Drugs that affect the Cardiovascular system

1. Drugs that affect the Cardiovascular system Chemeketa Community College F ’08 P. Andrews, Instructor

2. What about ‘em?

3. LEAD Drugs • Lidocaine • Interferes with sodium channels to block conduction abnormalities • Epinephrine • Increases heart rate, blood pressure and stimulates liver • Atropine • Blocks acetylcholine, speeds heart • Dopamine - Increases contractile force • Amiodarone • Prolongs action potential and refractory period

4. Let’s Review First • Most drugs treat dysrhythmias • Most prevalent • Tachycardia • Bradycardia • Generated through abnormal impulse formation (automaticity) • OR abnormal conductivity

5. Dysrhythmias - Most often caused by imbalance between sympathetic and parasympathetic nervous systems

6. Bradycardia • Excessive parasympathetic stimulation through muscarinic receptors

7. Tachycardia • Variety of causes • Ischemia, mycoardial infarction, excessive sympathetic stimulation

8. Develop phase 4 depolarization, generate abnormal impulse • Ectopic foci • Abnormal conduction; • One-way valve

10. Antidysrhythmics • SODIUM CHANNEL BLOCKERS

11. What do they do, anyway? • -amide, ester forms of local anesthetics elevate the threshold of electric excitation of the nerve • Enter open, inactive sodium channels • Anesthetic closes the channel, blocking sodium influx • Delays impulse • Decreases action potential • Blocks conduction

12. Lidocaine • Class • Antidysrhythmic • Indications • VT, Vf, malignant PVC’s • Action • Decreases ventricular automaticity & excitability • Raises fibrillation threshold • Decreases conduction in ischemic cardiac tissue without affecting normal conduction

13. Contraindications • Advanced AV block (Mobitz II , 3rd degree blocks • Torsades de pointes • Stokes-Adams syndrome • Precaution: • Heart rate less than 60 • Hepatic disease - reduce by 50% • >70 y/o – reduce by 50%

14. Side effects • Drowsiness • Dizziness • Confusion • Hypotension • Nausea, vomiting • Dysrhythmias • Respiratory depression • Cardiac arrest

15. Route & Dosage: • Loading dose of 1 – 1.5 mg/kg IVP q 5 min. Max dose of 3 mg/kg • After perfusion is reestablished, admin. Lidocaine gtt at 2-4 mg/min (start gtt at 1 mg/min if pt > 70 y/o • How supplied • 10 mg/ml in 100 mg preload

16. Lidocaine is drug of choice for • Most types of drug-induced monomorphic VT or Vf, and for VT, Vf associated with cocaine-induced myocardial ischemia

17. Antidysrhythmics • Potassium Channel Blockers

18. amiodarone (Amrinone, Cordarone) • Class • antiarrhythmic • Indications • recurrent VF, unstable VT • When other therapies are ineffective

19. Action • Prolongs action potential and refractory period • Slows sinus rate, increases PR, QT intervals • Contraindications • Severe sinus node dysfunction • 2nd and 3rd degree AV block • Precautions • CHF, severe pulmonary or liver disease

20. Adverse reactions • ARDS, pulmonary fibrosis, CHF, worsening of arrhythmias • Liver function abnormalities • Anorexia, constipation, N/V, ataxia, involuntary movement, paresthesia, periphreal neuropathy, tremors • Bradycardia, hypotension • Dizziness, fatigue, malaise, corneal microdeposits

21. Route & dosage • Requires large initial loading dose (IV route) to prevent delay in onset action • Must use filter needle • Draw up slowly – Foams!

22. For VT hemodynamically stable (SBP> 85) • 150 mg IV over 10-30 minutes • 900 mg IV over 24 hrs by infusion • Repeat 150 mg IV bolus for VT • For VT/VF unstable or no BP • 150-300 mg IV bolus • IV infusion (1mg/min) • May repeat bolus

23. Not water soluble – must use solventPolysorbate 80 • Polysorbate 80 clinical effects: • Decrease heart rate • Depress AV node conduction • Increase atria and ventricularrefractory periods • Available only in glass ampules

24. How supplied • 50mg/ml in 3-ml ampules

25. Bretylium Tosylate (Bretylol) • Class; antiadysrhythmic • Different from all other antidysrhythmics • Does not suppress automaticity • Has no effect on conduction velocity

26. Indications • VT, Vf refractory to lidocaine and defibrillation • Recurrent Vf • VT with a pulse that fails to respond to lidocaine or procainamide • Wide complex tachycardias not controlled by lidocaine and adenosine

27. Action • Causes an initial but transient release of norepinephrine; effect lasts ~ 20 min. • Then inhibits release of norepinephrine and blocks reuptake of norepinehprine, resulting in depletion of norepinephrine. Results in: • Increased fibrillation threshold • Prolonged effective refractory period • Suppression of reentry dysrhythmias

28. Contraindication and precautions • No contraindications when used for Tx of life-threatening dysrhythmias • Contraindicated in Torsades • Can result in prolonged hypotension in postresuscitation phase • Side effects • Initial transient elevated BP followed by hypotension • Dizziness, syncope • Angina • Bradycardia • If administered by rapid IVP, N/V

29. Dosage • Vf, pulseless VT: 5 mg/kg IVP • Repeat with 10 mg/kg q 15 min to max dose of 30-35 mg/kg • If conversion, administer bretylium drip at 1-2 mg/min. • How supplied • 50 mg/ml in 10 ml preload

31. Antidysrhythmics • Calcium Channel Blockers

32. Verapamil (Isoptin, Calan) • Class • Antianginal, Antiarrhythmic, antihypertensive agent • Indications • Hypertension, angina, Prinzmetal’s angina, Af or AF with rapid ventricular response • Action • Inhibits transport of calcium into myocardial and vascular smooth muscle • Decreases SA and AV conduction

33. Contraindications • Hypersensitivity • Precautions • Severe hepatic impairment • Adverse reactions, SE • Arrhythmias, CHF

34. Dosage and route • 5 – 10 mg, IV • How supplied • 2.5 mg/ml in 2 & 4 ml vials, ampules and syringes

35. diltiazem (Cardizem) • Class • Antianginal, antiarrhythmic, antihypertensive • Indication • Hypertension, angina, SVTs and Af & AF with rapid ventricular response • NEW ONSET Af/AF (onset 48 hours or less) • Diltiazem OR cardioversion • Action • Inhibits the transport of calcium into myocardial and vascular smooth muscle

36. Contraindications • Hypersensitivity • Sick sinus syndrome • 2nd or 3rd degree AV block • Precautions • Severe hepatic impairment

37. Adverse reactions, SE • Arrhythmias • CHF • Peripheral edema • Dosage & route • 0.25 mg/kg • May repeat in 15 minutes with dose of 0.35 mg/kg • Follow with gtt at 10 mg/hr • How supplied • 5 mg/ml in 10 ml vials • 25 mg preloads

39. Antidysrhythmics • Miscellaneous

40. Adenosine (Adenocard) • Class • Antiarrhythmic agent • Indication • Conversion of PSVT • As a diagnostic tool to assess myocardial perfusion

41. Action • Restores normal sinus rhythm by interrupting re-entry pathways in AV node • Slows conduction through AV node • Contraindications • 2nd or 3rd degree block • Precautions • Asthma • Unstable angina

42. Adverse reactions & side effects • SOB • Facial flushing • Transient arrhythmias • Dosage & route • 6 mg rapid IVP • Repeat in 1 – 2 min. prn at 12 mg rapid IVP • Repeat in 1 – 2 min. prn at 12 mg rapid IVP

43. How supplied • 6 mg and 12 mg preload syringes or vials • Onset is immediate • Duration is 1 – 2 min • Note: Proximal IV, RAPID bolus, 20 ml flush with arm raised is critical!!

44. digoxin (Lanoxin) • Class • Antiarrhythmic agent • Cardiotonic and inotropic agent • Indications • CHF • Tachyarrhythmias • Af & AF • PAT

45. Action • Increases force of myocardial contractility • Prolongs refractory period of AV node • Decreases conductiion through SA and AV nodes • Contraindications • Hypersensitivity • Uncontrolled ventricular arrhythmias • AV block • IHSS

46. Precautions • Electrolyte abnormalities • Adverse reactions, SE • Dysrhythmias • Fatigue • Blurred, yellow vision • Anorexia, N/V

47. Dosage & route • 0.6 – 1.0 mg (10-15 mcg/kg) initially • Give additional fractions at 4 – 8 h intervals • Total dose 200 mg • How supplied • 0.25 mg/ml in 1 ml preload

48. Magnesium Sulfate • Class: CNS depressant, anticonvulsant. • Indications • Refractory Vf/pulseless VT • Torsades de Pointes • Digoxin-induced VT/Vf • Seizures 2ndary to eclampsia

49. Contraindications and precautions • None in refractory Vf, VT, Torsades • Renal disease • Heart block • Hypermagnesemia

50. Side effects • Hypotension • Asystole • Cardiac arrest • Respiratory and CNS depression • Flushing • Sweating