Certified Nephrology Nurse Certification (CNN) Practice Exam

The presence of flat neck veins is indeed indicative of hypovolemia. When a patient is hypovolemic, which means they have a decreased volume of blood circulating in the body, there is not enough pressure to fill the veins adequately, leading to their appearance as flat or collapsed, especially when the person is in a sitting position. This observation is often used in clinical assessments to gauge a patient's fluid status.

Hypovolemia can result from various causes, such as excessive fluid loss due to dehydration, hemorrhage, or inadequate fluid intake. In contrast, conditions like hypervolemia would lead to distended neck veins due to increased fluid volume. Congestive heart failure can also cause distension in the neck veins due to heart dysfunction and fluid retention. Cirrhosis can lead to portal hypertension and fluid accumulation, which may also result in distended neck veins rather than flat ones. Thus, the appearance of flat neck veins is a clear sign consistent with a lower venous return associated with hypovolemia.