Midterm 4a

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KHW
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Midterm 4a
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2011-10-05 18:47:33
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Midterm 4a
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  1. What does the cardiovascular system play a major role in?
    Maintenance of homeostasis
  2. The 3 primary pathways by which the heart can increase its cardiac output in response to body needs are what?
    • Intrinsic response to changes in muscle length
    • HR
    • Contractile response
  3. What depends directly on heart rate, myocardial wall tension, and inotropic state?
    Myocardial oxygen demand
  4. During cardiac failure, the body attempts to compensate by what intrinsic homeostatic mechanisms?
    • Activation of sympathetic system
    • Renin-angiotensin-aldosterone system
    • Myocardial hypertrophy
  5. What happens when the compensatory mechanisms act long term?
    • Increased myocardial demand
    • Results in CHF
  6. What is chronic failure of the cardiac pump, resulting in an inadequate cardiac output and insufficient delivery of oxygen to meet the tissue requirements?
    CHF
  7. What are clinical signs of CHF(5)?
    • Exercise intolerance
    • Labored breathing
    • Edema in extremities
    • Dry cough
    • Ascites
  8. Clinical signs of CHF are due to fluid accumulation in the lungs (pulmonary edema as what side heart failure?
    Left sided
  9. What compounds are important cardiac glycosides and collectively referred to as digitalis (3)?
    • Digoxin
    • Digitoxin
    • Ouabain
  10. The therapeutic response to digitalis in CHF includes what (5)?
    • Improved myocardial contractility
    • Increased CO
    • Diuresis
    • Diminution of edema
    • controls cardiac arrhythmias
  11. Cardiac glycosides increase contractile strength of the normal as well as failing heart by what?
    Increasing calcium availability in the myocardial fiber
  12. Digitalis exerts a positive inotropic action on the heart muscle, this is due to what?
    Inhibition of Na/K ATPase enzyme in sarcolemmal membrane of cardiac tissue
  13. The increase in intracellular Ca+ ion increases the amount of calcium available for contractile proteins, this induces what?
    Increased myocardial contraction (positive inotropic action)
  14. How does digitalis decrease heart rate?
    • Decreasing the rate of discharge from the SA node
    • (due to stimulation of vagal afferents)
  15. The increase of intracellular Na+ ion with decrease in K+ ion induces partial depolarization of the cell, thus reduces diastolic potential to threshold level which leads to...
    Enhanced excitability
  16. In CHF, the diuretic effect produced by digitalis is due to what?
    Increased renal blood flow, and an associated decrease in aldosterone secretion
  17. What is not a prominent feature of digitalis therapy, if edema does not accompany with CHF?
    Diuresis
  18. Digitalis does not induce diuresis if edema is not what?
    Cardiogenic
  19. Diuretic response to digitalis is secondary to what?
    • Circulatory improvement
    • (Not a direct effect on the kidney)
  20. Digitalis induces vomiting in dogs, after intravenous injection of digoxin, due to stimulation of what?
    Chemoreceptor trigger zone
  21. Where is the chemoreceptor trigger zone located?
    Floor of the 4th ventricle of the brain and connected by neural pathways to the emetic center in the lateral reticular formation of the medulla oblongata
  22. Vomiting accompanied by protracted diarrhea in dogs undergoing therapy with oral digitalis preparations is suggestive of what?
    Digitalis toxicity
  23. How is higher bioavailability of digoxin achieved?
    When administered in elixir form
  24. Why are cardiac glycosides absorbed to a new low extent in ruminant species?
    Because of metabolism by ruminal microorganisms
  25. Since digoxin is not well distributed to fat, it is always baded on what?
    • Lean body weight
    • (to avoid overdose in obese animals)
  26. What is mostly preferred to treat atrial fibrillation/ flutter?
    Digitalis
  27. What reduces ventricular rate by slowing AV conduction in atrial arrhythmias?
    Digitalis
  28. Digitalis is indicated to treat (2)?
    • CHF
    • Atrial Arrhythmias
  29. What involved initial administration of a large amount of digitalis, in several divided doses over a relatively short period of time to achieve rapid desirable therapeutic effect?
    Digitalization
  30. What is the main aim of therapy with digitalis?
    Determine the smallest amount of glycoside that will effectively maintain the patient in a state of cardiac compensation
  31. In digoxin in dogs, steady state concentration will be attained on what days of maintence?
    • 6 to 8 day of therapy
    • (assessed P for response to Tx)
  32. Since the renal and hepatic functions are considered to be important in digitalis elimination, dose levels should be reduced in what? Animals with kidney or liver disease
  33. When is IV administration of digitalis indicated (3)?
    • when animal does not retain oral medications
    • Acute cardiac decompensation
    • Respiratory distress
  34. What administration route of digoxin is not preferred?
    IM
  35. What is the therapeutic plasma concentration in digoxin?
    0.6 to 2.4 ng/ml
  36. What can digitalis toxicity evoke?
    • Incomplete/Complete heart block with dropped beats
    • (Ventricular bigeminal rhythm)
  37. The antiarrhythmic activity of K+ in digitalis intoxication is due to what?
    Inhibition of cardiac glycoside binding to Na, K-ATPase enzyme
  38. Increased Ca++ ion may enhance the toxic effects of digitalis by what?
    Increasing the intracellular calcium stores
  39. What is an exchange esin that binds to glycoside within digestive tract, thus enterohepatic circulation of bound form of glycoside is hindered, thereby hastening elimination of digitalis glycosides?
    Cholestyramine
  40. Intermittent administration of a diuretic during maintenance therapy of digoxin induces diuresis, thus what?
    Cardiac preload can be effectively reduced.
  41. What is the preferred loop action diuretics?
    Furosemide
  42. What diuretic produces a higher K+ excretion in urine, it increases Ca++ binding proteins in distal renal tubule and enhances renal tubular reabsorption of Ca++?
    Thiazide diuretics
  43. What is the limitation of potassium sparing diuretics?
    Slow onset of action
  44. An oral combination preparation containing what produces diuresis without either delayed onset of action or excessive urinary excretion of potassium?
    Hydroflumethiazide, spironolactone
  45. What is decreased volume of distribution of digoxin due to its displacement by quinidine from tissue binding sites?
    Quinidine-digoxin interaction
  46. What exerts a positive inotropic action on the failing heart without increasing the myocardial oxygen consumption, also decreases ventricular filling pressure (preload) and vascular resistance (afterload)?
    Amrinone
  47. What enzyme is responsible for the selective metabolism of CAMP, accumulation of intracellular CAMP leads to increased cardiac contractility and peripheral vasodilation?
    Phosphodiesterase isoenzyme III
  48. What produces positive inotropic effect and vasodilation; increases the binding efficiency of cardiac myofibril to the calcium ions without increasing oxygen demand?
    Pimobendan
  49. What is a B1 agonist, produces myocardial contraction of heart, decreases ventricular filling pressure, and has weak positive chronotropic action?
    Dobutamine
  50. What are 2 drawbacks in the use of dobutamine?
    • Arrhythmias
    • Tachyphylaxis

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