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Chapter: Clinical Anesthesiology: Clinical Pharmacology: Hypotensive Agents

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Non-Nitrovasodilator Hypotensive Agents: Calcium Antagonists

Dihydropyridine calcium channel blockers (nicardipine, clevidipine) are arterial selective vasodilators routinely used for perioperative blood pressure control in patients undergoing cardiothoracic surgery.

CALCIUM ANTAGONISTS

Dihydropyridine calcium channel blockers (nicardipine, clevidipine) are arterial selective vasodilators routinely used for perioperative blood pressure control in patients undergoing cardiothoracic surgery. Clevidipine is a relatively new drug with a short half- life, which facilitates its rapid titration. Unlike verapamil and diltiazem, the dihydropyridine calcium channel blockers have minimal effects on cardiac conduction and ventricular contractility. Calcium channel block-ers bind to L-type calcium channel and impair cal-cium entry into the vascular smooth muscle. These L-type receptors are more prevalent on arterial ves-sels than venous capacitance vessels. Consequently, cardiac filling and preload is less affected by these agents than nitrates, which might dilate both arte-rial and venous systems. With preload maintained, cardiac output often increases when vascular tone is reduced by use of dihydropyridine calcium blockers. Nicardipine infusion is titrated to effect (5–15 mg/h).

Other intravenous agents that can produce hypotension perioperatively include the intravenous angiotensin-converting enzyme inhibitor enala-prilat (0.625–1.25 mg). The role of enalaprilat as a nondirect-acting agent in the acute treatment of a hypertensive crisis is limited.

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