Viscosity of human blood hemodiluted with crystalline hemoglobin solution.

Hemoglobin solution has been proposed as a blood substitute and, when administered intravenously, causes hemodilution that affects the viscosity of the circulation fluid. To quantitate the changes in viscosity, hemodilutions were made by mixing freshly drawn human blood with a 7-g/dl hemoglobin solution in different proportions. Viscosity measurements were made with a micro-cone plate viscosimeter at various shear rates. The results demonstrate that even at low or moderate hemodilutions with hemoglobin solution, the viscosity of blood decrease considerably at each shear rate investigated. The decrease of viscosity is greater with increasing hemodilution. A shear thinning effect is observed with whole blood and with each hemodiluted sample. The viscosity-hematocrit relationship, which could be demonstrated not only by cone-plate but also by the Ostwald viscosimeters at a fixed shear rate, shows that the concentration of red blood cells significantly affects the viscosity of blood. Hemodilution of blood with hemoglobin solution not only reduces the viscosity but also may improve the blood flow.

Oxygen transport after hemodilution of human blood with crystalline hemoglobin solution.

Fresh human blood and hemoglobin solution were mixed in different proportions to simulate hemodilution volumes occurring when blood is replaced by hemoglobin solution. Oxygen dissociation curves, P50 and hematocrit value of blood, hemoglobin solution and mixtures of blood and hemoglobin solution were determined. Total hemoglobin and oxygen content of the samples and the contribution to the total content by the two components in the mixtures were also measured. From these data, calculations were made of the oxygen release, at different pO2, by blood, hemoglobin solution and mixtures of blood and hemoglobin solution with contribution by each of two components. An in vitro analysis of static equilibrium between hemoglobin and oxygen demonstrates that the contribution of hemoglobin to the total oxygen released is affected by three factors, the left shift of the oxygen dissociation curve, the pO2 at the tissue level and the concentration of the hemoglobin in the solution used for hemodilution.

Lyophilization of crystalline hemoglobin solution and exchange transfusions with lyophilized, reconstituted hemoglobin.

Crystalline hemoglobin solution was lyophilized following deoxygenation or addition of several compounds, or both, to establish protective conditions for obtaining freeze-dried hemoglobin chemically and functionally unaltered and clinically suitable as a blood substitute. Glucose and sucrose were most active in protecting the hemoglobin molecule from deterioration. The results of stability studies demonstrated that lyophilized hemoglobin maintained at 4 degrees C. did not show any significant alteration in structure and function for a period of nine months. Freeze-dried hemoglobin samples stored at room temperature were unchanged for six months, but after this time, a progressive increase in methemoglobin content and a decrease in P50 were observed. The effectiveness of lyophilized hemoglobin in vivo was investigated by transfusions in rats exchanged to blood replacements of 75 or 95 per cent, using lyophilized hemoglobin reconstituted soon after lyophilization or after seven months of storage at room temperature. The data show that lyophilized, reconstituted hemoglobin is effective in restoring or maintaining, or both, vital signs. In rats transfused to a 75 per cent blood replacement, several hematologic and physiologic parameters change soon after transfusion but return to normal pretransfusion levels within seven days after transfusion.