limited duration. GI symptoms were treated with smooth muscle relaxants. Yellow skin and sclera were self-limiting, caused by Hb metabolism. The most important clinical management errors were lack of understanding of volume expansion effects and the half-life properties of HBOC-201, and failure to repeat infusions. Early use of HBOC-201 for Expanded Access when Hb less than 5 g/dL optimized survival and minimized advanced resource utilization. For phase 3 trials, there was transfusion avoidance of 96% for 24 h, 70% for 1 week, with no difference in serious adverse events or mortality whether patients received at most 10 bags HBOC-201 or at most 3 units blood. More nonserious events occurred with HBOC-201. Age, history of cardiac disease, and Hb deficit, but not randomization to HBOC-201, were significantly predictive of cardiac ischemic events. Administration of HBOC-201 in1,701 humans showed it was well tolerated in a wide range of doses and clinical settings. HBOC-201 should be considered when blood is not available or an option.

Mechanisms of Toxicity and Modulation of Hemoglobin-based Oxygen Carriers

ABSTRACTSeveral adverse events have been associated with the infusion of hemoglobin-based oxygen carriers (HBOCs), including transient hypertension, gastrointestinal, pancreatic/liver enzyme elevation, and cardiac/renal injury in humans. Although several mechanisms have been suggested, the basis of HBOC toxicity is still poorly understood. Scavenging of vascular endothelial nitric oxide (NO) and heme-mediated oxidative side reactions are thought to be the major causes of toxicity. However, based on more recent preclinical studies, oxidative pathways (driven by the heme prosthetic group) seem to play a more prominent role in the overall toxicity of free Hb or HBOCs. HBOCs display a diversity of physicochemical properties, including molecular size/cross-linking characteristics leading to differences in oxygen affinity, allosteric, redox properties, and even oxidative inactivation by protein/heme clearing mechanisms. These diverse characteristics can therefore be manipulated independently, leaving open the possibility of engineering a safe and effective HBOC. To date, several antioxidative strategies have been proposed to counteract the redox side reactions of current generation HBOCs.

The Management of Acute Blood Loss With Hemoglobin-Based Oxygen Carriers in Jehovah’s Witness Patients: A Case Series and Review of Literature

Abstract Managing anemia and acute blood loss in critical patients has long been reliant on the judicious use of red blood cell transfusions. The primary goal of blood transfusion is the efficient delivery of oxygen to end organs, especially the brain. Provided that appropriate guidelines are followed, allogenic blood transfusions are considered a safe and effective therapeutic option. Some patients refuse or decline blood transfusions due to cultural and/or religious beliefs, with the most well known being followers of Jehovah’s Witnesses (JWs). For this patient population, hemoglobin-based oxygen carriers (HBOCs) are a potential therapeutic option. Hemoglobin-based oxygen carriers are infusible oxygen-carrying fluids prepared from purified human or animal hemoglobin, which do not need to be refrigerated or crossmatched. We describe our experience at our institution where three JW patients were administered HBOCs. As HBOCs are not approved by the Food and Drug Administration and undergoing clinical trials, a compassionate use protocol was used to obtain HBOC-201 or Hemopure (Biopure Corporation). We explored factors attributing to overall response to treatment and laboratory effects of HBOC use. The first patient (24-year-old male, recurrent gastrointestinal bleed) received 8 units over a period of 2 weeks of HBOC. Pretransfusion hemoglobin and reticulocyte counts of 3.8 g/dL and 18.15% and posttransfusion counts were 12.8 g/dL and 16.97, respectively, with stable vital signs and renal function. Patient 2 (49-year-old female, chronic renal failure) received 8 units of Hemopure over 1 week. Before HBOC and erythropoietin administration, her hemoglobin and reticulocyte count were 4.2 g/dL and 0%, respectively, with stable vital signs and renal function. Post, her hemoglobin levels increased to 11.4 g/dL with a reticulocyte count of 16.0%. Unfortunately, the third patient (61-year-old female) expired secondary to complications from her initially diagnosed pulmonary embolism and massive stroke. She had received two units of HBOC and experienced a rise in hemoglobin (2.9 to 4.1 g/dL) and reticulocyte count (0% to 2.7%) with stable vitals during administration. Rapid resuscitation along with HBOC administration correlated with improved recovery in two of the three patients and yet none experienced hypertensive events. Younger age (24 and 49 years old) and their comorbid conditions are two factors that could explain the positive response to administration of HBOCs. Hemoglobin and hematocrit levels were often inaccurate as well as platelet counts, electrolytes, and liver enzymes. Coagulation tests (partial thromboplastin time, prothrombin time) were also affected by HBOC use. Overall, the utilization of HBOCs was beneficial in the hemodynamic management of two of our JW patients who refused allogenic blood transfusions. Additional research is needed to further understand the effectiveness of HBOCs on this patient population.