Blood Pressure Regulation Atherosclerosis Dyslipidemia NUR 41500

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Blood Pressure Regulation Atherosclerosis Dyslipidemia

NUR 41500

Pathophysiology

Hypertension

A consistent elevation of systemic arterial blood pressure

The most common primary diagnosis in the United States

Occurs in 1 out of 3 Americans and in 2/3 of those older than 60.

Risk increases with age

More common in blacks and those with diabetes

Pathophysiology

Hypertension results from

A sustained increase in peripheral resistance

An increase in circulating blood volume

Or— both of the above

Definitions

Systolic pressure: arterial pressure during ventricular contraction(systole)

Diastolic pressure: the arterial pressure during ventricular filling(diastole)

Pulse pressure: the difference between systolic and diastolic pressure

Mean arterial pressure: the average pressure in the arterial system during ventricular contraction and relaxation

Arterial Blood Pressure

Represents the pressure of the blood as it moves through the arterial system

Cardiac output = HR x SV

Vascular resistance (VR)

Mean arterial pressure = CO x VR

Mechanisms of Regulation

Short-term regulation: corrects temporary imbalances in blood pressure

Neural mechanisms

Humoral mechanisms

Long-term regulation: controls the daily, weekly, and monthly regulation of blood pressure

Renal mechanism

Factors determining BP

Systolic pressure

The characteristics of the stroke volume being ejected from the heart

The ability of the aorta to stretch and accommodate the stroke volume

Diastolic pressure

The energy stored in the aorta as its elastic fibers are stretched during systole

The resistance to the runoff of blood from the peripheral blood vessels

Systolic and Diastolic Pressure

Factors affecting BP

Age

More common in younger men than younger women

More common in the elderly

Race

More common in blacks than whites

Socioeconomic group

More common in lower socioeconomic groups

Categories of Hypertension

Primary hypertension (essential hypertension)

Occurs without evidence of other disease

Secondary hypertension

Results from some other disorder, such as kidney disease

Complicated Hypertension

Chronic hypertension resulting in target organ damage

Classifications of Hypertension

Systolic/diastolic hypertension

Both the systolic and diastolic pressures are elevated.

Diastolic hypertension

The diastolic pressure is selectively elevated.

Systolic hypertension

The systolic pressure is selectively elevated.

Non-modifiable Risk Factors for Hypertension

Family history

Age-due to arterial stiffness

Race

Gender

Modifiable Risk Factors (lifestyle)

High salt intake

Obesity

Excess alcohol consumption

Dietary intake of potassium, calcium, and magnesium

Oral contraceptive drugs

Stress

Stress does not cause hypertension but it can exacerbate it

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Target Organ Damage in Complicated Hypertension

Heart

Hypertrophy, angina, heart failure, MI, sudden death

Brain

TIA, stroke, aneurysm, thrombosis, hemorrhage, dementia

Peripheral vascular

Atherosclerosis

Kidney

Nephrosclerosis, renal insufficiency or renal failure

Retinal vascular disease, exudates, hemorrhage

Pharmacological Tx

Diuretics

β-adrenergic–blocking drugs

Angiotensin-converting enzyme (ACE) inhibitors

Angiotensin II receptor blockers

Calcium-channel–blocking drugs

Central α2-adrenergic agonists

α1-adrenergic receptor blockers

Vasodilators

Question

Renal failure results in Na+ and water retention. This results in hypertension. How would you classify this type of hypertension?

Primary hypertension

Secondary hypertension

Malignant hypertension

Systolic hypertension

Answer: secondary hypertension

Most common causes of secondary HTN:

Kidney disease –this is the number 1 cause of secondary hypertension

Adrenal cortical disorders

Pheochromocytoma

Coarctation of the aorta

Sleep apnea

Types of Hypertension in Pregnancy

Gestational hypertension

Chronic hypertension

Preeclampsia/eclampsia

Preeclampsia superimposed on chronic hypertension

Diagnosis & Tx of Hypertensionin Pregnancy

Early prenatal care

Refraining from alcohol and tobacco use

Salt restriction

Bed rest

Carefully chosen antihypertensive medications

Hypertension in Children

Blood pressure norms are based on age, height, and gender-specific percentiles.

Secondary hypertension is the most common form in this group

Kidney abnormalities

Coarctation of the aorta

Pheochromocytoma and adrenal cortical disorders

In infants, hypertension is associated most commonly with high umbilical catheterization and renal artery obstruction caused by thrombosis.

Orthostatic Hypotension

Definition

An abnormal decrease in blood pressure on assumption of the upright position

Causes

Decrease in venous return to the heart due to pooling of blood in lower part of body

Inadequate circulatory response to decreased cardiac output and a decrease in blood pressure

Causes of Orthostatic Hypotension

Conditions that decrease vascular volume

Dehydration (prolonged vomiting, GI suction)

Diuretics

Diaphoresis

Conditions that impair muscle pump function

Bed rest (↓ Fluid Volume)

Spinal cord injury

Conditions that interfere with cardiovascular reflexes

Medications

Disorders of autonomic nervous system

Effects of aging on baroreflex function

Clinical Manifestations Orthostatic Hypotension

Dizziness

Visual changes

Head and neck discomfort

Poor concentration while standing

Palpitations

Tremor, anxiety

Presyncope, and in some cases syncope

Question

Increased vascular compliance may contribute to which condition?

Systolic hypertension

Orthostatic hypotension

Diastolic hypertension

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Answer

Systolic hypertension

Orthostatic hypotension: Orthostatic hypertension is the result of lower pressures, and increased compliance would decrease the vascular resistance and result in lower pressures.

Diastolic hypertension

Atherosclerosis

Arteriosclerosis

Thickening and hardening of the vessel wall.

Formation of a lesions called a plaques.

Results in ischemic syndromes that can vary widely in their severity and clinical manifestations.

The leading cause of coronary artery and cerebrovascular disease.

Evolution of Atherosclerosis

Pathophysiology of Atherosclerosis

Atherosclerosis begins with injury to the endothelial cells that line artery walls.

Possible causes of endothelial injury:

Smoking

Hypertension

Diabetes,

Increased levels of low-density lipoprotein (LDL)

Decreased levels of high-density lipoprotein (HDL)

Autoimmunity

Pathophysiology (Cont.)

Injured endothelial cells become inflamed. Inflammation plays a fundamental role in mediating the steps in the initiation and progression of atherogenesis.

The next step in atherogenesis occurs when inflamed endothelial cells express adhesion molecules that bind macrophages and other inflammatory and immune cells.

Macrophages are activated by binding to damage-associated molecular patterns (DAMPs) released from injured cells.

Hyperlipidemia, diabetes, smoking, and hypertension contribute to LDL oxidation and its accumulation in the vessel wall.

Lipid-laden macrophages are now called foam cells, and when they accumulate in significant amounts, they form a lesion called a fatty streak.

Pathophysiology (Cont.)

Macrophages also release growth factors that stimulate smooth muscle cell proliferation. Smooth muscle cells in the region of 610endothelial injury proliferate, produce collagen, and migrate over the fatty streak, forming a fibrous plaque.

Many plaques, however, are “unstable,” meaning they are prone to rupture even before they affect blood flow significantly and are clinically silent until they rupture

Plaques that have ruptured are called complicated plaques. Once rupture occurs, exposure of underlying tissue results in platelet adhesion, initiation of the clotting cascade, and rapid thrombus formation.

The thrombus may suddenly occlude the affected vessel, resulting in ischemia and infarction. Aspirin or other antithrombotic agents are used to prevent this complication of atherosclerotic disease.

Signs and Symptoms

Partial vessel obstruction may lead to transient ischemic events, often associated with exercise or stress.

As the lesion becomes complicated, increasing obstruction with superimposed thrombosis may result in tissue infarction. Obstruction of peripheral arteries can cause significant pain and disability.

Coronary artery disease (CAD) caused by atherosclerosis is the major cause of myocardial ischemia and is one of the most important health issues in the United States.

Atherosclerotic obstruction of the vessels supplying the brain is the major cause of stroke.

Treatment of Atherosclerosis

Obtaining a complete health history (including risk factors and symptoms of ischemia) is essential.

Physical examination may reveal arterial bruits and evidence of decreased blood flow to tissues.

Laboratory data that include measurement of levels of lipids, blood glucose, and hs-CRP are also indicated.

Current management with drugs aimed at stabilizing and reversing plaques before they rupture.

Prevention includes implementation of an exercise program, smoking cessation, and control of hypertension and diabetes where appropriate while reducing LDL cholesterol level by diet or medications, or both.

Dyslipidemia

The term lipoprotein refers to lipids, phospholipids, cholesterol, and triglycerides bound to carrier proteins. Lipids (cholesterol in particular) are required by most cells for the manufacture and repair of plasma membranes. Cholesterol is also a necessary component for the manufacture of such essential substances as bile acids and steroid hormones. Although cholesterol can easily be obtained from dietary fat intake, most body cells also can manufacture cholesterol.

The cycle of lipid metabolism is complex. A series of chemical reactions in the liver results in the production of several lipoproteins that vary in density and function. These include very-low-density lipoproteins (VLDLs), primarily triglyceride and protein; low-density lipoproteins (LDLs), mostly cholesterol and protein; and high-density lipoproteins (HDLs), mainly phospholipids and protein.

Dyslipidemia (or dyslipoproteinemia) refers to abnormal concentrations of serum lipoproteins. It is estimated that nearly half of the U.S. population has some form of dyslipidemia, especially among white and Asian populations.

Combination of genetic and dietary factors.

Secondary causes:

Diabetes, hypothyroidism, pancreatitis, and renal nephrosis, as well as the use of certain medications.

Criteria for Dyslipidemia

	Optimal	Near-Optimal	Desirable	Low	Borderline	High	Very High
Total cholesterol			<200		200-239	≥240
LDL	<100	100-129			130-159	160-189	≥190
Triglycerides			<150		150-199	200-499	≥500
HDL				<40		≥60

The role of LDL in Dyslipidemia

LDL is responsible for the delivery of cholesterol to the tissues, and an increased serum concentration of LDL is a strong indicator of coronary risk.

High dietary intake of cholesterol and saturated fats, in combination with a genetic predisposition to accumulations of LDL in the serum (e.g., dysfunction of the hepatic LDL receptor), result in high levels of LDL in the bloodstream.

LDL also plays a role in endothelial injury, inflammation, and immune responses that have been identified as being important in atherogenesis.

The term LDL describes several types of LDL molecules. Measurement of LDL subfractions allows for a better prediction of coronary risk.

HDL and VLDL

Low levels of HDL cholesterol also are a strong indicator of coronary risk. HDL is responsible for “reverse cholesterol transport,” which returns excess cholesterol from the tissues to the liver for processing or elimination in the bile. HDL also participates in endothelial repair and decreases thrombosis. It can be fractionated into several particle densities (HDL-2 and HDL-3) that have different effects on vascular function.

Exercise, smoking cessation,weight loss, fish oil consumption, and moderate alcohol use result in modest increases in HDL level. Despite the wealth of evidence that HDL plays an important role in preventing atherosclerotic coronary disease, studies have suggested that raising overall levels of HDL is not adequate to prevent cardiovascular disease.

Niacin and fibrates are drugs that can cause modest increases in HDL levels that are not correlated with an improvement in cardiovascular risk in individuals without documented coronary disease (primary prevention). Drugs that are aimed specifically at increasing HDL levels include recombinant apolipoprotein A-I (ApoA-I) mimetics, thiazolidinediones (used to treat diabetes), and cholesteryl ester transfer protein inhibitors, but they have not been shown to be effective in preventing heart disease.

Other lipoproteins associated with increased cardiovascular risk include elevated levels of serum VLDLs (triglycerides) and increased lipoprotein(a) levels. Triglycerides are associated with an increased risk for CAD, especially in combination with other risk factors such as diabetes.

HDL and VLDL, continued

Risk Factors

Risk Factors

Hypertension is responsible for a twofold to threefold increased risk of atherosclerotic cardiovascular disease.

Cigarette smoking. Both direct and passive (environmental) smoking increase the risk of CAD.

Diabetes mellitus. Good diabetic control is linked to reduced risk for CAD.

Obesity/sedentary lifestyle. It is estimated that 65% of the adult population in the United States is overweight or obese, and an estimated 47 million U.S. residents have a combination of obesity, dyslipidemia, hypertension, and insulin resistance, called the metabolic syndrome, which is associated with an even higher risk for CAD events.

Atherogenic diet. Diet plays a complex role in atherogenic risk. Diets high in salt, fats, trans-fats, and carbohydrates have all been implicated.