Adequate cardiac output is necessary in order to supply oxygen and other nutrients to all body tissues. Cardiac output is influenced by stroke volume and heart rate. Factors affecting the stroke volume includes PRELOAD, CONTRACTILITY and AFTERLOAD.
In the following conditions, indicate what factor/s influence the cardiac output: PRELOAD, CONTRACTILITY, AFTERLOAD, HEART RATE. Explain the why the factor/s affects cardiac output in 1 to 2 sentences.
a. High blood pressure
- Factors include sympathetic stimulation, epinephrine, norepinephrine, thyroid hormones, and increased calcium ion levels (5.15: Factors That Influence Blood Pressure, 2019). High BP makes the arteries less elastic; hence making blood circulation difficult, and the heart needs to work harder (American Heart Association, 2016).
b. Massive bleeding
- Massive bleeding results in massive blood loss and reduction of blood volume that circulates the body; hence, leading to decreased cardiac output. Massive bleeding hinders the oxygen and nutrient transportation by the RBCs to the tissues; thus, cardiac output is directly proportional to the blood flow (Gutierrez et al., 2004).
c. the drug dopamine
- Dopamine is used to support cardiac output, blood pressure, and blood flow to the kidneys (Jakob et al., 2002). It can increase blood pressure, heart rate, and cardiac contractility; hence, dopamine drug can increase cardiac output (Dopamine, n.d.).
d. Running a sprint
- Running a sprint increases blood flow and assists its circulation (AXA Health, n.d.). Hence, cardiac output is increased dramatically along with heart rate (Dl, 1985).
e. Hyperthyroidism with increased secretion of thyroid hormones
- Hyperthyroidism or overactive thyroid results from too much production and secretion of thyroxine; it is the most prominent cause of hyperkinetic circulatory disease, wherein there is an increase in the blood ejection rate (Gorlin, 1962). Thyroxine increases cardiac output by lowering the total peripheral resistance due to the vasodilation of circulatory beds (deGroot & Leonard, 1970).
f. Massive myocardial infarction (cardiac tissue death)
- Myocardial infarction compromises the contractility of the myocardium. Hence, massive myocardial infarction or heart attack decreases cardiac output and arterial blood pressure (Dhakam & Khalid, 2008).
g. Hypothermia
- Hypothermia or decreased body temperature due to exposure to cold temperatures, triggers thermoregulatory vasoconstriction on the skin. The narrowed blood vessels put a strain on the heart and cause bradycardia or slow heart rate; hence, decreasing the cardiac output (Deussen, 2007).
h. Emotional distress
-Hormones like cortisol and adrenaline can be secreted because of emotional distress; this makes the heart beat faster and blood vessels constrict (University of Rochester Medical Center, 2019). As a result, emotional distress can increase blood pressure, heart rate, and cardiac output (Crestani, 2016).
REFERENCES:
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