Disorders of Blood Pressure Regulation PDF

DISORDERS OF BLOOD PRESSURE REGULATION  Objectives 8.3.1. Discuss the causes of primary and secondary hypertension 8.3.2. Discuss the effect of obesity and high salt intake on primary hypertension 8.3.3. Discuss the etiology and pathogenesis of primary hyperten...

DISORDERS OF BLOOD PRESSURE REGULATION  Objectives 8.3.1. Discuss the causes of primary and secondary hypertension 8.3.2. Discuss the effect of obesity and high salt intake on primary hypertension 8.3.3. Discuss the etiology and pathogenesis of primary hypertension 8.3.4. Discuss the conditions causing secondary hypertension. 8.3.5. Describe the pathogenesis of malignant hypertension 8.3.6. Discuss the pathogenesis and etiology of orthostatic hypotension  HYPERTENSION Hypertension, or high blood pressure, is probably the most common of all health problems in adults and is the leading risk factor for cardiovascular disorders. Men have higher blood pressures compared to women up until women reach menopause. Hypertension is more common (1) in blacks compared with whites, (2) in people from lower socioeconomic groups, and (3) in older adults.  HYPERTENSION PRIMARY (ESSENTIAL) SECONDARY Is the term applied to 95% of The elevation of blood pressure cases in which no cause for results from an identifiable hypertension can be identified. underlying secondary cause, such as kidney or endocrine disease. Many conditions causing primary hypertension cannot be corrected Many conditions causing secondary or cured. hypertension can be corrected or cured by surgery or specific medical treatment.  PRIMARY (ESSENTIAL) HYPERTENSION A diagnosis of hypertension is made if the systolic blood pressure is 140 mm Hg or higher and the diastolic blood pressure is 90 mm Hg or higher.  PRIMARY (ESSENTIAL) HYPERTENSION ❖ Etiology Although the cause or causes of essential hypertension are largely unknown, both constitutional (non-modifiable risk factors) and lifestyle factors (modifiable risk factors) have been implicated, either singly or collectively, as contributing factors. ❑ Non-modifiable Risk Factors: The constitutional risk factors include: 1. Family History 2. Age-Related Changes in Blood Pressure 3. Race  PRIMARY (ESSENTIAL) HYPERTENSION ❑ Modifiable Risk Factors: Lifestyle factors can contribute to the development of hypertension by interacting with the constitutional risk factors. 1. High Salt Intake 2. Obesity 3. Excess Alcohol Consumption 4. Dietary Intake of Potassium, Calcium, and Magnesium 5. Obstructive Sleep Apnea  1. HIGH SALT INTAKE Increased salt intake Water retention Increased blood volume Increases sensitivity of CV or renal mechanisms to SNS Hypertension Vasoconstriction Activate renin-angiotensin-aldosterone system Release of renin by kidneys Acts on angiotensinogen (ACE) Increased SVR Forms angiotensin II Forms angiotensin I ▪ Numerous studies have shown that a reduction in salt intake can lower BP.  2. OBESITY (1) Excess adipose tissue Adipocyte derived leptin Increases aldosterone levels Adipocyte derived angiotensinogen Act on CV Act on Acts on kidneys Activation of system hypothalamus renin-angiotensin-aldosterone Na & fluid retention system Increased SVR Activation of SNS Increased blood volume Hypertension Vasoconstriction Hypertension Hypertension  2. OBESITY (2) Obesity High levels of circulating free fatty acids Stimulate SNS Vasoconstriction Hypertension  SECONDARY HYPERTENSION Secondary hypertension, which describes an elevation in blood pressure due to another disease condition, accounts for 5% to 10% of hypertension cases. It tends to be seen in people younger than 30 and older than 50 years of age. The most common causes of secondary hypertension are: 1. Kidney disease (i.e., renovascular hypertension) 2. Adrenal cortical disorders 3. Pheochromocytoma (tumor in adrenal gland) 4. Coarctation of the aorta (narrowing)  1. RENAL HYPERTENSION Renovascular hypertension refers to hypertension caused by reduced renal blood flow and activation of the renin–angiotensin–aldosterone mechanism. It is the most common cause of secondary hypertension There are two major types of renovascular disease: 1. Atherosclerosis of the proximal renal artery (70-90%) and 2. Fibromuscular dysplasia, a noninflammatory vascular disease that affects the renal arteries and branch vessels.  1. RENAL HYPERTENSION Renovascular disease Reduced renal blood flow Kidneys release excessive amounts of renin Increases circulating levels of angiotensin II Vasoconstriction Stimulates increased aldosterone levels Increased peripheral vascular resistance Na & fluid retention Hypertension Increased blood volume Hypertension  2. DISORDERS OF ADRENOCORTICAL HORMONES Increased levels of adrenocortical hormones also can give rise to hypertension. Disorders of adrenocortical hormones that tend to raise the blood pressure are: 1. Primary hyperaldosteronism (excess production of aldosterone due to adrenocortical hyperplasia or adenoma) and 2. Excess levels of glucocorticoid (Cushing disease or syndrome). 2. DISORDERS OF ADRENOCORTICAL HORMONES Increased levels of adrenocortical hormones Na and fluid retention by kidneys Increased blood volume Hypertension  3. PHEOCHROMOCYTOMA A pheochromocytoma is a tumor of chromaffin tissue, which contains sympathetic nerve cells that stain with chromium salts and release catecholamine. Pheochromocytoma Produce & secrete catecholamines SNS stimulation Vasoconstriction Hypertension  4. COARCTATION OF THE AORTA Coarctation represents a narrowing of the aorta. In the adult form of aortic coarctation, the narrowing most commonly occurs just distal to the origin of the subclavian arteries.  4. COARCTATION OF THE AORTA Coarctation of the aorta Blood flow to the lower parts of the body and kidneys reduced Decreased renal blood flow Activation of renin-angiotensin-aldosterone system Release of renin by kidneys Increases circulating levels of angiotensin II Vasoconstriction Stimulates increased aldosterone levels Hypertension Na & fluid retention Increased blood volume Hypertension  5. ORAL CONTRACEPTIVE DRUGS The use of oral contraceptive pills is probably the most common cause of secondary hypertension in young women. Oral contraceptive pills (estrogen & synthetic progesterone) Na & fluid retention Increased blood volume Hypertension ▪ The hypertension associated with oral contraceptives usually disappears after the drug has been discontinued, although it may take as long as 3 months for this to happen.  MALIGNANT HYPERTENSION A small number of people with hypertension develop an accelerated and potentially fatal form of the disease termed malignant hypertension. This usually is a disease of: ✔ Younger people ✔ Particularly young black men ✔ Women with toxemia of pregnancy and ✔ People with renal and collagen diseases. Malignant hypertension is characterized by sudden, marked elevations in blood pressure, with diastolic values above 120 mm Hg complicated by evidence of  MALIGNANT HYPERTENSION (1) Malignant Hypertension Intense arterial spasm of the cerebral arteries Hypertensive encephalopathy Cerebral edema Papilledema Produce effects of pressure on the optic nerve and retinal vessels Visual disturbances  MALIGNANT HYPERTENSION (2) Prolonged and severe exposure to exaggerated levels of blood pressure Injures the walls of the arterioles Intravascular coagulation and fragmentation of red blood cells. ▪ The renal blood vessels are particularly vulnerable to hypertensive damage.  ORTHOSTATIC HYPOTENSION Orthostatic or postural hypotension, which is a physical finding and not a disease, is an abnormal drop in blood pressure on assumption of the standing position. In 1995, the Joint Consensus Committee of the American Autonomic Society and the American Academy of Neurology defined orthostatic hypotension as a drop in systolic pressure of 20 mm Hg or more or a drop in diastolic blood pressure of 10 mm Hg or more within 3 minutes of standing.  ORTHOSTATIC HYPOTENSION ❖ Etiology: A wide variety of conditions, acute and chronic, are associated with orthostatic hypotension. It is seen associated with the following conditions: 1. Aging 2. Reduced Blood Volume 3. Bed Rest and Impaired Mobility 4. Drug-Induced Hypotension  1. AGING After 70 years of age there is an increasing tendency toward arterial pressure instability and postural hypotension. Orthostatic hypotension may be either systolic or diastolic, that associated with aging seems more often to be systolic.  2. REDUCED BLOOD VOLUME Common causes of orthostatic hypotension related to hypovolemia are: ✔ Excessive use of diuretics ✔ Excessive diaphoresis ✔ Loss of gastrointestinal fluids through vomiting and diarrhea and ✔ Loss of fluid volume associated with prolonged bed rest.  3. BED REST AND IMPAIRED MOBILITY Prolonged bed rest Reduction in plasma volume Decrease in venous tone & loss of skeletal muscle tone Failure of peripheral vasoconstriction Orthostatic hypotension  4. DRUG-INDUCED HYPOTENSION Drugs that are the most common cause of chronic orthostatic hypotension are: ✔ Antihypertensive drugs and ✔ Psychotropic drugs  5. DISORDERS OF THE AUTONOMIC NERVOUS SYSTEM Peripheral neuropathies associated with DM, after injury or disease of the spinal cord, or as the result of CVA Altered ANS function Disruption of sympathetic outflow from the brain stem Failure of peripheral vasoconstriction Orthostatic hypotension  ORTHOSTATIC HYPOTENSION ❖ Pathogenesis: After the assumption of the upright posture from the supine position, approximately 500 to 700 mL of blood is momentarily shifted to the lower part of the body, with an accompanying decrease in central blood volume and arterial pressure.  ORTHOSTATIC HYPOTENSION - PATHOGENESIS Assuming standing position Absence of normal circulatory (baroreceptor) reflexes or blood volume Blood pools in the lower part of the body Cardiac output falls Blood pressure drops Inadequate blood flow to the brain Light-headedness, dizziness, palpitations and syncope.