INDEX hemodynamic effects

Sodium nitroprusside is a mixed arterial-venous vasodilator that acts directly on vascular smooth muscle to increase cardiac index and decrease venous pressure. Despite its lack of direct inotropic activity, nitroprusside exerts hemodynamic effects that are qualitatively similar to those of dobutamine and milrinone. However, nitroprusside generally decreases PAOP, SVR, and blood pressure more than those agents do. 

The hemodynamic effects of dofetilide 500 micrograms bd and sotalol 160 mg bd for 3-5 days have been studied in 12 patients with ischemic heart disease and sustained ventricular tachycardia (56). There were significant reductions in heart rate, mean systemic pressure, and cardiac index (-13%) with sotalol, but cardiac index increased significantly with dofetilide (11%) with no effect on heart rate or systemic blood pressure. The authors suggested that oral dofetilide could be useful in patients with ventricular tachydysrhythmias associated with impaired left ventricular function. One patient taking dofetilide reported mild dizziness and there were no cardiac dysrhythmias. 

The effects of giving calcium chloride 10 mg/kg after induction of anesthesia with propofol, fentanyl, and pancuronium have been investigated in 58 patients undergoing elective coronary artery bjq)ass grafting (16). Calcium chloride reduced the fall in arterial blood pressure and prevented the reductions in heart rate, stroke volume index, cardiac index, and cardiac output, compared with placebo. Propofol reduces the availabihty of calcium to the myocardial cells, and calcium chloride effectively minimizes the hemodynamic effects of... 

The hemodynamic effects of ritodrine have been assessed in 12 fetuses by cardiac and extracardiac Doppler sonography (1). Ritodrine significantly increased maternal and fetal heart rates, left cardiac stroke volume, and cardiac output. There was also an increase in the pulsatility index of the middle cerebral artery and a fall in the pulsatility index of the umbilical artery during ritodrine infusion. The authors suggested that ritodrine vasodilates fetal vessels in the placenta. 

Measurements of arterial pressure, cardiac output, stroke work index, and pulmonary capillary wedge pressure are particularly useful in patients with acute myocardial infarction and acute heart failure. Such patients can be usefully characterized on the basis of three hemodynamic measurements arterial pressure, left ventricular filling pressure, and cardiac index. One such classification and therapies that have proved most effective are set forth in Table 13-4. When filling pressure is greater than 15 mm Hg and stroke work index is less than 20 g-m/m2, the mortality rate is high. Intermediate levels of these two variables imply a much better prognosis. 

Vasopressin is emerging as a potentially useful therapy in the hemodynamic support of vasodilatory septic shock. Case series and small clinical trials have reported its use in patients who remain hypotensive on vasopressors. Arginine vasopressin has little pressor activity in normal subjects but markedly increases blood pressure when sympathetic nerve function is impaired, including in septic shock. Unlike the catecholamine vasopressors, vasopressin is a direct vasoconstrictor agent and does not have inotropic or chronotropic effects. As a result, it may decrease cardiac output and hepatosplanchnic flow. In fact, studies of vasopressin in septic shock generally do not enroll patients with a cardiac index of less than 2 to 2.5 L/m per minute. 

FIGURE 7 Percentage changes in hemodynamic variables from baseline values during a 15-rain administration of inhaled nitric oxide in postoperative neonates with no residual anatomic obstruction to pulmonary blood flow. There was a marked pulmonary vasodilating effect. HR, Heart rate Cl, cardiac index BP, systemic artery pressure SVR, systemic vascular resistance PAP, mean pulmonary artery pressure PVR, pulmonary vascular resistance. 

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