BACKGROUND-We conducted a trial of prophylactic platelet transfusions to evaluate the effect of platelet dose on bleeding in patients with hypoproliferative thrombocytopenia.

No abstract

Effects of acute and maintained isovolemic anemia on oxygen transport was studied during rest and exercise in normal males. Following 34% reduction in hemoglobin concentration (Hb), supine and standing Q rose acutely by 56% and 20%, respectively, but returned nearly to the control value by 10-14 days, producing a decrease in PVO2. Redistribution of blood flow appeared to compensate significantly for the decrease in systemic oxygen transport. 2,3-Diphosphoglycerate rose by 18%, in vivo PO2 at half-saturation of hemoglobin (P50) rose by approximately 2 mm over 7-9 days and probably afforded some compensation. The relationship between VO2 and external work intensity was independent of Hb. During exercise, Q/VO2 and VE/VO2 were increased in acute anemia, but PVO2, for a given VO2, decreased below control levels. After 10-14 days the relative increase in VE with exercise persisted; the increase in Q was less pronounced; and PVO2 was further decreased. With both acute and extablished anemia maximal exercise capacity and maximal VO2 (VO2 max) decreased in proportion to the Hb reduction.

The rationale for immunosuppressive therapy of thrombotic thrombocytopenic purpura (TTP) was established by observations that TTP may be caused by autoantibodies to ADAMTS13. Patients with high-titer autoantibodies to ADAMTS13 may have a higher mortality, and survivors may require prolonged plasma exchange therapy in spite of adjunctive glucocorticoid treatment. More intensive immunosuppressive therapy with rituximab may provide benefit for many of these patients. The Transfusion Medicine/Hemostasis Clinical Trials Network is developing a randomized, clinical trial to test the hypothesis that addition of rituximab to standard treatment of TTP with plasma exchange and glucocorticoids will decrease initial treatment failure rates as well as subsequent relapses over the following 3 years. To provide the background data for this clinical trial, a systematic review of all published reports on rituximab treatment of immune-mediated disorders was performed. Twelve articles have reported 27 patients treated with rituximab for TTP, with benefit described in 25 (93%) of the patients. Additional reports have described rituximab treatment of 37 other immune-mediated disorders, with clinical response in most patients. These observations from small uncontrolled case series provide the background and rationale for a randomized clinical trial to establish the role of rituximab in the management of patients with TTP.