What vital sign change might indicate dehydration?

An increased heart rate is indicative of dehydration due to the body's compensatory mechanisms in response to a reduced blood volume. When a person is dehydrated, there is a loss of fluid that can lead to decreased blood volume. As the body attempts to maintain adequate blood perfusion to vital organs, the heart compensates by increasing the heart rate in order to pump blood more efficiently.

This compensatory increased heart rate can help to maintain blood pressure and ensure that oxygen and nutrients continue to reach tissues despite the lower volume of circulating fluid. Other options do not reflect the same direct correlation with dehydration; for instance, a decreased temperature typically does not indicate dehydration and is more commonly associated with other conditions. Lowered blood pressure can also occur as a result of significant dehydration but is less immediate and may not always manifest early on. A constant respiration rate generally does not provide any specific indication of hydration status.