TMCC EMT-B Medications Practice Test

Nitroglycerin works by dilating veins and arteries, which lowers preload and afterload and reduces the heart’s oxygen demand. But that drop in blood pressure can be dangerous if the patient is already hypotensive. When BP is too low, giving nitroglycerin can cause a further significant decrease in perfusion to the brain, kidneys, and heart, and can worsen ischemia or trigger shock. That’s why hypotension is a contraindication to nitroglycerin in EMS. In contrast, high or normal blood pressure isn’t an automatic reason to withhold it, as long as the patient’s blood pressure remains above the minimum threshold and there are no other contraindications (like recent use of ED meds).