Hypernatremic dehydration
Case 8
A 4-week-old baby presents with seizures and signs of hypernatremic dehydration. A serum sodium level is 159. A urine sodium test was sent to the laboratory. The teenage mother lives alone with her first child. She states that she has been preparing the formula correctly. She reports that the baby frequently vomits after feeds. The mom has brought her to the primary care physician six times for complaints of vomiting since birth.
If the urine sodium is elevated, which of the following is most likely true?
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A. The baby has been fed hypertonic fluids and the mother should be reported immediately to child protective services for suspicion of medical child abuse.
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B. The baby has a renal problem.
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C. The baby has been fed hypertonic fluids and a further dietary history is needed.
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D. The symptoms of vomiting were most likely fabricated.
If the urine sodium is elevated, which of the following is most likely true?
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A. The baby has been fed hypertonic fluids and the mother should be reported immediately to child protective services for suspicion of medical child abuse.
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B. The baby has a renal problem.
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C. The baby has been fed hypertonic fluids and a further dietary history is needed.
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D. The symptoms of vomiting were most likely fabricated.
The best answer is C
Most likely, this mother has been erroneously mixing the formula with the wrong dilution, causing the symptoms and later the seizure. The mother needs to be asked about the dietary history in more detail. Hypervolemic hypernatremia is caused by inappropriately mixing too little free water with powdered formula.
It is not possible to determine if the vomiting was actual or fabricated. Repeated presentations to a physician for the same, similar or even different, unverified complaints are the first sign of medical abuse. However, we cannot yet jump to the conclusion that symptoms were induced. For more information on medical abuse, see the reference below. In this case, the vomiting could have been a symptom of hypernatremia, due to hypertonic formula, or have been unrelated. The infant may have had increased losses of free water due to vomiting and this may have contributed to her hypernatremia, but this symptom alone does not explain this significant degree of sodium overload.
If the baby had a renal problem and was wasting sodium in the urine, we would likely observe hyponatremia, not hypernatremia. However, hypernatremia may be secondary to a renal problem, for example hypovolemic hypernatremia can occur with the use of osmotic diuretics, or intrinsic renal disease. In these situations, water losses are greater than sodium losses. Central or nephrogenic diabetes insipidus can present as euvolemic hypernatremia. Again, the issue is related more to water loss exceeding salt loss. If an infant presents with hyponatremia, use of inappropriate amounts of free water (e.g., over dilution of the formula) should be suspected. This is commonly the situation when parents try to "stretch" out remaining powdered formula due to lack of resources to purchase or acquire enough formula.
The fact that the baby became ill due to incorrectly mixing the formula may not warrant a neglect investigation and the need for investigation by the authorities depends on other factors. For example, the dietary problem may be a symptom of other cognitive or compliance related problems of the mother and/or family. In that case, future risk of harm to the baby without intervention might be predictable. At the very least, preventive services to assist the new teenage mother with the baby can be considered as an appropriate referral and resource for the family. Neglect or medical child abuse may be present if in fact there is documentation in the medical record or documentation by other professionals that the correct mixture for the formula has been previously taught and, despite this, the mother continues to provide an incorrect mixture.
- Roesler TA, Jenny C. Medical child abuse : Beyond Munchausen Syndrome by Proxy . American Academy of Pediatrics, [Elk Grove Village, IL],. 2008;