Treatment of Increased Afterload

Characteristics

• Increased SVR • Hypertension

• Increased CVP/PAWP • Increased sympathetic stimulation

• Decreased CO/CI

• Decreased SvO2

• Variable BP

Treatment

• Improve ventricular performance

• Expected Response

• decreased SVR

• decreased BP

• decreased CVP/PAWP

• increased CO/CI

• increased SvO2

• Vasodilators

• nitroprusside

• hydralazine

• ACE inhibitors

• enalapril

• captopril

• Calcium channel blockers

• diltiazem

• Beta Blockers

• Metoprolol

• Breviboc (esmolol)

• labetolol

CAUTION! Excessive afterload reduction may result in hypotension and decreased tissue perfusion.

Nitroprusside (Nipride)

• Powerful arterial dilator

• Mild venodilator

• Dose 0.5 mcg to 10 mcg/kg/min

• Byproduct of breakdown is cyanide

• short term use

• observe symptoms of toxicity

• thiocyanate levels

• Rapid onset of action

ACE Inhibitors: Prevent Production of Angiotensin II

• Captopril

• (Capoten)

• 25-450 mg/day PO

• (bid or tid)

• Enalapril

• (Vasotec)

• 5-40 mg/day PO

• (once daily or bid)

• Enalaprilat

• (Vasotec IV)

• 1.25-5.0 mg IV Q 6 hr

• Given over 5 minutes

• Lisinopril

• (Prinivil, Zestril)

• 5-20 mg/day PO

• (once daily)

Calcium Channel Blockers

• Inhibit contraction of smooth vascular muscle

• Reduce myocardial workload through vasodilatation

• Negative contractility effect

• May cause bradycardia and heart block

Diltiazem (Cardizem)

• Initial dose 0.25mg/kg IV bolus

• Second bolus of 0.35mg/kg IV over 2 minutes may be given if desired response not obtained

• Continuous infusion of 5mg to 10 mg/hr

Beta-Adrenergic Blockers

• Non-selective blockers-produce decrease in BP without reflex tachycardia or reduction in heart rate, through a mixture of β-blocking effects.

• Selective blockers competitively block stimulation of β1 receptors in cardiac smooth muscle; produce chronotopic and inotropic effects

• Uses-hypertension, ventricular dysrhythmias, prophylaxis for angina

• Common side effects: orthostatic hypotension, bradycardia, diarrhea, nausea, vomiting

 


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