The Pathophysiology of Cardiogenic Shock

Shock has different types, and the manifestations are different for every type. We’ve made a series of lectures talking about these types. Here, we’ll be talking about cardiogenic shock, what it really is, and how it differs from the other types of shock.

The important detail that you have to remember with cardiogenic shock is this: low pressure equals low perfusion.

For those who are unfamiliar with what perfusion is, it is the amount of oxygen being distributed around the body. Therefore, cardiogenic shock is decreased oxygen perfusion in the body.

Functions of the Heart

To fully understand what is happening with cardiogenic shock, we must first discuss, very quickly, the heart’s main function and how blood is pumped effectively in and out of the organ.

The heart’s primary function is to pump blood throughout the body. Blood is composed of a lot of components, and one of them is hemoglobin. Hemoglobin is a protein that holds oxygen and is responsible for transporting oxygen to different parts of the body.

Hematocrit is another blood component that is basically the liquid portion of the blood which helps hemoglobin to move around every system.

Decreased H&H

If there is decreased hemoglobin and hematocrit (H&H), there will be decreased perfusion since these two components are primarily tasked with transporting oxygen to all parts of the body. Insufficient hemoglobin and hematocrit are directly correlated with cardiac output.

H&H Ratio

If there is a decrease in hemoglobin, the hematocrit will also decrease because the two are intertwined with each other. If they go down, they go down together. The ratio is 1:3. One hemoglobin is equivalent to three hematocrit. For example, in your client’s laboratory values, if the hemoglobin is eight, the hematocrit will be 24.

Borderline H&H

If the hemoglobin value is eight or less, the client will immediately need a blood transfusion; therefore, the borderline value for hemoglobin around 10 g/dl.

Blood Flow

So, this is what happens with proper blood flow inside the heart and lungs:

The right side of the heart will push unoxygenated blood to the lungs to get oxygenated. Then, oxygenated blood will get pushed into the left atrium down to the bicuspid valve and into the left ventricle. The left ventricle is the area of the heart that pumps out all the blood to the rest of the body through the aorta. This is also called as the preload and afterload.

Stroke Volume

Now that we have a clearer picture of hemoglobin and hematocrit, the next thing that you have to know is the stroke volume. The stroke volume is referred to the amount of blood that comes out from the left ventricle in one pump. Stroke volume is composed of the preload and the afterload.

Question: How much blood is normally pushed out of the left ventricle?

Answer: About an ounce or two of fluid per stroke.

Preload and Afterload

Preload and afterload are phases of stroke volume. Preload refers to the time it takes for the left ventricle to be filled with blood, while afterload is the pumping of the blood out of the left ventricle. You can think of the preload and afterload as a slingshot. Preload is the pull while the release is the afterload. So, preload and afterload is equivalent to the stroke volume.

Cardiac Output

Cardiac output is simply the amount of blood being pumped out in 60 seconds or one minute. The normal cardiac output is between four to eight liters per minute. Cardiac output is also influenced by a client’s body build.

Blood Pressure

Blood pressure is a mixture of cardiac output (amount of blood coming out of the heart in a minute) and heart rate (how hard the heart pumps blood to get out of the heart).

Cardiogenic Shock

Knowing about cardiac output, stroke volume, and blood pressure will provide a better understanding of what happens in cardiogenic shock. Basically, cardiogenic shock is decreased pressure which equates to reduced perfusion.

Therefore, there’s decreased cardiac output which will result in decreased blood pressure. Instead of the normal cardiac output of four to eight liter per minute, there would be two liters per minute. And anything that’s less than two liters per minute can be categorized as cardiogenic shock.

Remember that shock, in any form, is decreased pressure which influences perfusion. If there is decreased perfusion, there will be decreased oxygen. A body that has decreased oxygen will become anxious and hypoxic, and the client will have really faint pulses.

Aside from those basic signs and symptoms, there are other manifestations that a client with cardiogenic shock will present. This will be tackled in our next lecture. Drop by SimpleNursing’s website and YouTube channel.