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Essential Applied Biology Sciences for Nursing
A patient is recorded as having a high blood pressure, describe how the blood pressure is normally maintained within homeostatically defined limits. Describe what treatment would be given to this patient who develops high blood pressure.
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This essay describes how homeostasis affects the body’s blood pressure (how healthy blood pressure is maintained), as well as the various treatments involve in reducing blood pressure in case of high blood pressure. The cardiovascular system is responsible for regulating blood pressure. It also describes the normal physiology of the heart and how homeostasis balances the internal and external environment. This essay also looks at the family names of the drugs used to treat patients with high blood pressure to restore homeostasis balance.
Homeostasis is a process that ensures the body’s internal environment is maintained in equilibrium, regardless of the changes that occur inside and outside the body (Tortora and Derrickson, 2013). The nervous system and endocrine systems are the main systems responsible for controlling the homeostatic mechanisms of the body (Scanlon and Sanders, 2007). The endocrine system controls homeostasis by releasing hormones while the nervous system detects various body changes and sends nerve impulses to sustain homeostasis (Emeritus et al., 2016).
Blood pressure can be monitored and changes in blood pressure constitute a stimulus. These stimuli can be internal or external. Stimulus from the internal environment can be because of low blood glucose. Stimuli from the external environment can be because of high heat or low oxygen. Homeostasis is always temporal, and the body’s internal cells respond quicker and establish a balance in the internal environment (Tortora and Derrickson, 2013). Blood pressure is the force applied by blood as it pushes against the walls of the arteries. Cardiac output, peripheral resistance, and chemical control mechanism are a few factors that influence blood pressure. Blood pressure is measured by the top number systolic pressure and the bottom number diastolic pressure (Tortora and Derrickson, 2013). Systolic measures the force of blood pushed around the body when the ventricle contracts. Diastolic measures the pressure when the heart relaxes between beats (Kario, 2015). The ideal blood pressure for a physically healthy adult is about 120/80mmHg (Richard and Edwards, 2003). 120/80mmHG is usually read as 120 over 80 and it implies a systolic pressure of 120mmHg and a diastolic pressure of 80mmHg. The normal range of blood pressure is between 90/60mmHg and 120/80mmHg and sustained blood pressure above 140/90mmHg is high blood pressure or hypertension.
The cardiovascular system comprises of the heart (fig. 1) and the blood vessels. Blood circulates around the body, the heart pumps blood to various parts of the body while the blood vessels help to carry blood from the heart to the cells and from the cells back to the heart (Rose and Wilson, 2018). The heart has four chambers; the two top chambers are the left and right atrium and two bottom chambers are the left and right ventricles (Rose and Wilson, 2018). The heart is located between the two lungs in the thoracic cavity. The left ventricle pumps oxygenated blood to the rest of the body (systemic circulation), hence it has thicker walls than that of the right ventricle, which enables it to generate the pressure required. The right ventricle pumps deoxygenated blood to the lungs (Tortora and Derrickson, 2013). The heart wall has three layers: epicardium, myocardium, and endocardium. The epicardium consists of connective tissues and mesothelium. It can also be called the visceral layer of the serous pericardium. Myocardium acts as the pump for the heart and it consists of specialised cells found only in the heart. The endocardium consists of a thin layer of simple squamous epithelium that lines the inside of myocardium and protects the tendons and valves of the heart (Scanlon and Sanders, 2007).
Pulmonary veins carry blood towards the heart. The pulmonary artery carries blood from the heart to the lungs. The right atrium receives deoxygenated blood through the inferior vena cava, superior vena blood vessels, and coronary sinus. The superior vena cava drains blood from the top section of the body (Rose and Wilson, 2018). The inferior vena cava drain blood from the bottom part of the body Both the superior and inferior vena cava drains blood into the right atrium. The deoxygenated blood is then conveyed into the right ventricle which is then pushed into the pulmonary trunk (Tortora and Derrickson, 2013). Arteries carry deoxygenated blood away from the heart. The deoxygenated blood in the lungs empties carbon dioxide and take in oxygen. This blood full of oxygen enters the left atrium through pulmonary veins (Tortora and Derrickson, 2011). This blood then goes into the left ventricle, which is then pumped into the ascending aorta. The heart has three valves. Tricuspid Valve which is situated between the atria and the ventricle. The bicuspid valve which enables blood to pass from an atrium to a ventricle. This is also called the mitral valve, and the aortic valve (Rose and Wilson, 2018).
Figure 1. diagram of the heart (Emeritus et al., 2016)
The regulation of blood pressure is coordinated by a collection of interconnected neurons known as the cardiovascular centre (CVC), which is in the medulla and pons of the brain stem (Emeritus et al., 2016). The CVC process inputs from baroreceptors and chemoreceptors. Chemoreceptors are nerve endings in the aortic and carotid bodies, which controls blood pressure through respiration. They detect fall in arterial blood pH, rise in CO2, fall in blood oxygen that normally accompanies fall in tissue perfusion and blood pressure (Emeritus et al., 2016). In response, they signal the CVC, which triggers the sympathetic nervous impulses to the heart and blood vessels causing the blood pressure to rise.
Baroreceptors are stretch-sensitive mechanoreceptors located in the walls of ascending aorta and carotid sinus arch, which are found in the bottom of carotid arteries (Perez et al., 2015). Baroreceptors control blood pressures and it is important in maintaining normal perfusion and cardiovascular function throughout the body (Cooper et al., 2005). Baroreceptors send impulses to the CVC to control blood pressure. An increase in blood pressure causes baroreceptors to stretch more tightly and action potentials are initiated at a higher rate. However, when the blood pressure is low the action potentials initiated at a lower rate. The medulla oblongata in the brain receives these impulses and maintains homeostasis (Perez et al., 2015). When the body’s blood pressure is too high (greater than 120/80mmHg), the baroreceptors reflex increases which activate the parasympathetic stimulations of the heart, which leads to a fall in cardiac output. Sympathetic stimulations in the peripheral arterioles will fall leading to vasodilation (the relaxation of the walls of blood vessels) and a consequent fall in blood pressure (Martín-Vázquez and Reyes del Paso, 2010) is achieved.
On the other hand, when there is drop-in blood pressure (lower than 90/60mmHg), the rate of baroreceptors stimulation reduces (Fussey et al., 1973). This activates a rise in sympathetic stimulation of the heart, inducing an increase in cardiac output. This activates sympathetic stimulation of the peripheral vessel leading to vasoconstriction (this is when the blood vessels constrict) and a rise in blood pressure (Perez et al., 2015). As more blood returns to the right atrium than the blood leaving the left ventricles, the atrial receptors will trigger the cardiovascular centre to release more sympathetic impulses until homeostasis is restored (Tortora and Derrickson, 2013).
The baroceptors transmit nerve impulses to the brain, these nerve impulses are interpreted by the Cardiovascular Centre (CVC) of the brain, which response by conveying the nerve impulses to the heart. The heart rate drops, which causes blood pressure to drop (Tortora and Derrickson, 2013). These bring the blood pressure to normal and restores homeostasis. Homeostasis in blood pressure is caused by a negative feedback system. However, when patient blood pressure is consistently high, this condition may be referred to as hypertension (Richard and Edwards, 2003)
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Hypertension is usually diagnosed when a patient’s blood pressure is above 140/90mmHg (Richards and Edwards, 2003). Patients with hypertension are at a higher risk of developing stroke and coronary heart diseases (Richards and Edwards, 2003). Hypertension is classed into three categories: mild hypertension (140/85 – 160/100), moderate hypertension (160/100 – 180/115) and severe hypertension (over 180/115m) (Richards and Edwards, 2003). With most patients, the cause of hypertension is usually not known. However, some environmental factors may be linked to hypertension. In the past, it was thought that baroreceptors control just short-term blood pressure changes based on observations in Sino aortic denervation (SAD) animal model (Kougias et al., 2010). Recent studies show baroreceptors can influence blood pressure by controlling sympathetic output on an additional long-term basis and partake in fluid volume regulations by the kidneys. These findings have been harmonious with the observations in humans (Kougias et al., 2010).
Mild hypertension can be managed with a change in lifestyle choices like eating healthy, exercising regularly, stress reduction, reduced salt intake and stopping smoking (Richards and Edwards, 2003). Cardiovascular diseases are most likely to occur in the morning to the peak ambulatory blood pressure. In order to treat morning hypertension, it is important to monitor a patient twenty-four hour blood pressure (Kario, 2015).
Blood pressure is determined by the volume and viscosity of the blood, the peripheral vascular resistance and the output of blood from the heart: The sympathetic nervous system releases adrenaline which causes an increase in the output of blood and pulse rate. By changing one or more of these elements will be possible to change the blood pressure (Greenstein, 2009).
The peripheral vascular resistance: The arterioles are controlled by the sympathetic nervous system which releases noradrenaline that causes a contraction in muscles and the narrowing of the arterioles leading to a rise in blood pressure (Greenstein, 2009).
The volume and viscosity of the blood are managed by the kidneys. When the receptors recognise a change in the blood pressure falls, the kidneys produce a substance called renin, which when undergoes difficult changes may lead to water and salt retention by the kidneys and the emergence of angiotensin two, which causes vasoconstriction and eventually causes a raised blood pressure (Greenstein, 2009).
In emergency situations when a patient has high blood pressure, they are usually given sodium nitroprusside which is a strong vasodilator. It is used to treat emergency hypertension and severe cardiac failure. It expands both arterial and venous blood vessels, and consequently a reduced peripheral resistance and venous return (Greenstein, 2009). Ace inhibitors also help to reduce blood pressure, however, if a patient is taking this drug with diuretics the initial dose should be low because it can lead to a sudden fall in blood pressure (Greenstein, 2009). ACE inhibitors should not be given to pregnant women as it can lead to feotus damage.
Beta blockers help to reduce cardiac output. Beta blockers are used to treat conditions including angina, heart failure, and some heart rhythm disorders, and after a heart attack (Wiliams and Wilkins, 2005). Beta blockers work by slowing the heart rate, thereby reducing oxygen demand of the heart and the frequency of angina attacks (Greenstein, 2009). 40 percent of patients on beta blockers will experience a fall in blood pressure. When nurses administer beta blockers, they need to monitor patients’ blood pressure regularly. It is not known how beta blockers cause a fall in blood pressure, however, beta blockers are known to interfere with the sympathetic nervous system and may prevent the rise in blood pressure and cardiac output (Greenstein, 2009).
Diuretics are commonly used to reduce the body’s storage of sodium. Diuretics help the body get rid of excess fluid and salt through urine, which helps in the treatment of hypertension and other cardiovascular conditions. (Greenstein, 2009). Diuretics cause a rise in bicarbonate, magnesium, phosphate, bromide, and iodide excretion, and reduce excretion of ammonia. This causes a rise in serum ammonia levels, intensifies renal excretion of sodium chloride, calcium, water, and potassium and obstruct sodium transport across tubules of the cortical diluting segment of the nephron (Wiliams and Wilkins, 2005). Side effects of patients on diuretics include electrolyte imbalances, such as hypokalemia (leg cramps and muscle aches). Diuretics are given in the morning to prevent nocturia (nocturia is excessive urinating at night) to prevent potassium loss diuretics may be used with a potassium-sparing diuretic. Patients on diuretics are usually on input and output chart, these aids with patients’ assessments. To check patients progress, patients will need to be weighed daily in the same clothing and on the same scale (Wiliams and Wilkins, 2005).
Essential hypertension is identified in more than 90 percent of patients and may not cause symptoms. The reason for treating hypertension is to prevent the development of future complications like renal failure, coronary thrombosis, cardiac problems, and stroke. Adequate treatment will reduce morbidity and mortality (Greenstein, 2009). Patients on hypertensive treatment will need their blood pressure monitored on a regular basis. Patients who have raised blood pressure are advised by doctors and nurses to make necessary adjustments like eating healthy and exercising. Hypertension is not curable, however with necessary lifestyle adjustments and medication the condition can be managed (Richards and Edwards, 2003).
My first placement was in cardiology ward. This assignment has helped me understand so many things during my placement. It has helped clarify why patients on diuretic often have high urinary output. I have a broader picture of why nurses are always advised to take lying blood pressure and standing blood pressure for some patients.
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