Which of the following is a contraindication to nitroglycerin administration?

• A. On nitrates
• B. Low blood pressure
• C. Recent head injury
• D. All of the above

Answer: (D)

Nitroglycerin lowers preload and blood pressure through vasodilation, which is helpful for chest pain with adequate perfusion but risky if perfusion is already compromised. If a patient is already taking nitrates, giving more can cause an additive drop in blood pressure, leading to fainting or shock. A low blood pressure reading itself is a direct red flag, because additional lowering of BP can worsen organ perfusion, including the brain and heart. In someone with a recent head injury, reducing blood pressure can reduce cerebral perfusion and potentially worsen brain injury or intracranial hemorrhage. Taken together, each of these scenarios is a reason to withhold nitroglycerin, so all of the listed conditions are contraindications.