Arthur L. Rosen

Fluosol-DA as a red-cell substitute in acute anemia.

Abstract We assessed the safety and efficacy of Fluosol-DA as a red-cell substitute in acute anemia. Twenty-three surgical patients with blood loss and religious objections to receiving blood transfusions were evaluated. Fifteen moderately anemic patients with a mean hemoglobin level (±SE) of 7.2±0.5 g per deciliter had no evidence of a physiologic need for increased arterial oxygen content and did not receive Fluosol-DA. Eight severely anemic patients with a mean hemoglobin level of 3.0±0.4 g per deciliter met the criteria of need and received the drug until the physiologic need disappeared or a maximal dose of 40 ml per kilogram of body weight was reached. We observed no adverse reactions to Fluosol-DA. The average peak increment in arterial oxygen content with the drug was only 0.7±0.1 ml per deciliter. There were no appreciable beneficial effects of Fluosol-DA, perhaps because of the small increase in arterial oxygen content, the brief half-life of the drug (24.3±4.3 hours), and the limited total dose...

Perfluorocarbon blood substitutes

The salient physicochemical properties of the fluorocarbons are briefly reviewed, including their solubility for the physiologically important gases and their properties relevant to formulation (nonmiscibility with water). The preparations used to date are described, including their properties and compositions, with some comment about the available knowledge of the properties of the constituents. A critical review of the biological aspects and the possible uses of fluorocarbon emulsions constitutes the main body of the manuscript. Gas-transporting capabilities are considered quantitatively. The biological effects of these preparations are reviewed in in vivo, whole body systems, with some in vitro evidence where appropriate. The usefulness of these preparations investigated to date are reviewed under the broad headings of cardiovascular system, radiology, intoxications, and organ preservation. Finally, the shortcomings and potential usefulness are discussed, with recommendations for potential modifications.

Preparation and in vitro characteristics of polymerized pyridoxylated hemoglobin

Stroma‐free hemoglobin solutions have been the subject of extensive studies as potential acellular oxygen carriers. Oncotic pressure considerations limit the hemoglobin concentration of the solutions (6–8 g/dl) to one‐half the normal whole blood values. Furthermore, the free hemoglobin has a short plasma half‐life (2–4 hours). In principle, polymerization offers a means of normalizing the oxygen‐carrying capacity as well as extending the plasma half‐life. Pyridoxylation of hemoglobin prior to polymerization provides an acceptable P50. Pyridoxylated hemoglobin (14–16 g/dl) was polymerized with a 12.5 percent glutaraldehyde solution. Since the goal was to obtain a 15 g per dl solution iso‐oncotic with plasma, the polymerization reaction was monitored by the drop in colloid osmotic pressure. The reaction was quenched with 1.3 M lysine when the colloid osmotic pressure reached normal values (20–25 torr). The polymerization yield was 80 percent, with molecular weights ranging from 120,000 to 600,000 Dalton. The polymerized hemoglobin had a binding coefficient of 1.32, a Pso of 16 torr, a Bohr coefficient of –0.12, and a Hill coefficient of 1.7. The viscosity of the solution was 4.5 centipoise. The methemoglobin levels were comparable to that of unpolymerized stroma‐free hemoglobin. Polymerized hemoglobin solutions provide a normal oxygen‐carrying capacity with a P50 comparable to that of unpolymerized stroma‐free hemoglobin solutions.

Physiologic effects of acute anemia : implications for a reduced transfusion trigger

The risks of transfusion‐associated infectious disease have led to a reassessment of transfusion practice, which in turn has resulted in a trend toward the reduction of homologous transfusion. This reduction is primarily due to the initiation of hemotherapy at more severe levels of anemia. The optimum threshold for the initiation of transfusion therapy, or the transfusion trigger (TT), is unknown. The purpose of this study is to evaluate the effects of withholding transfusion or lowering the TT to a hematocrit (Hct) of 15 percent in unanesthetized animals. Nineteen adult baboons underwent a laparotomy to simulate surgical stress. Upon their recovery from anesthesia, hemodynamic measurements were obtained, and the animals underwent an exchange transfusion (ET) with 6‐percent hetastarch to a final Hct of 15 percent. After ET, hemodynamic measurements were repeated, and the animals were followed for 2 months. There was no morbidity after ET or during the 2‐month observation period. After ET, there was a significant increase in both the cardiac output (3.3 vs. 2.5 L/min, p less than 0.001) and the oxygen extraction ratio (59.9 vs. 38.2%, p less than 0.0001). Oxygen delivery fell after ET (18.9 vs. 11.1 cc/kg/min, p less than 0.001), but there was no significant change in oxygen consumption after ET. The unanesthetized animals adapted well to severe anemia and experienced no adverse effects on their long‐term survival in this setting, which suggests that the reduction of the TT to a Hct of 15 percent in normal animals is safe. Adoption of this TT could result in a significant reduction in the requirements for homologous transfusion with its attendant risks.

Oxygen extraction ratio: a valid indicator of myocardial metabolism in anemia.

We have shown that primates adequately compensate for acute normovolemic anemia to hematocrits (HCT) of 10%. We have described a whole-body extraction ratio (O2 consumption/O2 delivery; ER) of 50% as a reliable physiologic indicator of transfusion need. There is concern that whole-body ER may not accurately reflect impaired myocardial metabolism. The onset of significant lactate production by the left ventricle is an indicator of anaerobic metabolism. Our purpose is to compare left ventricular lactate metabolism (arterial-coronary sinus lactate; delta [L]) to ER in acute normovolemic anemia. Fourteen adult baboons were anesthetized, paralyzed, and ventilated on room air. Left atrial, coronary sinus, aortic, and Swan-Ganz catheters were inserted. Experimental animals (N = 7) were hemodiluted, at constant left atrial pressure (LAP), with 5% human serum albumin (HSA) to a HCT below 4%. Control animals (N = 7) underwent similar volume exchanges, also at constant LAP, with homologous RBCs resuspended in HSA. Whole-body extraction ratio and left ventricular lactate production were measured at baseline and at hematocrits of 20, 10, 6, and 4% in the experimental group. Data were obtained at similar volume exchange points in the control group. Significant lactate production occurred only in the experimental animals (P less than 0.05) when extraction ratio exceeded 50%. Significant lactate production does not occur before the whole-body ER exceeds 50%. ER appears to be a valid indicator of myocardial metabolism in anemia, in this setting.

Large-volume preparation of pyridoxylated hemoglobin with high P50☆☆☆

A technique is described for the preparation of a stroma-free pyridoxylated hemoglobin solution in volumes of up to 20 liters and hemoglobin concentrations of 18–20 g%. The methemoglobin concentration is 3–7%; the phospholipid content is 5–10% of lysate; and normal values for prothrombin time and activated partial thromboplastin time are obtained. Electrophoresis on cellulose acetate strips shows that 70% of the hemoglobin is covalently linked to pyridoxal-5′-phosphate. This proportion can be raised to greater than 85% (PLP fraction) by batch purification with DEAE-Sephadex. The final solution has an in vitroP50 of 22–26 mm Hg (pH = 7.40, pCO2 = 40 mm Hg, temperature = 37°C). Both the proportion of pyridoxylated to unmodified hemoglobin and the P50 remain unchanged throughout the course of total exchange transfusion in the baboon.

Treatment of Acute Postoperative Anemia with Recombinant Human Erythropoietin

Risks inherent in the administration of blood products have increased efforts to avoid homologous transfusion. Although this has increased interest in autologous transfusion and intraoperative salvage, little attention has been focused on efforts to enhance endogenous erythropoiesis as a method of minimizing exposure to homologous blood. Recombinant human erythropoietin (rHuEPO) has been shown to enhance erythropoiesis. The purpose of this study is to evaluate the effect of rHuEPO, administered postoperatively, on a model of acute blood loss. Eleven adult male baboons were randomized into two groups. All animals underwent a laparotomy and an exchange transfusion, with 6% hetastarch, to a final hematocrit of 15%. Group I (N = 6) received 1,000 units/kg of recombinant human erythropoietin daily for the first 14 postoperative days. Group II (N = 5) received an equivalent volume of placebo. All animals were given supplemental vitamin B12, folate and 200% of shed iron, as iron dextran IV, after exchange transfusion. Response was observed for a period of 35 days. All animals survived the protocol. There were no adverse reactions to rHuEPO or surgical complications. The hematocrits were similar between groups at baseline and after exchange transfusion. The maximal rate of erythropoiesis was significantly faster in the rHuEPO group (2.1 vs. 1.3%/day; p less than 0.01). The time required to return to hematocrits of 30% (9.9 vs. 17.4 days, p less than 0.001) and to baseline hematocrits (11.9 vs. 32.1 days, p less than 0.01) were both significantly shorter in the rHuEPO group. The data show that rHuEPO accelerates the recovery from anemia in the postoperative setting. Acceleration of erythropoiesis represents another alternative to homologous transfusion.(ABSTRACT TRUNCATED AT 250 WORDS)

The efficacy of polymerized pyridoxylated hemoglobin solution as an O2 carrier.

A polymerized pyridoxylated hemoglobin solution (Poly SFH-P) has been prepared with a normal [Hb] of 14 g/dL, a normal COP of 20 to 25 torr, a P50 of 16 to 20 torr, and a plasma T1/2 of 40 to 46 hours. Animals underwent a total exchange transfusion with Poly SFH-P to assess its ability to support hemodynamics and oxygen transport in the absence of red cells. All animals survived the exchange transfusion. Mean arterial pressure (MAP), heart rate (HR), cardiac output (CO), and oxygen consumption (VO2) remained at baseline values at zero hematocrit after the exchange. The final plasma [Hb] at Hct less than 1% was 9.7 +/- 0.4 g/dL. These results are significantly better than previous data with unmodified tetrameric hemoglobin solution (SFH). Poly SFH-P supports life in the absence of red cells. In contrast to SFH, Poly SFH-P achieves a nearly normal [Hb], a longer T1/2, and maintains baseline hemodynamics and oxygen consumption at zero hematocrit. These results document that Poly SFH-P is an effective oxygen carrier that offers greater potential than previous products as a clinically useful red cell substitute.

Accelerated erythropoiesis: the hidden benefit of autologous donation.

The risks associated with the administration of blood products have increased efforts to avoid homologous transfusions. Preoperative autologous donation has received renewed interest as a method of decreasing homologous transfusion requirements. Autologous donations may also stimulate postoperative erythropoiesis. The purpose of this study is to evaluate the effect of an aggressive autologous donation program on postoperative erythropoiesis. Ten adult male baboons were divided into two groups. The autologous group (n = 5) donated an average of 2 units of blood per week for 5 weeks before operation. The control group (n = 5) had no preoperative treatment. All animals then underwent a laparotomy and exchange transfusion with hetastarch to a final hematocrit of 15 percent. The time required to recover to hematocrits of 20 percent (3.3 vs. 5.7 days, p<0.01), 25 percent (7.0 vs. 8.8 days, p <0.05), and 30 percent (11.1 vs. 17.7 days, p<0.01) was shorter in the autologous group. The autologous group had more intense reticulocytosis during the first 4 postoperative days (p <0.03). The data show that participation in an aggressive autologous donation program improves the erythropoietic response to anemia in the postoperative setting. This represents a hidden benefit of preoperative autologous donations and suggests that more aggressive donation schedules may be clinically beneficial. Recognition of the acceleration of erythropoiesis by autologous donation could further reduce the need for transfusion of homologous blood.

Polymerized Pyridoxylated Hemoglobin: Efficacy as an O2 Carrier

We have prepared a polymerized pyridoxylated hemoglobin solution (Poly SFH-P) with a normal [Hb] of 14 gm/dl and a normal COP of 20 torr. Although this normal [Hb] is a significant improvement over prior products, the P50 of 16-20 torr raises a concern about the ability of Poly SFH-P to effectively transport O2 in the presence of red cells with their normal P50 of 26 torr. This study quantitatively assessed the contribution of Poly SFH-P to total O2 delivery and consumption in the clinically relevant range of hematocrits. The results document that Poly SFH-P supports life at zero hematocrit, and makes significant contributions to total O2 delivery and consumption in the presence of red cells. Poly SFH-P permits a higher plasma [Hb], and has a longer intravascular persistence than any unpolymerized hemoglobin solution. Poly SFH-P is thus an effective O2 carrier, and offers greater potential than prior products as a clinically useful red cell substitute.