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KEY CONCEPTS

KEY CONCEPTS

  • Image not available. Inhaled nitric oxide is a selective pulmonary vasodilator that is used in the treatment of reversible pulmonary hypertension.

  • Image not available. Acute cyanide toxicity is characterized by metabolic acidosis, cardiac arrhythmias, and increased venous oxygen content (as a result of the inability to utilize oxygen). Another early sign of cyanide toxicity is the acute resistance to the hypotensive effects of increasing doses of sodium nitroprusside (tachyphylaxis).

  • Image not available. By dilating pulmonary vessels, sodium nitroprusside may prevent the normal vasoconstrictive response of the pulmonary vasculature to hypoxia (hypoxic pulmonary vasoconstriction).

  • Image not available. Preload reduction makes nitroglycerin an excellent drug for the relief of cardiogenic pulmonary edema.

  • Image not available. Hydralazine relaxes arteriolar smooth muscle in multiple ways, including dilation of precapillary resistance vessels via increased cyclic guanosine 3',5'-monophosphate.

  • Image not available. The body reacts to a hydralazine-induced fall in blood pressure by increasing heart rate, myocardial contractility, and cardiac output. These compensatory responses can be detrimental to patients with coronary artery disease and are minimized by the concurrent administration of a β-adrenergic antagonist.

  • Image not available. Fenoldopam (infusion rates studied in clinical trials range from 0.01 to 1.6 mcg/kg/min) reduces systolic and diastolic blood pressure in patients with malignant hypertension to an extent comparable to nitroprusside.

  • Image not available. Dihydropyridine calcium channel blockers preferentially dilate arterial vessels, often preserving or increasing cardiac output.

A multitude of drugs are capable of lowering blood pressure, including volatile anesthetics, sympathetic antagonists and agonists, calcium channel blockers, β-blockers, and angiotensin-converting enzyme inhibitors. This chapter examines agents that may be useful to the anesthesiologist for perioperative control of arterial blood pressure.

As patients age, so too does their vasculature. When a pulse wave is generated by ventricular contraction, it is propagated through the arterial system. At branch points of the aorta, the wave is reflected back toward the heart. In younger patients, the reflected wave tends to augment diastole, improving diastolic pressure. In older patients, the wave arrives sooner, being conducted back by the noncompliant vasculature during late systole, which causes an increase in cardiac workload and a decrease in diastolic pressure (Figure 15–1). Thus, older patients develop increased systolic pressure and decreased diastolic pressure. Widened pulse pressures (the difference between systolic and diastolic pressures) have been associated with both increased incidence of postoperative kidney dysfunction and increased risk of cerebral events in patients undergoing coronary bypass surgery.

FIGURE 15–1

Illustration of the influence of increased vascular stiffness on peripheral (radial) and central (aortic) pressures. Note the similarity of peripheral radial pressures in individuals with normal (lower left panel) and increased (upper left panel) vascular stiffness. In young individuals with normal vascular stiffness, central aortic pressures are lower than radial pressures (lower panels). In contrast, in older individuals with increased vascular stiffness, central aortic pressures are increased and can approach or equal peripheral pressures as a result of wave reflection and central wave augmentation during systole (top panels). (Reproduced with permission from Barodka V, Joshi B, Berkowitz ...

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