This young patient needs fluid resuscitation for vomiting, diarrhea, and dehydration that is presumably due to an infection. An isotonic crystalloid is the appropriate choice here, either normal saline or lactated Ringer’s. Hypo- or hypertonic solutions may lead to electrolyte imbalances apart from the vomiting, diarrhea, and dehydration. These solutions may be used in select electrolyte abnormalities (e.g. hypertonic saline in hyponatremia). Blood products are used to treat hemorrhage, not water and electrolyte losses.