Which finding might indicate that a client with a thoracic aortic aneurysm requires immediate medical attention?

A sudden severe back pain in a client with a thoracic aortic aneurysm can be a critical finding that indicates the aneurysm may be expanding or rupturing. This type of pain typically arises from the aorta pressing on surrounding structures or from a hemorrhage, which can be life-threatening. The intensity and abrupt nature of this pain warrant immediate medical evaluation to prevent potentially fatal complications.

In contrast, a heart rate of 80 beats per minute is generally within the normal range and does not inherently indicate an emergency. A round, soft abdomen could be a normal finding or may relate to other non-urgent conditions. Decreased appetite, while it may be concerning in some contexts, does not usually lead to immediate medical intervention in the context of a thoracic aortic aneurysm. Only sudden severe back pain signals an urgent need for medical assessment in this situation.