Cardio Meds presentation started class 12may

Albuterol Administration via Endotracheal Tube

  • When administering albuterol through an endotracheal tube, a special adapter is required.
  • Approximately ten puffs are needed because the initial eight puffs coat the inside of the endotracheal tube.
  • After administering the ten puffs, the patient should be taken off the ventilator, the APL valve closed, and the bag squeezed to ensure the droplets go down the endotracheal tube and into the lungs.
  • Bronchospasm may make it difficult to squeeze the bag.

APL Valve

  • The APL valve controls the tightness of the bag during ventilation.

Terbutaline

  • Terbutaline is a beta-two agonist formerly used via subcutaneous injection.
  • It was used when albuterol couldn't be administered or as a tocolytic for premature labor.
  • It's currently on a shortage list and unlikely to be on the CP exam or board exams.

Cardiac Glycosides (Digitalis/Digoxin)

  • Derived from the digitalis plant (foxglove).
  • Digoxin was historically a primary treatment for heart failure before evidence-based practice.
  • Decreased morbidity and readmission rates, but recent studies did not demonstrate a decrease in mortality.
  • Now it's recommended when other treatments are ineffective, especially in heart failure patients with atrial fibrillation (AFib).
  • Linoxin is a brand name of Digoxin
  • Mechanism of Action:
    • Inhibits the sodium-potassium ATPase pump, regulating sodium and potassium levels in cells.
    • Increases intracellular levels of sodium and calcium.
  • Adverse Effects:
    • Harmful in patients with hypertrophic subaortic stenosis due to increased myocardial contractility.
    • IV calcium administration can precipitate cardiac dysrhythmias.
  • Pharmacokinetics:
    • Long half-life of one to two days.
  • Treatment for Digoxin Toxicity:
    • Correct predisposing causes (hypokalemia, hypomagnesemia, hypoxia).
    • Supplemental potassium to reduce digitalis binding in cardiac muscle.
    • Administer sodium channel blockers like lidocaine or insert a temporary pacemaker to manage cardiac dysrhythmias.

Phosphodiesterase Inhibitors

  • Mechanism of Action:
    • Inhibit PDE3, increasing intracellular cyclic AMP in cardiac muscle, which increases intracellular calcium and the force of contraction.
    • Increase the rate of relaxation by accelerating calcium return to the sarcoplasmic reticulum (positive lusitropy).
  • Effects on Vascular Smooth Muscle:
    • Cyclic AMP inhibits meiosis light chain kinase, causing vasodilation and decreased SVR.
  • Clinical Use:
    • Treat acute heart failure, especially when increased inotropy and decreased afterload are needed (e.g., coming off cardiopulmonary bypass).
  • Prototype:
    • Amrinone (brand name) - a non-selective PDE inhibitor.
    • Used for its bronchodilatory effects.
    • Xanthine derivative: Acts as a nonselective adenosine receptor antagonist, combined with phosphodiesterase actions, produces anti-inflammatory action.

Selective Phosphodiesterase Inhibitors

  • Examples: Milrinone (Primacor).
  • Mechanism of Action:
    • Prevents the breakdown of cyclic AMP, enhancing its action to promote positive inotropic action and vasodilation without tachycardia.
  • Benefits:
    • Increased contractility, decreased afterload, and no increase in heart rate.
    • Retain inotropic effect even with beta-blocking agents.
  • Effects on LV Function:
    • Increases LV function by increasing calcium uptake by the sarcoplasmic reticulum.
    • Inhibition of PDE3 in the sarcoplasm increases local cyclic AMP, enhancing intracellular calcium uptake.
    • Increased calcium enhances contraction, improving diastolic function and cardiac output, ultimately decreasing pulmonary capillary wedge pressure.
  • Clinical Uses:
    • Cardiogenic shock, right heart failure, and pulmonary artery dilation.
  • Vasodilation Mechanism:
    • Cyclic AMP action in smooth muscle causes calcium efflux, promoting blood vessel relaxation.
  • Clinical Results:
    • Decreased preload and afterload.
  • Side Effects:
    • Increased risk of arrhythmias due to increased cyclic AMP and calcium.
  • Elimination:
    • Via the kidneys; dose adjustment needed for renal impairment to prevent life-threatening arrhythmias.

Milrinone - Cardiovascular Effects Summary

  • Increases:
    • Cardiac Output (CO)
    • Cardiac Index (CI)
    • Myocardial Oxygen Demand (slightly)
  • Decreases:
    • Pulmonary Capillary Wedge Pressure (PCWP)
    • Mean Arterial Pressure (MAP)
    • Systemic Vascular Resistance (SVR)
    • Pulmonary Vascular Resistance (PVR)
    • Central Venous Pressure (CVP)
    • Left Ventricular End Diastolic Pressure (LVEDP)

PDE5 Inhibitors

  • Mechanism of Action:
    • Produce vasodilation.
  • Clinical Use:
    • Treat pulmonary hypertension.
    • Decrease pulmonary vasodilation, reducing the workload of the right ventricle and improving symptoms of right-sided heart failure.
  • Examples: Sildenafil (Viagra) and Revatio.

Calcium

  • Importance:
    • Neuromuscular transmission, promoting contraction in skeletal and cardiac muscle (inotrope).
    • Blood coagulation (procoagulant).
    • Exocytosis of neurotransmitter release.
    • Primary component of bones.
  • Classification:
    • Major cation (positive ion) in extracellular fluid.
  • Storage:
    • Mostly stored in bone, mobilized for use as needed. If dietary intake is insufficient, calcium is taken from bones, leading to potential osteoporosis and bone demineralization in hypocalcemia.
  • Regulation:
    • Extracellular calcium levels are maintained by homeostatic mechanisms, involving reabsorption from bone, dietary intake in the GI tract, and kidneys.
  • Supplementation:
    • May be needed after blood transfusions to counteract citrate toxicity.
  • Causes of Hypocalcemia:
    • Decreased plasma concentrations of albumin.
    • Hypoparathyroidism.
    • Pancreatitis.
    • Vitamin D deficiency (prevents calcium absorption from the GI tract).
    • Chronic renal failure (calcium loss, potassium retention).
    • Citrate binding during massive transfusion protocols.
  • Symptoms
    • Low calcium symptoms are due to decreased plasma concentrations of albumin.
  • Plasma Concentration:
    • Maintained at milliequivalent levels through endocrine control and GI absorption.
    • Total plasma calcium consists of calcium bound to albumin, complexes with citrate and phosphorus ions, and freely diffusible, ionized calcium.
  • Preparations:
    • Calcium Chloride.
      • Provides 272 mg of elemental calcium.
    • Calcium Gluconate (10% solution).
      • Provides 93 mg of elemental calcium.
    • Calcium chloride provides three times more calcium than calcium gluconate.
    • Calcium chloride is preferred in the operating room for its higher calcium content.

Key Concepts for Exam

  • Epinephrine dosing and toxicity.
  • Phosphodiesterase mechanism of action.
  • Beta-two albuterol mechanism of action.
  • Calcium supplementation: which preparation provides the most calcium (calcium chloride vs. calcium gluconate).