A nurse is administering a cold application to a client. Which of the following manifestations indicates the need to discontinue the application due to a systemic response by the client?

Discontinuing a cold application is warranted when a client exhibits shivering, as this response indicates that the body is attempting to generate heat in response to the cold stimulus. Shivering suggests that the body is experiencing a systemic reaction to the cold that could lead to a drop in body temperature and potential complications such as hypothermia.

In contrast, an increased heart rate, reduction of pain, or improved skin tone are not indicative of a systemic response that would necessitate stopping the cold application. An increased heart rate might occur as part of a stress response, but it is not a direct indicator of adverse effects from cold therapy. A reduction in pain is often a desired outcome of cold applications, as it can help alleviate discomfort. Likewise, improved skin tone may occur for various reasons and does not signal the need to discontinue cold therapy. Thus, shivering remains the key indicator of systemic response requiring cessation of the cold application.