135 - Cell-free hemoglobin levels in stored packed red blood cells and its relationship to changes in tissue oxygenation in preterm infants

Packed red blood cells (PRBC) can undergo morphologic and structural changes secondary to hemolysis that occurs during storage. Cell-free hemoglobin (cHb) released from hemolyzed red blood cells is a potent scavenger of nitric oxide (NO), a local vasodilator as well as a strong anti-oxidant. It has been implicated in the possible pathogenesis of neonatal conditions such as intraventricular hemorrhage (IVH) and necrotizing enterocolitis. Near Infrared Spectroscopy (NIRS) is a non-invasive device capable of measuring regional tissue oxygenation (rSO2).

Objective:

To determine any correlation between the level of cHb in the PRBC unit and changes that occur in cerebral oxygenation (CrSO2) and splanchnic oxygenation (SrSO2) after a blood transfusion in preterm infants.

Design/Methods:

Prospective observation study. NIRS values were recorded in preterm infants with a gestational age of 25-31 weeks and birth weight between 500-1500 grams both before and after the transfusion. Subjects with congenital heart disease, major congenital malformations, abdominal surgery, and grade III/IV IVH were excluded. The cHb level was measured from the PRBC bag with a portable plasma/low Hb system.  Student t-test and Pearson correlation test were used for statistical analysis.

Results:

17 transfusions monitored with corresponding cHb levels. Subject mean birth weight was 897.6 ±275.7g and mean weight at transfusion was 1253.8 ±317.g. Mean birth GA was 27.7 ±1.4 wks and mean GA at transfusion was 31.6 ±2.9 wks. The mean cHb level in the transfused blood was 147.6 ±80.6 mg/dl. There was an average increase in CrS02 of 6.65± 3.4 from 64.5± 6.43 before transfusion to 71.0± 6.64 after transfusion (p= 0.001). There was an inverse significant correlation between cHb levels and the rise in CrSO2 after transfusion (p = 0.006 and R² = 0.4) [Fig. 1]. We also noticed a change in mean Sr02 of 10.1±9.35 from 38.5±14.8 before transfusion to 48.7± 17.5 after transfusion (p = < 0.001) [Table 1] but there was no correlation between cHb values and change in Sr02 (p =0.92 and R² = 0.0006) [Fig. 2].

Conclusion(s):

We found that PRBC units with high cHb levels that might reflect increased hemolysis have less of an impact on the increase in cerebral tissue oxygenation that occurs after blood transfusion. Blood banks and clinicians may consider sampling cHb levels in PRBC units prior to transfusion in this vulnerable preterm population.