To study plasma hemoglobin cats were given serial enemas of 0.5 and 0.25% H₂O₂ with human who1e blood, single enemas of 0.5% H₂O₂ and single intravenous administration of 0.5% H₂O₂. Plasma hemoglobin levels were abnormally high in both the serial enema group and the intravenous group, while the plasma hemoglobin level was within normal range in the single enema group. Therefore a single enema of 0.5% H₂O₂ with human whole blood can be utilized with safety clinically for 60 to 75 minutes to relieve hypoxia.