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39 Cards in this Set
- Front
- Back
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Which 3 cardiac drugs account for the majority of fatalities?
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Digoxin
Verapamil Propranolol |
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What is the plant form of digitalis called?
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Digitalis purpurea
Foxglove |
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What are digoxins therapeutic effects?
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1 - Increased force of myocardial contraction (useful in CHF)
2 - Decreased AV conduction (useful in AFib) |
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How does digoxin increase the force of myocardial contraction?
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Inhibition of Na/K ATPase causing an increase in intracellular Na and Ca and extracellular K.
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Why does K rise in digoxin toxicity?
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The Na-K ATPase pump is paralyzed and K cannot be transported intracellularly.
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What effect does digoxin have on the SA node?
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Therapeutic - increased vagal tone, decreased HR
Toxic - can stop SA node conduction and decreases sympathetic sensitivity |
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What effect does digoxin have on Purkinje fibers?
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Results in increased PVC's
1 - decreased resting potential causing slowed phase 0 depolarization 2 - decreased action potential duration 3 - enhanced automaticity due to increased phase 4 repolarization |
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What dysrhythmia do digoxin toxic patients characteristically present with? (Rosen Box 150-1)
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Digoxin toxicity con produce virtually any tachyarrhthmia, bradyarrhythmia or conduction block.
More specific ones include: -AFib with a slow ventricular rate (AV dissociation) -Junctional tachycardia (rate 70-130) -Atrial tachycardia with block (atrial rate 150-200) -Bidirectional VTach |
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List factors that put a patient at increased risk of digoxin toxicity (Rosen Box 150-2)
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Elderly women
Dumb chemistry -Electrolyte abnormalities (K/Mg/Ca) -Alkalosis Disease -Hypothyroidism -Cardiac disease -Renal insufficiency Drugs -Sympathomimetics -Other cardiac drugs (BB/CCB/TCA/Amiodarone/Captopril) |
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What are the noncardiac symptoms of digitalis intoxication? (Rosen Box 150-3)
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General - weakness, fatigue, malaise
GI - N/V/D/Abd pain Opthalmic - snowy vision, photophobia, chromatopsia, amblyopia, diplopia Neurologic - Dizzy, HA, delirium, hallucinations, psychosis, somnolence, paresthesias, aphasia, seizures |
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Contrast chronic and acute digitalis intoxication
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Mortality - chronic higher
Potassium - chronic low-normal, acute normal-high Dysrhythmia - chronic ventricular, acute brady/blocks Age - chronic elderly, acute younger Need for Fab - more often in chronic Underlying disease - chronic likely, acute less likely |
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What correlates best with digoxin toxicity?
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The steady-state digoxin level (6-8 hours post po ingestion). Levels drawn earlier will read falsely high.
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Are activated charcoal, gastric lavage or whole bowel irrigation indicated for acute digoxin OD?
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No. There is a good antidote and no proven efficacy of these therapies. Because of significant entero-hepatic circulation this was once thought to be useful, but Digibind is now widely available.
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How should hypokalemia be treated in digoxin intoxication?
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Acute ingestion - do NOT replace K. It will rise as the Na/K ATPase is blocked
Chronic ingestion - replace K. Oral replacement is safer than IV. |
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What is stone heart syndrome?
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A syndrome described in case studies where giving calcium to a hyperkalemic digoxin OD patient caused their heart to stop. There is poor evidence for this phenomenom. It is reasonable to give Calcium to hyperK digoxin OD patients.
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Should hypomagnesemia be corrected in digoxin OD?
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Maybe. Consider especially in tachydysrhythmias if significant HypoMg but give slowly (2g over 30 minutes).
HyperMg can exacerbate toxicity and is a negative inotrope and slows AV conduction. |
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Should atropine be used in digoxin intoxication?
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Worth a shot in brady-arrhythmias
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How should a bradycardic patient with digoxin toxicity be paced?
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TV pacing has been found to induce tachydysrhythmias. Rosen's advices temporizing with external pacing until Fab takes effect.
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Should carotid massage be used to treat digoxin toxicity?
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Rosen's says you'll make them go bradycardic or kill them if you try this.
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How should a tachydysrhythmia in digatalis toxicity be treated?
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Digibind +/- dilantin or lidocaine.
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What is Digibind/Fab?
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It contains digitalis antibodies derived from sheep immunized with digoxin.
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When is Digibind indicated and how fast will it work?
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It is indicated in for hyperkalemia (>5.5) and/or hemodynamic compromise related to heart block or dysrhythmia.
Time to onset is 19 minutes with complete resolution taking hours. |
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What is the dose of Digibind?
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Use the formula on the package insert.
1 - empirical - history, symptoms, life threat --> 10 vials over 30 minutes. Cardiac arrest - 20 vials IV bolus. 2 - calculate - for each 1mg of digoxin ingested give 2 vials (78mg) 3 - calculate - base dose on the steady-state serum digoxin level after 6-8 hours |
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How do BB work?
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They competitively inhibit endogonous beta-adrenergic agents at the beta receptor preventing cAMP formation.
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What are beta1 effects?
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Inotropy (contraction), dromotropy (conduction) & chronotropy (heart rate).
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What are beta2 effects
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Vascular - vasodilation
Hepatic - glycogenolysis, gluconeogenesis Lung - bronchodilation Adipose - FA release Uterus - relaxation |
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What are the relevant pharmacodynamics of BBs?
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D - Vd >1 (more in tissue than serum, hard to dialyze)
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What are the symptoms of BB OD? (Rosen Box 150-8)
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Cardiovascular
-Bradycardia (SA and AV node function depressed, QRS widens) -Hypotension -VT/VF Respiratory -Respiratory insufficiency -Bronchospasm (uncommon) Neurological -Unsconsciousness -Seizures (only propranolol) -Hypoglycemia (more common in children) |
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Are activated charcoal, gastric lavage or whole bowel irrigation indicated for BB/CCB OD?
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Worth a try
-Activated charcoal, multidose if enterohepatic circulation (unproven) -Gastric lavage or whole bowel irrigation are equally unproven but can be considered |
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How should BB OD be treated?
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-IV fluids for hypotension
-Trial of atropine for bradycardia -Trial of Glucagon for hypotension (50mcg/kg IV loading dose then 1-10mg/h IV infusion) -Sodium bicarbonate for QRS widening (slow push) -High dose insulin (0.5-1U/kg/h) for hypotension with titrated dextrose infusion -Pressors for hypotension - no consensus, but I'd start high and titrate rapidly with epi (10-50mcg/m -Trial of calcium (1-2g over 5-10 minutes -Pacing -Consider intralipid -Consider hemodialysis -Consider balloon-pump -Consider ECMO |
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How does glucagon work in a BB/CCB OD?
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It is able to bypass the B-blocker receptor to activate cAMP
CCB's have an effect downstream from cAMP so it's unclear how it would work in these cases. However, there is some evidence that it does. |
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How does high-dose insulin therapy work in BB/CCB OD?
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Somehow, it increases inotropy by getting glucose into the cell while improving tissue perfusion and coronary blood flow
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How do CCB work?
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By blocking the slow calcium channels in the myocardium and vascular smooth muscle they affect the heart and vasculature.
Heart - decreased contractility, depressed SA activity, decreased AV conduction Vasculature - coronary and peripheral vasodilation |
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How are CCB classified?
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Dihydropyridine - more vasculature, less heart (amlodipine, felodipine, nifedipine)
Nondihydropyridine - more heart, less vasculature (verapamil & diltiazam) |
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What are the relevant pharmacodynamics of CCBs?
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A - slower absorption of SR preparations
D - Vd generally >1 so hemodialysis is not very effective. ++ protein binding |
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What are the symptoms of CCB OD? (Rosens Box 150-10)
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Cardio - hypotension, bradycardia, sinus arrest, AV block, AV dissociation, junctional rhythm, asystole
Pulmonary - respiratory depression, pulmonary edema, ARDS Gastrointestinal - N/V, bowel infaction - rare Neurologic - lethargy, confusion, slurred speech, stroke/seizure - rare Metabolic - lactic acidosis, hyperglycemia, hyperkalemia Dermatologic - flushing, diaphoresis, pallor, cyanosis |
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How should a CCB OD be treated?
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-IV fluids for hypotension
-Calcium for blockade - give 10-20mL of 10% CaCl3 slow push over 5-10 minutes then 5-10mL/h infusion (bring no higher than 14mg/dL as this is severe hypercalcemia) -Atropine for bradycardia -High dose catecholamine - high and rapidly titrated epinephrine or isoproterenol -High dose insulin/glucose (0.5-1U/kg/h) for hypotension with titrated dextrose infusion -Glucagon (50mcg/kg IV loading dose then 1-10mg/h IV infusion) -Pacing -Consider intralipid -Consider dialysis -Consider balloon pump -Consider ECMO |
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In what situation can iatrogenic methemoglobinemia occur?
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Patients with glucose-6-phosphate dehydrogenase deficiency can get this complication when exposed to nitrites. Their blood looks chocolate brown and skin looks blue (although they are clinically okay)
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What is the treatment for methemoglobinemia?
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IV methylene blue - usually only needed if methemoglobin approaches 30% or patient is symptomatic.
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