Blood volume reduction due to rapid plasma loss after birth in preterm piglets

Abstract

Background: Understanding changes in blood volume after preterm birth is critical to preventing cardiovascular deterioration in preterm infants. The aims were to determine if blood volume is higher in preterm than term piglets and if blood volume changes in the hours after birth.

Methods: Paired blood volume measurements were conducted in preterm piglets (98/115d gestation, ~28wk gestation infant) at 0.5-5 h (n = 12), 0.5-9 h (n = 44) and 5-11 h (n = 7) after birth, and in a term cohort at 0.5-9 h (n = 40) while under intensive care.

Results: At 30 min after birth, blood volume was significantly lower in preterm piglets compared to term piglets. By 9 h after birth, blood volume had reduced by 18% in preterm piglets and 13% in term piglets. By 5-9 h after birth, preterm piglets had significantly lower blood volumes than at term (61 ± 10 vs. 76 ± 11 mL/kg).

Conclusions: In contrast to clinical resources, preterm piglets have a lower blood volume than at term. Substantial reductions in blood volume after birth leave some preterm piglets hypovolemic. If this also occurs in preterm infants, this may have important clinical consequences. Modern studies of blood volume changes after birth are essential for improving preterm outcomes.

Impact: Preterm piglets do not have a higher blood volume than their term counterparts, in contrast to current clinical estimates. Rapid reduction in blood volume after birth leads to hypovolemia in some preterm piglets. There is a critical need to understand blood volume changes after birth in preterm infants in order to improve clinical management of blood volume.

Fig. 1. Rapid blood volume reducation in the hours after preterm birth.

Blood volume in preterm piglets between baseline (31 ± 6 min) and 11 h postnatal age. *P < 0.001, indicates that blood volumes at 5–11 h postnatal are significantly lower than at 0.5 h. Values were similar at 5, 9 and 11 h postnatal age. Data is mean ± SEM.

Fig. 2. Blood and plasma volume reductions after birth.

Changes in a blood volume (mL/kg), b plasma volume and c red cell volume between baseline (31 ± 6 min postnatal age) and 9 h postnatal age in term (open/blue circles, n = 40) and preterm (solid/red circles, n = 44) piglets. *indicates significant reduction in both groups between baseline and 9 h. ^#Indicates that preterm piglets have a significantly lower volume than term piglets. Data is mean ± SEM.

Fig. 3. Haemoconcentration in the hours after birth.

Haemoglobin concentration from birth (0 h: cord) to 9 h postnatal age in term (open/blue circles, n = 15) and preterm (solid/red circles, n = 15) piglets. Data is mean ± SEM.

Fig. 4. Low plasma protein predicts low blood volume in preterm piglets.

a Change in plasma protein concentration between baseline (~30 min after birth) and 9 h postnatal age in preterm (solid red circles, n = 50) and term piglets (open blue circles, n = 36), and the relationships between plasma protein concentration at 0.5 h postnatal age and blood volume at 5–9 h in b preterm piglets (R² = 0.10, P = 0.028, n = 50) and c term piglets (R² < 0.001, P = 0.97, n = 36). *Indicates preterm piglets had significantly plasma protein levels at 5–9 h compared to at term.