Finally, in most instances the neonatal kidney has the capacity to not only dilute urine, but also to concentrate it, reaching values of 600-700 m0sm/L (specific gravity ≤ 1.015). The surface of the newborn is large and increases with decreasing size therefore there is a greater likelihood of excess insensible water loss (IWL), which may be exaggerated as birth weight and gestational age decrease and open radiant warmers rather than incubators are used. The renin-angiotensin system is in high gear during the first week after birth thus not only is plasma angiotensin II likely to be elevated, but also aldosterone, which is a mineralocorticoid and has the potential to modulate sodium excretion/reabsorption. Firstly, the neonate has an excess of total body water at birth, particularly extracellular water, which must be redistributed and excreted. Addition of sodium should be considered at 16-18 h.įluid therapy for the neonate can be rationally planned if several physiologic concepts are kept in mind. This danger is greater the greater rate of glucose needed to maintain blood glucose. glucose because of increased danger of hypoglycemia however, they frequently do not receive sodium and have been found to develop rather substantial hyponatremia at 24 h if this is not added at or before this time. Infants of diabetic mothers: These infants receive i.v.Treatment of SIADH is by restriction of fluids, not increased sodium intake. These infants require close monitoring of serum sodium and weight. Their fluid intake should be kept on the low side for 48-72 h, i.e., ≤ 60 ml/kg/day, or until seizures are no longer considered a problem. Asphyxiated infants: These infants may have increased secretion of arginine vasopressin (which is likened to SIADH) and are thought to be at increased risk for cerebral edema.Increase fluids for urine output 3 sec.).In preterm infants 145 mEq/L, increase infusate by ~10 mL/kg/d without Na+ in the infusate.Sodium retention is aided by increased aldosterone levels in newborns.

Sodium is required for fetal growth with an accretion rate of 1.2 mEq/kg/day between 31-38 weeks.

However, the neonatal kidney is less efficient at excreting an acute sodium or water load than the kidney of an infant or child.

Renal Hemodynamics: After birth, renal blood flow increases in response to increased blood pressure (renin-angiotensin) with a secondary increase in glomerular filtration rate.

AVP secretion is increased in response to stress, such as birth, asphyxia, RDS, positive pressure ventilation, pneumothorax and intracranial hemorrhage.

Arginine vasopressin (AVP, ADH) levels rise after birth.

Increased aldosterone levels enhance distal tubular reabsorption of sodium resulting in an impaired ability to excrete a large, or acute, sodium load.

The Renin-angiotensin system is very active in the first week of neonatal life resulting in increased vascular tone and elevated levels of aldosterone.

Therefore, insensible water losses will be greatest with small size and decreased gestational age. The surface area of the newborn is relatively large and increases with decreasing size.

A proportion of the diuresis observed in both term and preterm infants during the first days of life should be regarded as physiologic.After birth this excess water must be mobilized and excreted.

The preterm fetus or neonate is in a state of relative total body water and extracellular fluid excess.The body composition of the fetus changes during gestation with a smaller proportion of body weight composed of water as gestation progresses.A rational approach to the management of fluid and electrolyte therapy in term and preterm neonates requires the understanding of several physiologic principles. Excess fluid administration in the very low birth weight infant is associated with patent ductus arteriosis and congestive heart failure, intraventricular hemorrhage, necrotizing enterocolitis and bronchopulmonary dysplasia. In the near term and term neonate excess fluid administration results in generalized edema and abnormalities of pulmonary function. Inadequate administration of fluids can result in hypovolemia, hypersomolarity, metabolic abnormalities and renal failure. Fluid and electrolyte management in the newbornĬareful fluid and electrolyte management is essential for the well being of the sick neonate.

Sodium normal range in infants