A nurse in an emergency department is caring for an infant who has a 2-day history of vomiting and an elevated temperature. Which of the following should the nurse recognize as the most reliable indicator of fluid loss?

A. Respiratory rate can be affected by many factors and is not the most reliable indicator of fluid loss. B. Body weight is the most reliable indicator of fluid loss, as it directly reflects changes in body fluid levels. C. Blood pressure changes can occur with fluid loss but may not be as sensitive or immediate as changes in body weight. D. Skin integrity is important to monitor, but changes in body weight provide a more direct measure of fluid status.