Exam Review Week 2 Flashcards
What is normal BP?
systolic: under 120; diastolic: under 80
What is prehypertension?
systolic: 120-139; diastolic: 80-89
What is Stage 1 hypertension?
systolic: 140-159; diastolic: 90-99
What is Stage 2 hypertension?
systolic: 160+; diastolic: 100+
What is the % of patients with hypertension? Pre-hypertension?
30% prehypertension, 30% hypertension
What can hypertension lead to?
increased afterload, leading to heart failure, MI and myocardial ischemia; arterial damage and atherosclerosis, leading to aortic aneurysm and dissection, stroke, retinopathy, and nephrosclerosis and renal failure
How do you calculate BP?
BP = CO x TPR
What factors regulate CO?
filling pressure, heart rate, force of contraction
How does sodium retention affect CO?
retaining sodium means retaining fluid - volume goes u,p, causing filling pressure to go up and CO to increase
How does the sympathetic system affect CO?
increases HR, increases force of contraction
How does the parasympathetic system affect CO?
decreases HR
What increases vasoconstriction?
norepinephrine, angiotensin; these both increase vascular resistance
What decreases vasoconstriction?
nitric oxide - this decreases vascular resistance
What are the 2 major systems that regulate blood pressure?
- autonomic nervous system; 2. Renin-Angiotensin-Aldosterone System
How does the autonomic nervous system affect blood pressure?
Regulated through the brain, sympathetic nerves, and adrenal glands; Increases cardiac output and peripheral resistance; Increases renin release from the kidneys; Feedback loop by baroreceptors
How does the Renin-Angiotensin-Aldosterone System affect blood pressure?
Regulated through the kidney, blood stream, and adrenal glands; Increases sodium (and water) retention and peripheral resistance (increases BP); Feedback loop in kidney
How do the carotid and aortic arch baroreceptors work?
responsive to stretch - BP goes up, vessel stretches, baroreceptors notice (activation increases); if BP goes down, then there is less activation up the nerves pretty easy to palpate can be manipulated by MD b/c it’s a mechanical receptor
What is the reflex to acute bleeding?
Response of the baroreceptor reflex to acute hemorrhage. The reflex is initiated by a decrease in mean arterial pressure (Pa). The compensatory responses attempt to increase Pa back to normal. These responses include decreased stretch on baroreceptors, decreased firing rate of carotid sinus, decreased parasympathetic activity to the heart (and increased HR), and increased sympathetic activity to the heart and blood vessels.
How does standing affect BP?
Standing leads to pooling of blood in veins, decrease in arterial pressure, baroreceptor reflex, increase in sympathetic outflow, and therefore increase in arterial pressure toward normal
What are the steps of the Renin-Angiotensin-Aldosterone System?
Prorenin is in the Juxtaglomerular cells, renin is formed, released into plasma, Angiotensinogen, Angiotensin I, and then Angiotensin-converting Enzyme (from lungs, kidney) causes production of Angiotensin II
What is Angiotensin II?
Stimulates the synthesis/secretion of aldosterone in the adrenal cortex, and Aldosterone acts on renal distal tubule and collecting duct – increases Na+ reabsorption (increases ECF volume and blood volume, increases CO); leads to vasoconstriction in arterioles (increases TPR); directly stimulates Na+ - H+ exchange in renal proximal tubule and increases reabsorption of Na+ and HCO3- (increases CO); Increases thirst and water intake; stimulates antidiuretic hormone (increases water reabsorption in collecting ducts - increases CO; vasoconstriction – increases TPR)
What stimulates renin secretion?
Renin secretion is stimulated by decreased renal perfusion (sensed by mechanoreceptors), decreased Na+, also sympathetic activation
What is the difference in timing between the major systems that regulate pressure?
autonomic nervous system reacts in seconds to minutes, while renin-angiotensin-aldosterone system takes hours to days (even weeks!)
What other mechanisms (beside the major systems) can regulate BP?
- Chemoreceptors in Carotid and Aortic Bodies
- Central chemoreceptors
- Antidiuretic hormone
- Cardiopulmonary (Low-Pressure) Baroreceptors
How do chemoreceptors in aortic carotid bodies affect BP?
Affects sympathetic vasoconstrictor centers; Sensitive to decreases in PO2 and increases in CO2; Also, sensitive to decreases in pH (particularly when PO2 is decreased)
What do central chemoreceptors do to affect BP?
Medullary chemoreceptors are sensitive to changes in PCO2 or pH (less sensitive to changes in PO2); they affect changes in outflow of the medullary vascular centers; Ischemic brain causes PCO2 increases and pH decreases which causes sympathetic outflow increase leading to arteriolar vasoconstriction, which increases TPR
What is antidiuretic hormone?
Stimulated by angiotensin II; Also increased by increases in serum osmolarity; produced by posterior lobe of the pituitary gland; in V1 receptors (vascular smooth muscle) cause vasoconstriction (increased TPR); in V2 receptors (renal collecting ducts) cause increased water reabsorption
What are the cardiopulmonary baroreceptors?
found in veins, atria, and pulmonary artery; Increase in blood volume leads to increase in venous and atrial pressure and baroreceptor activation; increases atrial natriuretic peptide (ANP) secretion by atria - Relaxation of vascular smooth muscle causes vasodilation and decreased TPR. Also, vasodilation in the kidney leads to increased Na+ and water excretion; Decreases antidiuretic hormone
How do cardiopulmonary baroreceptors increase HR?
Information from atrial receptors travel in vagus nerve to the nucleus tractus solitarius (just like with high pressure baroreceptors); the response, however is different (the medullary cardiovascular center activation leads to heart rate increase – Bainbridge reflex); increases CO, increasing renal perfusion and Na+ and water excretion
What is the percentage of hypertension that is essential?
90% (unknown cause, potentially multifactorial)
How does BP change with age?
systolic increases and diastolic decreases (therefore pulse pressure increases); in youth, CO is most important for BP; as you age, TPR becomes more significant (likely due to stiffening)
What are the best drugs for congestive heart failure?
Diuretics, Vasoactive Drugs, Beta-blockers, Drugs that affect the RAAS (renin angiotensin-aldosterone system)
What are the best drugs for hypertension?
diuretics, adrenergic inhibitors, direct vasodilators (usually used in combination therapy), calcium channel blockers, RAAS blockers
What are types of drugs that affect the vasculature?
direct-acting vasodilators, nitrates and phosphodiesterase-5 inhibitors, calcium channel blockers, and adrenergic inhibitors
What are the Direct-Acting Vasodilators?
Hydralazine, Sodium nitroprusside; Minoxidil and Fenoldopam used less
What is Hydralazine?
Potent and direct arteriolar dilator –Acts at the level of the precapillary arterioles, has no effect on systemic veins; Cellular mechanism unknown; Arteriolar dilation results in fall in blood pressure, which leads to baroreceptor-mediated increase in sympathetic outflow (e.g. reflex tachycardia); used less often now
What are the contraindications for Hydralazine?
use with caution in patients with underlying CAD because could precipitate myocardial ischemia - Often combined with beta-blocker to blunt the reflex tachycardia response
When is Hydralazine particularly helpful?
Remains helpful in hypertensive patients with increasing creatinine (where want to avoid ACEi or ARB in the acute setting); Also used in combination with venodilator isosorbide dinitrate to treat systolic heart failure
What are the drawbacks of Hydralazine?
Low bioavailability - Extensive first pass hepatic metabolism and great variety of metabolizers; Short half-life (2-4 hours), although effect persists up to 12 hours since it binds avidly to vascular tissues
What are the side effects of Hydralazine?
Headache (increased cerebral vasodilation), Palpitations (secondary to reflex tachycardia), Flushing (increased systemic vasodilation), Nausea, Anorexia; NOTE: rare, but can cause Lupus like syndrome (especially in slow acetylators)
What is Minoxidil?
Arteriolar vasodilator – No significant venodilation; Mechanism of Action: Increase in potassium channel permeability leading to smooth muscle cell hyperpolarization and relaxation; used in Severe or refractory hypertension; Good, reliable GI absorption
What are the drawbacks of Minoxidil?
Can lead to reflex adrenergic stimulation and subsequent increased heart rate (like Hydralazine); Also can decrease renal perfusion, resulting in fluid retention – Attenuated with co-administration of a diuretic; Short half-life – Longer pharmacologic effects (binds avidly to vascular tissues); usually dosed once or twice per day
What are the side effects of Minoxidil?
Reflex tachycardia, Fluid retention, Hypertrichosis (excessive hair growth) - it’s the topical formulation in Rogaine; Pericardial effusion (rare)
What is Sodium Nitroprusside?
Potent “balanced” vasodilator – Acts on both arterioles and veins; Hemodynamic effect: Decrease arterial/systemic resistance, Increase venous capacitance; Sum of these effects depends on LV function –Normal LV function: decrease in cardiac output due to reduction in venous return –Reduced LV function: decreased systemic resistance (afterload) results in improved forward flow (cardiac output)
When should Sodium Nitroprusside be used?
Hypertensive emergency (Very potent, rapid action; often used with concurrent beta-blocker); Severe congestive heart failure
How is Sodium Nitroprusside used?
Administered by continuous IV infusion; Onset of action begins within 30 seconds and peak affect is achieved in 2 minutes; Effect wanes within minutes of discontinuation
What are the side effects/toxicities of Sodium Nitroprusside?
Risk of thiocyanate accumulation/toxicity (Clinically: blurred vision, tinnitus, disorientation, and/or nausea followed; Routine to monitor serum levels of thiocyanate if sodium nitroprusside is used for more than 24 hours; Higher risk of toxicity in the setting of renal impairment)
What is Fenoldopam?
Rapid acting potent arteriolar vasodilator; Maintains or enhances renal perfusion (unlike other IV antihypertensives) –Facilitates natriuresis via activation of renal tubular D1 receptors; Does not stimulate alpha- or beta-adrenergic receptors like Dopamine does
What is the mechanism of Fenoldopam?
Selective agonist of peripheral dopamine 1 (D1) receptors; Activation of D1 receptors results in arteriolar vasodilation via a cAMP-dependent pathway
How is Fenoldopam administered?
Continuous intravenous infusion –Rapid onset of action
(Achieves 50% of maximal effect within 15 minutes, reaches steady state in 30 to 60 minutes) AND Rapid offset of action (Elimination half-life less than 10 minutes)
What are the side effects of Fenoldopam?
Headache, Dizziness, tachycardia; Increased intraocular pressure by slowing aqueous humor drainage (therefore avoid in patients with history of glaucoma); NOTE: Does not cause thiocyanate toxicity
When are nitrates used?
–Angina pectoris
–Acute coronary syndromes
–Heart Failure
What is the nitrate mechanism of action?
Result in vascular smooth muscle relaxation
What are the hemodynamic effects of nitrates?
–Venodilation (Venous pooling, Diminished venous return, Decreased right sided filling, Decreased left sided filling)
–Systemic arterial resistance generally unaffected
–Cardiac output may fall secondary to decreased preload (especially in intravascular deplete or “preload sensitive” patients)
–At higher doses, arteriolar dilation (Coronary artery dilation)
Venodilation ultimately leads to decreased LV preload, lowers LV wall stress, causing decreased myocardial oxygen demand
What are the different kinds of nitrates?
Many formulations are available, and which one to use depends on clinical objective; In Acute Angina: sublingual nitroglycerin tablets or sprays (Peak action within 3 minutes (rapid absorption into blood stream via oral mucosa) and effect diminished after 15-30 minutes (deactivated in the liver), Can also be used prophylactically before situations that are known to precipitate angina; Chronic management of CAD: long-acting nitrates (sustained release formulations) include Oral (duration of action up to 14 hours), Isosorbide dinitrate, Isosorbide mononitrate, Transdermal patch or topical paste
What is unique about nitrate use?
Drug tolerance develops with continued use – Need for a “drug holiday” in order to avoid tachyphylaxis (some docs say take during the day but not overnight)
When is IV nitroglycerin used?
Most useful in the acute treatment of the hospitalized patient with unstable angina, pulmonary edema, or heart failure; Can be given with continuous administration
What are the side effects of nitroglycerin?
Hypotension, Reflex tachycardia, Headache, Flushing
What is Sildenafil?
Phosphodiesterase-5 Inhibitor; Decreases pulmonary vascular resistance in patients with pulmonary arterial hypertension, inhibits the breakdown of cGMP in the pulmonary vasculature, leads to enhancement of vasodilation (and oxygenation); also known as Viagra!
What are the contrandications for Sildenafil?
Cannot be used with nitrates (Can result in severe systemic hypotension)
What are calcium channel blockers?
Common property is ability to impede the influx of Ca++ through membrane channels in cardiac and smooth muscle cells
What are the 2 types of calcium channels in cardiac tissue?
- L-type channel (target of currently available CCBs) - Responsible for Ca++ entry that maintains phase 2 (“plateau”) of the action potential; 2. T-type channel - Plays a role in the initial depolarization of nodal tissues
How do calcium channel blockers work?
Decreases the concentration of intracellular Ca++ available to contractile proteins; In vascular smooth muscle cells: leads to vasodilation; in cardiac cells: leads to a negative inotropic effect
What are the 2 main groups of calcium channel blockers and what are their names?
Non-dihydropyridines (Verapamil, Diltiazem); Dihydropyridines (Amlodipine, Felodipine, Isradipine, Nicardipine, Nifedipine, Nisoldipine)