Perfusion: Heart Failure Drugs & More

• Study notes on Perfusion, including drugs for heart failure, antidysrhythmics, drugs for acute coronary syndrome, and hematopoetic agents
• Also includes clotting and acid-base balance

Drugs for Heart Failure

• Diuretics (Furosemide, Hydrochlorothiazide) are first-line drugs for patients with fluid overload, reducing venous/arterial pressure, pulmonary edema, and cardiac dilation

  • Benefits include symptom reduction, but diuretics do not prolong survival
  • Thiazide diuretics are ineffective when GFR is low and can cause hypokalemia, increasing the risk of digoxin-induced dysrhythmias
  • Loop diuretics are preferred when GFR is low
  • Potassium-sparing diuretics counteract K+ loss from thiazide and loop diuretics but can cause hyperkalemia, especially with ACE inhibitors or ARBs
  • Aldosterone antagonists (Spironolactone, Eplerenone) block aldosterone receptors, reducing symptoms and prolonging life

• ACE Inhibitors ("-PRIL" such as Captopril) improve functional status and reduce mortality for all HF patients unless contraindicated

  • Cause dilation of veins/arterioles, promote water excretion, and alter cardiac remodeling
  • Adverse effects of ACE Inhibitors are hypotension, hyperkalemia, cough, angioedema, and birth defects

• ARBs ("-SARTAN" such as Losartan) have similar hemodynamic effects to ACEIs but do not include beneficial cardiac remodeling effects

  • They are reserved for patients intolerant to ACE inhibitors due to cough

• Beta Blockers ("-LOL" such as Metoprolol) prolong survival in HF patients and are considered first-line therapy

  • Dose must be very low initially and gradually increased to avoid excessive cardio suppression

• Vasodilators such as Isosorbide dinitrate and Hydralazine can be used if ACEs or ARBs cannot, dilating veins and arterioles

• Inotropic Agents (Digoxin and Dopamine) increase myocardial contraction force, increasing cardiac output

  • Digoxin is effective and safer orally for long-term use but does not affect BP

• Digoxin nursing implications include:

  • Assessing HR and rhythm before administration, withholding if HR is less than 60 bpm or a rhythm change is detected
  • Cautioning patients to avoid doubling doses if a dose is missed
  • Monitoring cardiac status closely for 1-2 hours following IV injection
  • Educating patients about potential toxicity/treatment failure if medications are not taken as prescribed
  • Limiting salt intake to 1500 mg/day and avoiding excess fluids
  • Limiting alcohol consumption to no more than 1 drink/day
  • Establishing an appropriate exercise program
  • Recognizing the danger of dysrhythmias and educating patients to monitor HR and rhythm
  • Watch for early signs of hypokalemia (muscle weakness)
  • Be aware that GI or CNS effects may foreshadow more serious toxicity

• Contraindications for Digoxin are V-fib, V-tach, or digoxin toxicity

• Drug Interactions of Digoxin include:

  • Diuretics increase dysrhythmia risk by promoting K+ loss
  • ACEIs and ARBs can elevate K+ levels and decrease therapeutic responses to digoxin
  • Sympathomimetics increase HR and tachydysrhythmia risk
  • Quinidine can elevate plasma levels of digoxin

Antidysrhythmics

• Should be closely monitored because these drugs can worsen existing dysrhythmias or generate new ones

• Dysrhythmias can be caused in different ways, particularly through QT prolongation

• Drugs that prolong QT can cause Torsades de pointes

• Class I: Sodium Channel Blockers

  • Quinidine (Class IA) blocks sodium channels and delays ventricular repolarization (prolonging QT interval)
    • Adverse effects include GI issues (diarrhea) and dysrhythmias
    • Minimize GI effects by taking with meals
    • Warnings for Dysrhythmias- QRS widening by over 50% and excessive QT prolongation
    • Monitor ECG for cardiotoxicity and HR for changes in rate/regularity
    • If cardiotoxicity signs appear, withhold medication and notify the provider
    • Drug Interactions- Quinidine increases digoxin levels, so if using together, must reduce digoxin dose
  • Lidocaine (Class IB) is indicated for ventricular dysrhythmias
    • Administer via continuous IV infusion because lidocaine undergoes rapid liver inactivation

• Class II: Beta Blockers (-LOL), such as Propranolol

  • MOA is to block cardiac beta1 receptors and prolong the PR interval
  • Indicated for treating dysrhythmias caused by excessive sympathetic stimulation
  • Be aware of the risk of hypoglycemia in diabetic patients

• Class III: Drugs that delay repolarization, such as Amiodarone

  • MOA is to block K+ channels, thereby delaying repolarization of fast potentials (prolonging QT interval)
  • Indicated highly effective against atrial and ventricular dysrhythmias
    • But can have multiple serious adverse affects
  • Education is vital. Instruct patients to inform of: -S/S of lung injury, HF, or liver damage
  • Inform to avoid taking it if breast feeding, and during the months after cessation
  • Don't take with grapefruit juice, as it can increase levels and cause toxicity

• Class IV: Calcium Channel Blockers, such as Verapamil

  • MOA is to block cardiac calcium channels and prolong the PR interval

• Other Antidysrhythmics

  • Adenosine is used to terminate paroxysmal SVT
    • Action: Very short half-life (less than 10 seconds)
    • Must be given IV bolus
  • Digoxin is another antidysrhythmic

Drugs for Acute Coronary Syndrome

• Angina Pectoris drugs include:

  • Organic Nitrates: Nitroglycerin
  • Beta Blockers: Metoprolol & Propranolol
  • Calcium Channel Blockers: Nifedipine & Verapamil
  • Drugs That increase Myocardial Efficiency: Ranolazine

• Nitroglycerin acts on vascular smooth muscle to promote vasodilation

  • It is highly lipid soluble and readily absorbed through the skin and oral mucosa
  • Administration- SL: Used to abort anginal attacks; Transdermal/Sustained Release Oral caps: Used for extended protection
    • PATCNES: Apply to hairless area, using new patch & new site each day; only have patch on for 12-14 hours/day
    • TOPICAL OINTMENT: Rotate application sites to reduce local irritation

• Adverse effects of Nitroglycerin include: (1) headache, (2) orthostatic HOTN, (3) reflex tachycardia

• Education for Nitroglycerin includes:

  • Headache will diminish with continued drug use
  • Watch for symptoms of HOTN
  • Nitroglycerine can be given with BETA Blocker or Verapamil to minimize reflex tachycardia

• It should be cautiously used with other vasodilators

• Tolerance can develop with continuous use. Take lowest effective dose for 8 hours free of medication to prevent it

• Drugs for ST-Elevation Myocardial Infarction

  • Morphine lowers cardiac O2 demand, helping preserve the myocardium and decreasing pain
  • Oxygen is used to give supplemental support
  • Nitroglycerin is used to dilate, and reduce pressure
  • Aspirin suppresses platelet aggregation

• Other Treatments include:

  • BETA Blocker decreases infarct size and short-term mortality

• Reperfusion Therapy restores blood flow

• Lowering risk of 2nd MI with: (1) ↓ CV risk factors (smoking, hypercholesterolemia, HTN, diabetes) (2) exercise 30 mins a day, 3-4 days a week (3) long term therapy w/ 4 drugs: beta blocker, ACE-I or ARB, antiplatelet drug or warfarin, & a statin

• Fibrinolytic Therapy can be utilized, mostly Alteplase

Clotting

• Clot Differentiation:

  • Thrombus: a blood clot formed within a blood vessel or the atria of the heart
  • Arterial Thrombi- Begin w/ formation of a platelet plug, which is then reinforced w/ fibrin
    • Prevented w/ antiplatelet drugs (e.g., aspirin, clopidogrel)
  • Venous Thrombi- Begin w/ formation of fibrin, which then enmeshed RBCs & platelets
    • Prevented w/ anticoagulants (e.g., heparin, warfarin, dabigatran)

• Drugs for Thromboembolic Disorders include: (1) Anticoagulants:

  • Warfarin: inhibits synthesis of clotting factors
  • Others: inhibit activity of clotting factors (2) Antiplatelets: inhibit platelet aggregation (3) Thrombolytics: promote lysis of fibrin causing dissolution of thrombi

• Drugs That Activate Antithrombin include:

• Heparin (Unfractionated) is a rapid-acting anticoagulant that suppresses coagulation by helping antithrombin inactivate clotting factors

• Used to treat DIC and as an adjunct to thrombolytic therapy of acute MIs. Do not utilize of thrombocytopenia is present

• Vitamin K Antagonist: Warfarin -- Responses develop slowly/persist for several days post discontinuation -- Monitor aPTT (normal: 40secs, therapeutic range: 60-80 secs)

Acid-Base Balance

• Acid-base balance is maintained by:

  • Bicarbonate-carbonic acid buffer system
  • Respiratory system
  • The Kidneys

• Acidosis is caused by:

• Retention of CO2

• Chronic renal failure

• Severe diarrhea

• Metabolic disorders

• Poisoning

• Alkalosis is caused by:

• Hyperventilation

• Excessive loss of gastric acid

• Administration of alkalizing salt