What does contractility refer to?
The health of the cardiac muscle. The more the muscle is stretched, the greater the snap will be, like a rubber band . . . until it breaks.
The amount of blood coming into the right side of the heart.
- Think of the B/P . . . for now.
- The higher it is, the harder it is for the left ventricle to push the aortic "door" open and deliver the blood to the rest of of the body.
What is the formula of Cardiac Output?
- Heart Rate x Stroke Volume = Cardiac Output.
- HR x SV = CO
What is the Cardiac Index (CI)?
Individualized CO divided by the Body Surface Area (BSA), which is weight x height.
CO / BSA = CI
What is the best way to determine whether a person has good perfusion?
- Mean Arterial Pressure (MAP)
- You must have a MAP of 60 - 70 to adequately perfuse your organs.
What two criteria need to exist, to say someone is in shock?
Systolic B/P of <90 AND the person is symptomatic.
What determines Cardiac Output?
Heart Rate and Stroke Volume
If the heart rate is increased, what does it do to the cardiac output?
Increased heart rate, means increased cardiac output.
What systems or illnesses can increase your heart rate?
- a. Autonomic Nervous System (ANS) Sympathetic natural and synthetic (medications such as Albuterol which give you a sympathetic response)
- b. Temperature
- c. Emotions
- d. Medications
- e. Excess thyroid hormone (either natural or sympathetic)
- f. Dehydration
- g. Sepsis
What is the direct relationship between HR and O2 consumption?
Increased HR requires more O2.
If all of your vital signs (HR, temp., RR, and B/P) are high, what organ disorder should you suspect?
If all vital sins are high, think thyroid.
What determines the amount of stroke volume?
- a. The contractility of the heart
- b. Afterload
- c. Preload
How is contractility measured?
Through the Ejection Fraction (EF), which measures the volume ejected from the ventricle wit each contraction. A normal value is 55-75%.
How is the Ejection Fraction (EF) tested or measured?
- NON-INVASIVE: Echo Cardio Gram (ECG), this takes a picture of the ventricle when it is full and again when it is empty. What % moves forward with each contraction?
- INVASIVE: Cath Lab (using dye), taking a picture of the ventricle when it is full and empty.
What is the normal range for the Ejection Fraction (EF)?
- 10% = Cardiac Cripple
What parts of the arterial system influence afterload?
- SVR: Systemic vascular resistance which is a calculated value
- PVR: Pulmonary vascular resistance which is a much lower pressure than the systemic (20/5-10)
What influences afterload?
HINT: Think B/P
- a. Vascular resistance against the ventricular action
- b. Influenced by the arterial system (SVR and PVR)
- c. Pulmonic and Aortic valves
How is afterload assessed?
Through the B/P (systolic)