Am J Physiol Heart Circ Physiol. 2025 Oct 10. doi: 10.1152/ajpheart.00428.2025. Online ahead of print.
ABSTRACT
There are limited studies of changes in blood volume after birth in preterm infants. This study aimed to develop a method to measure blood volume in preterm piglets that could potentially be adapted for use in a clinical setting. A tracer dilution method using fluorescent labelled dextran was optimised and tested in vitro and in vivo in preterm (98/115 d gestation) and term piglets. In vitro, the dextran method had error of individual samples ranging from -14.2% to +15.9% with a mean bias of +0.1%. Smaller tracer size (150kDa) significantly overestimated volume with bias of >20%, compared to the 500kDa tracer. Using 3 or 4 sampling timepoints fitted with a linear or log-linear curve had only small bias for all groups (<2.3ml/kg), despite significant differences compared to using a 1-phase decay curve fitted to 2h of sampling (14 timepoints). Single samples at 10 or 20min after injection had biases of +4±4mL/kg (range -7 to +14mL/kg) and +8±4mL/kg (range -5 to +19mL/kg), respectively. Repeated measures are feasible from birth with minimal blood sample losses (0.5mL). In neonates, the dextran tracer method requires use of a large tracer size (500kDa) with multiple, timed samples (minimum 3 samples over first 40min after injection). This simple fluorescent labelled dextran method prevents overestimation of blood volume in neonates and allows for repeat measurements from birth. This method can be adapted for use in preterm infants which is critical to testing the efficacy of interventions designed to support preterm blood volume.
PMID:41071705 | DOI:10.1152/ajpheart.00428.2025
