Hyponatremic Seizures Among Infants Fed with Commercial Bottled Drinking Water -- Wisconsin, 1993

In 1993, two infants were treated at a pediatric referral hospital in Wisconsin for hyponatremic seizures caused by water intoxication associated with bottled drinking water. This report summarizes information about these cases and a review of hospitalizations for hyponatremic seizures in this hospital during 1984-1993. Patient 1

In October 1993, a 55-day-old infant was taken by her mother to the emergency department (ED) of a local hospital for evaluation of "eye twitching." During transport, she had onset of generalized, tonic-clonic seizures. Examination at the hospital revealed periorbital and gluteal edema; her serum sodium level was 116 mEq/L (normal: 135-145 mEq/L), and metabolic acidosis was documented by blood gas analysis. Status epilepticus secondary to hyponatremia was diagnosed.

Treatment was initiated with intravenous anticonvulsants. Forty-five minutes after onset of seizures, the infant experienced respiratory depression. Following endotracheal intubation, the infant was transported to the children's hospital, where she received intravenous normal saline. Serum sodium subsequently normalized, and metabolic acidosis resolved. The infant was discharged after 5 days and recovered fully.

The infant's mother had been buying cow's milk-based infant formula and had been supplementing feedings with several ounces of bottled water for several days. She reported using bottled water as a supplement because the product was inexpensive and because she interpreted the labeling to indicate that the product had been produced specifically for infants and contained nutrients adequate for use as a feeding supplement. The mother later reported to the Food and Drug Administration (FDA) that she had substituted tap water for infant formula during the 24 hours before hospitalization. Patient 2

In December 1993, a 56-day-old infant was transported to the ED at the children's hospital following an apparent brief seizure. He had had mild upper-respiratory tract symptoms for several days but otherwise had been in good health. At the hospital, he appeared alert, healthy, and in no distress. His serum sodium level was 121 mEq/L, and urine specific gravity was less than 1.005. Computed tomography of his head was normal. Seizures secondary to hyponatremia was diagnosed.

Treatment with intravenous saline was initiated, and his serum sodium level reached normal limits after 9 hours. He was discharged 24 hours after admission and recovered fully.

The infant's mother had supplemented feedings of soy-based formula with bottled drinking water since the onset of symptoms of an upper-respiratory illness. Daily feedings consisted of three bottles of formula and three bottles of drinking water. She believed the water was a safe and economical liquid that would help relieve the upper-respiratory symptoms, and she indicated that she interpreted the bottle label to depict a product specially made for infants.

Reported by: RC Bruce, MD, RM Kliegman, MD, Dept of Pediatrics, Medical College of Wisconsin, Milwaukee. Office of Special Nutritionals, Center for Food Safety and Applied Nutrition, Food and Drug Administration. Maternal and Child Health Br, Div of Nutrition, National Center for Chronic Disease Prevention and Health Promotion, CDC.

Editorial Note

Editorial Note: Manifestations of water intoxication include altered mental status (typically irritability or somnolence), hypothermia, edema, and seizure (1-7). Symptoms are preceded by a rapid decline in serum sodium levels (to less than or equal to 125 mEq/L) and result from an acute overload of solute-free water that increases total body water by 7%-8% or more (8). The rapid decline in serum sodium may result in cellular dysfunction (i.e., abnormal ion gradients and cellular swelling) in the central nervous system. Factors that increase the risk for water intoxication among infants (especially those aged less than 6 months) include immature renal function and the powerful hunger drive of early infancy (1,3,8).

Hyponatremic seizures among infants resulting from improper feeding practices and water intoxication were first reported in 1967 (1). The risk for this problem may be increased among infants of parents living in poverty (1-7). This possible increased risk may be associated with a lack of resources to purchase infant formula or oral rehydration solution and a lack of knowledge about the potential dangers of feeding infants solute-free water. The risk for hyponatremia may be particularly increased among infants aged less than 6 months who are vomiting or have diarrhea but who are fed fluids lacking sufficient sodium. However, symptomatic hyponatremia also may occur in infants with no acute medical conditions who are fed excess solute-free water. This problem has been caused most commonly by tap water, given either as supplemental feedings or in overly diluted formula; juices, soda, and tea also have been implicated.

Bottled water products marketed specifically for infants may be mistaken by parents and other caregivers as an affordable and appropriate feeding supplement or substitute for infants. In some stores, these products are placed on shelves alongside infant formulas or oral electrolyte solutions. Product packaging may advocate the use of bottled water for mixing with baby foods or juices but also for drinking by infants. Labels also may indicate that the water contains added minerals that babies need, including calcium, magnesium, and potassium. However, the quantity of such minerals -- which are often used for flavor enhancement -- may be unspecified. These products, generally priced at less than $1 per gallon, are considerably less expensive than infant formula or juices.

The physician who reported both cases in Wisconsin reviewed the medical records for all infants aged less than 1 year who had been admitted to the children's hospital during 1984-1993 for diagnosis and/or treatment of hyponatremic seizures; 27 additional cases were identified. All 27 infants had been fed solute-free water in excessive amounts; 25 cases were attributed to dietary water intoxication. No cases were associated with bottled water products. In addition to the two cases described in this report, from August 1993 through January 1994, FDA received reports of three other infants who were hospitalized because of water intoxication. For two of these cases, the reporting physician believed that bottled drinking water was used instead of oral rehydration solution.

Because of the reports of bottled water use associated with hyponatremia, FDA has recommended to the International Bottled Water Association that the labels of these products clearly indicate their contents and appropriate uses (e.g., rehydrating infant formula and mixing with juices) and that they should not be used in lieu of infant formula. Several manufacturers have submitted their existing labels for FDA review.

Human milk and infant formula provide infants with sufficient quantities of water for growth and for replacement of water lost through the skin, lungs, feces, and urine. Supplemental water generally is not indicated for healthy infants who are not yet receiving solid foods (i.e., breast-fed or formula-fed), except possibly during hot weather for formula-fed infants (9). Physicians and other health-care providers should discourage parents from using water (either tap or bottled) as a supplement for infants aged less than 6 months and should advise parents that children of any age who have diarrhea or vomiting should be given oral rehydration solution instead of solute-free water (10). Parents, guardians, and other child-care providers should be educated about the potential hazard solute-free water poses to the health of infants if used inappropriately. Cases of hyponatremia associated with excessive water intake should be reported to the local health department.

References

1. Dugan S, Holliday MA. Water intoxication in two infants following the voluntary ingestion of excessive fluids. Pediatrics 1967;39:418-20.

2. Nickman SL, Buckler JM, Weiner LB. Further experiences with water intoxication. Pediatrics 1968;41:149-51.

3. Crumpacker RW, Kriel RL. Voluntary water intoxication in normal infants. Neurology 1973;23:1251-5.

4. Partridge JC, Payne ML, Leisgang JJ, Randolf JF, Rubenstein JH. Water intoxication secondary to feeding mismanagement: a preventable form of familial seizure disorder in infants. Am J Dis Child 1981;135:38-40.

5. Keating JP, Schears GJ, Dodge PR. Oral water intoxication in infants: an American epidemic. Am J Dis Child 1991;145:985-90.

6. Finberg L. Water intoxication: a prevalent problem in the inner city. Am J Dis Child 1991;145:981-2.

7. Schaeffer AV, Ditchek S. Current social practices leading to water intoxication in infants. Am J Dis Child 1991;145:27-8.

8. Gruskin AB, Baluarte HJ, Prebis JW, Polinsky MS, Morgenstern BZ, Perlman SA. Serum sodium abnormalities in children. Pediatr Clin North Am 1982;29:907-32.

9. Committee on Nutrition, American Academy of Pediatrics. Pediatric nutrition handbook. 3rd ed. Elk Grove Village, Illinois: American Academy of Pediatrics, 1993.

10. CDC. The management of acute diarrhea in children: oral rehydration, maintenance, and nutritional therapy. MMWR 1992;41(no. RR-16).

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