According to Grossman & Porth (2014), secondary hypertension describes an increase in blood pressure that occurs because of another disease or condition. It is responsible for 5%-10% of all instances of hypertension (Grossman &Porth, 2014). Below is a brief discussion of five causes.
First, renal disease is the most common cause of secondary hypertension and occurs because of decreased blood flow to the kidneys (Grossman & Porth, 2014). According to Bakris (2018), the two main causes of renovascular hypertension are atherosclerosis and fibromuscular dysplasia, both of which lead to either a partial or complete blockage of the renal artery or one of its branches. Stenosis due to atherosclerosis is more common in elders and fibromuscular dysplasia is more often seen in younger women (Grossman & Porth, 2014). In both cases, when blood flow to the kidney is deficient, the kidney responds by increasing the release of renin (Grossman & Porth, 2014). This increase in renin then increases the amount of Angiotensin I in circulation which is then converted to Angiotensin II (Grossman & Porth, 2014). Angiotensin II, which acts as a vasoconstrictor causes an increase in peripheral vascular resistance and increases the release of aldosterone (Grossman & Porth, 2014). As described by (Bayer, n.d) aldosterone impacts the kidney’s ability to filtrate molecules and causes an increase in the retention of sodium and water, with a subsequent increase in the excretion of potassium. These effects cause an increase in blood pressure and can cause damage to both kidneys (Grossman ; Porth, 2014). Finally, symptoms of both include: the onset of hypertension in someone who had normal BP prior, hypokalemia due to increased aldosterone levels, and an abdominal bruit (Grossman ; Porth, 2014).
As described by Cicala & Mantero (2010) Cushing’s Syndrome involves increased amounts of glucocorticoids due to conditions such as tumors and exogenous steroids. Due to several mechanisms related to this disease state, 80% of people with Cushing’s develop systemic hypertension (Cicala & Mantero, 2010). The hypertension that accompanies this syndrome is due to the increased levels of glucocorticoids, which increase salt and water retention by the kidneys (Grossman & Porth, 2014). Specifically, as described by Singh, Kotwal, and Menon (2011) there are several mechanisms by which the increase in glucocorticoids cause hypertension. First, in Cushing’s there is a decreased conversion of cortisol to cortisone, leading to elevated levels of cortisol in circulation (Singh et al., 2011). This occurs because the enzyme known as 11 beta-hydroxysteroid dehydrogenase (11bHSD2), which normally functions to control the cortisol levels in the body by converting cortisol to cortisone is overwhelmed by the increased levels of cortisol circulating (Singh et al, 2011). As described by Sacerdote et al., (2005) and Singh et al. (2011) the increased levels of cortisol over stimulates the mineralocorticoid receptors leading to increased sodium reabsorption by the kidneys, hypokalemia, increased volume in the intravascular space, and subsequent hypertension (Singh et al., 2011). Furthermore, glucocorticoids such as cortisol decrease production of nitric oxide synthase which works to synthesize a vasodilator known as nitric oxide (Singh et al., 2011). This action by glucocorticoids causes a decrease in vasodilation of the peripheral arteries and a subsequent increase in BP (Singh et al.,2011). Finally, activation of the RAAS is thought to also play a role in the development of hypertension in Cushing’s (Singh et al., 2011)
Pheochromocytoma, a tumor of the chromaffin tissue most often found in the adrenal medulla, is another cause of secondary hypertension (Grossman & Porth, 2014). This tumor is composed of sympathetic nerve cells that produce catecholamines including epinephrine and norepinephrine (Grossman & Porth, 2014). This tumor causes hypertension through the increased release of these catecholamines (Grossman & Porth, 2014). Specifically, as described by Zuber, Kantorovich, Pacak, (2011) both epinephrine and norepinephrine exert their effects through stimulation of the alpha and beta-adrenergic receptors. With a pheochromocytoma, there is an increased release of catecholamines and thus increased stimulation of these receptors, amplifying their effects (Zuber et al., 2011). Alpha-1 adrenergic receptors which are located on the smooth muscle tissues, cause vasoconstriction when stimulated by these catecholamines (Zuber at al., 2011). Additionally, Beta-1 adrenergic receptors when stimulated cause the release of renin and the subsequent conversion of angiotensin to angiotensin I, causing vasoconstriction and an increase in blood pressure (Zuper et al., 2011). The excessive production of the catecholamines with this tumor over stimulates the receptors and hypertension occurs due to the vasoconstrictive effects (Zuper et al., 2011). This increased systemic blood pressure leads to symptoms such as headaches, palpitations, and sweating and can be constant or periodic, based on the how frequent the release of the catecholamines occurs (Zuper et al., 2011; Grossman & Porth, 2014).
According to Tonelli, 2014, Cystic Fibrosis, a progressive disease that impacts the lungs can cause secondary pulmonary hypertension through several mechanisms. First, cystic fibrosis is inherited as an autosomal recessive disease and results in the production of thick viscous mucus due to the ineffective CFTR gene (Grossman & Porth, 2014). This thick mucus and the inability of the body to clear it results in hypoxemia, and subsequent vasoconstriction (Tonelli, 2014). Specifically, when the cells of the pulmonary artery detect the low oxygen levels, they vasoconstrict to improve the ventilation and perfusion balance (Tonelli 2014). This attempt to compensate is not sustainable and remodeling of the pulmonary arteries occurs, leading to increased pressure and pulmonary hypertension (Tonelli, 2014). Furthermore, cystic fibrosis causes chronic inflammation in the airways which over time leads to remodeling of the pulmonary arteries and subsequent pulmonary hypertension (Tonelli, 2014).
Coarctation of the Aorta
This condition which describes the narrowing of the aorta is a cause of secondary hypertension and can occur both in adults and children (Grossman & Porth, 2014). As described by Children’s Hospital of Philadelphia, 2018, the aorta functions to transport oxygenated blood from the heart to the rest of the body. However, when the aorta is narrowed, the left ventricle of the heart must increase its effort to move blood forward and a resultant increase in pressure occurs (Children’s Hospital of Philadelphia, 2018) Specifically, in adults with this condition, hypertension develops because of an increased stroke volume pushed into the stenotic aorta (Grossman & Porth, 2014). With an increased volume of blood ejected with each beat, the narrowed aorta cannot move the entire volume of blood forward, and there is a subsequent increase in systolic blood pressure and more blood flowing to the upper part of the body (Grossman & Porth, 2014). Additionally, because there is a decreased volume of blood able to move forward, the lower part of the body including the kidneys receives insufficient blood flow (Grossman & Porth, 2014). As described by Patnana (2017), this reduced renal blood flow also contributes to hypertension due to the activation of the renin- angiotensin system which results in vasoconstriction and increased retention of salt by the kidneys, both of which raise blood pressure (Pantana, 2017; Grossman & Porth, 2014).
#5 Summarize the pathogenesis of cystic fibrosis, at the tissue level (i.e., salt & water transport) and the organ system level. Also, summarize the treatments that are being used to alleviate the respiratory & the digestive problems.
Cystic Fibrosis, an autosomal recessive disorder, is a leading cause of respiratory disease in pediatric patients and has widespread effects on various organs (Grossman& Porth, 2014). First, at the tissue level, cystic fibrosis is caused by various mutations of the CFTR gene which is located on the arm of chromosome 7 (Grossman & Porth, 2014). As described by Shannon (2015), the CFTR proteins exerts its effects within the epithelial membrane of organs throughout the body and functions as a channel for chloride ions out of the cell. When functioning normally, the exit of chloride ions from cells leads to the influx of sodium ions to the cell membrane followed by water (Shannon, 2015). This dilutes the mucus, making it less sticky and easy to remove from the body (Shannon, 2015). However, in cystic fibrosis, a mutation of the CFTR protein causes ineffective secretion of chloride and increased absorption of sodium and water, resulting in thick mucus that is not easily cleared (Grossman & Porth, 2014). Furthermore, the effects of a faulty chloride channel at the tissue level depend on the tissue involved (Grossman & Porth, 2014). Within the sweat glands for instance, reabsorption of chloride through the chloride channel and subsequent sodium reabsorption within the ducts of the sweat glands does not take place, resulting in large amounts of NaCl in the sweat of a patient with CF (Grossman & Porth, 2014). Additionally, at the tissue level within the airway, chloride is not successfully secreted resulting in abnormal absorption of both sodium and water from the airways into the bloodstream (Grossman & Porth, 2014). This results in thick mucus as described above due to the lack of water, and the mucus is difficult to remove by the lungs and sticks to internal structures (Grossman & Porth, 2014).
Next, because of the thick, purulent mucus that develops due to the defective chloride channel, many organs are subsequently affected (Grossman & Porth, 2014). First, within the lung’s the thick dehydrated mucus builds up within the bronchi making it difficult for the cilia to remove. (Grossman ; Porth, 2014). As described by the American Lung Association (2018), when the mucus is not effectively removed from the airway it produces an environment conducive to bacterial growth that predisposes the patient to frequent respiratory infections. Over time, the consequences and effects of built up mucus are compounded, as mucus continues to get stuck and infections continually reoccur (American Lung Association, 2018). The lungs and airway are eventually damaged over time (American Lung Association, 2018). Finally, a defective CFTR gene and its subsequent effects in CF lead to inflammation of the pulmonary system (Grossman ; Porth, 2014). Specifically, as described by Cantin et al., (2015), the inflammation occurs due to the migration of neutrophils to the areas of initial and persistent infections, and their subsequent release of oxidants and proteases which further damage lung tissue (Cantin et al, 2015; Grossman ; Porth, 2014). These changes and effects on the lungs eventually cause chronic bronchitis, bronchiectasis, and ultimately respiratory failure (Grossman ; Porth, 2014).
In addition to the lungs, other organ systems including the pancreas are damaged in Cystic Fibrosis (Grossman ; Porth, 2014). According to John Hopkins Medicine (n.d), the ineffective chloride ion channels causes pancreatic secretions to also become very thick and viscid, blocking the pancreatic ducts. This blockage impairs the function of the pancreas, which works to release enzymes that aid in the digestion process and in the regulation of blood sugar (John Hopkins Medicine, n.d). The insufficient release of the pancreatic enzymes results in impaired absorption of fats, protein, and vitamins A, D, E, and K (John Hopkins Medicine, n.d). Clinically this results in fat in the stool, diarrhea, and abdominal pain (Grossman ; Porth, 2014). As described by the Cystic Fibrosis Foundation (n.d), diabetes can also occur at the organ level due to the disease process. Specifically, over time the thick mucus accumulates on the pancreas causing scarring and subsequent insufficient production of insulin (Cystic Fibrosis Foundation, n.d). Without sufficient insulin production, patients become insulin deficient and may display clinical symptoms such as weight loss, fatigue, and excessive thirst and urination (Cystic Fibrosis Foundation, n.d).
Next, at the organ system level, the pathogenesis of cystic fibrosis can also impact the reproductive system, especially in males (John Hopkins Medicine, n.d). In most male patients with CF, a condition known as congenital bilateral absence of the vas deferens occurs because thick mucus blocks the van deferens and prevents them from fully developing (John Hopkins Medicine, 2018). This results in blockage of the canal that transports sperm and thus patients with this condition are often infertile (John Hopkins Medicine, n.d). Furthermore, according to Sandford Children’s Health, 2018, women with this disease are also likely to be infertile due to the accumulation of thick cervical mucus. Clinical symptoms associated with the effects of CF on the reproductive organs include: Delayed puberty, irregular or lack of menstruation, and inflammation in the cervix (Stanford Children’s Health, 2018)
As described by the Mayo Clinic (2018) in addition to respiratory, digestive, and reproductive effects, Cystic Fibrosis due to the pathogenic mechanisms described above can also result in: osteoporosis, dehydration, intestinal obstruction, nasal polyps, and blocked bile ducts.
Finally, there are many treatment options available to manage the respiratory and digestive effects of CF (Grossman ; Porth, 2014). First, techniques to clear the airway are utilized to help rid the body of the thick mucus and help prevent infections (Cystic Fibrosis Foundation, n.d). These techniques include chest physical therapy such as implementation of chest percussion and postural drainage, proper coughing techniques, and regular exercise (Cystic Fibrosis Foundation, n.d., Grossman ; Porth, 2014). Antibiotics are also utilized in CF and are often taken daily to prevent bacterial infections, as well as when acute infections occur (Cystic Fibrosis Foundation, n.d). Other medications used include: mucolytics, bronchodilators, and CFTR modulator therapies (Cystic Fibrosis Foundation, n.d) Specifically, mucolytics such as hypertonic saline work by drawing salt into the airways which causes water to follow, resulting in thinner mucus (Cystic Fibrosis Foundation, n.d) Dornase Alfa, another mucolytic alternately works by breaking up the mucus, making it easier to clear (Cystic Fibrosis Foundation, n.d). Bronchodilators furthermore work to relax and open the airways, making it easier for other medications to reach the lungs and CFTR modulator therapies can be used in patients with certain defects and work to improve symptoms by modifying and correcting the defective protein produced by the CFTR gene (Cystic Fibrosis Foundation, n.d). Finally, patients may eventually need a lung transplant due to the progressive nature of the disease (Cystic Fibrosis Foundation, n.d).
According to Sabharwal (2016), treatments aimed at managing digestive symptoms include: routine supplementation with the fat-soluble vitamins A, D, E, and K, administration of sodium chloride to prevent dehydration, increased calories for weight gain and to manage the energy requirements of the disease, and pancreatic enzyme replacement therapy which is used to promote absorption of nutrients by the pancreas. Additionally, if diabetes does occur, insulin, close monitoring of blood sugar, and regular exercise are treatments implemented to alleviate clinical associated symptoms (Cystic Fibrosis Foundation, n.d).
Overall, CF is a disease involving malfunctions of the CFTR gene which results in an ineffective chloride channel, and subsequent production of thick mucus which has many devastating effects on tissues and organs (Grossman ; Porth, 2014).