Final answer:
When a child with type 1 diabetes mellitus has positive ketones in their urine, the nurse would instruct the mother to increase the child's fluid intake and not skip their insulin dose, as this can exacerbate the situation.
Step-by-step explanation:
When a 6-year-old child with type 1 diabetes mellitus has positive ketones in their urine, it indicates that they are experiencing ketosis or ketoacidosis. This occurs when the body is not getting enough insulin to properly utilize glucose, so it starts breaking down fats for energy, resulting in the production of ketone bodies. To address this situation, the nurse would instruct the mother to increase the child's fluid intake. This will help to dilute the ketones and prevent further dehydration. Additionally, it is important to follow the child's prescribed insulin regimen and not skip their insulin dose, as this can exacerbate the situation.