Cardiotonic-Inotropic Drugs Nursing Considerations & Management

Cardiotonic-inotropic drugs are particularly useful for patients with heart failure (HF), wherein the heart is not able to effectively pump the blood towards different body organs. As a result, cells of the body are deprived of oxygen and nutrients. Cardiotonic agents are drugs used to increase the contractility of the heart. Included below is a pharmacology guide for nurses on the various effects of cardiotonic-inotropic agents.

Table of Common Drugs and Generic Names

Here is a table of commonly encountered cardiotonic-inotropic drugs, their generic names, and brand names:

Disease Spotlight: Heart Failure (HF)

Heart failure is a syndrome characterized by dysfunction of cardiac muscles.

• It can occur in a number of heart conditions which can overwork the heart muscles. Some of these conditions include:
• Coronary artery disease (CAD), which leads to insufficient blood supply for the myocardium and is also the most common cause of HF;
• Cardiomyopathy, which leads to enlargement of the heart and myocardial fatigue; and
• Valvular heart diseases, which can cause reflux and overloading of blood to the ventricles which consequently over stretches the myocardium.
• Clinical manifestations depend on the side of the heart which failed:

Left-sided HF

• Primarily reflects pulmonary manifestations because the left ventricle cannot push blood towards the peripheral systems.
• As a result, there is engorgement of pulmonary veins, which leads to difficulty of breathing.
• Other manifestations include: tachypnea (rapid breathing), dyspnea (discomfort associated with breathing), and orthopnea (increased difficulty of breathing when lying down). Patient also experiences coughing and hemoptysis (coughing up of blood). In severe cases, pulmonary edema (filling up of fluid in the lung spaces) occurs which is life-threatening because it interferes with gas exchange.

Right-sided heart failure

• Occurs when the right side of the heart has the need to exert more force in order to push blood towards the pulmonary circulation.
• This side is usually a low-pressure system so when this happens, the pressure in this side rises and venous return can’t enter.
• Neck veins become distended and central venous pressure is increased. Organs like liverand spleen are enlarged because they are congested with blood.
• Also, dependent areas like the limbs develop pitting edema because fluid pools in these areas.

Cardiac Glycosides

Description

• Cardiac glycosides are cardiotonic agents from foxglove or digitalis plants. They exert their effects on the cardiac muscles by affecting levels of intracellular calcium. In turn, the contractility of the muscles is increased.

Therapeutic Action

• Allows more calcium to enter during contraction, therefore increasing the force of contraction – positive inotropic effect.
• Consequently, there is increased cardiac output and renal perfusion. A good blood supply to the kidney decreases renin release. This downplays the activity of renin-angiotensin-aldosterone system (RAAS) which causes more fluid to be excreted in the body through urine. A decrease in blood volume eases the workload of the heart.
• Another mechanism of this drug is to decrease the workload of the heart and slow down relaxation of the cells. Therefore, this drug can increase the strength of contractility without increasing the rate of contraction (negative chronotropic effect).

Indications

• Primarily indicated for decreasing workload of the heart and relieving HF.
• Digoxin is especially indicated for atrial flutter, atrial fibrillation, and paroxysmal atrial tachycardia.

Children

• Widely used in the treatment of heart defects in children but the margin of safety for drug dosage is small so the nurse should recalculate and re-validate the dose with another nurse before administration.
• Serum level of digoxin and signs of digitalis toxicity should be monitored carefully.

Adults

• This age group should be educated on manifestations that should be reported signifying drug toxicity.
• Also, adults are cautioned against utilization of different brands of digoxin as differences in bioavailability can increase the chance of toxicity.
• It is important for these patients to be taught how to take their own heart rate and assess its regularity.
• Safety of this drug for pregnant women is not established. As for lactating women, although digoxin enters breast milk, it has not been associated with adverse effects in neonates but caution is still exercised.

Older adults

• Older adults are more susceptible to drug toxicity because of underlying conditions that would interfere with metabolism and excretion of drug.
• Renal and hepatic function should always be monitored.
• Relatives should be instructed on how to take heart rate and assess its regularity.
• Careful attention should be given to other drugs taken by older adult patients as well as their alternative therapies.

Pharmacokinetics

Contraindications and Cautions

• Allergy to any component of digitalis preparation. Prevent severe hypersensitivity reactions.
• Ventricular tachycardia or fibrillation. These are potentially fatal arrhythmias and should be treated with another drug.
• Heart block (sick sinus syndrome). Can be worsened by drug’s effect on slowing conduction through AV node
• Idiopathic hypertrophic subaortic stenosis (IHSS). Obstruction of outflow tract to the aorta can result from increasing the force of contraction and this can lead to other severe problems.
• Acute myocardial infarction (MI). Increasing the force of contraction can damage the heart muscles more.
• Renal insufficiency. Drug is excreted through urine and the existing renal insufficiency can contribute to development of drug toxicity.
• Pregnancy and lactation. Can cause potential adverse effects to the fetus or neonate.

Adverse Effects

• CNS: headache, weakness, drowsiness, vision changes (most commonly reported is seeing yellow halo around objects)
• CV: arrhythmias
• GI: GI upset, anorexia
•  NURSING ALERT!  Signs and symptoms of digitalis toxicity: anorexia, nausea, vomiting, malaise, depression, irregular heart rhythms (e.g. heart block, heart arrhythmias, and ventricular tachycardia)

Interactions

• Digoxin immune Fab or DigiFab: antidote; these antibodies bind molecules of digoxin, making them unavailable at site of action. Used when serum digoxin is >10 ng/mL and serum potassium is >5 mEq/L.
• Verapamil, amiodarone, quinine, erythromycin, tetracycline, cyclosporine:increased therapeutic and toxic effects of digoxin. Combination of digoxin with any of these drugs would warrant decrease in dose of digoxin to prevent toxicity.
• Potassium-losing diuretics: increased risk of cardiac arrhythmias
• Thyroid hormones, metoclopramide, penicillamine: decreased therapeutic effects of digoxin. Increasing the dose of digoxin is important.
• Cholestyramine, charcoal, colestipol, antacids, bleomycin, cyclophosphamide, methotrexate: decreased absorption of digoxin. In this case, digoxin must be taken 2-4 hours after taking any of these drugs.
• St. John’s wort, psyllium: decreased therapeutic effect of digoxin
• Ginseng, hawthorn, licorice: increased risk of digoxin toxicity

Nursing Considerations

Here are important nursing considerations when administering cardiac glycosides:

Nursing Assessment

These are the important things the nurse should include in conducting assessment, history taking, and examination:

• Assess for the mentioned contraindications to this drug (e.g. renal insufficiency, acute MI, hypersensitivity, etc.) to prevent potential adverse effects.
• Conduct thorough physical assessment before beginning drug therapy to establish baseline status, determine effectivity of therapy and evaluate potential adverse effects.
• Obtain baseline status for weight while noting recent manifestations that increase or decreases to determine patient’s fluid status.
• Assess closely patient’s heart rate and blood pressure to identify cardiovascular changes that may warrant a change in digoxin drug dose.
• Auscultate heart sounds to note the presence of abnormal sounds and possible conduction problems.
• Determine urinary pattern and output to assess gross indication of renal function.
• Obtain baseline electrocardiogram (ECG) to identify heart rate and rhythm.
• Monitor serum electrolyte and renal function test results to determine whether changes in drug dose is needed or not.

Nursing Diagnoses

Here are some of the nursing diagnoses that can be formulated in the use of this drug for therapy:

• Risk for fluid volume deficit related to increased renal perfusion as effect of the drug
• Decreased cardiac output related to inefficient myocardial contractility
• Ineffective tissue perfusion related to decreased blood flow to different parts of the body

Implementation with Rationale

These are vital nursing interventions done in patients who are taking cardiac glycosides:

• Check drug dose and preparation carefully to avoid medication errors because drug has narrow safety margin.
• Do not administer drug with food and antacids to prevent decreased in drug absorption.
•  IMPORTANT!  Count apical pulse for one full minute before administering drug to monitor for adverse effects.
  • Drug is withheld if pulse is less than 60 beats per minute in adults and 90 beats per minute in infants.
  • Apical pulse is taken after one hour and if it remains low, nurse must document it, withhold the dose, and inform doctor.
• Assess pulse rhythm to detect arrhythmias which are early signs of drug toxicity.
• Weigh the patient daily to monitor for fluid retention and HF. Assess dependent areas for presence of edema and note its degree of pitting to assess severity of fluid retention.
• Monitor serum digoxin level as ordered (normal: 0.5-2 ng/mL) to evaluate therapeutic dosing and development of adverse effects.
• Provide comfort measures (e.g. small frequent meals for GI upset, instituting safety measures for drowsiness and weaknesses, and providing adequate room lighting for patients with visual disturbances) to help patient tolerate drug effects.
• Promote rest periods and relaxation techniques to balance supply and demand of oxygen.
• Ensure maintenance of emergency drugs and equipment at bedside (e.g. potassium salts and lidocaine for arrhythmias, phenytoin for seizures, atropine in case of clinically significant low heart rate, and cardiac monitor) to promote prompt treatment in cases of severe toxicity.
• Educate patient on drug therapy including drug name, its indication, and adverse effects to watch out for to enhance patient understanding on drug therapy and thereby promote adherence to drug regimen.

Evaluation

Here are aspects of care that should be evaluated to determine effectiveness of drug therapy:

• Monitor patient response to therapy through assessing manifestations of HF, arrhythmia, and serum level of digoxin.
• Monitor for adverse effects (e.g. visual changes, HF, and arrhythmias).
• Evaluate patient understanding on drug therapy by asking patient to name the drug, its indication, and adverse effects to watch for.
• Monitor patient compliance to drug therapy.

Phosphodiesterase Inhibitors

Description

• Phosphodiesterase inhibitors aid in increasing force of myocardial contractility through their enzyme-blocking effect. This in turn, increases the flow of calcium into the myocardial cells.

Therapeutic Action

• By blocking the enzyme phosphodiesterase, cyclic adenosine monophosphate (cAMP) increases. cAMP stimulates flow of calcium towards the myocardium and thereby, increases force of cardiac contractility.
• Increases intracellular calcium and prolongs effect of sympathetic stimulation. This leads to three major effects: vasodilation, increased oxygen consumption, and arrhythmias.

Indications

• Only indicated for short-term treatment of patients not responding to cardiac glycosides, vasodilators, and diuretics.
•  Drug use is only limited to severe situations because it is associated with fatal ventricular arrhythmias.

Children

• Drug is not recommended for this age group

Adults

• This age group should be educated on manifestations that should be reported signifying drug adverse effects.
• It is important for these patients to be taught how to take their own heart rate and assess its regularity.

Pregnant women

• Safety of this drug for pregnant and lactating women is not established.

Older adults

• Are more susceptible to drug toxicity because of underlying conditions that would interfere with metabolism and excretion of drug.
• Renal and hepatic function should always be monitored. Relatives should be instructed on how to take heart rate and assess its regularity.
• Careful attention should be given to other drugs taken by older adult patients as well as their alternative therapies.

Pharmacokinetics

Contraindications and Cautions

• Allergy to phosphodiesterase inhibitors and bisulfites. Prevent severe hypersensitivity reactions.
• Severe aortic or pulmonary valvular disease. Exacerbated by increased contraction.
• Acute MI. Exacerbated by increased contraction and oxygen demand.
• Conditions with fluid volume deficit. Exacerbated by increased renal perfusion which ultimately leads to increased urine output.

Adverse Effects

• CV: ventricular arrhythmias, ventricular fibrillation, hypotension, chest pain
• GI: nausea, vomiting, GI upset, abdominal pain
• Hema: thrombocytopenia
• Associated hypersensitivity reactions: vasculitis, pericarditis, pleuritis, and ascites
• Burning at intravenous injection site

Interactions

• In solution together with furosemide: precipitate formation

Nursing Considerations

Here are important nursing considerations when administering phosphodiesterase inhibitors:

Nursing Assessment

These are the important things the nurse should include in conducting assessment, history taking, and examination:

• Assess for the mentioned contraindications to this drug (e.g. fluid volume deficit, acute MI, hypersensitivity, etc.) to prevent potential adverse effects.
• Conduct thorough physical assessment before beginning drug therapy to establish baseline status, determine effectivity of therapy, and evaluate potential adverse effects.
• Obtain baseline status for weight while noting recent manifestations that increases or decreases to determine patient’s fluid status.
• Assess closely patient’s heart rate and blood pressure to identify cardiovascular changes that may warrant change in drug dose.
• Determine urinary pattern and output to assess gross indication of renal function.
• Obtain baseline electrocardiogram (ECG) to identify heart rate and rhythm.
• Monitor serum electrolyte, complete blood count, and renal and hepatic function test results to determine whether changes in drug dose is needed or not.

Nursing Diagnoses

Here are some of the nursing diagnoses that can be formulated in the use of this drug for therapy:

• Risk for fluid volume deficit related to increased renal perfusion as effect of the drug
• Decreased cardiac output related to inefficient myocardial contractility and hypotension
• Risk for injury related to easy bruising 2⁰ thrombocytopenia
• Ineffective tissue perfusion related to decreased blood flow to different parts of the body

Implementation with Rationale

These are vital nursing interventions done in patients who are taking phosphodiesterase inhibitors:

• Protect drug from light to prevent drug from degradation.
• Ensure patency of intravenous access to promote safe administration of drug.
• Weigh patient daily and fluid intake and output to evaluate resolution of HF.
• Assess skin condition, noting presence of petechiae and other manifestations of easy bruising and bleeding to assess presence of thrombocytopenia.
• Monitor intravenous injection site to promote prompt interventions in cases of burning sensation and/or irritation.
• Provide comfort measures (e.g. small frequent meals for GI upset, instituting safety measures for drowsiness and weaknesses, and providing adequate room lighting for patients with visual disturbances) to help patient tolerate drug effects.
• Educate patient on drug therapy including drug name, its indication, and adverse effects to watch out for to enhance patient understanding on drug therapy and thereby promote adherence to drug regimen.

Evaluation

Here are aspects of care that should be evaluated to determine effectiveness of drug therapy:

• Monitor patient response to therapy through assessing for manifestations of resolution of HF.
• Monitor for adverse effects (e.g. thrombocytopenia, HF, and arrhythmias).
• Evaluate patient understanding on drug therapy by asking patient to name the drug, its indication, and adverse effects to watch for.
• Monitor patient compliance to drug therapy.

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