Patient History: The patient has angina pectoris, which means they have episodes of chest pain due to reduced blood flow to the heart muscle. Nitroglycerin is a common medication used to relieve this pain by dilating blood vessels.

Nitroglycerin Mechanism: Nitroglycerin works by relaxing and widening blood vessels, which decreases the workload on the heart and increases blood flow to the heart muscle. This process typically lowers blood pressure.

Assessment Concerns:

Heart rate of 90 bpm: This is within the normal range and does not typically contraindicate the use of nitroglycerin.

Blood sugar of 12 mmol/L: Elevated blood sugar is concerning but not directly affected by nitroglycerin administration.

Blood pressure of 190/110 mmHg: This is high and nitroglycerin can help reduce it. High blood pressure is often treated with nitroglycerin.

Blood pressure of 80/60 mmHg: This is hypotension (low blood pressure). Since nitroglycerin lowers blood pressure further, administering it to a patient withalready low blood pressure can lead to severe hypotension, which is life-threatening.

Conclusion: The most concerning finding is the low blood pressure (80/60 mmHg) because administering nitroglycerin in this situation can further lower the blood pressure to dangerous levels.References: NCLEX-RN review guides, pharmacology textbooks, clinical guidelines on the management of angina pectoris and nitroglycerin use.