American Association of Critical-Care Nurses (AACN) Certification Practice Test

When is it appropriate to use a V/Q scan instead of CT with contrast for diagnosing a pulmonary embolism?

1. If the patient is high-risk for cancer

2. If the patient has renal disease

3. If the patient is pregnant

4. If the patient has a history of allergic reactions to contrast media

The correct answer is: If the patient has renal disease

A V/Q scan, or ventilation/perfusion scan, is a diagnostic imaging test used to assess the circulation of air and blood within a patient's lungs. It is particularly useful for diagnosing conditions like pulmonary embolism while avoiding certain risks associated with other imaging modalities, such as CT scans with contrast. The correct choice highlights the importance of renal function when selecting an imaging technique. A CT scan with contrast requires the administration of a contrast agent, which can be nephrotoxic and is therefore not recommended for patients with renal disease. In these individuals, a V/Q scan serves as a safer alternative because it does not involve the use of contrast agents that could further impair kidney function. When evaluating patients with renal disease, healthcare professionals must be cautious about the risk of contrast-induced nephropathy, making the decision to choose a non-contrast option like the V/Q scan a prudent choice in this context. For other scenarios such as being high-risk for cancer, pregnant, or having a history of allergic reactions to contrast media, options exist that may still allow for the use of CT with contrast, provided that the risks are adequately managed or alternative imaging strategies are considered. However, renal disease stands out as a definitive contraindication for CT with contrast and clearly presents