Cardiovascular System II Topics Antidysrhythmic Diuretics Antihypertensives Antidysrhythmic Cardiac Action Potential Please watch this video before class, to understand how antidysrhythmics work: https://www.youtube.com/watch?v=rIVCuC-Etc0 • Cardiac Action Potential has 5 phases • These phases define transient depolarization followed by repolarization: i.e., Cardiac Contractions • Caused by electrolyte transfer through cardiac muscle cell membrane Cardiac Action Potential Phase 0 • Rapid depolarization; influx Na+ Phase 1 • Initial repolarization; end Na+ influx Phase 2 • Plateau; influx Ca++; prolongs contraction Phase 3 • Rapid repolarization; efflux K+ Phase 4 • Resting membrane potential between heartbeats Dysrhythmia: Types (Refer to AE II lecture) • Atrial • Prevents proper filling of ventricles • Decreases cardiac output by 33% - how does it do that? • Ex: • atrial fibrillation (a-fib) • atrial flutter (a-flutter) • Ventricular • Life-threatening • Ineffective ventricular filling results in decreased or absent cardiac output • Ex: • premature ventricular complexes (PVCs) • ventricular tachycardia (v-tach) • ventricular fibrillation (v-fib) Antidysrhythmic: Pharmacodynamics • Block adrenergic stimulation of heart • Depress myocardial excitability & contractility • Decrease conduction velocity in cardiac tissue • Increase myocardial recovery time (repolarization) • Suppress automaticity (spontaneous depolarization to initiate beats) Note: Most Antidysrhythmics are also proarrhythmic and vasodilator Antidysrhythmic: Classes • Class I: Fast (Na+) Channel Blockers • IA: slows conduction, prolongs repolarization (procainamide) • IB: slows conduction, shortens repolarization (lidocaine) • IC: prolongs conduction w/ little/no effect on repolarization (flecainide) • Class II: Beta Blockers • Metoprolol • Esmolol • Sotalol • Class III: Prolongs repolarization • Amiodarone • Class IV: Slow (Ca+) Channel Blockers • Verapamil • Diltiazem Antidysrhythmic: Class IA Normal QT Interval: 0.34 to 0.34 seconds • Prototype: procainamide • MOA: depress action potential leading to slow conduction and prolonged repolarization • Uses: paroxysmal atrial tachycardia, supraventricular dysrhythmia • Adverse reactions: prolonged QT interval, bradycardia, heart blocks, hypotension, heart failure, torsade de pointes • FDA Warning: Agranulocytosis, bone marrow depression, neutropenia Torsade de pointes Antidysrhythmic: Class II • Prototype: metoprolol • MOA: blocks beta-adrenergic receptors, causing depression of phase 4 of the action potential. Slows the recovery of the cells, leading to slowing of conduction and automaticity. • Uses: ventricular (SVT) and atrial dysrhythmias (rapid a-fib etc.0 • Adverse reactions: bronchospasm (for non-selective), dyspnea, bradycardia, hypotension Antidysrhythmic: Class III • Prototype: amiodarone • MOA: unclear mechanism of action, results in prolonged repolarization and slowed rate and conduction of the heart • Uses: ventricular tachycardia/fibrillation, atrial flutter/fibrillation • Adverse reactions: hypotension, bradycardia, heart blocks, hypo/hyperthyroidism, hepatic dysfunction, peripheral neuropathy, bluegray discoloration of skin • Note: grapefruit juice inhibits enzymes in GI tract that metabolize amiodarone, concurrent use = ↑ levels of risk & toxicity • Drug interactions: quinidine, digoxin, increases blood level of warfarin, increased risk of QT prolongation w/ certain antibiotics From: Photodistribution of Blue-Gray Hyperpigmentation After Amiodarone Treatment: Molecular Characterization of Amiodarone in the Skin Arch Dermatol. 2008;144(1):92-96. doi:10.1001/archdermatol.2007.25 Figure Legend: Blue-gray amiodarone hyperpigmentation of the face (rare). The eyelids, area under the nose, nasolabial folds, and wrinkles are spared. Amiodarone-related hyperpigmentation should be considered a skin storage disease that is secondary to drug deposition. Date of download: 2/5/2016 Copyright © 2016 American Medical Association. All rights reserved. Antidysrhythmic: Class III (Amiodarone) • Nursing Considerations/Patient Education • • • • • • For IV amiodarone – monitor IV site frequently Teach patient to take pulse, monitor vitals Assess for neurotoxicity, monitor thyroid function, have regular eye exams Food increases absorption rate of amiodarone Monitor ECG during IV therapy or initiation of PO therapy Assess for signs of pulmonary toxicity (SOB) Antidysrhythmic: Class IV (Calcium Chanel Blockers) • Prototype: diltiazem (a non-dihydropyridine) • MOA: blocks calcium channel in the heart muscle cells, leading to depression of depolarization and prolongation of phases 1 and 2 of repolarization, slowing conduction through the AV node. • Uses: ventricular tachycardia/fibrillation, atrial flutter/fibrillation, SVT • Adverse reactions: bradycardia, hypotension, prolonged QT Antidysrhythmic: Nursing Interventions • Give medications as scheduled • Monitor vital signs • Monitor ECG (prolonged QT), liver (AST/ALT), & renal function (creat) • Monitor drug levels of procainamide • Monitor for s/s of toxicity – such as? • Avoid alcohol, caffeine, tobacco • Monitor for orthostatic hypotension – define orthostatic hypotension How do you know the antidysrhythmic worked? Try your knowledge – Name ECG Rhythm Try your knowledge - – Name ECG Rhythm Diuretics • Promote Na+ and water depletion • Decreases extracellular fluid volume Diuretics: Loop Diuretic • Prototype: furosemide • Uses: HTN, HF/pulmonary edema • MOA: inhibits absorption of Na+ and Cl in the proximal and distal tubules and in the loop of Henle • Uses: HF, pulmonary edema, HTN, ascites, renal disease, Meniere's disease • Adverse Reactions: tinnitus and reversible or permanent hearing loss (at higher doses), hypokalemia, hyponatremia, hypomagnesemia, hyperglycemia, Stevens-Johnson syndrome, toxic epidermal necrolysis, metabolic alkalosis • Contraindications: anuria, cross-reactivity with sulfonamides (sulfa) What do you check before giving the medication? Diuretics: Furosemide • Nursing Considerations • Onset 30-60 minutes • Monitor serum glucose closely in diabetics – can cause hyperglycemia • Avoid direct sunlight • Monitor electrolytes, BUN, creatinine, digoxin level • Monitor for cramps, rashes, incontinence, hearing loss • Risk for falls Diuretics: Thiazide • Prototype: Hydrochlorothiazide (HCTZ)] • Uses: First line treatment of mild hypertension. HF, pulmonary edema, ascites, renal disease, and Meniere's disease • MOA: inhibits absorption of Na+ and Cl in the distal collecting tubules • Adverse Reactions: hypokalemia, hyponatremia, hypomagnesemia, hypercalcemia (by increasing calcium reabsorption from the luminal membrane into the interstitium in exchange for sodium) • Contraindications: anuria Diuretics: Potassium-Sparing • Prototype: spironolactone • MOA: aldosterone antagonist, promotes Na+ and water excretion in the distal convoluted renal tubule • Uses: HF, pulmonary edema, liver cirrhosis, ascites, HTN, nephrotic syndrome, gender transitioning drugs, primary hyperaldosteronism • Adverse Reactions: hyperkalemia, gynecomastia, erectile dysfunction, irregular menses, metabolic alkalosis Diuretics: Carbonic Anhydrase Inhibitors • Prototype: acetazolamide • MOA: inhibits action of carbonic anhydrase causing Na+, K+, and HCO3 excretion in proximal renal tubule • Uses: ↓ intraocular pressure in open-angle (chronic) glaucoma, altitude sickness, metabolic alkalosis • Adverse Reactions: metabolic acidosis, paresthesia, Stevens-Johnson Syndrome, toxic epidermal necrolysis, renal calculus, bone marrow suppression, thrombocytopenic purpura, hemolytic anemia, pancytopenia, agranulocytosis How do you know it works? Diuretics: Osmotic • Prototype: mannitol • MOA: osmotic effect pulls large amounts of fluid into the urine • Uses: reduction of intracranial pressure and treatment of cerebral edema, patients w/ ↑ intraocular pressure • Adverse Reactions: fluid/electrolyte imbalance, pulmonary edema • Contraindications: HF, renal failure, hyperglycemia How do you know it works? Diuretics: Nursing Process • Nursing Interventions • • • • • • • • • • • Monitor vital signs Monitor serum electrolytes Observe for s/s hypokalemia Monitor daily weight and urine output Take drug early in the morning to prevent nocturia Instruct patient to slowly change positions from lying to standing Monitor vital signs and note decrease in BP Administer IV furosemide slowly dt/ potential for hearing loss Avoid K+ rich foods/Na+ substitutes if taking K+-sparing diuretics Monitor neuro status for patients on mannitol Lithium should not be given with diuretics Antihypertensives 2017 Hypertension Guidelines Antihypertensives: Cultural Variations • African Americans get HTN at an earlier age and have higher mortality than Caucasian-Americans • Beta blockers & ACE inhibitors < effective • Alpha1 blockers & calcium channel blockers > effective • Respond to diuretics as initial monotherapy • Asian patients twice as sensitive to beta blockers & other antihypertensives than Caucasian Americans • Caucasian Americans respond well to all antihypertensive agents • Native Americans experience a reduced response to beta blockers Antihypertensives: Older Adults • By age 65, 26% AMAB & 30% AFAB have HTN • Both systolic & diastolic HTN associated with ↑ CV mortality & morbidity • Side effect of antihypertensives • Orthostatic hypotension • May need to ↓ dose & use another drug • Instruct on need to modify lifestyle • 2 Gm Na+ diet • avoid tobacco • lose weight if overweight/obese & alcohol avoidance Antihypertensives: Classes • Beta blockers • Alpha2 agonists • Alpha1 blockers • Alpha1 and beta blockers • Direct-acting arteriolar vasodilators • Angiotensin converting enzyme (ACE-I) inhibitors • Angiotensin II receptor blockers (ARBs) • Direct renin inhibitor Review: Adrenoreceptors Antihypertensives: Beta Blockers Nonselective blocks both beta1 and beta2 Selective blocks only beta1 Beta1 works on heart Beta2 works on bronchial receptors Antihypertensives: Beta Blockers Nonselective (β1 & β2) Selective (Mostly β1) • Prototype drug: propranolol • Effect: ↓ HR & BP • Adverse Reactions: • Prototype drug: metoprolol • Effect: ↓ HR & BP • Adverse Reactions: • Bronchoconstriction/spasm • Impotence • Considerations: • Monitor vital signs closely in early treatment • Assess lungs • May also be used for anxiety • Hypotension • Bradycardia • 1st degree AV block • Considerations: • Monitor vital signs closely in early treatment Antihypertensives: Alpha2 Agonists • Prototype: clonidine • MOA: • ↓ sympathetic activity – causing a ↓ in HR and BP → ↓ CO • ↓ serum epinephrine, norepinephrine, renin release – causing vasodilation and ↓ PVR • Adverse Reactions: peripheral edema d/t Na+ and H2O retention, heart blocks (use w/ caution with digoxin, CCBs, and beta blockers), bradycardia, dizziness, rebound hypertensive crisis if D/C abruptly • Considerations: never given with beta blockers = could cause intensified bradycardia, monitor liver enzymes How do you know it works? Antihypertensive: Alpha1 Blockers • Prototype: prazosin • MOA: Blocks alpha-adrenergic receptors = vasodilation & ↓BP • Uses: effective for African Americans with HTN, selective alpha1blockers are used to treat BPH by relaxing the bladder sphincter = ↑ urine flow • Adverse reactions: orthostatic hypotension, dizziness, sudden loss of consciousness, impotence, mydriasis What should the nurse do before giving the medication? Antihypertensives: Alpha1 and Beta Blockers • Prototype drug: carvedilol • MOA: combines selective alpha1-adrenergic blocking and nonselective beta adrenergic blocking activity • Uses: may be used alone or in combination with other antihypertensive agents, especially thiazide and loop diuretics. • Adverse Reactions: hypotension, bradycardia • Contraindications: heart failure, heart block, cardiogenic shock, severe bradycardia Beta blockers: even those with apparent cardioselectivity, should not be used in patients with a history of obstructive airway disease, including asthma Antihypertensives: Calcium Channel Blockers • Prototype: • diltiazem (inpatient) – non-dihydropyridine • nifedipine (outpatient) - dihydropyridine • MOA: • Inhibits Ca+ ion from entering vascular smooth muscle & myocardium during depolarization → coronary muscle relaxation and vasodilation • ↑ myocardial oxygen delivery in patients with vasospastic angina • ↓ peripheral vascular resistance • Uses: antihypertensive, antianginal, antidysrhythmic • Adverse reactions: headache, hypotension, dizziness, flushing of skin, reflex tachycardia (d/t ↓ BP), peripheral edema Antihypertensives: Direct-Acting Arteriolar Vasodilators • Prototype drug: hydralazine • MOA: relaxes smooth muscles of arteries → vasodilation • Uses: severe HTN or hypertensive emergencies • Adverse Reactions: tachycardia, palpitations, edema, headache, hair growth, dizziness, nasal congestion, GI bleeding, lupus-like symptoms Renin Angiotensin Aldosterone System (RASS) Antihypertensives: Angiotensin-Converting Enzyme (ACE-I) Inhibitors • Prototype: lisinopril • MOA: • Inhibits angiotensin-converting enzyme • Prevent conversion of angiotensin I to angiotensin II • Blocks release of aldosterone • Uses: HTN, HF • Adverse reactions: angioedema, cough, hyperkalemia, agranulocytosis • Considerations: • African Americans & elderly do not respond well to these alone • Should not be used in pregnancy Antihypertensives: Angiotensin II Receptor Blockers (ARBs) • Prototype: losartan • MOA: blocks angiotensin II from angiotensin II receptors, thereby preventing release of aldosterone • Uses: HTN • Adverse Reactions: dizziness, diarrhea, insomnia • Considerations: • Less effective in treating HTN in African Americans • Does not cause the nagging cough of ACE-I Antihypertensives: Direct Renin Inhibitor • Prototype: aliskiren • MOA: inhibits renin in the RAAS cascade, which decreases angiotensin I and II and aldosterone levels • Uses: Mild to moderate HTN • Adverse Reactions: hypotension, peripheral edema, hyperkalemia, diarrhea, HF, Stevens-Johnson syndrome Antihypertensives: Patient Education • • • • • • • • • • Take drug same time every day Do not stop abruptly → rebound HTN Do not stop beta blockers for surgery Teach how to take BP & pulse daily Change positions slowly Report side effects Schedule F/U for labs & check-ups, eye exam Avoid OTC cold and cough remedies Reduce alcohol intake Stress management Test your knowledge (Enhanced Hot Spot) The nurse has received the following transfer report from an RN in the Emergency Department over the phone. Highlight the statements in the transfer report that require action by the receiving nurse. This is a 73-year-old female admitted for fall. The patient sustained a left forehead laceration (6 stitches). The has a history of HTN, HLD, HF, atrial fib., pneumonia, and UTI. She has a 2-gauge IV line on the left forearm. The patient is NPO and reports dizziness and nausea, and nonproductive cough. Home meds include: digitalis, lisinopril, atorvastatin, aspirin, and acetaminophen (PRN for headache). CBC, BMP, and LFTs drawn and sent to lab. Test your knowledge Which statement should the nurse include when teaching a patient who takes loop diuretics? A. B. C. D. Take the medication after 6 in the evening. Take the medication on an empty stomach. Rise slowly from a lying or sitting to standing. Avoid concurrent order with beta-blockers. Try your knowledge A patient is receiving an angiotensin II receptor blocker. The nurse should monitor the patient for which of these manifestations? A. B. C. D. Constipation Tremors Stridor Dizziness
