Respiratory Variation in Aortic Blood Flow Velocity in Hemodynamically Unstable, Ventilated Neonates: A Pilot Study of Fluid Responsiveness.

Abstract

To assess whether respiratory variation in aortic blood flow peak velocity can predict preload responsiveness in mechanically ventilated and hemodynamically unstable neonates. Prospective observational diagnostic accuracy study. Third-level neonatal ICU. Hemodynamically unstable neonates under mechanical ventilation. Fluid challenge with 10 mL/kg of normal saline over 20 minutes. Respiratory variation in aortic blood flow peak velocity and superior vena cava flow were measured at baseline (T0), immediately upon completion of the fluid infusion (T1), and at 1 hour after fluid administration (T2). Our main outcome was preload responsiveness which was defined as an increase in superior vena cava flow of at least 10% from T0 to T1. Forty-six infants with a median (interquartile range) gestational age of 30.5 weeks (28-36 wk) were included. Twenty-nine infants (63%) were fluid responders, and 17 (37%) were nonresponders Fluid responders had a higher baseline (T0) respiratory variation in aortic blood flow peak velocity than nonresponders (9% [8.2-10.8] vs 5.5% [3.7-6.6]; p < 0.001). Baseline respiratory variation in aortic blood flow peak velocity was correlated with the increase in superior vena cava flow from T0 to T1 (rho = 0.841; p < 0.001). The area under the receiver operating characteristic curve of respiratory variation in aortic blood flow peak velocity to predict preload responsiveness was 0.912 (95% CI, 0.82-1). A respiratory variation in aortic blood flow peak velocity cut-off point of 7.8% provided a 90% sensitivity (95% CI, 71-97), 88% specificity (95% CI, 62-98), 7.6 positive likelihood ratio (95% CI, 2-28), and 0.11 negative likelihood ratio (95% CI, 0.03-0.34) to predict preload responsiveness. Respiratory variation in aortic blood flow velocity may be useful to predict the immediate response to a fluid challenge in hemodynamically unstable neonates under mechanical ventilation. If our results are confirmed, this measurement could be used to guide safe and individualized fluid resuscitation in critically ill neonates.