Management of systemic and pulmonary hypertension.
The major therapeutic approach to systemic and pulmonary hypertension and vasospasm in cardiac surgery patients involves the use of parenteral agents that reverse systemic vasoconstriction and produce vasodilation. Potential pharmacologic approaches include 1) alpha1-adrenergic receptor blockers, ganglionic blockers, and calcium channel blockers; 2) central alpha2-adrenergic receptor agonists, dopamine1-adrenergic receptor agonists, potassium channel modulators, and vascular cyclic nucleotide stimulators; 3) phosphodiesterase enzyme inhibitors, and 4) angiotensin-converting enzyme inhibitors. Of the currently available intravenous vasoactive therapies, the mainstay agents are the nitrovasodilators and the dihydropyridine-type calcium channel blockers. The nitrovasodilators, a diverse group of drugs that achieve vascular relaxation by stimulating cyclic nucleotides and thereby releasing nitric oxide, include nitroglycerin and sodium nitroprusside. Although these drugs are useful, rapid development of tolerance is a drawback to nitroglycerin, while nitroprusside can cause coronary steal and increase intracranial pressure. Intravenous dihydropyridine-type calcium channel blockers inhibit mechanical responses of cardiac muscle and vascular smooth muscle by blocking inward calcium currents. Nicardipine is an arterial specific vasodilator. Treatment for vasospasm is usually empiric; pharmacologic options include nitroglycerin, but dihydropyridine calcium channel blockers and phosphodiesterase inhibitors should also be considered.
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