Anemia/therapy; Erythrocyte Transfusion; Erythrocytes/metabolism; Microcirculation/physiology; Oxygen/blood; Acute Disease; Anemia/blood; Anemia/metabolism; Anemia/physiopathology; Animals; Blood Flow Velocity; Blood Pressure; Cricetinae; Data Interpretation, Statistical; Dextrans/administration & dosage; Dextrans/chemistry; Erythrocytes/drug effects; Heart Rate; Hematocrit; Hemodilution/methods; Hemoglobins/metabolism; Hemorheology; Male; Mesocricetus; Molecular Weight; Osmotic Pressure; Partial Pressure; Perfusion; Plasma Substitutes/administration & dosage; Plasma Substitutes/chemistry; Random Allocation; Viscosity