Which laboratory result suggests a need for fluid intervention in a dehydrated patient?

A blood urea nitrogen (BUN) level can indicate the hydration status of a patient. In the context of dehydration, elevated BUN levels suggest that the kidneys are concentrating urea due to decreased blood volume. A BUN level of 28 is significantly higher than the normal range, which typically falls between 7 and 20 mg/dL. When BUN levels rise above 20, it may be indicative of potential dehydration as the body is unable to adequately eliminate waste products.

In a dehydrated patient, an elevated BUN suggests that fluid intervention is necessary to rehydrate and restore proper kidney function. The other BUN levels mentioned (10, 15, and 22) are either within or close to the normal range, thereby not indicating a significant need for immediate fluid intervention. A BUN of 22 may warrant monitoring, but it does not point as clearly to a need for intervention as the 28 does. Thus, when assessing the hydration status and need for fluid therapy in a dehydrated patient, the significantly elevated BUN of 28 clearly indicates a requirement for fluid intervention to address potential dehydration.