Cerebral tissue oxygen saturation and extraction in preterm infants before and after blood transfusion

Objective Preterm infants often need red blood cell (RBC) transfusions. The aim of this study was to determine whether haemoglobin levels before transfusion were associated with regional cerebral tissue oxygen saturation (r(c)SO(2)) and fractional tissue oxygen extraction (FTOE) and whether RBC transfusions were associated with r(c)SO(2) and FTOE during the 24-h period thereafter. Design Prospective observational cohort study. Setting Third level neonatal intensive care unit. Patients Thirty-three preterm infants (gestational age 25-34 weeks, birth weight 605-2080 g) were included. Interventions None. Main Outcome Measures RcSO2 was measured during a 1-h period, before, 1 h after and 24 h after a 15 ml/kg RBC transfusion in 3 h. Using r(c)SO(2) and transcutaneous arterial oxygen saturation (tcSaO(2)) values, FTOE was calculated: FTOE=(tcSaO(2) - r(c)SO(2))/tcSaO(2). Results Forty-seven RBC transfusions were given. RcSO2 and FTOE correlated strongly with haemoglobin before transfusion (r=0.414 and r=-0.462, respectively, p<0.005). TcSaO(2) did not correlate with haemoglobin before transfusion. 24 h after transfusion, r(c)SO(2) increased from a weighted mean of 61% to 72% and FTOE decreased from a weighted mean of 0.34 to 0.23. The decrease in FTOE was strongest in the group with haemoglobin below 6.0 mmol/l (97 g/1). The decrease in FTOE was already present 1 h after transfusion and remained unchanged at 24 h after transfusion. Conclusion Following RBC transfusion, cerebral tissue oxygen saturation increases and FTOE decreases. The data suggest that cerebral oxygenation in preterm infants may be at risk when haemoglobin decreases under 6 mmol/l (97 g/l).