Untitled Quiz

Antihypertensive Drugs

• Roger Carlo P. Pineda, RN, MD lectured
• Regie De JESUS, RN, PhDN provided slides
• This is a nursing lecture

Review of Blood Pressure

• Four variables influence blood flow and blood pressure:
  • Cardiac output
  • Compliance
  • Volume of blood
  • Resistance

Cardiac Output

• Cardiac output is the measurement of blood flow from the heart through the ventricles
• Measured in liters per minute
• Factors that increase cardiac output (elevate heart rate/stroke volume/both) elevate blood pressure and promote blood flow
• Increased by:
  • Sympathetic stimulation
  • Thyroid hormones
  • Increased calcium ion levels
• Decreased by:
  • Parasympathetic stimulation
  • Elevated or decreased potassium ion levels
  • Decreased calcium levels
  • Anoxia
  • Acidosis

Compliance

• Compliance is the ability of a compartment to expand to accommodate increased content
• Metal pipe is not compliant, balloon is
• Greater the compliance of artery, more effectively it expands to accommodate surges in blood flow without increased resistance or blood pressure

Blood Volume

• Relationship between blood volume, blood pressure, and blood flow is intuitive
• Decrease in blood volume decreases pressure and flow
• Increase in blood volume increases pressure and flow

Resistance

• Blood viscosity is the thickness of fluids affecting their ability to flow
• Blood viscosity is directly proportional to resistance and inversely proportional to flow.
• Conditions that cause viscosity to increase also increase resistance and decrease flow
• Blood vessel length is proportional to its resistance: longer the vessel, greater the resistance, lower the flow
• Blood vessel diameter inversely proportional to resistance
• Vessel diameter change through the body in different types of vessels with vascular tone reflecting contractile state of smooth muscle
• Greater the blood vessel diameter, the less blood contacts vessel wall (lower friction), lower resistance, thus increasing flow

A. Baroceptors (Pressure Receptors)

• Specialized cells in the arch of the aorta and other tissues
• Sensory input from baroreceptors received in the medulla (vasomotor center)
• High pressure stimulates medulla to cause vasodilation, decrease in cardiac rate and output

B. Renin-Angiotensin-Aldosterone System (RAAS)

• Drop in blood pressure/fluid volume releases renin from the kidney
• Renin acts on angiotensinogen in the liver to form angiotensin I
• ACE (enzyme) from the lungs converts angiotensin I to angiotensin II
• Angiotensin II acts on the adrenal gland to release aldosterone
• Aldosterone acts on kidneys to stimulate reabsorption of salt (NaCl) and water (H₂O)

Types of Hypertension

• 1. Essential Hypertension (Primary):
  • Ninety percent of cases have no known cause
  • Elevated total peripheral resistance
  • Organs perfused effectively and no symptoms ("Silent Killer")
• 2. Secondary Hypertension:
  • Elevated blood pressure due to a known cause
  • E.g., tumor in the adrenal medulla (pheochromocytoma) causes high amount of catecholamine release, greatly increasing blood pressure

Blood Pressure Categories

• This section presents categories of blood pressure measurements (systolic and diastolic in mm Hg) for normal, elevated, high blood pressure (stage 1 & 2), and hypertensive crisis.

Antihypertensive Drugs (List)

• Angiotensin-converting enzymes inhibitors (ACE Inhibitors)
• Angiotensin II-Receptor Blockers (ARBs)
• Renin Inhibitors
• Calcium-Channel Blockers
• Vasodilators
• Diuretic Agents
• Sympathetic Nervous System Blockers

A. Angiotensin-converting enzymes inhibitors (ACE Inhibitors)

• Antihypertensive agents that act in the lungs
• Prevent conversion of angiotensin I into angiotensin II (potent vasoconstrictor)
• Decrease blood pressure with associated loss of serum sodium and fluid but with a slight increase in serum potassium
• Generic examples: benazepril, captopril, enalapril, lisinopril, quinapril, fosinopril, ramipril, etc.
• Indications: hypertension, diabetic nephropathy
• Not allowed during pregnancy
• Older adults: Renal and hepatic function monitored
• Adverse effects: GI irritations, ulcer, constipation, liver injury; GU: renal insufficiency, renal failure, proteinuria; CV: reflex tachycardia, chest pain, heart failure, cardiac arrhythmias (from HYPERKALEMIA); EENT: rash, alopecia, dermatitis, photosensitivity; Captopril associated with sometimes-fatal pancytopenia, cough, and GI distress
• Nursing considerations: Educate patient on healthy lifestyle, administer drug on empty stomach (1 hr before/2 hrs after meal), monitor for manifestations of decreased fluid volume (hypotensive effects)

B. Angiotensin II-Receptor Blockers (ARBs)

• Antihypertensive agents that block vasoconstriction and aldosterone release
• Block angiotensin II receptors in vascular smooth muscles and adrenal cortex
• Generic examples: azilsartan, candesartan, eprosartan, irbesartan, losartan, olmesartan, telmisartan, valsartan
• Indications: hypertension, heart failure in patients who do not respond to ACE inhibitors, slow progress of renal disease in patients with type 2 diabetes and hypertension
• Not allowed during pregnancy
• Older adults: Renal and hepatic function monitored
• Adverse effects: CNS: headache, dizziness, syncope, weakness; Respiratory: URTI symptoms, cough; GI: diarrhea, abdominal pain, nausea, dry mouth, tooth pain; EENT: rash, alopecia, dry skin
• Nursing considerations: Healthy lifestyle choices, administer with food, monitor for manifestations of decreased fluid volume (hypotensive effects), comfort measures

C. Renin Inhibitors

• A new drug (Aliskiren, Tekturna) released in 2007 inhibits renin and the conversion of angiotensinogen to angiotensin I
• This stops the renin-angiotensin-aldosterone system causing decreased blood pressure, decreased aldosterone release, decreased sodium reabsorption

D. Calcium-Channel Blockers

• Inhibit calcium ion movement across myocardial and arterial muscle cell membranes
• Resulting in altered action potentials and blocked cell contractions
• Resultant effects: depressed myocardial contractility, slow cardiac impulse, arterial dilation, relaxation
• Effective in angina treatment as decrease cardiac workload
• Indications: Hypertension, used alone or in combination, extended-release preparations for adults, children (first considered drug group in hypertension cases)
• Not allowed during pregnancy for adults
• Older adults: Renal and hepatic function monitored
• Adverse reactions: CNS: headache, dizziness, light-headedness, fatigue; CV: hypotension, bradycardia, peripheral edema, heart block; GI: nausea, hepatic injury; EENT: rash, skin flushing
• Generic names: amlodipine, felodipine, nifedipine, nicardipine, diltiazem, verapamil
• Nursing considerations: Healthy lifestyle, monitor blood pressure & heart rate/rhythm, comfort measures

E. Vasodilators

• Act directly on smooth muscles causing muscle relaxation and vasodilation (drops blood pressure)
• Used in severe hypertension and hypertensive emergencies
• Generic examples: hydralazine, minoxidil, nitropruisside
• Indications: hypertension that do not respond to other drug therapies, maintain controlled hypotension during surgery
• Adverse effects: CNS: headache, dizziness, anxiety; GI: nausea, vomiting, GI upset; EENT: rash, lesions (e.g., minoxidil causing abnormal hair growth); Cyanide toxicity from nitroprusside characterized by dyspnea, and other symptoms
• Nursing considerations: Healthy lifestyle choices, monitor blood pressure/heart rate/rhythm, comfort measures

F. Diuretic Agents

• Drugs that increase sodium and water excretion from the kidneys
• Often the first line of treatment for mild hypertension (e.g., Thiazide and Loop)
• Other uses include managing edema and glaucoma
• Five classes: Thiazide, Loop, Carbonic Anhydrase Inhibitors, Potassium Sparing, Osmotic
• Detailed information on each class

G. Sympathetic Nervous System Blockers

• Block many compensatory effects of the sympathetic nervous system
• Classes:
  • Beta-blockers (selective & non-selective)
  • Alpha-1 Blockers (Alpha-1 Adrenergic Blockers)/Alpha- Blockers (Alpha-2 Adrenergic Blockers)/Centrally Acting Adrenergic Drugs (i.e., Alpha2-agonists)
• Detailed information on each block class