Question

The nurse is administering nitroglycerin, which he knows decreases preload as well as afterload. Preload refers to which of the following?

A. The amount of resistance to the ejection of blood from the ventricles
B. The force of the contraction related to the sympathetic nervous system
C. Fluid overload and tissue perfusion status
D. The amount of blood presented to the ventricles just before systole

Answer 1

Preload refers to the end diastolic volume (EDV), which is the quantity of blood present in the ventricles just before systole. Preload indicates the stretch on the ventricles prior to their contraction. Nitroglycerin reduces preload and afterload, thus decreasing the heart workload.

Step-by-step explanation:

The term preload refers to the end diastolic volume (EDV), which is the amount of blood in the ventricles at the end of atrial systole just before ventricular contraction. Essentially, preload is an indication of the ventricular stretch prior to contraction. When administering nitroglycerin, which reduces both preload and afterload, the primary aim is to decrease the work the heart has to perform. Nitroglycerin achieves this by dilating blood vessels to lower the amount of blood returning to the heart (thus reducing preload), and by dilating arteries to decrease the resistance the heart must overcome when it pumps blood (reducing afterload). Calcium channel blockers such as dihydropyridine, phenylalkylamine, and benzothiazepine types may also be administered to impact contractility and thus stroke volume (SV).