What are common signs of dehydration in a pediatric patient?

The signs listed in the correct choice highlight key indicators of dehydration in pediatric patients. Dry mucous membranes indicate a lack of adequate fluids, as moisture levels in the mouth and surrounding tissues drop when the body is dehydrated. Decreased urine output is another critical sign; when a child is not well-hydrated, their kidneys conserve water, leading to reduced urine production. Lethargy is a significant concern as it reflects a lack of energy and alertness that can result from insufficient fluid intake.

In contrast, while increased thirst and irritability may be related to early signs of dehydration, they are not as definitive as the combination of dry mucous membranes, decreased urine output, and lethargy, which more directly indicate the body's state of hydration. Vomiting and diarrhea can contribute to fluid loss but are not signs of dehydration themselves; they are causes of it. High fever might indicate an illness that could lead to dehydration, but it is not a direct sign of dehydration. Similarly, symptoms like swelling and rash do not correlate with dehydration and might point to other medical issues.