ScvO 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 ) is a clue of metabolic matching between O 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 were collected through a central venous catheter before and after transfusion. In order to identify a ScvO threshold, analysis of ScvO 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 was 66·9% [60-73]. A 5% increase in ScvO after transfusion has the best specificity and positive predictive values, with a ScvO threshold of 65%. After transfusion (RBC units, 2 [1-2]), ScvO increased only in patients with ScvO ≤65%, from 58% [53-62] to 69% [64-73] (P < 0·001).

CONCLUSION

In anaemic patients, RBC transfusion induced a significant increase in ScvO , provided it was low before transfusion. A 65% cut-off value of ScvO before transfusion showed good specificity and good positive predictive value for a 5% increase after transfusion.