Page 161 - Critical Care Nursing Demystified

146 CRITICAL CARE NURSING DeMYSTIFIED

Open-Heart Surgery (OHS)

OHS is a general term for any surgery where the chest is opened and the heart
is surgically corrected. Two types of OHS are common: valve replacement and
coronary artery bypass grafting (CABG).

Valve Replacement

What Went Wrong?
Any valve in the heart can become stenotic (narrowed) or loose (regurgitation/
insufficiency). Stenotic valves are caused by atherosclerosis and fibrosis of aging.
They are also caused by vegetation collecting on them in conditions like bacte-
rial endocarditis. Valves become loose from congenital problems like a floppy
mitral value (mitral stenosis), and they can become loose when the chordae
tendineae become weak or fail to close when the myocardium they are attached
to become necrotic and do not function. The valves that are most prone to wear
and tear are on the left side of the heart. These “keep on a ticking although they
keep getting a licking” from the high-pressure state of the left heart.
Let us take stenosis first. No matter what the cause in a stenotic valve such as
mitral stenosis, look at what it does to the preceding chamber, in this case the Downloaded by [ Faculty of Nursing, Chiangmai University 5.62.158.117] at [07/18/16]. Copyright © McGraw-Hill Global Education Holdings, LLC. Not to be redistributed or modified in any way without permission.
left atrium. The left atrium has to work harder to pump blood through this very
tight valve. The left atrium rises to the challenge by increasing its size to meet
the job it is now required to do; therefore, left atrial hypertrophy (enlarged
muscle) results. Over time, this chamber becomes overworked and the muscle
becomes flabby and does not eject blood as efficiently. This can lead to decreased
blood flow with a damming effect. If you remember what happened in left-sided
heart failure, fluid will now alarmingly build up in the lungs, causing pulmonary
edema and all of the symptoms of left-sided heart failure. This is a backward
problem so you will sometimes hear this referred to as backward failure.
What happens in front of this tight mitral valve is also affected. Since blood
cannot get through very well, the left ventricle is stressed as well. To propel the
little blood that gets through, that left ventricle also has to work harder. As it
overworks due to this stress, it enlarges as well. This sets the heart up for forward
failure. No matter what valve is affected, if you use the model of backward and
forward flow problems, you can piece together what happens in the heart.
A valve can also be loose or cause regurgitation. Let us take the mitral valve
again and piece this through. If the mitral valve is very floppy, the valve leaflets
cannot maintain their shape and turn back upon themselves into the atria.
Therefore the mitral valve can never really shut tight, thus allowing blood back
into the previous chamber during ventricular contraction. Blood flows back