💊Pharmacology for Nurses Unit 22 – Cardiac Emergency and Shock Drugs

Key Concepts and Definitions

• Cardiac emergencies involve life-threatening conditions affecting the heart and circulatory system that require immediate medical intervention
• Shock is a critical condition characterized by inadequate tissue perfusion and oxygen delivery to vital organs
• Hemodynamic instability refers to abnormal or unstable blood pressure, heart rate, and blood flow that can lead to organ dysfunction
• Inotropic agents are drugs that increase the force of cardiac muscle contraction and improve cardiac output (dopamine, dobutamine)
• Vasopressors are medications that constrict blood vessels and increase blood pressure (norepinephrine, epinephrine)
  • Used to treat hypotension and maintain adequate tissue perfusion during shock
• Thrombolytics are drugs that dissolve blood clots and restore blood flow in occluded coronary arteries (alteplase, reteplase)
• Antiarrhythmics are medications used to treat abnormal heart rhythms by altering the electrical activity of the heart (amiodarone, lidocaine)

Pathophysiology of Cardiac Emergencies and Shock

• Myocardial infarction (heart attack) occurs when coronary artery blockage leads to decreased blood flow and oxygen supply to the heart muscle
  • Causes irreversible damage to cardiac tissue and impairs heart function
• Cardiogenic shock results from severe impairment of cardiac function, leading to reduced cardiac output and inadequate tissue perfusion
• Hypovolemic shock occurs due to significant loss of blood or fluid volume, causing decreased preload and cardiac output
• Distributive shock involves vasodilation and increased vascular permeability, leading to inadequate tissue perfusion despite normal cardiac function (septic shock, anaphylactic shock)
• Obstructive shock occurs when a physical obstruction impedes blood flow, such as in cardiac tamponade or pulmonary embolism
• Compensatory mechanisms, such as increased heart rate and vasoconstriction, attempt to maintain blood pressure and organ perfusion during shock
• Prolonged or severe shock can lead to multiple organ dysfunction syndrome (MODS) and death if not promptly treated

Types of Cardiac Emergency and Shock Drugs

• Inotropes (dopamine, dobutamine, milrinone) increase cardiac contractility and improve cardiac output
• Vasopressors (norepinephrine, epinephrine, vasopressin) constrict blood vessels and raise blood pressure
• Thrombolytics (alteplase, reteplase, tenecteplase) dissolve blood clots in coronary arteries to restore blood flow during acute myocardial infarction
• Antiarrhythmics (amiodarone, lidocaine, procainamide) suppress or prevent abnormal heart rhythms
• Antiplatelet agents (aspirin, clopidogrel, ticagrelor) prevent platelet aggregation and reduce the risk of blood clot formation
• Anticoagulants (heparin, enoxaparin, bivalirudin) inhibit blood clotting and prevent thrombus formation
• Vasodilators (nitroglycerin, sodium nitroprusside) dilate blood vessels, reduce cardiac workload, and improve coronary blood flow

Mechanism of Action

• Inotropes stimulate beta-1 receptors in the heart, increasing cyclic AMP production and calcium influx, leading to enhanced cardiac contractility
• Vasopressors activate alpha-1 receptors in blood vessels, causing vasoconstriction and increased systemic vascular resistance
  • Some vasopressors also stimulate beta receptors, providing inotropic effects
• Thrombolytics convert plasminogen to plasmin, which breaks down fibrin clots and restores blood flow in occluded arteries
• Antiarrhythmics work through various mechanisms, such as sodium channel blockade (Class I), beta-receptor blockade (Class II), potassium channel blockade (Class III), or calcium channel blockade (Class IV)
• Antiplatelet agents inhibit platelet activation and aggregation by blocking specific receptors or enzymes involved in platelet function
• Anticoagulants interfere with the coagulation cascade by inhibiting specific clotting factors or enhancing the activity of antithrombin
• Vasodilators relax smooth muscle in blood vessels by increasing nitric oxide production or activating potassium channels

Indications and Usage

• Inotropes are used to treat acute decompensated heart failure, cardiogenic shock, and low cardiac output states
• Vasopressors are indicated for the management of septic shock, hypovolemic shock, and other forms of distributive or vasodilatory shock
• Thrombolytics are administered in the early stages of acute myocardial infarction to restore coronary blood flow and limit infarct size
• Antiarrhythmics are used to treat life-threatening ventricular arrhythmias (ventricular tachycardia, ventricular fibrillation) and to maintain sinus rhythm in atrial fibrillation
• Antiplatelet agents are prescribed for the prevention and treatment of atherothrombotic events, such as myocardial infarction and stroke
• Anticoagulants are used to prevent and treat venous thromboembolism, pulmonary embolism, and to reduce the risk of stroke in patients with atrial fibrillation
  • Also used in the management of acute coronary syndromes and during percutaneous coronary interventions
• Vasodilators are used to treat hypertensive emergencies, acute coronary syndromes, and to reduce afterload in heart failure

Administration and Dosing

• Inotropes and vasopressors are typically administered as continuous intravenous infusions, with doses titrated to achieve desired hemodynamic goals
  • Requires close monitoring of blood pressure, heart rate, and cardiac output
• Thrombolytics are given as a bolus dose or short infusion, with specific dosing regimens depending on the agent used
• Antiarrhythmics are administered intravenously or orally, with loading doses followed by maintenance doses
  • Dosing is adjusted based on patient response and monitoring of ECG and drug levels
• Antiplatelet agents are usually given orally, with loading doses followed by daily maintenance doses
• Anticoagulants can be administered intravenously (heparin) or subcutaneously (low-molecular-weight heparins), with dosing based on body weight and renal function
  • Oral anticoagulants (warfarin, direct oral anticoagulants) are dosed according to specific protocols and require regular monitoring
• Vasodilators are given as intravenous infusions (nitroglycerin, sodium nitroprusside) or sublingual tablets (nitroglycerin) for acute management, with doses titrated to achieve target blood pressure

Side Effects and Adverse Reactions

• Inotropes can cause tachycardia, arrhythmias, and increased myocardial oxygen demand
  • May worsen ischemia in patients with underlying coronary artery disease
• Vasopressors can lead to excessive vasoconstriction, resulting in decreased tissue perfusion and organ dysfunction
  • May cause hypertension, tachycardia, and arrhythmias
• Thrombolytics carry a risk of bleeding complications, including intracranial hemorrhage and gastrointestinal bleeding
• Antiarrhythmics can cause proarrhythmic effects, worsening existing arrhythmias or inducing new ones
  • May cause hypotension, bradycardia, and conduction disturbances
• Antiplatelet agents can increase the risk of bleeding, particularly when used in combination with other antithrombotic agents
• Anticoagulants are associated with an increased risk of bleeding complications, requiring close monitoring and dose adjustments
  • Heparin-induced thrombocytopenia is a rare but serious adverse reaction
• Vasodilators can cause hypotension, reflex tachycardia, and headaches
  • Abrupt discontinuation of nitrates may lead to rebound hypertension and ischemia

Nursing Considerations and Patient Education

• Monitor vital signs, hemodynamic parameters, and end-organ function closely in patients receiving inotropes, vasopressors, and other cardiac emergency drugs
• Assess for signs and symptoms of bleeding, especially in patients receiving thrombolytics, antiplatelet agents, or anticoagulants
  • Educate patients about the importance of reporting any unusual bleeding or bruising
• Monitor ECG and assess for changes in rhythm or conduction in patients receiving antiarrhythmics
• Ensure proper dose calculations and programming of infusion pumps to avoid medication errors
• Provide patient education on the purpose, administration, and potential side effects of prescribed medications
  • Emphasize the importance of adherence to the prescribed regimen and follow-up appointments
• Teach patients and caregivers about the signs and symptoms of worsening cardiac condition or shock, and when to seek immediate medical attention
• Promote lifestyle modifications, such as smoking cessation, healthy diet, and regular exercise, to reduce the risk of future cardiac events

Drug Interactions and Contraindications

• Inotropes and vasopressors can interact with other cardiovascular medications, such as beta-blockers and calcium channel blockers, potentially altering their effectiveness
• Thrombolytics should not be administered to patients with active bleeding, recent major surgery, or severe uncontrolled hypertension
  • Concomitant use of anticoagulants or antiplatelet agents may increase the risk of bleeding
• Antiarrhythmics can interact with other drugs that prolong the QT interval, increasing the risk of torsades de pointes
  • Some antiarrhythmics (e.g., amiodarone) have multiple drug interactions due to their effects on cytochrome P450 enzymes
• Antiplatelet agents should be used with caution in patients with a history of gastrointestinal bleeding or ulcers
  • Concurrent use of NSAIDs can increase the risk of bleeding complications
• Anticoagulants have numerous drug interactions, requiring close monitoring and dose adjustments when used with other medications
  • Contraindicated in patients with active bleeding or severe liver disease
• Vasodilators should be used cautiously in patients with severe aortic stenosis or hypertrophic cardiomyopathy
  • Nitrates are contraindicated in patients taking phosphodiesterase inhibitors (sildenafil, tadalafil) due to the risk of severe hypotension

Emergency Protocols and Procedures

• Establish a patent airway, provide oxygen, and ensure adequate ventilation in patients with cardiac emergencies or shock
• Obtain intravenous access and initiate fluid resuscitation in patients with hypovolemic or distributive shock
• Perform a rapid assessment of hemodynamic status, including blood pressure, heart rate, and signs of tissue hypoperfusion
• Administer inotropes or vasopressors as needed to maintain adequate blood pressure and cardiac output
  • Titrate doses based on patient response and hemodynamic goals
• Initiate thrombolytic therapy within the recommended time window for patients with acute myocardial infarction meeting eligibility criteria
• Treat life-threatening arrhythmias with appropriate antiarrhythmic medications or electrical cardioversion/defibrillation
• Consider mechanical circulatory support (intra-aortic balloon pump, ventricular assist devices) for patients with refractory cardiogenic shock
• Coordinate with the interdisciplinary team to provide comprehensive care and facilitate prompt transfer to a higher level of care when necessary

Case Studies and Clinical Applications

• A 62-year-old man presents with acute chest pain and ST-segment elevation on ECG, consistent with an acute myocardial infarction
  • After assessing eligibility, the patient receives thrombolytic therapy with tenecteplase, resulting in the resolution of chest pain and ST-segment elevation
• A 48-year-old woman is admitted to the ICU with septic shock secondary to pneumonia
  • Despite fluid resuscitation, she remains hypotensive, and norepinephrine is initiated to maintain a mean arterial pressure ≥ 65 mmHg
• A 75-year-old man with a history of heart failure presents with acute decompensation and cardiogenic shock
  • Dobutamine is started to improve cardiac output, and diuretics are administered to reduce fluid overload
• A 56-year-old woman develops sustained ventricular tachycardia following an acute myocardial infarction
  • Amiodarone is administered as a bolus dose followed by a continuous infusion, successfully converting the arrhythmia to sinus rhythm
• A 68-year-old man with a mechanical mitral valve presents with acute shortness of breath and hypoxemia
  • Diagnostic tests reveal a massive pulmonary embolism, and the patient is started on intravenous heparin to prevent further thrombus formation and propagation