Neonatal Hypernatremic Dehydration Secondary to Lactation Failure

Scott E. Rand, MD, University of Texas Medical Branch, Conroe; Amy Kolberg, MD, Department of Obstetrics and Gynecology, University of Missouri, Kansas City.

J Am Board Fam Med. 2001;14(2) 

In This Article

Case Report

A 7-day-old female infant was the product of a normal spontaneous vaginal delivery at 36 weeks, 6 days' gestation. The pregnancy was complicated by preterm labor treated with bedrest and terbutaline from 18 weeks' gestation. Terbutaline was stopped 10 days before delivery. Her course in the nursery was normal, and she was discharged at 30 hours of life, breast-feeding, voiding, and passing stools normally. She was seen through the emergency department the evening of admission for complaints of poor feeding for the previous 12 hours. Her parents believed the infant was doing well until the day of admission, when the mother had noted decreased milk production and decreased activity in the infant. The infant appeared to have had adequate urine output throughout the day, and no fevers were noted. There had been no vomiting or diarrhea. Family history was notable for a sister who had had jaundice and difficulties with breast-feed early in life.

At admission the infant was jaundiced and dehydrated but responsive with good tone and a good suck reflex. Admission weight was 2.30 kg, 680 g (23%) below birth weight. Her sclera were icteric, the anterior fontanel was sunken, and her skin was jaundiced with poor turgor. Findings on heart and lung examinations were unremarkable. Her reflexes were brisk and symmetric. Findings during the remainder of the physical examination were unremarkable.

Laboratory studies disclosed the following values: white cell count, 4800/µL; hemoglobin, 17.9 g/dL; hematocrit, 52.5%; platelets, 433,000/µL; serum sodium, 167 mEq/L; potassium, 6.8 mEq/L; chloride, 132 mEq/L; bicarbonate, 16 mEq/L; blood urea nitrogen, 40 mg/dL; creatinine, 1.1 mg/dL; and serum glucose, 53 mg/dL. Total bilirubin was 29.6 mg/dL with a direct fraction of 0.9 mg/dL. A urinalysis disclosed a large amount of blood and proteinuria (2+); specific gravity was 1.025. A diagnosis of hypernatremic dehydration was made, and she was admitted for therapy.

There appeared to be no clear cause of the child's marked hypernatremic dehydration, so on the first hospital day, the mother's breast milk was tested. Her breast milk sodium content was 82 mEq/L. At 1-week post partum, her sodium level was approximately 10 times the expected level for mature breast milk. The volume of breast milk was not measured, but the mother believed it was adequate until the day of admission.

The child was treated with an initial fluid bolus of 15 mL/kg of lactated Ringer solution to restore intravascular volume, then free water deficit and sodium excess were corrected during the next 48 hours by calculating maintenance requirements and fluid deficits. She required fluid at a rate of 26 mL/h of one-third normal saline with 5% dextrose. Hypernatremic dehydration requires careful, slow rehydration to prevent cerebral edema and neurologic sequelae. Figure 1 illustrates the calculations used to correct the hypernatremia and dehydration. The goal is to return the sodium level to normal within a period of 48 hours. The jaundice responded to rehydration and phototherapy, and the infant was discharged from the hospital bottle-feeding well on the third hospital day.

Figure 1. Fluid deficit calculation.
Birth weight 2.98 kg
    Admission weight 2.30 kg
    Weight loss 680 g
    Percent dehydration = 680/2980 = 0.228 = 23%
    Fluid deficit = weight loss = 680 mL

Step 1: Emergency phase
Restore vascular volume with bolus of 10-20 mL/kg of lactated Ringer's solution
    Patient was given 15 mL/kg, or 40 mL, of lactated Ringer's solution as a bolus for 20 min

Step 2: Rehydration phase
Aim to correct water deficit and sodium excess within 48 hours. The fluid should be administered evenly for 48 hours
    100 mL/kg/d x 2 d x 2.9 kg = 580 mL maintenance
    Maintenance + deficit = 580 mL + 680 mL = 1,260 mL
    1,260 mL/48 h = 26 mL/h

Fluid composition should be 5% dextrose in 25% or 20% normal saline with 30-40 mEq/L of potassium. Choose lactate or acetate anions if serious hyperchloremia or metabolic acidosis exists. Monitor serum electrolytes every 8-12 hours. Expect a linear regression to a sodium concentration of 140 mEq/L to take place during 48 hours.

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