The development of hemoglobin solutions as red cell substitutes

It is clear from the trials described here that the number of different products being tested and the potential variation between batches of the same product present major problems in evaluating the safety and efficacy of hemoglobin-based oxygen carriers. The recent CBER "Points to Consider" document [42] makes clear that an understanding of the safety of oxygen carriers in humans is of paramount importance. In the event of phase II or indeed phase III trials being approved, the need may still remain for additional phase I or preclinical studies, particularly as unwanted or toxic properties of the solutions affect efficacy. It is likely that demonstrating safety and efficacy in acute hemorrhagic shock will be the most difficult task, as this is a complex clinical indication and is often accompanied by multisystem damage. The use of a hemoglobin-based oxygen carrier in this setting must have a distinct advantage over a plasma expander alone. In the application of perioperative transfusion, a decreased requirement for red cell transfusion has already been accepted as a basis for the efficacy for erythropoietin. However, in the case of a hemoglobin-based oxygen carrier, the reduction of red cell requirement in perioperative procedures would need to be balanced against any adverse drug reactions or unacceptable hemodynamic effects that may be caused by the product. It appears that there are still numerous hurdles to overcome in the development of hemoglobin-based red cell substitutes. Before these products can become established in medical practice, it is imperative that the potential mechanisms of toxicity of cell-free hemoglobin are clearly understood. Approval of hemoglobin-based oxygen carriers for clinical use will depend not only on clear demonstration of both safety and efficacy but also on risk-versus-benefit issues. Our understanding of the physiological effects of these products will evolve as progress is made in their clinical evaluation.     

Role of intestinal bacteria in nutrient metabolism

Perfluorocarbons are now being used as oxygen carriers in clinical settings. Because these chemicals may have a role as a blood substitute, in organ preservation, and in the management of respiratory failure, we have reviewed some of the research leading to these applications.     

Perfluorocarbons: recent developments and implications for neurosurgery

Over the last 30 years, perfluorocarbons (PFCs) have been extensively investigated as oxygen carriers. Early studies indicated that these compounds could be used as blood substitutes or protective agents against ischemia. Adverse characteristics such as instability, short intravascular half-life, and uncertainties concerning possible toxicity precluded wide clinical application. However, advances in PFC technology have led to the development of improved second-generation oxygen carriers that incorporate well-tolerated emulsifiers (egg-yolk phospholipids). The authors review recent developments in this field and consider the potential role of PFCs in future neurosurgical practice. Diagnostic applications could include their use to assess cerebral blood flow, local oxygen tension, and brain metabolism or to achieve enhanced imaging and precise staging of inflammatory, neoplastic, or vascular disease processes by means of computerized tomography, ultrasonography, and magnetic resonance studies. Therapeutic applications could include cerebral protection, an adjunctive role in radiotherapy of malignant brain tumors, protection against air embolism, the preservation of organs for transplantation, and ventilatory support in head-injured patients with compromised lung function. In addition, PFCs have been used successfully as a tool in ophthalmic microsurgery and potentially they could fulfill a similar role in microneurosurgery.     

Oxygen-carrying macromolecules: therapeutic agents for the treatment of hypoxia

A stabilized form of hemoglobin as oxygen-carrying macromolecules was developed. It had an approximately 90,000 dalton molecular weight, and its intravascular half-life was 36 h. Its molecular size was less than 0.1 microm. Its hemoglobin concentration was 6% and its P50 value was 24 mm Hg. Oxygen carried inside plasma performs differently than oxygen carried inside red cells. Less than 0.3 cc of oxygen in 100 ml of blood is available in the plasma while 14-19 ml of oxygen is carried inside the red cells. Thus, less than 5 cc of oxygen is available inside the plasma of the entire body. When a patient develops hypovolemic shock, the red cells are bypassed and are not perfused directly inside the tissues. However, the plasma should reach hypoxic tissues. Thus, infusion of oxygen-carrying macromolecules into the plasma should be therapeutically effective even when infusing less than 100 ml of stabilized hemoglobin solution under shock conditions. The basic physiology of oxygen-carrying macromolecules is described in detail, which is different from the physiology of oxygen-carrying red cells.     

Chicken anemia virus strains with a mutated enhancer/promoter region share reduced virus spread and cytopathogenicity

Clinical cancer prevention studies that use disease as an endpoint are of necessity, large, lengthy, and extremely costly. Development of the field of cancer chemoprevention is being accelerated by the application of intermediate markers to preclinical and clinical studies. Sensitive and specific analytic methods have been developed for detecting and quantifying levels of covalent adducts of aflatoxins with cellular DNA and blood proteins at ambient levels of exposure. Such biomarkers can be applied to the preselection of exposed individuals for study cohorts, thereby reducing study size requirements. Levels of these aflatoxin-DNA and albumin adducts can be modulated by chemopreventive agents such as oltipraz and chlorophyllin in experimental models. Overall, a good concordance is seen between diminution of biomarkers and reductions in tumor incidence and/or multiplicity in these settings. Thus, these markers can also be used to rapidly assess the efficacy of preventive interventions. However, the successful application of these biomarkers to clinical prevention trials will be dependent upon prior determination of the associative or causal role of the marker to the carcinogenic process, establishment of the relationship between dose and response, and appreciation of the kinetics of adduct formation and removal. The general approach that has been utilized for the development, validation and application of aflatoxin-DNA and protein adduct biomarkers to cancer chemoprevention trials is summarized.     

Hemoglobin solutions: volume replacement or oxygen therapy?

The development of haemoglobin solutions has progressed significantly in the last 15 years because of a perceived short fall in allogeneic blood within the next decades and increased concern about transmitted infectious diseases. Animal studies have shown that modern highly purified and chemically modified haemoglobin preparations are free of toxic side effects, provide adequate volume replacement and have vasoconstrictive effects that enhance systemic vascular resistance and mean arterial pressures after haemorrhage and in models of nearly complete blood replacement. Microcirculatory effects of haemoglobin-based oxygen carriers are dependent on the respective organ and species in which they are applied and on their degree of purification and chemical modification. Because of different physico-chemical properties in comparison with red cells, haemoglobin solutions provide sufficient tissue oxygenation in areas with critically restricted perfusion even when applied in small doses. First studies in volunteers and patients showed efficacy and tolerability of different newly developed haemoglobin solutions during acute normovolaemic haemodilution and in perioperative blood replacement. However, only little information exists to date in terms of metabolism of haemoglobin preparations and their potential immunogenicity and immunosuppressive side effects. Technical problems with the clinical use of haemoglobin solutions arise because of interference of plasma haemoglobin with routine laboratory tests and oximetry. Future indications for haemoglobin solutions as an oxygen therapeutic allow for application of small doses of such preparations and may help to avoid major technical problems. More clinical studies have to be undertaken to confirm the effectivity and safety of the different haemoglobin solutions and to find out the optimal indications beyond acute preclinical and perioperative blood replacement.     

A new salutary resuscitative fluid: liposome encapsulated hemoglobin/hypertonic saline solution

Low-volume resuscitation with hypertonic (7.5%) saline (HTS) is an evolving therapeutic modality for patients with hemorrhagic shock. This solution has been shown to exert protective hemodynamic effects in models of controlled hemorrhagic shock and in several clinical trials. However, HTS has no oxygen-carrying capacity and therefore does not improve oxygen delivery directly. One of the leading strategies in developing an oxygen-carrying resuscitative fluid is the encapsulation of hemoglobin within phospholipid vesicles (LEH). This preparation has the advantage of being blood type and antigen free, easily adaptable to scale-up production, and remarkably stable with a long shelf life. We therefore tested the hypothesis that lyophilized LEH reconstituted with HTS will improve tissue oxygenation and survival in rats exposed to a lethal controlled hemorrhagic shock. Shock was induced by withdrawal of 70% of blood volume and therapy (n = 10-16) with HTS (5 mL/kg), LEH (5 mL/kg), lactated Ringer's solution (vol:vol = 1:3), LEH-HTS (5 mL/kg), or oxygen (100%) was initiated 15 minutes later. The LEH-HTS improved skeletal muscle oxygen tension directly measured using a thin-film chamber oxygen sensor (PO2 87 +/- 13 mm Hg vs. 40-50 mm Hg in other groups, p < 0.05). This was associated with improved blood pressure, reduced acidosis, and increased survival at 24 hours (75% vs. 6%-25% in other groups, p < 0.05). In conclusion, the study demonstrates a remarkably salutary effect of LEH reconstituted with HTS as a blood substitute in the treatment of hemorrhagic shock.     

No time for handwashing!? Handwashing versus alcoholic rub: can we afford 100% compliance?

Leukocytes present in allogeneic blood components have been associated with adverse effects to the recipient. These include the development of febrile transfusion reactions, alloimmunization to human leukocyte antigens, graft-versus-host disease, and immunomodulatory effects. In addition, such leukocytes may be the vector of infectious agents such as CMV, HTLV-I/II, and EBV. It has been postulated that the use of white blood cell filters to reduce the leukocyte content in allogeneic blood products may minimize the occurrence of these biological adverse effects associated with leukocytes present in transfused blood products. However, it is still to be determined the clinical effectiveness of leukodepletion. It has been suggested that 1 log10 leukocyte reduction prevents febrile non-hemolytic transfusion reactions; that a 2 log10 reduction may prevent the transmission of viruses; and that a > or = 3 log10 reduction may be necessary to prevent platelet alloimmunization. However, because there are no data available as guidelines for the use of leukodepleted blood products for most clinical indications, the use of white cell filters should be restricted to selected patients for whom such data exist. Properly designed prospective clinical trials are necessary to provide data to help to define the cost-benefit of the clinical application of leukodepletion.     

Microcomputer-assisted qualitative analysis: A research tool for scientist-practitioners.

The potential role of microcomputers in qualitative research in psychology has yet to be explored. Such applications might be of particular value at this time, given recent discussions of the role that more case-intensive methodologies might play in improving the integration of clinical practice and scientific research. In this article I present a rationale for exploring the use of microcomputer-assisted qualitative analysis in psychology, and I describe an approach and a technology for such analysis that is widely accessible to individual scientist-practitioners, regardless of the settings in which they work. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Some extensions and applications of a Bayesian strategy for monitoring multiple outcomes in clinical trials

We present some practical extensions and applications of a strategy proposed by Thall, Simon and Estey for designing and monitoring single-arm clinical trials with multiple outcomes. We show by application how the strategy may be applied to construct designs for phase IIA activity trials and phase II equivalence trials. We also show how it may be extended to incorporate the use of mixture priors in settings where a Dirichlet distribution does not adequately quantify prior experience, randomized phase II selection trials involving two or more experimental treatments, and trials with group-sequential monitoring for applications involving multiple institutions.     

Contributions and prospects of hemoglobin derivatives

Anoxia-reoxygenation leads to severe metabolic alterations, which result in a generalized inflammatory reaction and multiple organ dysfunction. Direct blood transfusion limits these alterations, but is accompanied by risk of transmission of infections or viral diseases. To avoid these risks, "blood substitutes" have been designed. The modified hemoglobins are not true blood substitutes because they do not possess the complex functions of erythrocytes. They are only oxygen carriers, with a short intravascular life, adapted for temporary use. They are stable, devoid of toxicity and antigenicity, and are able to carry and deliver O2 without regulation of this oxygen transport and without chemical reaction with O2. They possess rheologic properties and an oncotic pressure like those of blood. The use of natural hemoglobin solutions, obtained after lysis of erythrocytes, remains "at risk" because these solutions easily form methemoglobin, increase the oncotic pressure, present renal toxicity, and possess a too high affinity for O2. For these reasons, 5 types of modified hemoglobin solutions have been designed, prepared from human or bovine hemoglobin or by genetic engineering. These hemoglobins are highly purified to eliminate trace amounts of stroma, lipids and endotoxins, which are responsible for acute toxicity. They are modified by internal cross-linking between the monomers, or by binding to macromolecules. Afterwards, they can be polymerized or encapsulated in liposomes. The purpose of these modifications is to modulate the affinity for O2 (by decreasing the binding of O2 and increasing its delivery to tissue), to reduce the dissociation into monomers and to guard against oxidation into methemoglobin. Encapsulation in liposomes allows co-encapsulation of effector molecules and protective substances. Genetic engineering allows the production of recombinant hemoglobin with selective modifications. The modified hemoglobin solutions are essentially used in hemorrhagic shock and perioperative hemodilution. Experimental work in animals has afforded good results: restoration of normal O2 pressure and no toxicity. These assays allow frequent observation of an unexpected rapid hypertensive effect, transient, reversible, and that could be controlled by antihypertensive drugs. The mechanisms of this hypertensive effect remain controverted (stimulation of endothelin production, inhibition of nitric oxide effects, etc.). In humans, studies with healthy volunteers have been completed, while phase II clinical studies are under way in hypovolemic shock, in major abdominal, orthopedic and cardiac surgery, in stroke and in intensive care patients after surgery. The detailed results are awaited, but the modified hemoglobin solutions already appear to be without toxicity and present the same hypertensive effect as observed in animals. However, until now only low doses have been used, and the catabolism of these solutions remains largely unknown.     

Methodological analysis in behavioral toxicology: an ethotoxicological approach

A constraint in the development of laboratory animal models of human disease conditions is their applicability to the natural environment in which a given animal species evolved. The range of behavioral patterns that can be carefully assessed and quantified in the laboratory is sometimes limited. Although field studies reflect behavioral responses in natural settings, they may also have methodological limitations. Laboratory techniques are not applicable to wild species since natural conditions cannot be brought into a laboratory in an inexpensive or reliable way. However, it is possible to create near-natural settings which may not fulfill all the criteria of the actual context of evolution, but which can be controlled by the experimenter. We recommend an integrative style of approach considering laboratory constraints and, at the same time, the ecological niche in which a given behavioral pattern evolved. This type of ethological assessment may be useful when carrying out toxicological studies on both wild and laboratory mammals.     

Bedside diagnostic testing of body fluids

Numerous bedside diagnostic modalities are appropriate for the practice of emergency medicine. The proliferation of sophisticated technology is likely to increase both the availability and accuracy of commercial testing products. If health care reform in the United States results in a relaxation of the CLIA regulations, there will be a rapid expansion of research and development aimed at the biotechnology market. How much this would pertain to hospital-based emergency practice remains to be seen. Cost containment pressures may act in both directions on the utilization of available bedside technology. Although these tests are often less expensive than centralized laboratory determinations, the ready availability of near-patient testing may result in an increase in use that negates the lower cost. As with other diagnostic modalities, a thoughtful, considered approach based on scientific evidence will be necessary to formulate the appropriate use of bedside testing in individual emergency practice settings.     

A case for Bayesianism in clinical trials

This paper describes a Bayesian approach to the design and analysis of clinical trials, and compares it with the frequentist approach. Both approaches address learning under uncertainty. But they are different in a variety of ways. The Bayesian approach is more flexible. For example, accumulating data from a clinical trial can be used to update Bayesian measures, independent of the design of the trial. Frequentist measures are tied to the design, and interim analyses must be planned for frequentist measures to have meaning. Its flexibility makes the Bayesian approach ideal for analysing data from clinical trials. In carrying out a Bayesian analysis for inferring treatment effect, information from the clinical trial and other sources can be combined and used explicitly in drawing conclusions. Bayesians and frequentists address making decisions very differently. For example, when choosing or modifying the design of a clinical trial, Bayesians use all available information, including that which comes from the trial itself. The ability to calculate predictive probabilities for future observations is a distinct advantage of the Bayesian approach to designing clinical trials and other decisions. An important difference between Bayesian and frequentist thinking is the role of randomization.     

Antiseptics and disinfectants: activity, action, and resistance

Antiseptics and disinfectants are extensively used in hospitals and other health care settings for a variety of topical and hard-surface applications. A wide variety of active chemical agents (biocides) are found in these products, many of which have been used for hundreds of years, including alcohols, phenols, iodine, and chlorine. Most of these active agents demonstrate broad-spectrum antimicrobial activity; however, little is known about the mode of action of these agents in comparison to antibiotics. This review considers what is known about the mode of action and spectrum of activity of antiseptics and disinfectants. The widespread use of these products has prompted some speculation on the development of microbial resistance, in particular whether antibiotic resistance is induced by antiseptics or disinfectants. Known mechanisms of microbial resistance (both intrinsic and acquired) to biocides are reviewed, with emphasis on the clinical implications of these reports.     

A misleading review of response bias: Comment on McGrath, Mitchell, Kim, and Hough (2010).

In the May 2010 issue of Psychological Bulletin, R. E. McGrath, M. Mitchell, B. H. Kim, and L. Hough published an article entitled “Evidence for Response Bias as a Source of Error Variance in Applied Assessment” (pp. 450–470). They argued that response bias indicators used in a variety of settings typically have insufficient data to support such use in everyday clinical practice. Furthermore, they claimed that despite 100 years of research into the use of response bias indicators, “a sufficient justification for [their] use… in applied settings remains elusive” (p. 450). We disagree with McGrath et al.'s conclusions. In fact, we assert that the relevant and voluminous literature that has addressed the issues of response bias substantiates validity of these indicators. In addition, we believe that response bias measures should be used in clinical and research settings on a regular basis. Finally, the empirical evidence for the use of response bias measures is strongest in clinical neuropsychology. We argue that McGrath et al.'s erroneous perspective on response bias measures is a result of 3 errors in their research methodology: (a) inclusion criteria for relevant studies that are too narrow; (b) errors in interpreting results of the empirical research they did include; (c) evidence of a confirmatory bias in selectively citing the literature, as evidence of moderation appears to have been overlooked. Finally, their acknowledging experts in the field who might have highlighted these errors prior to publication may have prevented critiques during the review process. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Role of hematopoietic growth factors in transfusion medicine

Recombinant human growth factors are expected to have a significant impact on the use of allogeneic blood components. For example, recombinant human erythropoietin has had a significant impact on blood transfusion in renal dialysis patients. Likewise, myeloid growth factors have reduced infections and hospital stay by promoting hematologic recovery after high-dose ablative chemotherapy. The high costs of these agents mandate that their use be limited to settings where they are clinically indicated. This review discusses the emerging clinical data to help establish guidelines for the use of hematopoietic growth factors. Comments regarding the myeloid growth factors are restricted to their emerging role in stem cell transplantation, because this clinical setting is anticipated to have the greatest impact in the use of allogeneic blood components in oncology.     

A normative analytic framework for development of practice guidelines for specific clinical populations

BACKGROUND: A central problem in practice guideline development is how to develop guidelines that appropriately account for variations in clinical populations and practice settings. Despite recognition of this problem, there is no formal mechanism for assessing what the need is for flexibility in guidelines, or for deciding how to incorporate such flexibility into recommendations. OBJECTIVE: This research sought to provide a formal basis to determine when clinical circumstances vary sufficiently that guideline recommendations should differ, how recommendations should be tailored for a specific clinical setting, and whether the benefit associated with such site-specific guidelines justifies the expense of their development. RESULTS: The authors describe an approach for estimating the maximum health benefit that developers can obtain by eliminating uncertainty about differences in the patient populations and practice settings in which a guideline will be used. This estimate, the expected value of customization, provides a mechanism to evaluate the cost-effectiveness of the development of site-specific guidelines that account explicitly for variation in clinical circumstances. Application of this method to the development of screening guidelines for human immunodeficiency virus (HIV) infection indicates that the development of site-specific guidelines potentially is cost-effective. Site-specific guidelines either improve, or leave unchanged, the efficiency of HIV screening; whether they increase or decrease total expenditures and health benefits depends on the choice of a cost-effectiveness threshold, and the clinical problem. CONCLUSIONS: Development of guideline recommendations based on decision models provides a normative approach for evaluating the need for and the cost-effectiveness of site-specific guidelines that have been tailored to specific practice settings. Such site-specific guidelines can improve substantially the expected health benefit and the economic efficiency of practice guidelines.     

The alloimmune thrombocytopenic syndromes

We have summarized five thrombocytopenic syndromes caused by platelet-reactive alloantibodies. Increased awareness of these five syndromes, together with the greater availability of highly-specialized laboratory methods to detect and to characterize platelet-reactive alloantibodies, will lead to their more frequent diagnosis. It is important for the clinician to consider unusual alloimmune thrombocytopenic disorders in clinical settings in which alloantigens that could be limited to just one family could cause important disease (ie, NAT caused by a private alloantigen; theoretically, PAT or TAT related to directed donations of blood or bone marrow). These considerations underscore the need for serological investigations to involve the family members rather than to rely on standard platelet typing donor pools.