Critical Care Registered Nurse (CCRN) Practice Exam

What does high velocity in transcranial Doppler studies suggest?

1. Normal blood flow

2. Vessel dilation

3. Possible stenosis or vasospasm

4. Decreased cerebral perfusion

The correct answer is: Possible stenosis or vasospasm

High velocity in transcranial Doppler studies typically indicates the presence of possible stenosis or vasospasm within cerebral blood vessels. This is significant because an increase in blood flow velocity often occurs when there is a narrowing of the vessel (stenosis), which increases resistance to flow, thereby requiring the blood to move more quickly to maintain adequate perfusion. Similarly, vasospasm, which refers to the contraction of the smooth muscle in the walls of blood vessels leading to narrowing, also results in increased blood flow velocity. In assessing cerebral circulation, recognizing high velocity can help healthcare providers identify critical conditions such as cerebral vasospasm following subarachnoid hemorrhage or the presence of significant arterial narrowing. Monitoring these velocities allows for timely intervention, potentially preventing ischemic events. The context provided by other conditions could involve normal blood flow, which would not exhibit elevated velocities, vessel dilation, which would typically decrease flow velocities, or decreased cerebral perfusion, but these scenarios would not align with the specifics of elevated velocity readings noted in Doppler studies.