Intensive Care Medicine (ICM) Practice Exam

Why is the patient’s arm selection crucial for blood pressure measurement?

1. I.V. cannula on forearm

2. Recent smoking

3. Previous axillary lymph node removal

4. Arteriovenous fistula

The correct answer is: I.V. cannula on forearm

The selection of a patient's arm for blood pressure measurement is of utmost importance because it can significantly influence the accuracy of the readings obtained. In this scenario, the presence of an intravenous (IV) cannula in the forearm is a critical factor. When an IV cannula is in place, it can affect the blood flow in the arm, leading to potentially elevated or artificially low blood pressure readings due to the introduction of fluid or medication directly into the circulation. It may also cause discomfort or complications if the blood pressure cuff is inflated over the site of the IV. Therefore, choosing an arm without an IV cannula ensures that the measurement is taken in a location unaffected by these external influences, making the reading more reliable. Other factors, such as recent smoking or previous axillary lymph node removal, while they may affect blood pressure indirectly, do not have the same immediate and clear implications for the accuracy of the measurement. Additionally, an arteriovenous fistula is primarily relevant in patients undergoing hemodialysis and can also impact blood flow and reading accuracy, but the interference from an IV cannula is more direct and immediate in clinical settings.