There is described a water soluble compound having a molecular weight of from about 70,000 to about 2,000,000 and having the formula I,B--X--(PS)--X--(H) Iin which PS is a polysaccharide of molecular weight from about 2,000 to about 2,000,000,X is a covalently bonded chemical bridging group,H is a group Hb or Hb--ZB is a blocked activating groupHb is a hemoglobin residue, andZ is an oxygen affinity reducing ligand containing two or more phosphate groups.There are also described processes for making the compounds, and their formulations and use as oxygen transporting agents.