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Maintenance of normal fluid and electrolyte balance for the first few days of life in neonatal intensive care unit (NICU) patients, specifically those who cannot feed orally, is an important part of their management. Indeed, it is a significant and challenging part of NICU admission orders. Neonates initially should be in good fluid and electrolyte balance immediately after birth. Exceptions can and do occur rarely but need to be recognized in a timely fashion. At birth, babies have excess total body water that they need to diurese. Despite this, they generally have normal serum electrolytes, which means that they also have increased total body sodium. Thus, initial salt and water requirements are nil. However, sick neonates in an NICU usually need intravenous access, and some fluid may be needed to keep this patent stable. Furthermore, they often need glucose, calcium, protein, and so on, and if not feeding, intravenous fluids may be needed to provide these items. Thus, the goals of initial fluid management are as follows:

  1. Prevent excessive weight loss and dehydration, which can result in hypotension, cell damage, hyperkalemia, and intraventricular hemorrhage (IVH).

  2. Allow appropriate diuresis while avoiding salt and water overload, which may be associated with pulmonary edema, prolonged ductal patency, and an increased risk of chronic lung disease.

  3. Keep indwelling catheters patent.

  4. Provide adequate calcium, glucose, and amino acid (AA) delivery.

  5. Initiate enteral nutrition as soon as possible, preferably with maternal milk.

Maternal History

Occasionally, the maternal history can be an indicator of abnormal fluid and electrolyte status in the fetus and neonate. Some examples of maternal indicators of possible abnormal fluid and electrolyte balance include

  1. Renal diseases with abnormal electrolytes;

  2. Diuretic therapy;

  3. Endocrine disorders (eg, diabetes, hypoparathyroidism); or

  4. Malnutrition or very abnormal diet.

Fetal Findings

Rarely, there will be fetal evidence of increased risk for hyponatremia in the newborn. Findings on fetal ultrasonography suggestive of renal disease, such as

  1. Oligohydramnios;

  2. Renal cystic dysplasia;

  3. Marked hydronephrosis/hydroureter; or

  4. Inability to visualize a fetal bladder, and so on.

Neonatal Examination

Although there are usually no specific physical examination findings diagnostic of fluid and electrolyte imbalances, there can be findings suggestive of abnormal status:

  1. Edema/anasarca;

  2. Ascites, abdominal/flank masses;

  3. Very immature skin (translucent red and shiny) in extremely low gestational age neonate (ELGAN);

  4. Skin disorders with open bullæ, cracked skin, and the like; or

  5. Open spinal or abdominal wall defect.


In general, the newborn infant, even the very premature patient, does not need serum electrolytes measured immediately after birth. Initially, a neonate’s electrolytes and serum urea nitrogen (BUN)/creatinine should reflect the mother’s status. Patients with a history or physical findings such as those mentioned may need to have electrolyte panels ...

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