Diarrhea causes loss of water, Na and Bicarb. Remember that diarrhea is a cause of non anion gap metabolic acidosis because the loss of bicarbonate is compensated by increasing Chloride reabsorption. So she can have hyperchloremia or hyponatremia due to intake of only free water for 24 hours. But she has SEIZURES so hyponatremia is most likely

This is water intoxication. https://www.ncbi.nlm.nih.gov/pubmed/1877579

The key to this question is that the patient is 4 months old and getting water.

Newborns should NOT be getting plain water until after 6 months of age because it can cause hyponatremia --> seizures

Perhaps I under-thought this questions, but it is highly unlikely to have HYPER- of anything when consuming large amounts of water, because whatever ion is present is going to get diluted. So in the case of normal gap acidosis from diarrhea, yes there may be an initial hyperchloremia, but the water is going to dilute it out.

Between hypoglycemia and hyponatremia, it is more likely to be hyponatremia because the child had seizures

Diarrhea causes loss of water, Na and Bicarb. Remember that diarrhea is a cause of non anion gap metabolic acidosis because the loss of bicarbonate is compensated by increasing Chloride reabsorption. So she can have hyperchloremia or hyponatremia due to intake of only free water for 24 hours. But she has SEIZURES so hyponatremia is most likely

This kiddo has most likely secretory diarrhea (there are no clues in the question that this is osmotic diarrhea). Due to secretory diarrhea, the pt has eunatremic hypovolemia with hyperchloremia. However, the parents give the infant only H2O for 24 hh, which means that Na and Cl get diluted. It is more likely that the pt gets hyponatremic than hypochloremic considering that, before giving H2O, chloremia was high and Na was low. The low Naemia causes cerebral edema, which leads to seizures.

Glucose can easily be crossed out because is not an electrolyte and the question asks for electrolyte changes.