Blood substitutes. Haemoglobin therapeutics in clinical practice

Extracellular Hemoglobin: Modulation of Cellular Functions and Pathophysiological Effects

Hemoglobin is essential for maintaining cellular bioenergetic homeostasis through its ability to bind and transport oxygen to the tissues. Besides its ability to transport oxygen, hemoglobin within erythrocytes plays an important role in cellular signaling and modulation of the inflammatory response either directly by binding gas molecules (NO, CO, and CO2) or indirectly by acting as their source. Once hemoglobin reaches the extracellular environment, it acquires several secondary functions affecting surrounding cells and tissues. By modulating the cell functions, this macromolecule becomes involved in the etiology and pathophysiology of various diseases. The up-to-date results disclose the impact of extracellular hemoglobin on (i) redox status, (ii) inflammatory state of cells, (iii) proliferation and chemotaxis, (iv) mitochondrial dynamic, (v) chemoresistance and (vi) differentiation. This review pays special attention to applied biomedical research and the use of non-vertebrate and vertebrate extracellular hemoglobin as a promising candidate for hemoglobin-based oxygen carriers, as well as cell culture medium additive. Although recent experimental settings have some limitations, they provide additional insight into the modulatory activity of extracellular hemoglobin in various cellular microenvironments, such as stem or tumor cells niches.

Recognition of human hemoglobin with macromolecularly imprinted polymeric nanoparticles using non-covalent interactions

Hemoglobin (Hb) is the most abundant protein in the blood. It is vital for the living as oxygen carriers. Some of the very pure Hb-containing biological fluids are currently under clinical trial. However, the removal and purification of Hb from the blood are quite difficult, especially when it is at a low concentration level. In this study, the molecularly imprinted polymeric nanoparticles (MIPNs) were prepared using N-methacryloyl-histidine methyl ester (MAH) by mini-emulsion polymerization technique for specific binding of human hemoglobin (HHb). MIPNs in monosize form have a size of 152 ± 4 nm. They also have a high binding capacity (32.33 mg/g) of HHb. MIPNs retain 84% of the re-binding capacity for HHb after 10 cycles. The nanoparticles have 16 and 5 times higher binding capacity of HHb, respectively, in the presence of bovine serum albumin and lysozyme. Thanks to their high binding capacity and selectivity, MIPNs will allow them to be detected selectively for different target molecules. According to molecular docking, the main binding forces depend on hydrogen bonds and Van der Waals forces in the interaction within 5 Å around MAH molecule are observed through the amino acid residues of HHb at β1 and β2 subunit. The statistical mechanical analysis of docking showed that the free energy (ΔG) is -2732.14 kcal/mol, which indicates the interaction between MAH and HHb is energetically favorable at 298.15°K.

Normothermic machine perfusion of ischaemically damaged porcine kidneys with autologous, allogeneic porcine and human red blood cells

In porcine kidney auto-transplant models, red blood cells (RBCs) are required for ex-vivo normothermic machine perfusion (NMP). As large quantities of RBCs are needed for NMP, utilising autologous RBCs would imply lethal exsanguination of the pig that is donor and recipient-to-be in the same experiment. The purpose of this study was to determine if an isolated porcine kidney can also be perfused with allogeneic porcine or human RBCs instead. Porcine kidneys, autologous and allogeneic blood were obtained from a local slaughterhouse. Human RBCs (O-pos), were provided by our transfusion laboratory. Warm ischaemia time was standardised at 20 minutes and subsequent hypothermic machine perfusion lasted 1.5–2.5 hours. Next, kidneys underwent NMP at 37°C during 7 hours with Williams' Medium E and washed, leukocyte depleted RBCs of either autologous, allogeneic, or human origin (n = 5 per group). During perfusion all kidneys were functional and produced urine. No macroscopic adverse reactions were observed. Creatinine clearance during NMP was significantly higher in the human RBC group in comparison with the allogeneic group (P = 0.049) but not compared to the autologous group. The concentration of albumin in the urine was significantly higher in the human RBC group (P <0.001) compared to the autologous and allogeneic RBC group. Injury marker aspartate aminotransferase was significantly higher in the human RBC group in comparison with the allogeneic group (P = 0.040) but not in comparison with the autologous group. Renal histology revealed glomerular and tubular damage in all groups. Signs of pathological hyperfiltration and microvascular injury were only observed in the human RBC group. In conclusion, perfusion of porcine kidneys with RBCs of different origin proved technically feasible. However, laboratory analysis and histology revealed more damage in the human RBC group compared to the other two groups. These results indicate that the use of allogeneic RBCs is preferable to human RBCs in a situation where autologous RBCs cannot be used for NMP.

Shock index and prediction of traumatic hemorrhagic shock 28-day mortality: data from the DCLHb resuscitation clinical trials

INTRODUCTION

To assess the ability of the shock index (SI) to predict 28-day mortality in traumatic hemorrhagic shock patients treated in the diaspirin cross-linked hemoglobin (DCLHb) resuscitation clinical trials.

METHODS

We used data from two parallel DCLHb traumatic hemorrhagic shock efficacy trials, one in U.S. emergency departments, and one in the European Union prehospital setting to assess the relationship between SI values and 28-day mortality.

RESULTS

In the 219 patients, the mean age was 37 years, 64% sustained a blunt injury, 48% received DCLHb, 36% died, and 88% had an SI≥1.0 at study entry. The percentage of patients with an SI≥1.0 dropped by 57% (88 to 38%) from the time of study entry to 120 minutes after study resuscitation (p<0.001). Patients with a SI≥1.0, 1.4, and 1.8 at any time point were 2.3, 2.7, and 3.1 times, respectively, more likely to die by 28 days than were patients with SI values below these cutoffs (p<0.001). Similarly, after 120 minutes of resuscitation, patients with a SI≥1.0 were 3.9× times more likely to die by 28 days (40 vs. 15%, p<0.001). Although the distribution of SI values differed based on treatment group, the receiver operator characeristics data showed no difference in SI predictive ability for 28-day mortality in patients treated with DCLHb.

CONCLUSION

In these traumatic hemorrhagic shock patients, the shock index correlates with 28-day mortality, with higher SI values indicating greater mortality risk. Although DCLHb treatment did alter the distribution of SI values, it did not influence the ability of the SI to predict 28-day mortality.

Diaspirin cross-linked hemoglobin infusion did not influence base deficit and lactic acid levels in two clinical trials of traumatic hemorrhagic shock patient resuscitation

BACKGROUND

Diaspirin cross-linked hemoglobin (DCLHb) has demonstrated a pressor effect that could adversely affect traumatic hemorrhagic shock patients through diminished perfusion to vital organs, causing base deficit (BD) and lactate abnormalities.

METHODS

Data from two parallel, multicenter traumatic hemorrhagic shock clinical trials from 17 US Emergency Departments and 27 European Union prehospital services using DCLHb, a hemoglobin-based resuscitation fluid.

RESULTS

In the 219 patients, the mean age was 37.3 years, 64% of the patients sustained a blunt injury, 48% received DCLHb resuscitation, and the overall 28-day mortality rate was 36.5%. BD data did not differ by treatment group (DCLHb vs. normal saline [NS]) at any time point. Study entry BD was higher in patients who died when compared with survivors in both studies (US: -14.7 vs. -9.3 and European Union: -11.1 vs. -4.1 mEq/L, p < 0.003) and at the first three time points after resuscitation. No differences in BD based on treatment group were observed in either those who survived or those who died from the hemorrhagic shock. US lactate data did not differ by treatment group (DCLHb vs. NS) at any time point. Study entry lactates were higher in US patients who ultimately died when compared with survivors (82.4 vs. 56.1 mmol/L, p < 0.003) and at all five postresuscitation time points. No lactate differences were observed between DCLHb and NS survivors or in those who died based on treatment group.

CONCLUSIONS

Although patients who died had more greatly altered perfusion than those who survived, DCLHb treatment of traumatic hemorrhagic shock patients was not associated with BD or lactate abnormalities that would indicate poor perfusion.

The lack of consistent diaspirin cross-linked hemoglobin infusion blood pressure effects in the US and EU traumatic hemorrhagic shock clinical trials

Hemoglobin solutions have demonstrated a pressor effect that could adversely affect hemorrhagic shock patient resuscitation through accelerated hemorrhage, diminished perfusion, or inadequate resuscitation. Data from two parallel, multicenter traumatic hemorrhagic shock clinical trials in 17 US emergency departments and in 27 EU prehospital systems using diaspirin cross-linked hemoglobin (DCLHb), a hemoglobin-based resuscitation fluid. In the 219 patients, patients were 37 years old, 64% sustained blunt injury, 48% received DCLHb, and 36% expired. Although mean systolic blood pressure (SBP) and diastolic blood pressure values differed at 2 of the 10 measured time points, blood pressure (BP) curve analysis showed no SBP, diastolic blood pressure, or MAP differences based on treatment. Although SBP values 160 and 120 mmHg or greater were 2.2x and 2.6x more frequently noted in survivors, they were not more common with DCLHb use or in DCLHb patients who expired in US study nonsurvivors or in any EU study patients. Systolic blood pressure values 160 and 120 mmHg or greater were 2.8x and 1.3x more frequently noted in DCLHb survivors as compared with normal saline survivors. Only 3% of the BP variation noted could be attributed to DCLHb use, and as expected, injury severity and baseline physiologic status were stronger predictors. In the United States alone, treatment group was not correlated by regression with BP at any time point. Neither mean BP readings nor elevated BP readings were correlated with DCLHb treatment of traumatic hemorrhagic shock patients. As such, no clinically demonstrable DCLHb pressor effect could be directly related to the adverse mortality outcome observed in the US study.

Design of recombinant hemoglobins for use in transfusion fluids

Molecular biology has been applied to the development of hemoglobin-based oxygen carrier (HBOC) proteins that can be expressed in bacteria or yeast. The transformation of the hemoglobin molecule into an HBOC requires a variety of modifications for rendering the acellular molecule of hemoglobin physiologically acceptable when transfused in circulation. Hemoglobins with different oxygen affinities can be obtained by introducing mutations at the heme pocket, the site of oxygen binding, or by introducing surface mutations that stabilize the hemoglobin molecule in the low-oxygen-affinity state. Modification of the size of the heme pocket is also used to hinder nitric oxide depletion and associated vasoconstriction. Introduction of cysteine residues on the hemoglobin surface allows formation of intermolecular bonds and formation of polymeric HBOCs. These polymers of recombinant hemoglobin have the characteristics of molecular size, molecular stability, and oxygen delivery to hypoxic tissue suitable for an HBOC.

Fluids as oxygen carriers and the potential role in trauma resuscitation

Patients with major trauma present a challenge, often using large quantities of banked blood both at the time of injury and during their hospital stay. Blood transfusion is not without risk and is associated with high costs; it is immunosuppressive, rendering patients more susceptible to infection. In the western world, banked blood is fully screened and relatively safe; the same is not true in parts of the developing world, where high rates of HIV carriage make blood transfusion a risky undertaking. Additionally, blood transfusion as a vector for transmission of illnesses such as prion disease is a distinct possibility, for both the developed and developing world alike. The introduction of artificial blood substitutes would ameliorate some risk and also remove the cost of extensive blood testing. For trauma outside hospital, blood substitutes could compete directly with fluid resuscitation as donated blood is not usually available. Patients with prolonged transport times would appear to be the most obvious beneficiaries and volume expansion, along with improvement in oxygen-carrying capacity would be the ultimate goal. All clinicians confronted with the need for transfusion of homologous blood would welcome the development of a safe and reliable alternative to red blood cells in order to ensure oxygen transport to the tissues. However, even though research on red cell substitutes started more than 100 years ago, even now none of the heavily investigated compounds based on haemoglobin or perfluorocarbons has been released in Europe or the USA for routine clinical use.

[Systemic hemostatic drugs]

Understanding the haemostatic changes is crucial in developing strategies for the management of haemorrhage syndroma. In recent years, the revised model of coagulation ("cell based" model) provided a much more authentic description of the coagulation process. Pharmacological intervention, especially desmopresin, antifibrinolytics (synthetics and nature) and increasingly recombinant activated factor VII are being used in prevention and therapeutically to control bleeding of variety etiologies. Skillfull surgery combined with blood saving methods and careful management of blood coagulation will all help in sucessfull haemorrhage prevention and treatment, and reduce unnecessary blood loss and transfusion requirements and its attendant risks. Among the all avalaible tests, the use of thromboelastography has allowed for more detailed dynamic assessment of the various steps of hemostasis.

CD163 is the macrophage scavenger receptor for native and chemically modified hemoglobins in the absence of haptoglobin

CD163 mediates the internalization of hemoglobin-haptoglobin (Hb-Hp) complexes by macrophages. Because Hp binding capacity is exhausted during severe hemolysis, an Hp-independent Hb-clearance pathway is presumed to exist. We demonstrate that Hb interacts efficiently with CD163 in the absence of Hp. Not only is Hb internalized into an endosomal compartment by CD163 as a result of active receptor-dependent endocytosis; it also inhibits the uptake of Hb-Hp complexes, suggesting a common receptor-binding site. Free Hb further induces heme oxygenase mRNA expression in CD163+ HEK293 cells, but not in CD163- cells. Additional evidence for Hp-independent Hb-CD163 interaction is provided by the demonstration that CD163 mediates the uptake of alpha alpha-DBBF crosslinked Hb, a chemically modified Hb that forms minimal Hp complexes. Moreover, certain modifications to Hb, such as polymerization or the attachment of specific functional groups (3 lysyl residues) to the beta-Cys93 can reduce or enhance this pathway of uptake. In human macrophages, Hp-complex formation critically enhances Hb uptake at low (1 microg/mL), but not at high (greater than 100 microg/mL), ligand concentrations, lending support for a concentration-dependent biphasic model of macrophage Hb-clearance. These results identify CD163 as a scavenger receptor for native Hb and small-molecular-weight Hb-based blood substitutes after Hp depletion.

Resuscitation fluids

BACKGROUND AND OBJECTIVES

The aim of this review was to summarize the properties of the commonly available resuscitation fluids and highlight where knowledge of the characteristics of individual fluids might guide their use in clinical practice. Some of the current controversies surrounding resuscitation fluids are also discussed. Blood or blood products, or strategies of fluid administration, are not focused upon.

CONCLUSIONS

The clinical trial data does not support the concept of a therapeutic advantage for either crystalloids or colloids, despite claimed theoretical advantages for both classes of fluid. The available colloid solutions have quite distinct profiles of activity, both in terms of their plasma volume expansion profile and other physiological and pharmacological properties. Recent data suggests that physiologically balanced crystalloid and colloid solutions may improve clinical outcomes when compared with saline-based fluids.

Automated quantitation of hemoglobin-based blood substitutes in whole blood samples

It is necessary to develop methods for accurate monitoring of cell-free hemoglobin in circulation. Routine monitoring of circulating cell-free hemoglobin will be useful for evaluating the efficacy of blood substitute administration andfor determining the clearance rates of the blood substitute from circulation. In addition, discriminating between cell-free hemoglobin and cell-associated hemoglobin will enable accurate determination of RBC indices, mean cell hemoglobin and mean corpuscular hemoglobin concentration, in individuals receiving hemoglobin-based blood substitutes. As colorimetric methods used by hematology analyzers to quantitate the hemoglobin value of a blood sample cannot distinguish between cell-associated and cell-free hemoglobin, it is currently not feasible to quantitate the levels of hemoglobin substitutes in circulation. The advent of a technology that measures volume and hemoglobin concentration of individual RBCs provides an alternative strategy for quantitating the cell-associated hemoglobin in a blood sample. We document that the combined use of cell-based and colorimetric hemoglobin measurements provides accurate discrimination between cell-associated and cell-free hemoglobin over a wide range of hemoglobin levels. This strategy should enable rapid and accurate monitoring of the levels of cell-free hemoglobin substitutes in the circulation of recipients of these blood substitutes.