ScvO 2 changes after red‐blood‐cell transfusion for anaemia in cardiothoracic and vascular ICU patients: an observational study

Background and Objectives Haemoglobin threshold for transfusion has been significantly decreased, but haemoglobin plasma concentration may not be sufficient to assess the need of red‐blood‐cell ( RBC ) transfusion. Central venous oxygen saturation (ScvO 2 ) is a clue of metabolic matching between O 2 transport and consumption, which could help to assess when transfusion is appropriate once anaemia has been diagnosed in ICU patients. Materials and Methods Adult patients admitted consecutively to a cardiothoracic and vascular ICU were included in a prospective, observational and single‐centre study over a 6‐month period (September 2014 to February 2015), provided they were transfused with RBC . Patients with active bleeding or in unstable condition were excluded. Haemoglobin and ScvO 2 were collected through a central venous catheter before and after transfusion. In order to identify a ScvO 2 threshold, analysis of ScvO 2 changes after transfusion was performed. Results Fifty‐three patients received 100 RBC transfusions. Haemoglobin at the time of transfusion was 7·2 g/ dl [6·8–7·7], while ScvO 2 was 66·9% [60–73]. A 5% increase in ScvO 2 after transfusion has the best specificity and positive predictive values, with a ScvO 2 threshold of 65%. After transfusion ( RBC units, 2 [1‐2]), ScvO 2 increased only in patients with ScvO 2 ≤65%, from 58% [53–62] to 69% [64–73] ( P  < 0·001). Conclusion In anaemic patients, RBC transfusion induced a significant increase in ScvO 2 , provided it was low before transfusion. A 65% cut‐off value of ScvO 2 before transfusion showed good specificity and good positive predictive value for a 5% increase after transfusion.