Disorders of Blood Flow and Blood Pressure Flashcards
What are the Characteristics for Normal Blood Flow?
Hemodynamics and the biology of the cells that form the blood vessels need to be considered when thinking about blood flow.
Blood vessels that are open and unobstructed.
Blood pressure that is forceful enough to circulate blood to all tissues.
What is hemodynamics?
Mechanics of blood movement.
What is Laminar blood flow?
Blood flow is fastest in the middle of the stream.
Blood flow is slowest at the outer edge.
Slower blood flow promotes clotting.
What is the most important thing in determining blood flow?
Vessel radius
What are abnormalities of blood flow caused by?
Abnormal changes in blood vessels – atherosclerosis, vasculitis
Abnormal vessel dilation – aneurysms, varicose veins
Acute vessel obstruction – vasospasm, thrombus, extravascular force
What are endothelial cells?
Continuous innermost lining of blood vessels and with a semipermeable membrane.
The production or release of vasoactive substances are in response to…
Cytokines, bacteria, virus, parasites
Changes in blood flow and/or pressure
Level of lipids circulating in blood
What plays a major role in inflammation and immune reactions?
Vessel relaxation – nitric oxide - Hypotension (vasodilation)
Vessel contraction – endothelins - Hypertension (vasoconstriction)
Normally, these substances together balance for normal blood pressure.
What is Vascular Smooth Muscle Cells?
Major cell layer of tunica media (middle layer of vessels)
What is the function of Vascular Smooth Muscle Cells?
Constriction and dilation function.
What is Vascular Smooth Muscle Cells controlled by?
Controlled by sympathetic nerves that release norepinephrine
- Norepinephrine constricts blood vessels (raised BP)
How can Vascular Smooth Muscle Cells become harmful when being constricted?
Constriction decreases vessel/radius and increases circulating volume to a point BUT there can become a tipping point at which vasoconstriction will cause decreased blood supply to tissue.
Too much constriction = Harmful
What is arterial blood flow disorder?
Blood flow is pumped from the heart’s left ventricle and through the aorta into the circulation
EX: Atherosclerosis is a common cause of abnormal blood flow and can include hyperlipidemia (elevated cholesterol), blood flow obstruction, and loss of circulating volume
What is venous blood flow disorder?
Blood flow is generated from the venules and returns into the heart’s right atrium
EX: Impaired outflow of blood from tissues or organs causes an organ to become enlarged
EX: Back up of venous blood in organs/tissues causes impaired removal of wastes from cellular metabolism
What is Atherosclerosis?
A slow developing process involving inflammation within the endothelium
- Homocysteine and C reactive protein are elevated with inflammation and contribute to atherosclerosis risk.
What are the mechanisms of Atherosclerosis?
Vessel narrowing leading to ischemia
Sudden vessel obstruction due to plaque rupture or embolization
Aneurysm due to vessel weakening
What is Atherosclerosis made up of?
Fatty streak
Fibrous plaque
Complicated lesion
What are the etiology/risk factors for Atherosclerosis?
Hypercholesterolemia
Cigarette smoking
BP > 139/89
Increasing age
Family history of premature coronary artery disease:
- Male younger than 55
- Female younger than 45
Male sex
Postmenopausal female (due to decrease in estrogen)
What results from an arterial circulation disorder?
Ischemia and Infarction
What is ischemia?
Decreased blood supply
Inadequate oxygen, nutrients to support cellular metabolism
Impaired removal of end products of metabolism such as lactic acid
What is infarction?
Necrosis of tissue due to inadequate arterial supply and/or venous drainage
What is Acute Arterial Occlusion?
Acute arterial occlusion can be due to atherosclerosis buildup, a sudden clot, and/or spasms within an artery.
What are some clinical manifestations of Acute Arterial Occlusion?
The 7 P’s:
-Pistol shot
-Pallor
-Paresthesia
-Paralysis
-Pulselessness
-Polar
-Pain –Permanent tissue loss may already be possible.
What is an aneurysm?
Abnormal dilation of blood vessel.
More common in arteries than veins.
Aorta is the most common site.
Cause linked to gene mutation.
What are some clinical manifestations in an aortic aneurysm?
May be asymptomatic
Rupture may be 1st sign
Edema – jugular veins, face, neck
Localized pain due to pressure on associated tissues/structures:
-Acute myocardial infarction
-Bowel infarction
-Acute renal failure
-Acute paralysis from impaired blood flow to spinal cord
How can venous disorders be described?
Blood drainage from tissues returns to the heart through veins.
Low pressure system using skeletal muscle pump to help move blood back into heart.
Backup of blood in veins promotes clotting.
What are the alterations in venous blood flow?
Valve incompetence
Varicosities
Chronic venous insufficiency
Deep vein thrombosis
What are some etiologies of DVT?
Venous stasis:
- Immobility
- Unconscious client
Pregnancy
Obesity
Smoking
Oral contraceptives
Hypercoagulability
Cancer
Prolonged air travel
Inherited clotting disorder
Trauma to a vein (s)
What are the clinical manifestations of DVT?
Skin reddened.
Skin warm, hot.
Localized edema.
Pain in the calf and/or nearby area.
Pedal pulse is present and palpable because clot is in a vein, not in an artery that generates a pulse.
What are some complications with DVT?
Pulmonary embolism
- Sudden dyspnea
- Chest pain
- Low arterial oxygen by blood gas
- Low O2 saturation by blood gas or pulse oximetry
- High mortality
What is blood pressure?
Blood pressure is the pressure of blood pushing against the walls of your arteries. Arteries carry blood from your heart to other parts of your body.
What determines blood pressure?
The volume of blood in the vessels
Elasticity of blood vessels
Cardiac output
Cardiac contractility
Systemic vascular resistance
Vessel radius – dilation versus constriction or obstruction
How can we control BP with humoral control?
Renin-angiotensin-aldosterone system
Antidiuretic hormone (ADH) also called (vasopressin)
Epinephrine
How can we control BP with neural control?
Intrinsic reflexes
- Baroreceptors, chemoreceptors
Extrinsic reflexes
- Sensory receptors
(Pain, cold, Mood, emotions)
How is renal control of BP explained?
Decrease in arterial pressure by increased heart rate and/or increased vasoconstriction leads to decrease in blood flow into kidneys.
Change in neural-humoral control of BP can alter the diuresis-natriuresis balance to increase arterial pressure.
What is the break down of Renin-angiotensin-aldosterone system (RAAS)?
Renin – enzyme from kidneys
Angiotensinogen – circulating plasma protein
Angiotensin I
- Angiotensin-converting enzyme works in lung endothelium
Angiotensin II –potent vasoconstrictor
- Promotes sodium reabsorption by kidneys
- Stimulates release of aldosterone by adrenals
Antidiuretic Hormone
- Stimulates water reabsorption by kidneys
- Constricts arterial vessels, especially splanchnic (gastrointestinal) circulation
How does blood vessel diameter alter systemic vascular resistance?
Increases upon constriction.
Decreases upon dilation.
What is cardiac output?
Amount of blood ejected from heart each minute measured in liters/minute.
Cardiac Output = Heart Rate x Stroke Volume
Average Stroke Volume in adult = 80 milliliters
What is Primary hypertension?
Essential, Idiopathic
What is Secondary hypertension?
Occurs as effect of another underlying condition
Can be temporary if primary problem resolves
What is Hypotension?
Orthostatic
Shock
People with diabetes or chronic kidney disease should keep their blood pressure below what number?
130/80
What is the cause of primary hypertension?
Constitutional
- Increasing age
- Family history
- Insulin resistance – Type 2 diabetes mellitus
Lifestyle
- Excess calories, sodium, alcohol intake
- Inadequate potassium intake
What are the leading theories for primary HTN?
Heredity
Increased water & sodium retention
Insulin resistance/Hyperinsulinemia
Altered renin-angiotensin-aldosterone activity
Endothelial cell dysfunction
What are the components of sodium and water retention?
Excessive sodium intake
Possible activation of vasopressors
Hypertension can decrease with sodium restriction
What is Insulin Resistance / Hyperinsulinemia?
Abnormal metabolism of insulin, glucose, and lipoproteins with primary hypertension
Increased insulin level stimulates sympathetic nervous system and decreases vasodilation directed by nitric oxide
What is Endothelial Cell Dysfunction?
Endothelium produces many vasoactive substances
Not all substances and their functions identified
Possible role in hypertension development
What is the Altered Renin-Angiotensin Aldosterone System?
Hypertension normally inhibits kidney renin production.
Some people with hypertension have low renin.
Renin-angiotension mechanisms are altered.
Angiotension II is a highly potent vasoconstrictor.
What are symptoms of primary hypertension?
Symptoms are usually absent until target organ damage has occurred, therefore there are no symptoms of primary hypertension.
How does hypertension cause cardiac issues?
Heart workload is increased and leads to left ventricular hypertrophy.
Heart must pump harder against increased resistance in blood vessels and or heart valves.
Myocardial oxygen demand is increased.
What is secondary hypertension not a cause of?
Secondary hypertension is NOT a condition that occurs because primary hypertension was not “fixed”.
It is NOT a complication of primary hypertension.
What is secondary hypertension the cause of?
It IS related to an underlying disease, process, or medication:
- Renal disease – leading cause
- Pheochromacytoma
- Cushing’s syndrome
- Coarctation of aorta
- Brain tumors, brain injury
- Pregnancy
- Medications - Oral contraceptives are major risk > age 35
If the cause is removed/resolved, the secondary hypertension may be resolved.
How is pediatric primary hypertension explained?
Sedentary lifestyle
Excess calories
Excess salt
Obesity
How is pediatric secondary hypertension explained?
Remains most likely type of hypertension in pediatrics although primary hypertension increasing rapidly
About 80% related to kidney dysfunction
Coarctation of aorta
Endocrine disorders
Transplant medications
Drug abuse
What is Isolated Systolic Hypertension (ISH)?
SBP > 140 mm Hg
Diastolic < 90 mm Hg or within normal range
What are the etiologies of Isolated Systolic Hypertension (ISH)?
An expected anatomic age-related blood pressure elevation
Calcification of the great vessels and/or cardiac valves
Decreased vessel elasticity
What are the complications of Isolated Systolic Hypertension (ISH)?
Myocardial infarction
Cerebrovascular accident
Congestive heart failure
Caution – rapid lowering of BP can cause or worsen above conditions
What is Orthostatic Hypotension?
BP drops with posture elevation
What are the etiologies of Orthostatic Hypotension?
Medications side effects
Pregnancy
Starvation
Dehydration
Recent or prolonged immobility
What are the acute manifestations with Orthostatic Hypotension?
Dizziness
Syncope
Blurred vision
Sudden blindness
