Transfusions of polymerized bovine hemoglobin in a patient with severe autoimmune hemolytic anemia

Warm autoimmune hemolytic anemia and hemophagocytic lymphohistiocytosis/macrophage activation syndrome occurring after COVID19 infection and administration of Casirivimab + Imdevimab (COVID19 monoclonal antibody)

Warm Autoimmune Hemolytic Anemia (WAHA) is the most common form of autoimmune hemolysis and there is a growing body of evidence of an association between SARS-CoV-2 infection, WAHA and a hyperinflammatory state, including hemophagocytic lymphohistiocytosis/macrophage activation syndrome. However, there is no literature to date of WAHA or hyperinflammatory state following administration of anti-SARS-CoV-2 monoclonal antibody treatment. This report documents a case of a patient with history of WAHA who developed brisk hemolysis and a hyperinflammatory state consistent with hemophagocytic lymphohistiocytosis/macrophage activation syndrome after COVID-19 infection and treatment with an anti-SARS-CoV-2 monoclonal antibody. He was successfully treated with multimodal treatment involving steroids, intravenous immunoglobulins, rituximab, anakinra, and vincristine with resolution of the hemolysis.

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.

Liposomal encapsulation of trans-crocetin enhances oxygenation in patients with COVID-19-related ARDS receiving mechanical ventilation

Current therapeutic treatments improving the impaired transportation of oxygen in acute respiratory distress syndrome (ARDS) have been found to be relevant and beneficial for the therapeutic treatment of COVID-19 patients suffering from severe respiratory complications. Hence, we report the preclinical and the preliminary results of the Phase I/II clinical trial of LEAF-4L6715, a liposomal nanocarrier encapsulating the kosmotropic agent trans-crocetin (TC), which, once injected, enhance the oxygenation of vascular tissue and therefore has the potential to improve the clinical outcomes of ARDS and COVID-19 in severely impacted patients. We demonstrated that the liposomal formulation enabled to increase from 30 min to 48 h the reoxygenation properties of free TCs in vitro in endothelial cells, but also to improve the half-life of TC by 6-fold in healthy mice. Furthermore, we identified 25 mg/kg as the maximum tolerated dose in mice. This determined concentration led to the validation of the therapeutic efficacy of LEAF-4 L6715 in a sepsis mouse model. Finally, we report the preliminary outcomes of an open-label multicenter Phase I/II clinical trial (EudraCT 2020–001393-30; NCT04378920), which was aimed to define the appropriate schedule and dosage of LEAF-4L6715 and to confirm its tolerability profile and preliminary clinical activity in COVID-19 patients treated in intensive care unit.

Artificial Blood: A Futuristic Dimension of Modern Day Transfusion Sciences

Artificial blood is an innovative concept of transfusion medicine where specifically designed compounds perform the task of transport and delivery of oxygen in the body to replace this function of allogenic human blood transfusion. Several molecules have been developed in the past few decades to achieve this objective and continous refinements are being continuously made in the quest of the ideal blood substitute. Currently, available technology manufactures artificial blood from haemoglobin obtained from outdated human/bovine blood (Haemoglobin Based Oxygen Carriers) or utilizing Perfluorocarbons. These synthetic blood substitutes are advantageous in that they do not require compatibility testing, are free from blood borne infections, have prolonged shelf life and do not require refrigeration. Artificial blood is projected to have a significant impact on the development of medical care in the future. It can complement the current blood products for transfusion and create a stable supply of safe and effective products. It is likely to reduce the requirements of blood transfusions drastically especially in settings of trauma and surgery thereby reducing the reliance on banked donated blood.

Issues in the development of hemoglobin based oxygen carriers

Hemoglobin based oxygen carriers (HBOCs) have been developed as alternative oxygen transporting formulations for the acute treatment of anemia and ischemia. Efficacy has been demonstrated in a variety of preclinical models and selected human patients; however, a higher overall incidence of mortality and myocardial infarction in those dosed with HBOCs in later stage clinical trials has prevented widespread regulatory approval. Diagnosis of myocardial infarction is confounded by the fact that HBOCs interfere with troponin assays, as well as other clinical chemistry measurements. Analysis of data pertaining to potential toxicity mechanisms suggests that coronary vasoconstriction is an unlikely contributor, but promotion of intravascular thrombosis may occur by several mechanisms. In addition, fluid and anemia management in patients infused with HBOCs has been suboptimal. Elucidation of potential toxicity mechanisms, refinement of use protocols, and definition of improved patient inclusion/exclusion criteria remain active areas of inquiry in understanding the best manner in which to utilize HBOCs.

Haemoglobin-based oxygen carriers and myocardial infarction

The incidence of investigator diagnosed myocardial infarction (MI) is greater in patients treated with haemoglobin-based oxygen carriers (HBOCs) than controls. Clinical trials and literature pertaining to possible HBOC toxicity mechanisms have been analyzed in order to identify possible reasons for this imbalance. MI diagnosis is hampered by potential interference of troponin assays by haemoglobin, haemolysis and bilirubin. Nevertheless, insofar as the reported incidence correlates with actual occurrence, there is a positive relationship between MI and HBOC dose and size. Preclinical and clinical data suggest that direct cardiac toxicity and coronary vasoconstriction are unlikely. More probable are detrimental intravascular interactions between HBOCs and components of the coagulation cascade, particularly dysfunctional endothelium. Elucidation of mechanisms is impeded by a lack of clinical data. Measurement of relevant biomarkers would be extremely useful in this regard and in improving patient selection criteria. Conduct of clinical trials in carefully selected patient populations after the development of improved protocols for MI diagnosis, along with concomitant biomarker data collection, is recommended.

"Inside-Out" PEGylation of Bovine β-Cross-Linked Hemoglobin

The development of a blood substitute is urgent due to blood shortages and potential communicable diseases. A novel method, inside-out PEGylation, has been used here to conjugate a multiarm maleimide-PEG (Mal-PEG) to β-cross-linked (βXL-Hb) hemoglobin (Hb) tetramers through the Cys β93 residues. This method produces a polymer with a single PEG backbone that is surrounded by multiple proteins, rather than coating a single protein with multiple PEG chains. Electrophoresis under denaturing conditions showed a large molecular weight species. Gel filtration chromatography and analytical ultracentrifugation determined the most prevalent species had three βXL-Hb to one Mal-PEG. Thermal denaturation studies showed that the cross-linked and PEGylated species were more stable than native Hb. Cross-linking under oxy-conditions produced a high oxygen affinity Hb species (P₅₀  = 9.18 Torr), but the oxygen affinity was not significantly altered by PEGylation (P₅₀  = 9.67 Torr). Inside-out PEGylation can be used to produce a hemoglobin-based oxygen carrier and potentially for other multiprotein complexes.

Surgical management in treatment of Jehovah's witness in trauma surgery in Indian subcontinent

The Jehovah's Witness religion is a Christian movement, founded in the US in the 1870s, with 7 million followers worldwide with only 0.002% in India. There is minimal to complete absence of awareness about the existence of this community in our society. Astonishing is that fact that among medical professionals, there is almost no awareness about this unique population, regarding the fact that they completely refuse of blood transfusion even if it leads to their death. This is integral to their faith. Besides legal and ethical issues in treating these group of patients, the biggest challenge exist even in the western world is their management in trauma scenario where few options exist. We have discussed the issues and recommendations in management in trauma scenario in our Indian subcontinent.

Bovine hemoglobin: a nontraditional approach to the management of acute anemia in a Jehovah's Witness patient with autoimmune hemolytic anemia

INTRODUCTION

Management of severe symptomatic anemia in critically ill Jehovah's Witness patients remains a challenge. The paucity of therapeutic alternatives to human red blood cells has prompted the use of blood substitutes.

CASE REPORT

A 19-year-old female Jehovah's Witness patient presented to the emergency department following several episodes of syncope. She was found to have a positive Coombs test and was diagnosed with warm-bodied autoimmune hemolytic anemia. Upon admission, her hemoglobin was 8.4 g/dL, then dropped to a nadir of 2.8 g/dL 4 days later. She received traditional management with corticosteroids, intravenous immune globulin, rituximab, and partial splenic artery embolization. Despite these therapies, hemoglobin levels failed to respond, and she experienced signs of marked ischemia. A decision was made to give 2 units of Hemopure, a bovine hemoglobin-based oxygen carrier, and the hemoglobin levels increased to 8.7 g/dL 10 days later. The patient's overall clinical condition improved leading to subsequent hospital discharge.

CONCLUSION

This case exemplifies the ingenuity that health care practitioners must use in critical situations involving the medical management of anemic Jehovah's Witness patients who refuse blood products. Hemopure was used as "bridging treatment" to help save a patient from the devastating effects of ischemia resulting from severe anemia.

Bovine blood and neuromuscular paralysis as a bridge to recovery in a patient with severe autoimmune hemolytic anemia

Hemoglobin solutions have several advantages as substitutes for erythrocyte transfusions. They have a prolonged shelf life, do not require cross-matching, are associated with few transfusion reactions, and are effective in delivering oxygen to the tissues. Despite the potential clinical utility of these solutions, they have not achieved widespread use. HbOC-201 (Hemopure, Biopure, Cambridge, MA, USA) is a bovine hemoglobin solution that has been FDA approved for compassionate use in Jehovah's witness patients requiring transfusions. Here we report a case of a patient with hemoglobin H disease who developed a severe life-threatening mixed warm and cold antibody mediated autoimmune hemolytic anemia (AIHA) and immune thrombocytopenia (ITP) who was successfully treated with HbOC-201 as an adjunct to blood transfusion.

Toxicological consequences of extracellular hemoglobin: biochemical and physiological perspectives

Under normal physiology, human red blood cells (RBCs) demonstrate a circulating lifespan of approximately 100-120 days with efficient removal of senescent RBCs taking place via the reticuloendothelial system, spleen, and bone marrow phagocytosis. Within this time frame, hemoglobin (Hb) is effectively protected by efficient RBC enzymatic systems designed to allow for interaction between Hb and diffusible ligands while preventing direct contact between Hb and the external environment. Under normal resting conditions, the concentration of extracellular Hb in circulation is therefore minimal and controlled by specific plasma and cellular (monocyte/macrophage) binding proteins (haptoglobin) and receptors (CD163), respectively. However, during pathological conditions leading to hemolysis, extracellular Hb concentrations exceed normal plasma and cellular binding capacities, allowing Hb to become a biologically relevant vasoactive and redox active protein within the circulation and at extravascular sites. Under conditions of genetic, drug-induced, and autoimmune hemolytic anemias, large quantities of Hb are introduced into the circulation and often lead to acute renal failure and vascular dysfunction. Interestingly, the study of chemically modified Hb for use as oxygen therapeutics has allowed for some basic understanding of extracellular Hb toxicity, particularly in the absence of functional clearance mechanisms and in circulatory antioxidant depleted states.

Oxygen therapeutics: perfluorocarbons and blood substitute safety

Current demands over the blood supply in developed and developing nations will compound over time. Red cell substitutes have a promising value proposition for transfusion services, because they hold the promise of increasing the availability of blood products and removing donor and contamination safety risks. In this article, the authors note that existing products suffer from critical shortcomings such as vasoactivity; they also point out that substitutes not based on human blood introduce potentially more complex safety hurdles. The authors discuss the attributes of an ideal blood substitute, and the mechanism and current status of perfluorocarbons; they also review the shortcomings of all oxygen therapeutic products in development today.

Effects of Hemoglobin Vesicles on Resting and Agonist-Stimulated Human Platelets In Vitro

Hemoglobin vesicles (HbV) are artificial oxygen carriers that encapsulate a concentrated hemoglobin (Hb) solution with a phospholipid bilayer membrane. The oxygen transporting ability of HbV in vivo has been demonstrated by the transfusion of HbV into hemorrhagic shock rodent models. However, the compatibility of HbV with human blood cells must be evaluated. Preincubation of platelets with concentrations of 20% or 40% HbV had no effect on the binding of PAC-1, a monoclonal antibody that detects activation-dependent conformational changes in alphaIIbbeta3 on platelets, or the surface expression of CD62P in whole blood. ADP-induced increases in PAC-1 binding were significantly enhanced by exposing the platelets to concentrations of either 20% or 40% HbV, whereas the ADP-induced increases in CD62P expression were not affected by HbV treatment at either concentration. Preincubation of platelet-rich plasma (PRP) with HbV minimally reduced the spontaneous release of TXB2 and RANTES, but did not significantly affect the formation of TXB2 or the release of RANTES and beta-TG in platelets stimulated with ADP. Similarly, preincubation of PRP with HbV minimally reduced the spontaneous release of RANTES but did not significantly affect the formation of TXB2 or the release of RANTES and beta-TG in platelets stimulated with collagen, although collagen-induced serotonin release tended to decrease with HbV pretreatment. These data suggest that the exposure of human platelets to high concentrations of HbV (up to 40%) in vitro did not cause platelet activation and did not adversely affect the formation and secretion of prothrombotic substances or proinflammatory substances triggered by platelet agonists, although one of the earliest events in ADP-induced platelet activation was slightly potentiated by HbV pretreatment at the doses tested. Taken together, these results imply that HbV, at concentrations of up to 40%, do not have any aberrant interactions with either unstimulated or agonist-induced platelets.

Alternatives to allogeneic blood transfusions

Inherent risks and increasing costs of allogeneic transfusions underline the socioeconomic relevance of safe and effective alternatives to banked blood. The safety limits of a restrictive transfusion policy are given by a patient's individual tolerance of acute normovolaemic anaemia. latrogenic attempts to increase tolerance of anaemia are helpful in avoiding premature blood transfusions while at the same time maintaining adequate tissue oxygenation. Autologous transfusion techniques include preoperative autologous blood donation (PAD), acute normovolaemic haemodilution (ANH), and intraoperative cell salvage (ICS). The efficacy of PAD and ANH can be augmented by supplemental iron and/or erythropoietin. PAD is only cost-effective when based on a meticulous donation/transfusion plan calculated for the individual patient, and still carries the risk of mistransfusion (clerical error). In contrast, ANH has almost no risks and is more cost-effective. A significant reduction in allogeneic blood transfusions can also be achieved by ICS. Currently, some controversy regarding contraindications of ICS needs to be resolved. Artificial oxygen carriers based on perfluorocarbon (PFC) or haemoglobin (haemoglobin-based oxygen carriers, HBOCs) are attractive alternatives to allogeneic red blood cells. Nevertheless, to date no artificial oxygen carrier is available for routine clinical use, and further studies are needed to show the safety and efficacy of these substances.

Oxygen therapeutics: pursuit of an alternative to the donor red blood cell

CONTEXT

There is no true substitute for the many functions of human red blood cells, and synthetic products will not replace the need for blood donation in the foreseeable future. Hemoglobin-based oxygen carriers have many characteristics that would serve as a useful adjunct to red cells in clinical settings. Over time, these technologies have the potential to dramatically reshape the practice of transfusion medicine.

OBJECTIVE

To review the characteristics and potential utility of hemoglobin-based oxygen carriers and perfluorocarbon-based oxygen carriers. Several hemoglobin-based oxygen carriers are under study in phase III clinical trials. Novel uses for synthetic oxygen therapeutics are emphasized.

DATA SOURCES

All published reports with the key words oxygen therapeutics, blood substitutes, and red cell substitutes from 1933 until March 2006 were searched through Medline. Significant findings were synthesized.

CONCLUSIONS

Recognition of the true impact of red cell substitutes is still several years away. The most compelling products, hemoglobin-based oxygen carriers, have potential use in trauma, providing immediate oxygen-carrying support in the face of alloantibodies or autoantibodies, and in other clinical situations in which long-term survival of red cells is not essential. In the interim, efforts should be focused on enhancing the current blood supply system while supporting ongoing and planned blood substitute research efforts, including trials assessing novel clinical indications for these products.

Oxygen Therapeutics: Oxygen Delivery Without Blood

Nearly 14 million units of packed red blood cells are transfused in the United States each year. According to the U.S. Department of Health and Human Services, in 1999, 6% of hospitals reported a shortage of blood, resulting in the cancellation or postponement of surgical procedures. The many limitations and risks of transfusions of packed red blood cells in critically ill patients have facilitated interest in developing alternative agents for oxygen delivery. Over the past few decades, safe and effective substitutes have been in development. However, no currently approved agent provides both oxygen transport and volume in place of packed red blood cells. Oxygen therapeutic products have several advantages compared with packed red blood cells, including a prolonged shelf-life, lack of a cross-matching requirement, and minimal infectious risks or concerns about immunogenicity. Hemoglobin-based oxygen carriers and perfluorocarbons are being developed. Two products are undergoing clinical trials. Polyheme is undergoing a phase III study in trauma patients, and Hemopure is being evaluated in a phase II study in patients undergoing cardiopulmonary bypass surgery. A third product (Hemolink) was being evaluated in a phase III study in patients undergoing coronary artery bypass grafting surgery; however, the trial was suspended. In addition, several other hemoglobin-based oxygen carriers are in the preclinical stages. Oxygen therapeutics have several potential clinical applications in the management of perioperative blood loss, trauma, acute normovolemic hemodilution, traumatic brain injury, and blood requirements in patients who refuse or have contraindications to transfusions of red blood cells.

Plasma exchanges do not increase red blood cell transfusion efficiency in severe autoimmune hemolytic anemia: A retrospective case-control study

Severe autoimmune hemolytic anemia (AIHA) can cause life-threatening hemolysis requiring red blood cell transfusions (RBT). The efficiency of RBT could be improved with the use of plasma exchanges (PEx) before RBT. The objective of this study was to assess the effectiveness of PEx in severe AIHA of adults. All adult patients with severe AIHA requiring RBT were included in this single center retrospective case-control study. The end point was change in hemoglobin (Hb) level after RBT, depending on whether PEx was done (experimental group) or not (control group). Thirty-one sessions of RBT following PEx were performed on the 5 patients of the experimental group and were compared with the 7 sessions of BT without PEx performed on the 4 patients of the control group. Despite a lower mean Hb value before the session of RBT (5.7 g/dl vs. 7.2 g/dl, P = 0.04) in the control group, the mean Hb value 5 (4-7) days following RBT (8.7 g/dl vs. 8.6 g/dl, P = 0.85) was not different in the experimental and in the control group, respectively. In a second analysis in which each patient was his own control (31 sessions of RBT following PEx vs. 51 sessions of RBT alone), the gain in Hb was not different (1.4 g/dl vs. 1.9 g/dl, P = 0.67). When RBT are required in severe AIHA of adults, the use of a single PEx before BT does not increase the efficiency of RBT based on day 5 evaluation.

Hemoglobin Vesicles Containing Methemoglobin and l-Tyrosine to Suppress Methemoglobin Formation in Vitro and in Vivo

Hemoglobin (Hb) vesicles have been developed as cellular-type Hb-based O(2) carriers in which a purified and concentrated Hb solution is encapsulated with a phospholipid bilayer membrane. Ferrous Hb molecules within an Hb vesicle were converted to ferric metHb by reacting with reactive oxygen species such as hydrogen peroxide (H(2)O(2)) generated in the living body or during the autoxidation of oxyHb in the Hb vesicle, and this leads to the loss of O(2) binding ability. The prevention of metHb formation by H(2)O(2) in the Hb vesicle is required to prolong the in vivo O(2) carrying ability. We found that a mixed solution of metHb and L-tyrosine (L-Tyr) showed an effective H(2)O(2) elimination ability by utilizing the reverse peroxidase activity of metHb with L-Tyr as an electron donor. The time taken for the conversion of half of oxyHb to metHb (T(50)) was 420 min for the Hb vesicles containing 4 g/dL (620 microM) metHb and 8.5 mM L-Tyr ((metHb/L-Tyr) Hb vesicles), whereas the time of conversion for the conventional Hb vesicles was 25 min by stepwise injection of H(2)O(2) (310 microM) in 10 min intervals. Furthermore, in the (metHb/L-Tyr) Hb vesicles, the metHb percentage did not reach 50% even after 48 h under a pO(2) of 40 Torr at 37 degrees C, whereas T(50) of the conventional Hb vesicles was 13 h under the same conditions. Moreover, the T(50) values of the conventional Hb vesicles and the (metHb/L-Tyr) Hb vesicles were 14 and 44 h, respectively, after injection into rats (20 mL/kg), confirming the remarkable inhibitory effect of metHb formation in vivo in the (metHb/L-Tyr) Hb vesicles.

Advances in Transfusion Safety

Although transfusion is now extremely safe, the tools of molecular biology are continually being harnessed to improve diagnosis and therapy. Viral genome testing has been introduced in the developed world for HIV and HCV, to detect donors in the infectious “window period” before sero-conversion. Pathogen inactivated fresh frozen plasma and platelets are already available, but alloimmunization has halted trials of pathogen-inactivated red cells. Development of synthetic oxygen carriers has included perflurocarbons, and crosslinked, polymerized or mutated human or bovine hemoglobin, either free or encapsulated. No perfect replacement for the human red cell is yet on the horizon.

[Artificial oxygen carriers as an alternative to red blood cell transfusion]

The expected cost-explosion in transfusion medicine (increasing imbalance between donors and recipients, treatment of transfusion-associated complications) increases the socio-economic significance of the development of safe and effective synthetic oxygen carriers as an alternative to the transfusion of allogeneic red blood cells. Currently two types of artificial oxygen carriers have been tested for safety and efficacy in cases of severe anemia otherwise requiring transfusion. Solutions based on human or bovine hemoglobin (HBOC) possess vasoconstrictor properties in addition to their oxygen transport capacity. The impact of vasoconstriction on tissue perfusion and organ function is however not yet fully understood. Nevertheless, in 2001 the bovine HBOC Hemopure was approved in South Africa for treatment of acutely anemic surgical patients. The purely synthetic perfluorocarbon (PFC) emulsions increase the physically dissolved portion of arterial oxygen content. Due to their particulate nature (emulsion droplets) PFCs may only be infused in low doses to avoid overload and malfunction of phagocytic cells of the reticulo-endothelial system. As part of a multimodal blood conservation program (including normovolemic hemodilution and hyperoxia) the low-dose administration of Oxygent effectively increases intraoperative anemia tolerance. Although reduction of perioperative allogeneic blood transfusion has already been demonstrated for HBOC and PFC, the global clinical establishment of artificial oxygen carriers is not to be expected in the near future.

Long-term transfusion of polymerized bovine hemoglobin in a Jehovah's Witness following chemotherapy for myeloid leukemia: a case report

A 52-year-old female Jehovah's Witness presented with relapsed secondary acute myeloid leukemia. Because of chemotherapy-induced anemia, she was infused with the bovine hemoglobin (Hb)-based oxygen carrier HBOC-201 (Biopure) as the sole means of transfusion support. HBOC-201 has only been used for management of acute hemorrhage, and its utility in providing longer term transfusion support is unknown. Over a period of 18 days, a total dose of 1230 g of HBOC-201 was delivered. Although the patient succumbed to the disease after 18 days of treatment, this case documents our experience with the highest dose and duration of HBOC-201 ever used. Although possible renal toxicity could not be definitively excluded, the homogeneous extraction of oxygen by the brain in the presence of and perhaps from HBOC-201 was demonstrated.

Rationale for blood conservation

BACKGROUND

Exposure of patients to allogeneic blood transfusion can be minimized or avoided by the systematic use of multiple blood conservation techniques. Current use of these technologies is variable.

METHODS

Review of pertinent English language literature.

RESULTS

Enthusiasm for preoperative autologous blood donation (PAD) has declined considerably, perhaps due to increased cost and inconvenience to patients. Acute normovolemic hemodilution (ANH) has several practical advantages over PAD, but has not become generally accepted as a blood conservation strategy. Erythropoietin, iron, and artificial oxygen carriers are pharmacologic alternatives.

CONCLUSIONS

Pharmacologic stimulation of erythropoiesis offers substantial potential to progress toward a goal of bloodless medicine. The potential of artificial blood substitutes is still being defined.

Use of hemoglobin raffimer for postoperative life-threatening anemia in a Jehovah’s Witness

PURPOSE

To describe the successful treatment of acute, life-threatening anemia with the oxygen therapeutic agent, hemoglobin (Hb) raffimer.

CLINICAL FEATURES

A 53-yr-old female Jehovah's Witness developed severe anemia following total hip replacement. Due to prior patient directive, red blood cells were not transfused. Tachycardia, hypotension, electrocardiographic abnormalities and mental status changes developed with a nadir Hb concentration of 3.2 g x dL(-1). Hb raffimer is a purified, cross-linked, human Hb solution developed as a substitute for red blood cell Hb. After obtaining informed consent as well as Food and Drug Administration and Institutional Review Board approval for compassionate use, 2 L of Hb raffimer (Hemolink, Hemosol, Inc., Toronto, ON, Canada) were administered along with ferrous sulfate and epoetin alfa therapy. The patient's Hb level rose to 5.5 g x dL(-1) with resolution of symptoms. To allow recovery of red blood cell mass while maintaining Hb level > 4.5 g x dL(-1), additional 1000 mL doses of Hb raffimer were administered on postoperative days three, five and seven (total dose = 500 g Hb). The patient developed no serious adverse events related to treatment with Hb raffimer. By postoperative day 14, the patient's Hb level increased to 6.5 g x dL(-1) with a hematocrit of 23%. The patient was discharged.

CONCLUSIONS

Use of Hb raffimer as a bridge to recovery of this patient's red blood cell mass may have prevented adverse clinical outcome. Because this product is a purified Hb solution devoid of other cellular components, it may be accepted as therapy by patients who, due to religious conviction, refuse allogeneic red blood cell transfusion.

The effects of a polymerized bovine-derived hemoglobin solution in a rabbit model of arterial thrombosis and bleeding

Hemoglobin-based oxygen carriers (HBOCs) have been developed primarily for their oxygenating function and possible use as an alternative to red blood cells during surgery or after major trauma. However, their effect on hemostasis has not been studied extensively. We compared the effects on hemostasis of bovine-derived hemoglobin solution (HBOC-201) with gelatin solution and saline infusion in an experimental model of arterial thrombosis and bleeding. After anesthesia, the Folts model was constructed in 30 rabbits. The common carotid artery was exposed, and a 60% stenosis was induced. A compression injury of the artery was then produced, which triggered a series of cyclic episodes of thrombosis (cyclic flow reductions [CFRs]). After the number of baseline CFRs was counted, animals were assigned randomly to one of three groups (n = 10 each): saline (control), gelatin, or HBOC-201 solution. The effect of studied solutions was observed by recording the number of CFRs during another period and was compared with that of saline. Ear immersion bleeding time was recorded after each CFR period. Gelatin and HBOC-201 had similar effects, manifested by significantly decreased CFRs (from median of 7 to 1 and 6 to 1, respectively) and significantly lengthened bleeding time (from 88 to 98 s and 81 to 102 s, respectively; P < 0.05). Saline infusion had no significant effect on CFRs or bleeding time. HBOC-201 and gelatin had similar effects marked by a reduction in the arterial thrombosis rate and increased bleeding time in rabbits.

IMPLICATIONS

In a rabbit thrombosis and hemorrhagic model, a polymerized bovine-derived hemoglobin solution and a gelatin solution infusion decreased arterial thrombosis and lengthened bleeding time.

Autoantibody formation after alloimmunization: are blood tranfusions a risk factor for autoimmune hemolytic anemia?

BACKGROUND

The development of RBC autoantibodies resulting from or associated with allogeneic blood transfusions (i.e., RBC autoimmunization) is not a well-recognized complication of RBC transfusions.

STUDY DESIGN AND METHODS

T: he presentation, laboratory evaluation, clinical course, and management of two patients whose autoimmune hemolytic anemia followed allogeneic blood transfusion and occurred in association with the development of one or more alloantibodies is described. A retrospective analysis was performed of our blood-bank records over 1 year to determine the frequency of RBC autoimmunization associated with alloimmunization.

RESULTS

Out of 2618 patients who had a positive DAT or IAT, 121 were identified with RBC autoantibodies; 41 of these patients had both allo- and autoantibodies to RBC antigens, whereas the remainder, 80, had only autoantibodies. At least 34 percent (12/41) of these patients (none with hemoglobinopathy) developed their autoantibodies in temporal association with alloimmunization after recent blood transfusion(s).

CONCLUSION

RBC autoimmunization and the development of autoimmune hemolytic anemia should be recognized as a complication of allogeneic blood transfusion. The need for additional blood transfusion was successfully avoided in one patient by treatment with recombinant human EPO and corticosteroid therapy. Once RBC autoimmunization is identified, subsequent management should incorporate a strategy that minimizes subsequent exposure to allogeneic blood.

Doping with Artificial Oxygen Carriers

There is a long history of science seeking to develop artificial substitutes for body parts damaged by disease or trauma. While defective teeth and limbs are commonly replaced by imitations without major loss of functionality, the development of a substitute for red blood cells has proved elusive. There is a permanent shortage of donor blood in western societies. Nevertheless, despite whole blood transfusions carrying measurable risks due to immunogenicity and the transmission of blood-borne infectious diseases, red blood cells are still relatively inexpensive, well tolerated and widely available. Researchers seeking to develop products that are able to meet and perhaps exceed these criteria have responded to this difficult challenge by adopting many different approaches. Work has focussed on two classes of substances: modified haemoglobin solutions and perfluorocarbon emulsions. Other approaches include the creation of artificial red cells, where haemoglobin and supporting enzyme systems are encapsulated into liposomes. Haemoglobin is ideally suited to oxygen transport when encased by the red cell membrane; however, once removed, it rapidly dissociates into dimers and is cleared by the kidney. Therefore, it must be stabilised before it can be safely re-infused into humans. Modifications concomitantly alter the vascular half-life, oxygen affinity and hypertensive characteristics of raw haemoglobin, which can be sourced from outdated blood stores, genetically-engineered Escherichia coli or even bovine herds. In contrast, perfluorocarbons are entirely synthetic molecules that are capable of dissolving oxygen but biologically inert. Since they dissolve rather than bind oxygen, their capacity to serve as a blood substitute is determined principally by the oxygen pressure gradients in the lung and at the target tissue. Blood substitutes have important potential areas of clinical application including red cell replacement during surgery, emergency resuscitation of traumatic blood loss, oxygen therapeutic applications in radiography (oxygenation of tumour cells is beneficial to the effect of certain chemotherapeutic agents), other medical applications such as organ preservation, and finally to meet the requirements of patients who cannot receive donor blood because of religious beliefs. Given the elite athlete's historical propensity to experiment with novel doping strategies, it is likely that the burgeoning field of artificial oxygen carriers has already attracted their attention. Scientific data concerning the performance benefits associated with blood substitutes are virtually nonexistent; however, international sporting federations have been commendably proactive in adding this category to their banned substance lists. The current situation is vulnerable to exploitation by immoral athletes since there is still no accepted methodology to test for the presence of artificial oxygen carriers.

Red blood cell transfusion in autoimmune hemolytic anemia

PURPOSE OF REVIEW

Transfusion, in the setting of autoimmune hemolytic anemia, can be a complicated and potentially dangerous proposition.

RECENT FINDINGS

The selection and delivery of an appropriate red blood cell unit must focus on several areas: (1) the laboratory detection of the autoantibody, (2) the detection of clinically significant red blood cell alloantibodies potentially masked by the autoantibodies, and (3) the selection and delivery of appropriate, although potentially incompatible, units. In addition, alternatives to red blood cell transfusion, specifically red blood cell substitutes, may also play an important role in the clinical treatment of these patients in the future.

SUMMARY

In this article, we will review the most recent developments in the transfusion management of patients with autoimmune hemolytic anemia, specifically focusing on published articles between the period of May 2002 to April 2003.

Prolonged Oxygen-Carrying Ability of Hemoglobin Vesicles by Coencapsulation of Catalase in Vivo

Hemoglobin (Hb) vesicles (particle diameter, ca. 250 nm) have been developed as Hb-based oxygen carriers in which a purified Hb solution is encapsulated with a phospholipid bilayer membrane. The oxidation of Hb to nonfunctional ferric Hb (metHb) was caused by reactive oxygen species, especially hydrogen peroxide (H(2)O(2)), in vivo in addition to autoxidation. We focused on the enzymatic elimination of H(2)O(2) to suppress the metHb formation in the Hb vesicles. In this study, we coencapsulated catalase with Hb within vesicles and studied the rate of metHb formation in vivo. The Hb vesicles containing 5.6 x 10(4) unit mL(-1) catalase decreased the rate of metHb formation by half in comparison with Hb vesicles without catalase. We succeeded in prolonging the oxygen-carrying ability of the Hb vesicle in vivo by the coencapsulation of catalase.

Red cell antigens as functional molecules and obstacles to transfusion

Blood group antigens (BGAs) can act as functional molecules but also can evoke autoantibodies and alloantibodies, causing autoimmune hemolytic anemia, hemolytic disease of the newborn and hemolytic transfusion reactions. In Section I, Dr. Marilyn Telen discusses physiologic and pathologic functions of RBC BGA-bearing molecules. She reviews some associations of BGAs with RBC membrane integrity and hemolytic anemia; association of BGAs with enzymatic and transport functions; and adhesion molecules expressed by RBCs, especially with reference to their pathophysiological role in sickle cell disease. In Section II, Dr. Lawrence Petz discusses the problems of providing blood for patients who have RBC autoantibodies. He provides an algorithm for excluding the presence of "hidden" alloantibodies, when all units appear to be incompatible due to the autoantibody. He emphasizes that clinicians should be aware of these approaches and not accept "the least incompatible unit." In Section III, Dr. George Garratty describes two processes, in development, that produce RBCs that result in RBCs that can be described as "universal" donor or "stealth" RBCs. The first process involves changing group A, B, or AB RBCs into group O RBCs by removing the immunospecific sugars responsible for A and B specificity by using specific enzymes. The second process involves covering all BGAs on the RBC surface using polyethylene glycol (PEG). Results of in vitro and in vivo studies on these modified RBCs are discussed.

The use of haemoglobin glutamer-250 (HBOC-201) as an oxygen bridge in patients with acute anaemia associated with surgical blood loss

For the treatment of substantial blood loss in surgery, allogeneic blood is transfused to maintain stability and organ perfusion and function. Continued concerns about the availability, safety, efficacy and storage-related problems of allogeneic blood products have led to an intense effort to find alternatives that can serve the same physiologic functions. Haemoglobin-based oxygen carriers (HBOCs) are compounds that can match the oxygen-carrying capacity of red blood cells (RBCs), and several HBOCs have reached advanced stages of development and clinical testing. Multi-centre, randomised, Phase III, controlled trials have demonstrated the safety and efficacy of haemoglobin glutamer-250 (bovine) (Hemopure), Biopure Corporation, Cambridge, MA, USA), also known as HBOC-201. HBOC-201 is bovine-derived, modified haemoglobin that has been ultrapurified to remove any plasma proteins, RBC stroma and potential pathogenic material. During the manufacturing process, crosslinking and polymerisation stabilise the haemoglobin molecule, which increases its vascular persistence as well as the efficiency of oxygen transport to tissue. Results from clinical trials indicate that HBOC-201 can be used as an oxygen 'bridge' for patients experiencing anaemia due to surgical blood loss, until their own red blood cells are replenished or have regenerated (haematinic effect). HBOC-201 is generally well-tolerated and is approved for use in South Africa, where it is indicated for use in adult surgical patients who are acutely anaemic, and is used to eliminate, delay or reduce the need for allogeneic RBCs. A Biologics License Application for HBOC-201 is currently under review by the US FDA.

Plasmapheresis in immune hematology: review of clinical outcome data with respect to evidence-based medicine and clinical experience

The objective of this paper is to assess the role of plasmapheresis in immune hematology by reviewing published clinical outcome data and narrative review articles. This information will be used to define evidence levels for appraisal of the efficacy and rank of plasmapheresis among other management options. This evidence-based strategy conforms to the concepts of the American Society of Hematology (ASH). as put forward in 1996 in the context of immune thrombocytopenia (ITP) treatment. The term 'experimental' is used to describe indications where the only scientific evidence of the efficacy of plasmapheresis consists of pathophysiological reasoning and empiric clinical findings. We reviewed the available literature on the use of plasmapheresis in autoimmune hemolytic anemia (AIHA), hemolytic disease of the newborn (HDN), autoimmune thrombocytopenic purpura (AITP), heparin-induced thrombocytopenia type II (HIT II), post-transfusion purpura (PTP), refractoriness to platelet transfusion (RPT), coagulation factor inhibitor (CFI) and catastrophic antiphospholipid syndrome (CAS). Plasmapheresis completes the spectrum of management options as it eliminates physically circulating free antibodies involved in the pathogenesis of these immune hematological syndromes. Because of the paucity of data, evidence levels had to be defined based on the findings of uncontrolled case series and the opinions of independent experts. In many cases, randomized clinical trials were not feasible because the syndromes are so rare. When defined as an 'experimental indication', plasmapheresis has a firm scientific basis, but larger scale clinical experience with the method is still lacking. In these cases, the detection and monitoring of symptomatic disease-related circulating free antibodies or immune complexes is a mandatory prerequisite for the use of plasmapheresis. The therapeutic benefit of plasmapheresis is substantiated by the level V of evidence of its efficacy in treatment of HDN, HIV-associated AITP, induction of tolerance in CFI and in CAS. The goal of future studies should be to establish a firmer base of scientific evidence for indications classified as experimental by setting up case series large enough for proper assessment of plasmapheresis alone or combination with other treatment measures. This goal can only be achieved through multiinstitutional cooperation.