Blood Flow & Cardiac Output

Blood Flow Through the Heart

• Blood flow starts with the superior vena cava (from the upper body) and the inferior vena cava (from the lower body)
• Both empty into the right atrium
• Blood then flows from the right atrium through the tricuspid valve into the right ventricle
• Blood goes from the right ventricle through the pulmonary valve into the pulmonary artery
• Blood arrives in the left pulmonary veins and right pulmonary veins from the lungs
• Blood goes from the left atrium through the mitral valve into the left ventricle
• Blood travels from the left ventricle, through the aortic valve and into the aorta

Mechanical System

• Systole is the contraction of the myocardium
• Diastole is the relaxation of the myocardium
• Cardiac output refers to the amount of blood pumped by each ventricle in one minute
• CO = SV (stroke volume) x HR (heart rate)

Factors Influencing Blood Pressure

• Blood Pressure = Cardiac Output x Systemic Vascular Resistance
• Systemic Vascular Resistance is influenced by dilation of blood vessels
• Cardiac Output refers to the amount of blood pumping through the heart

Evidence Based Guidelines for Blood Pressure Management

• Blood pressure measurements are based on four stages: normal, elevated, Stage 1, Stage 2, and Hypertensive Crisis
• Elevated systolic blood pressure (SBP) has strong associations with heart failure, stroke, and renal failure
• Lifestyle modifications may be required to prevent cardiovascular disease
• Thiazide-type diuretics may be the initial drug therapy for most patients with hypertension; reduces volume of blood being pumped

Etiology of Hypertension

• Elevated blood pressure without an identified cause refers to primary (essential/idiopathic) hypertension
• 90% to 95% of all cases of hypertension are primary
• Factors that contribute to hypertension can include increased sodium-retaining hormones and vasoconstrictors, diabetes mellitus, > ideal body weight, increased sodium intake and excessive alcohol intake
• Elevated blood pressure with a specific cause is considered secondary hypertension
• Secondary hypertension accounts for 5% to 10% of adult cases
• Secondary hypertension contributing factors can include coarctation of the aorta, renal disease, endocrine disorders, neurologic disorders, cirrhosis and sleep apnea

Risk Factors for Primary Hypertension

• Risk factors can include with vessels becoming more rigid with age, alcohol use, cigarette smoking, and diabetes mellitus
• Elevated serum lipids, excess dietary sodium, gender, family history, obesity, ethnicity, sedentary lifestyle, socioeconomic status and stress can contribute to primary hypertension

Pathophysiology of Primary Hypertension

• Genetic factors make only little contribution to BP in the population
• Stress and increased SNS activity produce vasoconstriction, increase heart rate, and increase Renin release
• High sodium intake may activate pressor mechanisms, resulting in water retention
• Conditions like obesity, increasing age, and African American ethnicity can cause salt sensitivity
• High Insulin concentration stimulates SNS activity, impairs nitric oxide-mediated vasodilation and results in elevated blood pressure

Hypertension Clinical Manifestations

• Development is insidious because patients are frequently asymptomatic until target organ disease occurs
• Symptoms may be secondary to target organ diseases, and can include fatigue, reduced activity tolerance, dizziness, palpitations, angina and dyspnea.

Hypertension Complications

• Target organ diseases occur most frequently in the heart, brain, peripheral vasculature, kidneys and eyes
• Kidney failure from hypertension preserves blood flow to heart and brain
• Hypertensive heart disease is a complication
• Coronary artery disease, left ventricular hypertrophy (thickening/growing muscle)
• Heart failure

Hypertension Collaborative Care

• Overall goals include controlling blood pressure and reduce CVD risk factors
• Drug therapy is the primary mechanism of action of drugs to treat hypertension
• Goals for drug therapy: reduce SVR and reduce volume of circulating blood

Antihypertensive Drugs

• Categories include diuretics, adrenergic drugs, angiotensin converting enzyme (ACE) inhibitors, angiotensin II receptor blockers (ARBs), calcium channel blockers (CCBs), direct renin inhibitors and vasodilators

Diuretics

• Decrease plasma and extracellular fluid volumes
• This results in decreased preload, cardiac output, and total peripheral resistance
• Overall effect is decreased workload of the heart, and decreased blood pressure

Thiazide Diuretics

• Hydrochlorothiazide is the prototype
• It is the first line treatment for hypertension
• Thiazide has a mechanism of action at the site of action on distal convoluted tubule of kidney
• It inhibits the reabsorption of sodium, potassium and chloride and results in osmotic water loss
• Directly relaxes the small blood vessels which reduces peripheral vascular resistance (afterload)
• Indications can include heart failure, hypertension, edema, hypercalciuria and diabetes insipidus
• Contraindications include drug allergy, anuria, and renal failure
• Adverse effects of Thiazides include;
  • CNS: Dizziness, headache, blurred vision and paresthesia
  • GI: Anorexia, nausea, vomiting, diarrhea, pancreatitis, cholecystitis
  • GU: Decreased libido and impotence
  • Hematologic: Jaundice, leukopenia, purpura, thrombocytopenia
  • Integumentary: Urticaria, photosensitivity
  • Metabolic: Hypokalemia, glycosuria, hyperglycemia, hyperuricemia
• Overdose of Thiazides can lead to severe hypokalemia with symptoms such as lethargy, muscle weakness, confusion and severe hypotension

Adrenergic Drugs

• Binds to adrenergic receptors, but inhibit (block stimulation) of the sympathetic nervous system (SNS)
• Inhibits or lyses sympathetic stimulation
• Alpha-blockers and beta-blockers are types of drugs that block adrenergic receptors
• Classified by the type of adrenergic receptor they block
  • Alpha1 and alpha2 receptors target cardiac muscles
  • Beta1 and beta2 receptors

Centrally Acting Alpha₂ Agonists

• Clonidine (Catapres) is the prototype
• Other medications include methyldopa (Aldomet)
• Centrally acting alpha2 agonists stimulate alpha2-adrenergic receptors in the brain and decrease sympathetic outflow from the CNS
• Decreases norepinephrine production, and stimulate alpha2-adrenergic receptors
• Reduces Renin activity in the kidneys
• Decrease causes a reduction in blood pressure
• Indications can include hypertension and clonidine is useful in the management of withdrawal symptoms in opioid- or nicotine-dependent persons
• Can be used for hypertension in pregnancy with Methyldopa
• Contraindications in patients who have had stroke, recent MI, major depressive disorder and chronic renal failure
• Adverse effects/side effects can include Drowsiness, dry mouth and rebound hypertension
• Nursing administration includes being administered by oral, transdermal and epidural routes
• Medication is often administered twice daily, patients may take a larger dose at bedtime
• Transdermal patches are applied every seven days

Peripherally Acting Alpha₁ Blockers

• Doxazosin mesylate (Cardura) and terazosin (Hytrin) are used to treat hypertension
• Action blocks alpha1-adrenergic receptors that cause vasoconstriction
• Both arterial and venous dilation, reduces peripheral vascular resistance and blood pressure
• Final results in decreased blood pressure
• Tamsulosin (Flomax), has an effect on alpha1 receptors that relieve urinary obstruction and effects of BPH
• Contraindications include hypotension, angina and renal insufficiency;
• The first dose is often given at night
• Safety measures must be taught to patients

Alpha-Blockers: Adverse Effects

• Cardiovascular: Palpitations, orthostatic hypotension, chest pain, tachycardia, edema, dysrhythmias, hypotension or bradycardia
• CNS: Dizziness, headache, drowsiness, anxiety, depression, vertigo, weakness, numbness, fatigue
• Gastrointestinal: Nausea, vomiting, diarrhea, constipation, abdominal pain
• Other: Incontinence, nosebleeds, tinnitus, dry mouth, pharyngitis, rhinitis

Adrenergic Drugs Beta-Blockers

• Blocks stimulation of beta receptors in the SNS
• Competes with norepinephrine and epinephrine
• Can be selective or nonselective
• Nonselective beta-blockers block both beta₁ and beta2 receptors

Beta Receptors

• Beta1 receptors are located primarily on the heart
• Beta-blockers selective for these receptors are called cardioselective beta-blockers
• Beta2 receptors are located primarily on smooth muscle of bronchio and blood vessels

Beta-Blocker Mechanisms

• Reduce BP by reducing heart rate through beta1-blockade, which causes reduced secretion of renin
• Long-term use causes reduced peripheral vascular resistance

Beta Blocker Types

• Cardioselective (Beta 1) reduce SNS stimulation of the heart, decrease heart rate, prolong SA node recovery, slow conduction rate through the AV node and decrease myocardial contractility, reducing myocardial oxygen demand
• Non-selective (Beta 1 and 2) cause the same effects on heart as cardio selective beta-blockers
• Can also constrict bronchioles (resulting in airway narrowing and shortness of breath) and produce vasoconstriction of blood vessels through smooth muscle, and reduce heart rate owing to β1-blockade

Beta-Blocker Indications

• Can be used to treat angina as they decrease demand for myocardial oxygen
• Cardioprotective properties: inhibits stimulation from circulating catecholamines and reduces risk of post MI cardiac arrest
• Also used for dysrhythmias, migraine headaches, are antihypertensive, can treat heart failure and glaucoma (topical use)

Beta-Blocker Examples

• Carvedilol (Coreg)
• Labetalol (Normodyne)
• Metoprolol (Lopressor)
• Atenolol (Tenormin)
• Esmolol (Brevibloc)
• Propranolol (Inderal)

Beta Blocker Adverse Effects

• Blood includes thrombocytopenia.
• Cardiovascular: AV (heart) block, bradycardia (slowing heart rate), heart failure, peripheral vascular insufficiency
• CNS: Dizziness, mental depression, excitability decreases, lethargy, hallucinations, unusual dreams
• Gastrointestinal: Nausea, dry mouth, vomiting, diarrhea, cramps, ischemic colitis
• Other: Impotence, rash, alopecia, bronchospasm

Beta-Blocking Drugs: Nursing Implications

• Rebound hypertension or chest pain may occur if this medication is discontinued abruptly
• Tell patients to notify their physician if they become ill and unable to take medication
• Inform patients that they may notice a decrease in tolerance for exercise (dizziness and fainting with increased activity), notify physician if these problems occur
• Inform patients to report the following to their physician: weight gain of more than 2 pounds in 1 day or 5 pounds in 1 week (due to fluid shifting), edema of the feet or ankles, shortness of breath, excessive fatigue or weakness and syncope or dizziness.

Adrenergic Drugs: Summary of Adverse Effects

• High incidence of orthostatic hypotension often presents
• Can cause dry mouth, drowsiness, (CNS effect) sedation and constipation
• Can cause headaches, sleep disturbances, nausea, rash (allergy), cardiac disturbances (palpitations).

Adrenergic-Blocking Drugs: Nursing Implications

• Assess for allergies and history of COPD, hypotension, cardiac dysrhythmias, bradycardia or heart failure
• Assess conditions that may be contraindicated during the use of the medication
• Alpha-blockers and Beta-blockers can precipitate: bradycardia, hypotension, heart block, heart failure and bronchoconstriction
• Avoid over-the-counter medications because of possible interactions, especially those that Many trigger sympathetic nenous system
• Possible drug interactions may occur with: antacids (aluminum hydroxide type), antimuscarinics/anticholinergics, diuretics and cardiovascular drugs, neuromuscular blocking drugs and oral hypoglycemic drugs
• Teach patients to change positions slowly to prevent or minimize postural hypotension
• Instruct patients to avoid caffeine/stimulants (excessive irritability) and alcohol ingestion
• Patients should instruct their physician if palpitations, dyspnea, nausea, or vomiting occurs
• Monitor for therapeutic effects such as blood pressure and heart rate control

Angiotensin Converting Enzymes (ACE) Inhibitors

• Large group of drugs often used as a first-line treatment for HF and hypertension
• May be combined with a thiazide diuretic or calcium channel blocker
• Blocks angiotensin-converting enzyme, thus preventing the formation of angiotensin II
• this Action works on angiotensin I to prevent angiotensin II
• Prevents the breakdown of the vasodilating substance, bradykinin
• Result is decreased systemic vascular resistance (afterload), vasodilation, and decreased blood pressure
• Captopril has a very short half life
• Indications can include hypertension and heart failure
• Slows the progression of left ventricular hypertrophy after MI cardioprotective
• Renal protective effects in patients with diabetes, an extends life of kidneys
• Drugs of choice for hypertensive patients with Heart failure and also Diabetic patients
• Adverse effects can include fatigue, dizziness, headache mood changes, and impaired taste
• Possible hyperkalemia
• Can cause a Dry, nonproductive cough, which reverses when therapy is stopped, or rarely, angioedema
• Administered orally, except for enalaprilat (Vasotec IV)
• May contain an additional ACE inhibitor hydrochlorothiazide
• Advise providers if cough, rash, sign of infection are present
• Can cause first dose orthostatic hypotension
• Monitor for potassium levels

Angiotensin II Receptor Blockers (ARBS)

• Mechanism of Action: Angiotensin I is converted to angiotensin II, but the receptors that receive angiotensin II are blocked
• Blocks vasoconstriction and release of aldosterone
• Indications include hypertension and stroke prevention
• Adjunctive drugs are appropriate for treatment of heart failure
• Often used alone or with other drugs like diuretics, and primarily is prescribed when other ACE inhibitors cannot be tolerated
• Adverse effects include upper respiratory infections and headaches
• Hyperkalemia is rare
• Nursing Administration:
  • Orally administered
  • May be combined with hydrochlorothiazide
  • Can be taken with or without food
  • Doesn't preserve kidneys or the heart

Calcium Channel Blockers

• Verapamil, diltiazem, nifedipine, amlodipine, felodipine, and nicardipine are CCBs
• Action causes smooth muscle relaxation by blocking the binding of calcium to its receptors, preventing muscle contraction
• Decreases blood pressure
• Reduces peripheral smooth muscle tone and systemic vascular resistance
• Indications include hypertension, dysrhythmias, angina and migraine headaches, and Raynaud's disease
• Adverse effects include;
  • Cardiovascular: Hypotension, palpitations, tachycardia
  • Gastrointestinal: Constipation, nausea
  • Other: rash, flushing, peripheral edema
• Administration involves not chewing or crushing extended release tablets
• IV administration of verapamil should be over 2 to 3 minutes
• Blood pressure and chest pain must be monitored

Direct Renin Inhibitors

• Aliskiren is an example, and binds with renin to inhibit production of angiotensin I
• Decreases production of both angiotensin II and aldosterone
• Primary indication is to treat hypertension
• Adverse effects include allergic reaction, hyperkalemia, and diarrhea
• Contraindications include pregnancy risk in the second and third trimesters
• High fat meals interfere with absorption
• May be taken alone or in combination with other medications

Vasodilators

• Primary indication is to treat hypertension
• May be used in combination with other drugs, such as hydralazine HCI or minoxidil
• Sodium nitroprusside and intravenous diazoxide are reserved for hypertensive emergencies
• Action directly relax arteriolar and/or venous smooth muscle
• Results in decreased systemic vascular response, decreased afterload, and peripheral vasodilation
• Patients with an allergy to the medication, hypotension, or cerebral edema shouldn't take
• Vasodilators also shouldn't be taken when head injury, acute MI, Coronary Artery Disease, or Heart Failure is present
• Adverse effects of hydralazine include dizziness, headache, anxiety, Tachycardia (compensates for hypotension), nausea/vomiting, diarrhea, anemia, dyspnea, edema or Nasal congestion
• Sodium nitroprusside can cause Bradycardia, and hypotension, as well as delirium and possible cyanide toxicity
• Main symptom of toxicity: Hypotension
• Treatment: Trendelenburg position to Support blood flow to head, supportive and Symptomatic treatment, IV fluids, Sympathomimetics such dopamine and norepinephrine usage to increase BP

SDOH

• Includes low education, low SES, poverty, poor neighborhoods, diet high in processed foods, stressful environments and alcohol use, smoking, and lack of physical activity
• 36% of adults in Monroe County have HTN
• 14605 is the poorest zip code in Rochester
• Metropolol (generic) - $5 per month, Hydrochlorothiazide - $17 per month, Captopril - $23 per month, Verapamil - $10 per month

Nursing Implications

• Before beginning therapy, obtain a thorough health history and head-to-toe physical examination.
• Assess for contraindications to specific antihypertensive drugs and assess for conditions that require cautious use of these drugs
• Educate patients about the importance of not missing a dose and taking the medications exactly as prescribed. Patients should never double up on doses if a dose is missed instead
• Check with their physician for instructions
• Monitor BP during therapy instruct patients to keep a journal of regular BP checks
• Instruct patients that oral forms should be given with meals so that absorption is more gradual and effective
• Administer IV forms with extreme caution and use an IV pump
• Recommend that patients avoid smoking and eating foods high in sodium, and encourage supervised exercise
• Teach patients to change positions slowly to avoid syncope from postural hypotension

Additional Nursing Implications

• Patients should report unusual shortness of breath
• Inform providers about swelling of the feet, ankles, face, or around the eyes and weight gain or loss
• Tell of any chest pain, palpitations, or excessive fatigue
• Tell male patients who take alpha blockers that not be aware that impotence is a potential side effect that may influence compliance with drug therapy
• When a patient needs to have their dose is changed notify their physician immediately
• Educate against the use of hot tubs, showers, or baths, hot weather and prolonged sitting or standing
• Remind that physical exercise, alcohol ingestion may aggravate low blood pressure and to call for help when fainting
• Encourage that they sit or lie down until symptoms subside.
• Patients should not take any other any other non prescribed medications
• Remind patients the importance of: Weight loss, Stress management, Supervised exercise, and Dietary measures

Further Nursing Implications For Treating Hypertension

• Monitor for adverse effects
  • Dizziness
  • Orthostatic hypotension
  • Fatigue
  • Toxic effects
• Monitor for therapeutic effects related to less than
• 130/90 mm Hg
• Treat symptoms to help better manage diabetes
• Lower to less than 130/80 mm Hg [JNC - 7]

Gerontologic and Cultural Considerations

• Age alters the cardiovascular response to physical and emotional stress due to thickening and stiffening of the heart valves
• Frequent need frequent need for pacemakers
• Older adults are also less sensitive toB-adrenergic agonist drugs
• There is typically and increase in SBP, decrease or no change in DBP levels
• Beta-blockers and ACE inhibitors have been found to be more effective in white patients compared to African American patients
• CCBs and diuretics have proven to be more effective in African American patients compared to white patients