What vital sign change should a nurse expect in a client who reports vomiting and diarrhea for three days?

In a client experiencing vomiting and diarrhea for three days, a rapid heart rate is an expected vital sign change due to several physiological responses to fluid loss and dehydration. When patients lose fluids through vomiting and diarrhea, they can become dehydrated, leading to reduced blood volume. In response, the body compensates by increasing the heart rate to maintain adequate blood circulation and ensure that vital organs receive enough oxygen and nutrients. This tachycardia is a direct result of the body's effort to counteract the effects of decreased blood volume and maintain homeostasis.

Additionally, low blood pressure may also occur due to dehydration, as fluid loss can lead to decreased blood volume. However, the immediate compensatory mechanism that the body has in response to fluid loss is to increase heart rate rather than immediately decrease blood pressure. Elevated body temperature might occur due to an underlying infection, but it is not a direct consequence of vomiting and diarrhea. A normal respiratory rate is unlikely to change significantly unless the patient is severely dehydrated or in distress; thus, it does not typically reflect the primary physiological response to fluid loss in this scenario.

Overall, the rapid heart rate is the most reliable vital sign change that indicates the body's adaptive mechanisms when faced with significant fluid loss from vomiting and diarrhea.