Uses
Cardiac Arrythmias and CPR
Used in the treatment of Adams-Stokes syndrome (Stokes-Adams disease). May be used in ventricular arrythmias secondary to AV nodal block and treatment of carotid sinus hypersensitivity.
Has been used in the treatment of cardiac arrest until defibrillation or emergency pacemaker therapy could be employed. The drug may be used in ACLS only as a temporary measure until pacemaker therapy is instituted either for refractory atypical ventricular tachycardia (torsades de pointes) or for the immediate temporary control of hemodynamically significant bradycardia (e.g., in the denervated heart of patients undergoing heart transplantation).
Use of isoproterenol for temporary immediate control of hemodynamically significant bradycardia usually is limited to when atropine and dobutamine have failed and transcutaneous and transvenous pacing are not available.
Isoproterenol (at low doses and in patients with a pulse) should be used with extreme caution, if at all, in the management of symptomatic bradycardia since its potential beneficial chronotropic effect may be outweighed by possible deleterious effects on myocardial oxygen consumption and peripheral circulation.
Electrical cardiac pacemakers largely have replaced drug therapy in third-degree AV nodal block (complete heart block), but isoproterenol may be used temporarily until a pacemaker can be implanted or if the implanted pacemaker fails.
Electroshock may be required in the management of ventricular arrhythmias and usually is the treatment of choice.
Shock
Isoproterenol IV infusion is used as adjunct to correct hemodynamic imbalances in the treatment of shock characterized by low cardiac output and intense vasoconstriction that persists after adequate fluid replacement. The drug is not useful if the peripheral vascular bed is already dilated.
The value of isoproterenol therapy in shock has been questioned because the drug increases oxygen demand in the myocardium and other tissues to levels that may not be met by increased blood flow. The efficacy of isoproterenol in reducing the incidence of mortality in refractory shock has not been convincingly demonstrated.
Isoproterenol appears to be less effective than norepinephrine or metaraminol in increasing coronary perfusion. Also, isoproterenol-induced increases in myocardial oxygen consumption and the work of the heart usually outweigh the beneficial effects of the drug, and arrhythmias occur more readily when the drug is administered to patients with cardiogenic shock.
Isoproterenol generally is not recommended in shock caused by AMI. Norepinephrine is considered by some clinicians to be the vasopressor of choice for this condition; however, this type of shock generally has a poor prognosis even when vasopressors are used. If peripheral vascular resistance is elevated, isoproterenol sometimes is used in conjunction with norepinephrine, but dosage of both drugs must be adjusted carefully according to the specific hemodynamic imbalances present.
The efficacy of isoproterenol may be reduced if CHF is present.
Bronchospasm
IV isoproterenol may be useful in bronchospasm occurring during anesthesia but must be administered with extreme caution, if at all, in patients receiving cyclopropane or halogenated hydrocarbon general anesthetics.
Has been used as a bronchodilator in the symptomatic treatment of bronchial asthma and reversible bronchospasm that may occur in association with chronic bronchitis, pulmonary emphysema, bronchiectasis, and other chronic obstructive pulmonary disorders. However, oral, sublingual, and oral inhalation preparations of the drug no longer are commercially available in the US.
Pulmonary Embolism
Has been used by IV infusion to reverse decreases in cardiac output and circulating pulmonary blood volume and to reverse increases in pulmonary arterial pressure and pulmonary vascular resistance occurring during pulmonary embolism†.
Diagnosis of CAD and Other Cardiac Abnormalities
Has been used as an aid in the diagnosis of CAD†. Also has been used in the diagnosis of CAD by increasing myocardial oxygen consumption and intensifying symptoms of ischemia.
Has been used as an aid in diagnosing the etiology of mitral regurgitation†.
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