A method for the preparation of a pharmaceutical composition containing a highly purified and thermostable oxygen carrier, the oxygen carrier is non-polymeric crosslinked tetrameric bovine hemoglobin having a beta-beta crosslinking greater than 40%, the method comprising: a) obtaining of whole bovine blood that includes at least red blood cells and plasma； b) separation of red blood cells from plasma in whole bovine blood； c) filtration of the red blood cells that separated from the plasma to obtain a filtered red cell fraction； d) washing the filtered red blood cell fraction to remove impurities from plasma proteins, resulting in washed red blood cells； e) alteration of the washed red blood cells to create a solution comprising a lysate of altered red blood cells； f) filtering to remove at least a portion of the debris that has remained after the lysate； g) extraction of a first hemoglobin solution from the lysate； h) performing at least one purification process to remove one or more of the viruses, retained wastes or protein impurities； i) cross-linking of the first hemoglobin solution by bis-3,5-dibromosalicyl fumarate to form cross-linked hemoglobin in an oxygenated environment of approximately pO2 149mmHg or 760mmHg； j) disposal of any residual chemical； k) heat treatment of crosslinked hemoglobin in a deoxygenated environment； l) removal of the precipitate by centrifugation or filtration to form a clear solution； and m) adding the purified and thermostable crosslinked tetrameric hemoglobin to a pharmaceutically acceptable carrier.Un método para la preparación de una composición farmacéutica que contiene un portador de oxígeno altamente purificado y termoestable, el portador de oxígeno es hemoglobina bovina tetramérica reticulada no polimérica que tiene una reticulación beta-beta superior al 40 %, comprendiendo el método: a) obtención de sangre completa de bovino que incluya al menos glóbulos rojos y plasma； b) separación de los glóbulos rojos del plasma en la
