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PubMed2001

Co-oximetry interference by hemoglobin-based blood substitutes.

UNLABELLED: The blood substitutes now being developed from molecularly modified hemoglobin interfere with a wide variety of clinical analyzers, but their effects on cooximeters are unknown. Therefore, we investigated the effects of five hemoglobin-based blood substitutes on the measurements of eight different oximeters and cooximeters: the AVL Omni 6, the AVOXimeters 1000 and 4000, the Ciba Corning (now Bayer) CC270 CO-Oximeter, the Instrumentation Laboratory Synthesis 35, the IL482 and IL682 CO-Oximeters, and the Radiometer OSM3 Hemoximeter. The five blood substitutes in this study were obtained from Apex Bioscience (Research Triangle Park, NC), Baxter Healthcare Corp. (Deerfield, IL), Biopure Corp. (Cambridge, MA), Hemoglobin Therapeutics, and Hemosol, Inc. (Etobicoke, Ontario, Canada). A cooximeter control was used to compare the eight different instruments' measurements on unaltered human hemoglobin. The instruments yielded measurements of total hemoglobin concentration in undiluted blood substitutes that were generally not more variable than those on the control material. By contrast, when compared with readings on controls, the test instruments yielded measurements of the fractional concentrations of oxy-, deoxy-, carboxy-, and methemoglobin that showed greater instrument-to-instrument disparities and larger standard deviations about the all-instrument means. In some cases, the interference was even more obvious: five of six cooximeters gave negative carboxyhemoglobin readings on one particular product. Our findings indicate that the instruments will give less accurate but clinically useful measurements in the presence of these hemoglobin-based blood substitutes. IMPLICATIONS: We investigated the effects of five hemoglobin-based blood substitutes on the measurements of eight different cooximeters. Some blood substitutes caused obvious interference, such as negative carboxyhemoglobin readings; however, the findings indicate that cooximeters will generally give less accurate but clinically useful measurements in the presence of the hemoglobin-based blood substitutes that were tested.

Algorithms↗
PubMed1994

Hemoglobin blood substitutes in extended preoperative autologous blood donation: an experimental study.

BACKGROUND: The risks of homologous blood transfusion have stimulated interest in developing possible alternatives. In this study we examined the efficacy of using a hemoglobin-derived blood substitute to augment and extend preoperative autologous blood donation. METHODS: In an ovine model, two experimental groups (n = 6 each) of animals donated either 45% or 80% or more of calculated blood volume, which was replaced with a polymerized bovine hemoglobin solution. Two control groups (n = 6 each) either did not donate or donated 45% of calculated blood volume, which was replaced with a 6% hetastarch solution. Twenty-four hours after blood donation, sheep underwent a measured surgical stress with standardized intraoperative blood loss; donated blood was reinfused. RESULTS: Extended autologous blood donation and replacement with this blood substitute were efficacious in supporting oxygen consumption; there was no systemic toxicity. After the postoperative replacement of autologous blood, animals that donated 80% or more of red cell mass exhibited overall blood conservation with a final hematocrit of 25.7% +/- 3.6%, compared with 20.5% +/- 2.0% (p < 0.05) and with 21.5% +/- 1.1% (p < 0.05) in both control groups. CONCLUSIONS: This study suggests that the benefits of a blood substitute can be combined with autologous blood donation to (1) safely increase the amount of autologous blood donated while supporting oxygen consumption, (2) avoid the need for advanced preoperative donation, and (3) decrease the need for homologous blood transfusion.

Animals↗
PubMed1997

Recent advances in the development of haemoglobin-based blood substitutes.

The term 'blood substitute' is commonly used to describe products which can carry and deliver oxygen. These products are also referred to as 'oxygen carriers' or 'oxygen therapeutics'. Blood substitutes are a new generation of oxygen therapeutics and their introduction will redefine treatment approaches in a wide range of medical and surgical practices. There are two major classes of this new generation of oxygen therapeutics (1) modified haemoglobin solutions, referred to as haemoglobin-based blood substitutes (HBBS) and (2) perfluorocarbon emulsions. Tremendous progress has been made in the past four years with the development of HBBS. In comparison, not much progress has been made in the development of perfluorocarbons as oxygen carriers. In the present review we have limited our discussion to the development of HBBS. Several types of HBBS have been developed and are in different phases of clinical trials. Free haemoglobin has been crosslinked, conjugated, polymerised or encapsulated to prevent its dissociation into dimers. The stability and purity of HBBS are extremely important in overcoming most of the significant toxicities of these products. Commercial manufacturers have utilised better proprietary formulations and purification technologies, and HBBS developed by these organisations have demonstrated safety in both preclinical and clinical studies. Recent research activities suggest a broad range of therapeutic applications for these new generation of oxygen therapeutics, 'blood substitutes'. The introduction of HBBS in critical care medicine will introduce a new approach of not only improving perfusion, but delivering oxygen to tissues.

Journal Article↗
PubMed1990

Hemodynamic effects and oxygen transport properties of a new blood substitute in a model of massive blood replacement.

Recent concerns regarding the safety of the national blood supply have rekindled interest in the development of blood substitutes. Clinical studies have dampened the initial enthusiasm for fluorocarbon solutions as blood substitutes. The potential of hemoglobin solutions as blood substitutes has continued to stimulate investigations. However, the development of an ideal hemoglobin-derived blood substitute has eluded investigators for the past century. A persistent problem has been the inability to develop hemoglobin solutions that provide adequate oxygen and carbon dioxide exchange, while avoiding toxicity that precludes clinical safety and long-term survival. Traditionally, investigators have focused on human hemoglobin solutions. The use of outdated banked blood or pedigree human donor blood as a hemoglobin source poses continued disease transmission risks and a prohibitively limited supply. We evaluated the hemodynamic and gas transport effects of a new purified, polymerized bovine hemoglobin preparation. Bovine hemoglobin oxygen affinity is regulated by chloride ion. The concentration of chloride ions in human plasma results in excellent oxygen transport properties in a stroma-free environment. In addition, unlike human blood, bovine blood is a more disease-free hemoglobin source that is available in large supply. We exchange-transfused eight conscious sheep with this new polymerized bovine hemoglobin solution. All animals tolerated greater than or equal to 95% exchange transfusion to reach a final ovine hematocrit of 2.4 +/- 0.5% with stable hemodynamics and no clinical evidence of distress. The exchange transfusion with bovine hemoglobin polymer resulted in a final plasma hemoglobin concentration of 6.1 +/- 1.6 gm/dl, which supported oxygen consumption at baseline levels. All animals that were exchange transfused with this preparation survived long term with rapid resynthesis of ovine erythrocytes.

Animals↗
PubMed1985

Binding of warfarin by human albumin in the presence of a perfluorochemical blood substitute.

The effect of a perfluorochemical blood substitute on ligand binding by human albumin was examined using warfarin as a model drug. Binding of warfarin by four per cent human albumin solutions diluted with either buffer or blood substitute, and by blood substitute diluted with buffer was examined. Solutions containing 2 or 10 micrograms/ml warfarin were quantitated by liquid scintillation counting using 14C-warfarin. The per cent warfarin free at room temperature was determined by centrifugation followed by supernatant ultrafiltration. Warfarin was weakly bound by the blood substitute and the overall effect of albumin dilution with the blood substitute was an increase in per cent warfarin free. Blood substitute binding of warfarin may explain the decrease of per cent warfarin free observed when albumin solutions were diluted to 50 and 75% v/v with blood substitute rather than buffer. However, the per cent warfarin free increased when albumin solutions were diluted to 25% v/v with blood substitute rather than buffer. The fraction free increased by 39.0% and 30.4% at total warfarin concentrations of 2 and 10 micrograms/ml, respectively. This relative increase in per cent warfarin free may be the result of a direct and/or indirect displacement of albumin bound warfarin by a component(s) of the blood substitute.

Blood Substitutes↗
PubMed1994

Oxygen solubility, rheology and hemodynamics of perfluorocarbon emulsion blood substitutes.

Perfluorocarbon-based blood substitute emulsions have been under development for more than a quarter century. The first generation emulsions have provided confirmation that the physical principals of high gas solubility and low viscosity can effectively support organ and organism respiration and metabolism. Clinical trials led the US FDA in 1990 to be the first to approve a 20 w/v % perfluorocarbon emulsion for human use as coronary angioplasty adjuvant therapy. Hemodynamic responses to hemodilution with intravascular perfluorocarbon emulsions have varied with species and the mechanisms for adverse reactions are better understood now as second generation emulsions containing up to 100 w/v % perfluorocarbon are under development as blood substitutes, imaging agents, and for other therapeutic applications. This report describes the evolution of perfluorocarbon emulsions as blood substitutes by emphasizing oxygen solubility, rheology and hemodynamic aspects of the emulsions as they have been applied in experimental laboratory animal and human clinical settings.

Animals↗