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At least 19 recordsLinked to original sources
PubMed1992

Solubility of inert gases in PFC blood substitute, blood plasma, and mixtures.

Measurements are reported of the solubility of nonreactive gases, e.g., hydrogen and xenon, in the following liquids: (a) Oxypherol (FC-43 emulsion) blood substitute, (b) blood plasma, (c) mixtures of Oxypherol and blood plasma, and (d) perfluorotributylamine. Typical results for Ostwald solubility at 25 degrees C for Xe gas in various liquids are 0.118 in H2O, 0.12 in blood plasma, and 1.51 in N(C4F9)3. Observed solubilities for the mixtures can be calculated from the relation: L(mixture) = L(emulsion)xv(emulsion) + L (plasma)xv(plasma), in which the v's are the volume fractions in the mixture. This linear relation implies that the gas dissolves independently in each liquid in the mixture. The effect of the emulsifier (Pluronic F-68, 2.6%), on gas solubility in the mixture, is small. Results for the temperature dependence of Ostwald solubility, L(T), in the range 10-37 degrees C are reported.

Blood Substitutes↗
PubMed2003

Benefit and risk perceptions in transfusion medicine: blood and blood substitutes.

Blood transfusion is a remarkably safe, routine procedure in clinical medicine. However, little attention has focused on the perceptions of risk associated with the receipt of blood, blood products or 'blood substitutes'. It is pertinent to ask (i) what key stakeholder groups know about transfusion, (ii) how safe they perceive blood/blood products to be, (iii) how the latter information might influence their own and others' perceptions of risk linked to transfusion, and (iv) the extent to which approved blood substitutes might be preferred over autologous or donor blood. An appreciation of what stakeholders perceive to be the benefits and risks of the receipt of blood and blood substitutes will inform future transfusion strategies. To obtain such information, a programme of research has been initiated at Nottingham. Surveys have targeted key stakeholder groups, namely, UK adult blood donors and nondonors, anaesthetists, general practitioners and health care journalists. Experimental studies examining message framing and cueing have also been conducted with undergraduate students. Such research will improve misunderstandings about current issues associated with blood donation and transfusion against the backdrop of changing public trust of health care professionals and attitudes and expectations on blood safety and benefits of blood substitutes.

Attitude↗
PubMed1982

Canadian Red Cross lecture. Current concepts of oxygen-transporting blood substitutes.

Blood substitutes are being developed that will provide oxygen-transporting capabilities as well as volume replacement. Perfluorochemical and hemoglobin solutions have potential clinical use. A perfluorochemical blood substitute, Fluosol-DA 20%, is being used in clinical trials in several countries. These blood substitutes are not capable of totally replacing the need for blood transfusions but could be used temporarily in situations where blood is contraindicated or not available. They may be useful for a wide range of clinical conditions other than blood replacement, such as impending tissue ischemia. Before large-scale clinical use of these products is realized, more information is needed about drug efficacy and safety so that intelligent decisions can be made about indications for this type of transfusion therapy.

Animals↗
PubMed1986

Blood transfusion or blood substitution?

Blood transfusion has become a universally accepted, life-saving procedure in modern clinical medicine. In addition, specific blood fractions are widely used in the therapeutic treatment of haematological disorders. Problems are, however, encountered in conventional transfusion practice and in the clinical use of blood components. This paper outlines some of those problems and considers how plasma expanders and oxygen-carrying blood substitutes may be used to overcome some of them. The extent to which acceptable blood substitutes have been developed and tested in both animal and human studies is especially emphasized.

Blood Substitutes↗
PubMed2002

The unusual properties of effective blood substitutes.

Blood substitutes or oxygen carrying plasma expanders were originally formulated to simulate the transport properties of blood, particularly oxygen carrying capacity, viscosity, p50, and colloid osmotic pressure, under the hypothesis that blood is the most desirable fluid in volume restitution. However, changes introduced into the organism during hemorrhage adversely affect microvascular function due to reflex vasoconstriction which causes the fall of functional capillary density, and lowers tissue oxygenation, conditions that are not universally reversed with retransfusion of blood. The restoration of microvascular function is seldom complete upon retransfusion of blood. New formulations of hemoglobin molecules in solutions whose oncotic pressure is in the range of 60-100 mmHg, p50 is about 5 mmHg, viscosity 3-4 cP, and oxygen carrying capacity in the range of 4-7 g/dl equivalent hemoglobin deliver better microvascular function after resuscitation when compared to whole blood and oxygen carrying plasma expanders with transport properties similar to those of blood. The improved performance is in part due to the increased plasma viscosity which increases capillary transmural pressure which reverses capillary collapse induced during low perfusion pressures. High oncotic pressure reinforces this effect, since it brings more fluid into the circulation. Microvascular transport studies of the effects of resuscitation in shock show that functional capillary density is the primary determinant of survival, thus maintenance of an open and fully perfused microcirculation is more critical than insuring oxygen supply, since closed capillaries lead to the accumulation of slowly diffusing byproducts of metabolism which ultimately become toxic. The required combination of properties can be achieved by conjugating hemoglobin and polyethylene glycol. Resuscitation fluids based on hemoglobin containing vesicles may provide the next level of functional improvement in the formulation of volume restitution fluids since their biophysical properties can be specifically controlled through the inclusion of specialized compounds into the vesicles, and the formulation of the suspending medium.

Blood Circulation↗
PubMed2002

Blood substitutes.

Blood substitutes are solutions intended to replace transfusion of banked red blood cells. Several variations of products based on either hemoglobin (animal or human) or perfluorocarbon emulsions are in advanced stages of clinical development. The need for such products is pressing as shortages of banked blood worsen and awareness of the dangers of blood transfusion increases. Animal and human studies with these cell-free oxygen carriers have led to new concepts of how oxygen is delivered to tissue and how the microcirculation is regulated. Although development of products is exciting and timely, understanding how they function to perfuse and oxygenate tissue could be at least as important. Because cell-free oxygen carriers will perfuse every organ of the body, their effects are far-reaching, and the transition from the laboratory to the bedside can be expected to be slow and deliberate. Comparison of oxygen carriers with more traditional starch-based products provides new insight into the interaction of oxygen transport, microvascular perfusion, and blood volume expansion.

Animals↗
PubMed2001

Physiological properties of blood substitutes.

Blood substitutes (modified hemoglobin solutions, perfluorocarbon emulsions) serve as artificial oxygen carriers and are alternatives to blood transfusions. Hemoglobin solutions mimic the sigmoidal oxygen dissociation curve of natural blood. Perfluorocarbon emulsions exhibit a linear relation between PO2 and dissolved oxygen. The most advanced substances may enter medicine in few years.

Animals↗
PubMed2001

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.

Anemia, Iron-Deficiency↗
PubMed1975

"Bloodless" rats through the use of artificial blood substitutes.

Artificial blood substitutes have been prepared with liquid fluorocarbons, Pluronic polyols, hydroxyethyl starch, electrolytes, and bicarbonate buffer. Dispersing the fluorocarbons is by sonication in the presence of the polyols. A CO-2 atmosphere is provided to prevent the formation of fluoride ions which otherwise form. Viscosity, oncotic pressure, osmotic pressure, and pH are adjusted to that of rat blood. With such preparations all of the normal blood of rats can be replaced. Such animals survive, carry out usual functions, regenerate blood cells and plasma protein, and continue to grow and develop. Volumes up to 30 times the blood volume of the rat have been perfused. Perfluorotributylamine has been the most successful of the fluorocarbons, in spite of its prolonged retention in the tissues, but progress has been made with the perfluorodecalins which leave the tissues rapidly. "Bloodless" rats show no reaction to dextran which ordinarily causes acute hypersensitivity reactions in normal rats. Rabbit antirat serum, which has little effect on normal rats, is toxic to "bloodless" rats. Lack of circulating enzymes in "bloodless" rats. Lack of circulating enzymes in "bloodless" rats allows a) specific enzymes to be given to achieve the enzyme profile desired; and b) enzyme-labile compounds to be kept in circulation. "Bloodless" rats made possible by artificial blood substitutes afford a new biomedical research tool.

Adenosine Triphosphate↗