Influence of red blood cell transfusion on svco2 after cardiovascular surgery

The decision to transfuse is mainly taken according to hemoglobin level (Hb) (1,2) but venous oxygen saturation (SvO2) might be helpful to guide transfusion. We carried out a study to evaluate SvcO2 changes before and after blood transfusion after cardiovascular surgery. Methods. Patients admitted in ICU after cardiovascular surgery over 5 months (September 2014 to February 2015), who were transfused, have been included in the study. Patients with active bleeding, operated on emergency, or in critical condition were excluded. The decision to transfuse blood was made according to guidelines (1). Samples were collected through central venous catheter to measure respectively Hb and SvcO2 (co-oxymetry). Statistical analysis was performed with Mann-Whitney test. Data are expressed as median [25; 75%] and p o0.05 considered as statistically significant. Results. 100 consecutive patients have been included. Hb before transfusion was 7.3 g/dl [6.8; 7.8], SvcO2 66.9% [60; 73] without any correlation between both (Spearman r1⁄4 0.001; NS). SvcO2 was not significantly different between patients with Hb o 7 g/dL (n1⁄436) and patients with Hb Z 7g/dl (n1⁄464) (65.9% [59.3;77.7] vs. 67.7% [60.5;72.2] respectively; p1⁄40.92). SvcO2 after transfusion (RBC 2 [1;2]) increased significantly (71.9% [66.3;77.4]) as well as Hb (9.1 g/dL, [8.6;9.8]) (po0.001) but the observed change in Svc02 is related to patients with Svc02 o 65% before transfusion (po0.001), not when Svc02 Z 65%. Conclusions. According the study, 64% patients have high pretransfusion SvcO2 and experienced no SvcO2 improvement after transfusion, that questions its benefit. Whether a restrictive transfusion protocol guided by SvcO2 would be safe requires further studies.