HBOC-201 use in traumatic brain injury: case report and review of literature

New Applications of HBOC-201: A 25-Year Review of the Literature

If not cured promptly, tissue ischemia and hypoxia can cause serious consequences or even threaten the life of the patient. Hemoglobin-based oxygen carrier-201 (HBOC-201), bovine hemoglobin polymerized by glutaraldehyde and stored in a modified Ringer's lactic acid solution, has been investigated as a blood substitute for clinical use. HBOC-201 was approved in South Africa in 2001 to treat patients with low hemoglobin (Hb) levels when red blood cells (RBCs) are contraindicated, rejected, or unavailable. By promoting oxygen diffusion and convective oxygen delivery, HBOC-201 may act as a direct oxygen donor and increase oxygen transfer between RBCs and between RBCs and tissues. Therefore, HBOC-201 is gradually finding applications in treating various ischemic and hypoxic diseases including traumatic hemorrhagic shock, hemolysis, myocardial infarction, cardiopulmonary bypass, perioperative period, organ transplantation, etc. However, side effects such as vasoconstriction and elevated methemoglobin caused by HBOC-201 are major concerns in clinical applications because Hbs are not encapsulated by cell membranes. This study summarizes preclinical and clinical studies of HBOC-201 applied in various clinical scenarios, outlines the relevant mechanisms, highlights potential side effects and solutions, and discusses the application prospects. Randomized trials with large samples need to be further studied to better validate the efficacy, safety, and tolerability of HBOC-201 to the extent where patient-specific treatment strategies would be developed for various clinical scenarios to improve clinical outcomes.

Pharmacotherapy in Acutely Anemic Jehovah’s Witnesses: An Evidence-Based Review

Objective: To determine the pharmacological treatment methods available to anemic Jehovah’s Witnesses (JW). Data Sources: MEDLINE and PubMed were searched from inception through February 2018 using the search terms Jehovah’s Witnesses, treatment, erythropoietin, hemoglobin-based oxygen carrier, Sanguinate, Hemopure, bleeding, and anemia. Study Selection and Data Extraction: All clinical trials, cohort studies, case-control studies, and observational trials involving pharmacotherapy in anemic JW patients were evaluated. Case reports and bibliographies were also analyzed for inclusion. Data Synthesis: Two studies involving the use of erythropoietin (EPO) and one study involving recombinant factor VIIa were included. Information was also included from other pharmacotherapeutic modalities that had case report data only. Current published evidence is limited with regard to evidence-based management of JW patients. High-dose EPO, intravenous iron supplementation, and hemostatic agents have demonstrated good clinical outcomes in case reports. EPO doses as high as 40 000 units daily have been advocated by some experts; however, pharmacokinetic studies do not support dose-dependent effects. Hemoglobin-based oxygen carriers (HBOCs) are currently not Food and Drug Administration approved. They are available through expanded access programs and may represent a lifesaving modality in the setting of severe anemia. Conclusions: There are currently not enough data to make definitive recommendations on the use of pharmacological agents to treat severe anemia in the JW population. Further evidence utilizing EPO and HBOCs will be beneficial to guide therapy.

Hemoglobin-Based Oxygen Carrier for Traumatic Hemorrhagic Shock Treatment in a Jehovah's Witness

Introduction:

Treatment of severe hemorrhagic shock due to acute blood loss from traumatic injuries in a Jehovah’s witness (JW) trauma patient is very challenging since hemostatic blood product resuscitation is limited by refusal of the transfusion of allogeneic blood products.

Case Presentation:

We describe a multifaceted approach to the clinical care of a severely anemic JW trauma patient including the early administration of a bovine hemoglobin-based oxygen carrier (HBOC) as a bridge to resolution of critical anemia (nadir hemoglobin 3.9 g/dL). Hemoglobin-based oxygen carrier infusions were used to supplement oxygen delivery until endogenous erythropoiesis could restore adequate red blood cell mass. Subsequent endogenous bone marrow recovery was supported by early administration of high-dose erythropoiesis-stimulating agents and iron supplementation.

Conclusions:

Early HBOC administration can be used in the treatment of severe hemorrhagic shock in trauma patients who refuse allogeneic blood.

Blood substitutes: evolution from noncarrying to oxygen- and gas-carrying fluids

The development of oxygen (O2)-carrying blood substitutes has evolved from the goal of replicating blood O2 transport properties to that of preserving microvascular and organ function, reducing the inherent or potential toxicity of the material used to carry O2, and treating pathologies initiated by anemia and hypoxia. Furthermore, the emphasis has shifted from blood replacement fluid to "O2 therapeutics" that restore tissue oxygenation to specific tissues regions. This review covers the different alternatives, potential and limitations of hemoglobin-based O2 carriers (HBOCs) and perfluorocarbon-based O2 carriers (PFCOCs), with emphasis on the physiologic conditions disturbed in the situation that they will be used. It describes how concepts learned from plasma expanders without O2-carrying capacity can be applied to maintain O2 delivery and summarizes the microvascular responses due to HBOCs and PFCOCs. This review also presents alternative applications of HBOCs and PFCOCs namely: 1) How HBOC O2 affinity can be engineered to target O2 delivery to hypoxic tissues; and 2) How the high gas solubility of PFCOCs provides new opportunities for carrying, dissolving, and delivering gases with biological activity. It is concluded that the development of current blood substitutes has amplified their applications horizon by devising therapeutic functions for O2 carriers requiring limited O2 delivery capacity restoration. Conversely, full, blood-like O2-carrying capacity reestablishment awaits the control of O2 carrier toxicity.

Examining and mitigating acellular hemoglobin vasoactivity

SIGNIFICANCE

There has been a striking advancement in our understanding of red cell substitutes over the past decade. Although regulatory oversight has influenced many aspects of product development in this period, those who have approached the demonstration of efficacy of red cell substitutes have failed to understand their implication at the level of the microcirculation, where blood interacts closely with tissue.

RECENT ADVANCES

The understanding of the adverse effects of acellular hemoglobin (Hb)-based oxygen carriers (HBOCs) has fortunately expanded from Hb-induced renal toxicity to a more complete list of biochemical mechanism. In addition, various unexpected adverse reactions were seen in early clinical studies. The effects of the presence of acellular Hb in plasma are relatively unique because of the convergence of mechanical and biochemical natures.

CRITICAL ISSUES

Controlling the variables using genetic engineering and chemical modification to change specific characteristics of the Hb molecule may allow for solving the complex multivariate problems of acellular Hb vasoactivity. HBOCs may never be rendered free of negative effects; however, quantifying the nature and extent of microvascular complications establishes a platform for designing new ameliorative therapies.

FUTURE DIRECTIONS

It is time to leave behind the study of vasoactivity and toxicity based on bench-top measurements of biochemical changes and those based solely on systemic parameters in vivo, and move to a more holistic analysis of the mechanisms creating the problems, complemented with meaningful studies of efficacy.

The use of the Revised Trauma Score as an entry criterion in traumatic hemorrhagic shock studies: data from the DCLHb clinical trials

INTRODUCTION

The Revised Trauma Score (RTS) has been proposed as an entry criterion to identify patients with mid-range survival probability for traumatic hemorrhagic shock studies.

HYPOTHESIS/PROBLEM

Determination of which of four RTS strata (1-3.99, 2-4.99, 1-4.99, and 2-5.99) identifies patients with predicted and actual mortality rates near 50% for use as an entry criterion in traumatic hemorrhagic shock clinical trials.

METHODS

Existing database analysis in which demographic and injury severity data from two prior international Diaspirin Cross-Linked Hemoglobin (DCLHb) clinical trials were used to identify an RTS range that could be an optimal entry criterion in order to find the population of trauma patients with mid-range predicted and actual mortality rates.

RESULTS

Of 208 study patients, the mean age was 37 years, 65% sustained blunt trauma, 49% received DCLHb, and 57% came from the European Union study arm. The mean values were: ISS, 31 (SD = 18); RTS, 5.6 (SD = 1.8); and Glasgow Coma Scale (GCS), 10.4 (SD = 4.8). The mean TRISS-predicted mortality was 34% and the actual 28-day mortality was 35%. The initially proposed 1-3.99 RTS range (n = 41) had the highest predicted (79%) and actual (71%) mortality rates. The 2-5.99 RTS range (n = 79) had a 62% predicted and 53% actual mortality, and included 76% blunt trauma patients. Removal of GCS <5 patients from this RTS 2-5.99 subgroup caused a 48% further reduction in eligible patients, leaving 41 patients (20% of 208 total patients), 66% of whom sustained a blunt trauma injury. This subgroup had 54% predicted and 49% actual mortality rates. Receiver operator curve (ROC) analysis found the GCS to be as predictive of mortality as the RTS, both in the total patient population and in the RTS 2-5.99 subgroup.

CONCLUSION

The use of an RTS 2-5.99 inclusion criterion range identifies a traumatic hemorrhagic shock patient subgroup with predicted and actual mortality that approach the desired 50% rate. The exclusion of GCS <5 from this RTS 2-5.99 subgroup patients yields a smaller, more uniform patient subgroup whose mortality is more likely related to hemorrhagic shock than traumatic brain injury. Future studies should examine whether the RTS or other physiologic criteria such as the GCS score are most useful as traumatic hemorrhagic shock study entry criteria.

Microenvironment changes in mild traumatic brain injury

Traumatic brain injury (TBI) is a major public-health problem for which mild TBI (MTBI) makes up majority of the cases. MTBI is a poorly-understood health problem and can persist for years manifesting into neurological and non-neurological problems that can affect functional outcome. Presently, diagnosis of MTBI is based on symptoms reporting with poor understanding of ongoing pathophysiology, hence precluding prognosis and intervention. Other than rehabilitation, there is still no pharmacological treatment for the treatment of secondary injury and prevention of the development of cognitive and behavioural problems. The lack of external injuries and absence of detectable brain abnormalities lend support to MTBI developing at the cellular and biochemical level. However, the paucity of suitable and validated non-invasive methods for accurate diagnosis of MTBI poses as a substantial challenge. Hence, it is crucial that a clinically useful evaluation and management procedure be instituted for MTBI that encompasses both molecular pathophysiology and functional outcome. The acute microenvironment changes post-MTBI presents an attractive target for modulation of MTBI symptoms and the development of cognitive changes later in life.

A synthetic haemoglobin-based oxygen carrier and the reversal of cardiac hypoxia secondary to severe anaemia following trauma

We report a case of compassionate use of a haemoglobin-based oxygen carrier in a severely injured Jehovah's Witness patient, for whom survival was considered unlikely. Severe anaemia and cardiac hypoxia were reversed after slow infusion of this agent. No vasoactive side effects were associated with the treatment, possibly due to the slow infusion, and the patient survived.

Synthesis, biophysical properties and pharmacokinetics of ultrahigh molecular weight tense and relaxed state polymerized bovine hemoglobins

Hemoglobin-based oxygen carriers (HBOC) are currently being developed as red blood cell (RBC) substitutes for use in transfusion medicine. Despite significant commercial development, late stage clinical results of polymerized hemoglobin (PolyHb) solutions hamper development. We synthesized two types of PolyHbs with ultrahigh molecular weights: tense (T) state PolyHb (M(W)=16.59 MDa and P(50)=41 mmHg) and relaxed (R) state PolyHb (M(W)=26.33 MDa and P(50)=0.66 mmHg). By maintaining Hb in either the T- or R-state during the polymerization reaction, we were able to synthesize ultrahigh molecular weight PolyHbs in distinct quaternary states with no tetrameric Hb, high viscosity, low colloid osmotic pressure and the ability to maintain O(2) dissociation, CO association and NO dioxygenation reactions. The PolyHbs elicited some in vitro RBC aggregation that was less than 6% dextran (500 kDa) but more than 5% human serum albumin. In vitro, T-state PolybHb autoxidized faster than R-state PolybHb as expected from previously reported studies, conversely, when administered to guinea pigs as a 20% exchange transfusion, R-state PolybHb oxidized faster and to a greater extent than T-state PolybHb, suggesting a more complex oxidative processes in vivo. Our findings also demonstrate that T-state PolybHb exhibited a longer circulating half-life, slower clearance and longer systemic exposure time compared to R-state PolybHb.