Red blood cell transfusions and tissue oxygenation in anemic hematology outpatients
Background: There is little clinical evidence that red blood cell (RBC) transfusions improve oxygen availability at the microcirculatory level. We tested the hypotheses that anemia in chronically anemic patients with relatively healthy microcirculation would be associated with low tissue hemoglobin (Hb) and tissue oxygenation levels and that these conditions would be improved after RBC transfusions. STUDY DESIGN AND METHODS: Near-infrared spectroscopy (NIRS) was used to determine tissue oxygen saturation (StO2) and tissue Hb index (THI; an index of the amount of Hb in the NIRS measurement volume) in the thenar eminence and sublingual tissue before and 30 minutes after RBC transfusions in 20 chronically anemic hematology outpatients. Data are presented as median (25%-75%). RESULTS: The patients received three (two to three) bags of RBCs in saline-adenine-glucose-mannitol with an age of 21 (7-21) days, which was infused intravenously at the rate of 0.7 bag/hr. RBC transfusions significantly increased hematocrit level from 26% (24%-28%) to 32% (30%-34%; p<0.0001), Hb level from 8.2 (7.6-8.9) g/dL to 11.0 (9.9-11.8) g/dL (p<0.0001), whole blood viscosity from 3.4 (3.1-3.5) mPa/sec to 4.2 (4.0-4.5) mPa/sec (p<0.0001), thenar StO2from 81% (80%-84%) to 86% (81%-89%; p=0.002), thenar THI from 11.2 (9.3-13.3) AU to 13.7 (9.7-15.3) AU (p=0.024), sublingual StO2from 86% (81%-89%) to 91% (86%-92%; p<0.0001), and sublingual THI from 15.2 (13.0-17.4) AU to 17.2 (13.5-19.7) AU (p=0.040). CONCLUSION: Although anemia in chronically anemic hematology outpatients was not associated with low StO2and THI levels, RBC transfusions were successful in improving these variables.