Cardiac System

1. Cardiac System Chapter 47

3. The Heart • Heart        This organ is the driving force of the entire system. It rhythmically contracts at a self-generated pace, although heart rate can be modified by numerous external effects. The contractions propel blood through the vascular system to allow delivery of oxygen, carbon dioxide, and food to individual tissues.

4. Conduction System • Heart contains cells that carry electrical impulses more rapidly that ordinary muscle fibers. • Autonomic nervous system and the heart • Sympathetic nerves increase heart rate through release of epinephrine and norepinephrine. • Parasympathetic nerves, by way of vagus nerve, decrease heart rate.

5. Cardiac Conduction System

6. Sinoatrial SA Node In the upper part of the right atrium of the heart is a specialized bundle of neurons known as the sinoatrial node (SA node). Acting as the heart's natural pacemaker, the SA node "fires" at regular intervals to cause the heart of beat with a rhythm of about 60 to 70 beats per minute for a healthy, resting heart. The electrical impulse from the SA node triggers a sequence of electrical events in the heart to control the orderly sequence of muscle contractions that pump the blood out of the heart.

7. Cardiac Disorders • Most vascular disease result from the malfunction of endothelial cells or smooth muscle cells. • Dysfunctional endothelium is considered a major factor in atherosclerosis, acute coronary syndrome, myocardial infarction (MI), hypertension and thromboembolic disorders.

8. Drug Therapy • Drugs can be used to manage atherosclerosis, heart failure, cardiac dysrhythmias, ischemia, myocardial infarct, hypertension, hypotension and shock.

9. Goals of Drug Therapy • Restore homeostasis or physiologic balance • Increase or decrease cardiac output • Manage blood pressure and heart rate • Alter heart rhythm • Increase or decrease blood clotting • Alter the quality of blood • Decrease chest pain

10. Drug Therapy for Heart Failure Chapter 48

11. Causes of Heart Failure • HF stem from dysfunction of contractile myocardial cells and endothelial cells that line the heart and blood vessels. • Endothelial dysfunction allows blood vessels to narrow due to plaque formation, overgrowth of cells or inflammation. • Clot formation at the site and vasoconstriction further narrow the blood vessel lumen.

12. Blood Vessel

13. Signs and Symptoms of Heart Failure or HF • Often no symptoms at rest • Dyspnea (difficulty breathing) and fatigue occur with increased activity • Edema of ankle and distention of jugular veins • In acute cases pulmonary edema – cough and shortness of breath

14. Drug Therapy for Heart Failure • Diuretics • Angiotensin-converting enzyme (ACE) Inhibitor • Angiotension II receptor blocker (ARB) • Beta-adrenergic blocking agent • Digoxin

15. Cardiac Glycosides or Digoxin • Digoxin or Lanoxin is the only commonly used digitalis glycoside.

16. digoxin (Lanoxin, Digitek) • Classification Pharmacologic: digitalis, glycoside • Classification Therapeutic: antiarrythmic, inotropic

17. Actions • Digoxin improves the pumping ability of the heart • Increases the force of myocardial contraction by inhibiting the Na, K-adenosine triphosphatase, an enzyme in cardiac cell membrane that decreases the movement of sodium out of myocardial cell after contraction. • Calcium enter the cell in exchange for sodium. • The calcium activates the contractile proteins and increased myocardial contractility.

18. Administration • Can be given orally or IV • Onset of action occurs in 30 minutes to 2 hours • IV peaks within 10 to 30 minutes • PO peaks within 1 to 2 hours

19. Serum Blood Levels • Maximum drug action occurs when steady tissue concentration has been achieved – takes about 1 week • Loading dose or digitalizing dosage will be higher until this therapeutic level has been reached. • Dosage 0.75 to 1.5 mg every 6 to 8 hours • When adequate levels have been reached than a maintenance dose can be started

20. Maintenance Dose • Dosing is 0.125 – 0.5 mg • Average dose is 0.25 mg • Take daily at same time of day • Give with food or after meals

21. Dosing by mcg/kg in Adults • IV digitalizing dose = 0.6 to 1 mg (10 -15 mcg/kg) given at 50% initially and additional fractions given at 4-8 hour intervals. • PO adults digitalizing dose 0.75 – 1.25 mg (10 – 15 mcg/kg) • PO children digitalizing dose 10 to 15 mcg/kg

22. Nursing Responsibilities • Take apical pulse for one full minute before giving the medication – listen for any irregular heart beats • Specific guidelines for holding the drug and notifying physician • Adults: apical pulse less than 60 • Older child: apical pulse less than 60 • Infant or younger child: apical pulse less than 100

23. Nursing Responsibilities • Monitor ECG throughout IV administration and periodically during therapy. • Notify physician if bradycardia (heart rate less than 60 bpm) or new arrhythmias occur. • Assess for peripheral edema and auscultate lungs for rales/crackles.

24. Laboratory Values • Electrolyte imbalance: potassium, calcium and magnesium values need to be monitored • Hypokalemia (low potassium) or Hypomagnesemia (low magnesium) can lead to irregular heart rate. • Hypercalcemia (elevated calcium) enhances effect of drug

25. Digoxin Toxicity • Anorexia, nausea, and confusion are symptoms of digoxin toxicity • HR below 60 in adults and 100 in infants and small children • Digoxin should be discontinued by MD only– takes about 1 week for drug to be eliminated from the body.

26. Evaluation of Effectiveness • Decrease in severity of CHF • Increase in cardiac output • Decrease in ventricular response in atrial tachyarrhythmia • Termination of paroxysmal atrial tachycardia

27. digoxin Overdose • digoxin immune Fab or DigiFab • Therapeutic classification: antidotes • Pharmacologic classification: antibody fragments • Indications: serious life-threatening over dosage with digoxin. • Action: An antibody produced in sheep that binds anti-genetically to unbound digoxin in serum. • Therapeutic effect: Binding and subsequent removal of digoxin, preventing toxic effects in overdose.

28. Antianginal Drugs Chapter 50

29. Angina • Angina pectoris is a clinical symptoms characterized by episodes of chest pain. • There is deficit in myocardial oxygen supply (myocardial ischemia) in relation to myocardial oxygen demand. • Pain can be caused by coronary vasospasm

30. Classification of Angina • Class I: ordinary physical activity does not cause angina – strenuous activity only. • Class II: angina occurs with walking or climbing stairs rapidly or up hill. • Class III: marked limitation in ordinary daily activity. • Class IV: anginal symptoms may be present at rest.

31. Antianginal Drugs • Nitrates are used to treat and prevent attack of angina. Only nitrates can be used in the acute treatment of angina pectoris. • Calcium channel blockers and beta blockers are used prophylactically in long-term management of angina.

32. nitroglycerin • Most widely used nitrate • Antianginal • Used to relieve acute angina

33. nitroglycerine • Classification Pharmacologic: nitrates • Classification Therapeutic: antianginals

34. nitroglycerine • Action: Increases coronary blood flow by dilating coronary arteries and improving collateral flow to ischemic regions. Decreases left ventricular end-diastolic pressure and left ventricular end-diastolic volume. Reduces myocardial oxygen consumption. • Therapeutic effects: • Relief or prevention of anginal attacks. • Reduction of blood pressure.

35. Dosing • Oral dosage is rapidly metabolized in the liver and only small doses reach the systemic circulatory system • For more effective absorption drug is given: • Sublingually – under the tongue – acts in 1 to 3 minutes • PO: sustained-released tablet • Transdermal ointments – applied on hairless area on back, chest or upper arm • Patches – takes a 40 minutes to an hour to start working

36. Sublingual Nitroglycerine

37. Sublingual Administration • Tablet should be held under tongue until dissolved. Avoid eating, drinking, or smoking until tablet is dissolved. • Acute anginal attacks: • Advise patient to sit down. • Relief should occur in 5 minutes • May be repeated every 5 minutes for 3 doses. • If no relief call 911.

38. Sustained Released Tablet

39. Sustained Released Tablet • Administer dose 1 hour before or 2 hours after meal with a full glass of water for faster absorption. • Note: Sustained released preparations should be swallowed whole, do not crush, break or chew.

40. Nitroglycerine Patch

41. Nitroglycerin Patch • Place the patch on a hairless area of chest or upper arm each day. • Move patch to a different place on your body each day to prevent skin irritation. • Remove the patch for 8 to 12 hours each night and put on a fresh patch each day. • Do not leave on all the time. • Remove for defibrillation

42. Nitroglycerine Ointment

43. Nitroglycerine Ointment • Comes with paper with a ruled line for measuring the dose • Squeeze ointment onto the paper, carefully measuring the amount specified on the prescription label • Use the paper to spread ointment in a thin layer on a hair-free area of skin (2 by 3 inches) • Keep paper in place with bandage or tape • Ointment is applied three or four times a day

44. Side Effects • Dizziness or light-headedness • Flushing of face and neck • Increased heart rate • Restlessness • Rare side effects: • Blurred vision • Dry mouth • Weakness • Fatigue

45. Antihypertensive Drugs Chapter 52

46. Antihypertensives • Used to treat hypertension, a common, chronic disorder affecting about 50 to 60 million adults in the USA.

47. Why is Hypertension a Problem? • Increases risks of: • myocardial infarction MI • heart failure HF • cerebral vascular infarction CVA or stoke • renal disease

48. What is Hypertension? • Hypertension is persistently high blood pressure that results from abnormalities in regulatory mechanisms. • It is defined as a systolic pressure above 140 and a diastolic pressure above 90 on multiple blood pressure measures.

49. Two Types of Hypertension • Primary: no cause can be found – can usually be controlled by drugs. • Secondary: due to renal, endocrine, or central nervous system disorders and from drugs that stimulate the SNS or cause retention of sodium and water – may need a combination of surgery and drugs.

50. Hypertension Guidelines • Normal = systolic less than 120 and diastolic less than 80 • Pre-hypertension = systolic 120 – 139 or diastolic 80 – 89 • Stage I hypertension = systolic 140 -159 or diastolic 90 to 99 • Stage II hypertension = systolic greater than 160 or diastolic 100 or more