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Afterload reduction and cardiac ouptut in infants early after intracardiac surgery
Insights
Vasodilator therapy with nitroprusside improved cardiac output in infants after intracardiac surgery. Combining nitroprusside with blood volume expansion favorably impacted cardiac function in hypertensive infants.
Area of Science:
- Pediatric Cardiology
- Cardiovascular Physiology
- Pharmacology
Background:
- Infants undergoing intracardiac surgery often exhibit hypertension and low cardiac output post-operatively.
- Elevated systemic vascular resistance and pulmonary vascular resistance are common in this patient population.
Purpose of the Study:
- To evaluate the hemodynamic effects of nitroprusside infusion in hypertensive infants after intracardiac surgery.
- To assess the impact of vasodilator therapy combined with blood volume expansion on cardiac index and atrial pressures.
Main Methods:
- Hemodynamic parameters including mean arterial pressure, systemic vascular resistance, cardiac index, and atrial pressures were monitored in 16 infants.
- Nitroprusside was infused to reduce mean arterial pressure, followed by blood volume expansion while nitroprusside infusion continued.
Main Results:
- Nitroprusside infusion led to a 17% increase in cardiac index and decreased mean atrial pressures by 25% (left) and 22% (right).
- Combined nitroprusside and blood volume expansion further increased cardiac index by 24%.
- Discontinuation of nitroprusside resulted in decreased cardiac index and increased mean atrial pressure.
Conclusions:
- Vasodilator therapy with nitroprusside is effective in improving cardiac output in hypertensive infants post-intracardiac surgery.
- Combination therapy of nitroprusside and blood volume expansion demonstrates a favorable hemodynamic profile.
- The study derived an empirical equation relating hemodynamic variables in this critical patient group.
Abstract:
Sixteen infants less than 18 months old were studied within 3 hours of intracardiac surgery. Initial mean arterial pressure and systemic vascular resistance levels were higher than normal in each infant (99 +/- 17.2 mm Hg and 48 +/- 18.1 units'm2', respectively [mean +/- standard deviation]); cardiac index was low (1.9 +/- 0.48 liters'min-1-2) and mean left and right atrial pressures were 11.4 +/- 2.39 and 12.5 +/- 3.10 mm Hg, respectively. Mean pulmonary arterial pressure was 29 mm Hg; pulmonary vascular resistance was 8.6 units'm2'. When nitroprusside was infused to reduce mean arterial pressure to about normal, cardiac index increased 17 percent and mean left and right atrial pressures decreased 25 and 22 percent, respectively. Mean pulmonary arterial pressure decreased 31 percent. When atrial pressures returned to initial values after infusion of blood with continued infusion of nitroprusside, cardiac index increased another 24 percent. When administration of nitroprusside was discontinued, cardiac index decreased to 116 percent of the initial value and mean atrial pressure increased to 90 percent of the initial value. The study demonstrated the favorable effect on cardiac output of vasodilator therapy in combination with blood volume expansion in hypertensive infants early after intracardiac surgery. An empirical equation interrelating atrial and arterial pressures and cardiac index was derived from the data.