Cardiac Drugs for NCLEX part 1

Cardiac Drugs for NCLEX part 1

Mechanisms Regulating Arterial Pressure

• ANS helps control pressure by adjusting cardiac output (HR x SV) and peripheral resistance.
• The renin-angiotensin-aldosterone system helps control arterial pressure by:
• -Releasing angiotensin II – potent vasoconstrictor of arterioles and veins
• -Releasing aldosterone – promotes Na⁺ and H₂O retention by kidneys
• Vasopressin (ADH) is a potent vasoconstrictor and increases water reabsorption.
• Atrial natriuretic peptide (ANP) is a vasodilator and causes increases excretion of Na⁺ and H₂O by kidneys. It also inhibits renin
• Decreasing blood volume and dilating arterioles and veins help control BP

Epinephrine

Expected Action:

• Binds to: α₁ – > vasoconstriction
  β₁ – > increased HR, contractility, & AV conduction
  β₂ – > Bronchodilation

Epinephrine (Adrenaline) – Catecholamine Adrenergic Agonist

Therapeutic Uses:

decreased absorption of local anesthetics or extravasated meds
Manage superficial bleeding
decreased congestion of nasal mucosa
increased BP
Treatment of AV block and cardiac arrest
Asthma

Adverse Effects:

Hypertensive crisis
Necrosis from extravasation
Dysrhythmias / increased myocardial O₂ demand – > angina

Contraindications/Precautions:  Pregnancy (C)

Interactions:

MAOIs – > increased effect and duration
TCAs block uptake of epi.
General anesthetics – > lead heart to be hypersensitive to epi – > dysrhythmias
α-adrenergic blockers (phentolamine
β-adrenergic blockers (propanolol)

Education:

Stop infusion with evidence of extravasation; treat with α-blocker (phentolamine)

Dopamine

Dopamine (Intropin) – Catecholamine Adrenergic Agonist

Expected Action:

Low Dose (Dopamine receptors) – > Renal vasodilation
Mod Dose (Dopamine, β₁) – > Above + increased HR, increased contractility, increased AV conduction
High Dose (Dopamine, β₁, α₁) – > Above + vasoconstriction

Therapeutic Uses:

Shock, Heart failure

Contraindications/Precautions:

CI: Pheochromocytoma, Pregnancy (C)

Adrenergic Receptors

α_{1 —} Vasoconstriction of arterioles in skin, viscera, and mucous membranes, and veins

β_{1 —}  increased HR, increased contractility, increased AV conduction, Release of renin in kidneys

β_{2 —} Vasodilation of arterioles in heart, lungs, and skeletal muscle, Bronchodilation, Relaxation of uterine smooth muscle, Glycogenolysis in liver, Skeletal muscle contraction

Dopamine — Vasodilation of renal blood vessels

Dobutamine

Dobutamine (Dobutrex) – Catecholamine

Expected Action:

• Binds to: α₁ – > vasoconstriction / β₁ – > increased HR, contractility, & AV conduction

β₂ – > Bronchodilation

Therapeutic Uses:

Heart failure

Adverse Effects:

ñ heart rate

Contraindications/Precautions:

Pregnancy (B)

Education:

Stop infusion ĉ evidence of extravasation; treat with α-blocker (phentolamine)

α-Adrenergic Blockers

Examples : Prazosin (Minipress) – Others: doxazosin mesylate (Cardura), Phentolamine (Regitine), ergotamine tartrate

Expected Action:

Selective α₁ blockade resulting in venous and arterial dilation

Therapeutic Uses:

Hypertension
Phentolamine: Extravasation of adrenergic agonists
Doxazosin mesylate: ò symptoms of benign prostatic hypertrophy

Adverse Effects:

First-dose orthostatic hypotension (monitor BP for 2 hrs post-treatment)

Contraindications/Precautions:

Pregnancy (C)

Interactions:

Antihypertensives – > additive hypotensive effect

NSAIDs / clonidine – > decreased antihypertensive effects of prazosin