Aim: Blood sampling from umbilical artery catheters decreases cerebral blood volume and cerebral oxygenation. The aim of this study was to assess the impact of sampling volume and velocity.
Methods: Forty-eight infants, median birthweight 965 g (480-1500 g), median gestational age 27 wk (23-34 wk), were studied during routine blood sampling from umbilical artery catheters. The sampling procedure was performed following a strict protocol for draw-up volume (1.6 ml), sampling volume (1.7 ml or 0.2 ml), re-injection volume (1.6 ml) and flushing volume (0.6 ml), time of aspiration (40 s or 80 s), re-injection (30 s) and flushing (6 s). In each infant, sampling volume and aspiration time were subject to sequential variation in a randomized fashion (1.7 ml/40 s, 1.7 ml/80 s, 0.2 ml/30 s). Using near-infrared spectroscopy, changes in concentrations of cerebral oxygenated and deoxygenated haemoglobin were measured, and changes in cerebral blood volume and cerebral oxygenation were calculated.
Results: During all three sampling procedures, oxygenated haemoglobin decreased significantly from baseline, whereas deoxygenated haemoglobin did not change. Correspondingly, a decrease in cerebral blood volume and cerebral oxygenation occurred. This decrease was not affected significantly by extending the sampling time from 40 s to 80 s, whereas it was blunted by reducing the amount of blood withdrawn.
Conclusion: Blood sampling from umbilical artery catheters induces a decrease in cerebral blood volume and cerebral oxygenation. The magnitude of the decrease depends on the blood volume withdrawn but not on sampling velocity.