The purpose of this protocol is to provide treatment with HBOC-201 to patients with life-threatening anemia for whom blood is not an option. Such patients may also be referred to in this document as patients who refuse blood transfusion (PWRBT). Other patients who potentially may require HBOC-201 treatment include those with red blood cell alloantibodies for whom immunologically compatible red blood cell units cannot be found, although these patients are less common than PWRBT.