Milrinone : selective pulmonary and systemic vasodilator effects in children with left to right shunt with severe pulmonary artery hypertension / Darios Adriano, Eden Latosa, Juan Reganion, Ma. Bernadette Azcueta, Ma. Lourdes SR Casas, Wilberto Lopez

OBJECTIVES: To determine the systemic and pulmonary hemodynamic effects of milrinone in infants and children with cardiac left to right shunt accompanied by severe pulmonary hypertension and if there is a beneficial effect on the pathophysiology of this condition. MATERIALS AND METHODS: This is an experimental time series study design which was conducted at the Philippine Heart Center Cardiovascular Laboratory in pediatric patients with left to right shunts and severe pulmonary artery hypertension. A study group consisted of 17 patients (aged 14 months to 13 years) with one or more left to right cardiac shunt lesions who were evaluated during cardiac catheterization with direct hemodynamic measurements made before, during 02 challenge (02, mask for 15 minutes at 10 L/min) and during administration of milrinone (loading dose of 50 ug/kg IV for 10 minutes and at continuous infusion at 0.5 ug/kg/min). The Fick method was used to calculate pulmonary and systemic blood flow, pulmonary and systemic vascular resistances, cardiac output and stroke volume. RESULTS: Pre-O2 Challenge and Post 02 Challenge. There was a significant increase in pulmonary blood flow and Qp/Qs ratio after 02 challenge. There was also a significant decrease in the pulmonary arteriolar resistance (10.5 +/- 3.1 Wood u.m exponent 2 to 6.7 +/- 2.2 Wood u.m exponent 2, p:0.001) and PAR/SVR ratio. There were no significant changes in a systemic blood flow, aortic mean and diastolic pressures, mean LA pressure, systemic vascular resistance, heart rate and stroke volume Pre-O2 Challenge and Post-Milrinone Challenge. Milrinone significantly increased the pulmonary blood flow and Qp/Qs ratio. Significant increase was also observed in the heart rate. Milrinone significantly decreased the following parameters: pulmonary artery mean and diastolic pressures, pulmonary arteriolar resistance and PAR/SVR ratio. Other parameters showed no significant change after milrinone infusion Post-O2 Challenge and Post-Milrinone Challenge. Milrinone had more significant decrease in the pulmonary artery diastolic pressure (50.7 +/- 13.3 mmHg to 40.4 +/- 13.1 mmHg, p:0.000) and pulmonary artery mean pressure (69.2 +/- 17.0 mmHg to 60.6 +/- 16.3 mmHg, p 0.006). There was also a significant increase in heart rate (119 +/- 20.1 beats/min to 129 +/- 21.1 beats/min, p:0.000). Other parameters showed no significant difference in results. CONCLUSION: Both 02 and milrinone decreased the total pulmonary vascular resistance, resulting in an increase in pulmonary blood flow, Qp/Qs ratio and left to right shunt volume. Only milrinone significantly decreased the pulmonary artery diastolic pressure without significant change in the aortic diastolic pressure. Therefore, milrinone may effectively decrease pulmonary vascular resistance without causing serious systemic hypotension in children with one or more left to right cardiac shunt lesions.

Nursing.