In the emergency department, a client reports feeling lightheaded and dizzy. Blood pressure is 86/50 with tachycardia. The spouse reveals the client recently took sildenafil after taking nitroglycerin for angina. Which finding in the client's history may have contributed to the condition?

• A. Takes nitroglycerin tablets for angina.
• B. Has a history of diabetes.
• C. Uses daily aspirin.
• D. Has recently started a beta-blocker.

Answer: (A)

The key idea here is understanding a dangerous interaction between nitrates and PDE5 inhibitors that can cause severe low blood pressure. Nitrates such as nitroglycerin work by releasing nitric oxide, which boosts the level of cGMP and leads to vasodilation. Sildenafil, a PDE5 inhibitor, blocks the breakdown of cGMP, so when a nitrate is used with sildenafil, cGMP accumulates and vasodilation is amplified. The result is a significant drop in systemic vascular resistance, manifesting as hypotension and a compensatory tachycardia.

In this case, the history finding that contributes to the condition is that the patient takes nitroglycerin for angina. The use of nitroglycerin in combination with sildenafil explains the markedly low blood pressure and dizziness.

Other history options don’t fit this acute interaction as well. Diabetes might contribute to various vascular or autonomic issues, but it doesn’t explain the sudden hypotension caused by mixing a nitrate with a PDE5 inhibitor. Daily aspirin doesn’t affect this pathway, and starting a beta-blocker can affect heart rate and blood pressure but isn’t the specific interaction causing the profound hypotension seen here.