Fluid therapy in the neonate: not your mother's fluid space.

Fluid therapy is a universally used therapeutic modality in critical care patients. To effectively deliver fluids to neonates., an understanding of their fluid physiology is necessary. Neonates, as they make the transition from fetal physiology, have increased capillary filtration and a compliant interstitium producing a large ISF reserve. This reserve helps the neonate to adapt to fluid challenges, serving as a ready source of fluids in times of need, but it also frustrates therapeutic fluid administration by damping the effect of intravenous fluid therapy when treating hypovolemia. Additionally,it explains the difficulty neonates have in handling fluid overload. Successful treatment of hypovolemia requires aggressive volume repletion using 20-mL/kg fluid boluses. Once euvolemia is restored and ongoing losses are replaced, maintenance fluid rates should be conservative so as to avoid fluid overload. The neonate's unique sodium handling must also be recognized. Many critical neonates benefit from sodium restriction, whereas others may have high ongoing losses and require careful sodium replacement therapy. Careful attention to fluid therapy formulation ensures positive fluid support without adding to the physiologic stress of the critical neonate.