There is hardly any other topic in the field of neonatal intensive care that bears such controversy.

• When (indication)? How much fluid (5, 10, 20 ml/kg IV)? Crystalloid or colloid solutions? How fast (bolus, in 10, 30, 60, 120 min?)

• When (indication)? How much sodium bicarbonate? How fast (bolus, in 10, 30, 60, 120 min)?

Pathophysiology

Cardiac output principally is determined by all four of the following components: heart rate (main regulator in neonates), stroke volume, preload (≈ end-diastolic volume of the ventricle; or simplified as ≈ intravascular volume) and afterload (≈ combination of elastance of the great vessels, resistance of the small vessels, and ventricular wall stress).

In neonates, a low heart rate (HR <100 bpm) usually indicates respiratory failure and/or hemodynamic compromise. After birth, pulmonary vascular resistance (PVR) remains high whereas systemic arterial resistance (SVR) is low but starts rising when the umbilical cord is clamped.

The blood volume of a term neonate ranges between 80 and 85 ml/kg, in preterm infants between 90 and 100 ml/kg. Thus, administration of 50 ml volume IV given to a term newborn infant (body weight ≈ 3 kg) is equivalent to one-fifth of the intravascular volume (relative amount even higher in significant hypovolemia)! This will have notable impact on the hematocrit and hemoglobin value due to dilution effects (normal: 45%–60% and 14–20 g/dl, respectively). Oxygen delivery to the peripheral tissue and vital organs (brain, heart, kidneys) depends on perfusion pressure, total intravascular hemoglobin, and oxygenation (FiO2, lung function).