ABSTRACT
The preoperative dose response to inhaled nitric oxide (NO) was compared with the need for and response to NO after cardiac surgery in patients with congenital heart defect and secondary pulmonary hypertension. In a preoperative vasodilator test with inhaled NO 20, 40 and 80 ppm and oxygen, mean pulmonary artery pressure (PAP) was at least 40 mmHg and/or the pulmonary vascular resistance index (PVRI) 4 Wood units. Preoperatively, NO 40 ppm and FiO2 0.9 reduced systolic pulmonary/systemic arterial pressure (PAPs/SAPs) from 0.89 (SD 0.10) to 0.80 (0.18) and pulmonary/systemic vascular resistance (PVR/SVR) from 0.26 (0.13) to 0.13 (0.08). Haemodynamic assessment was repeated in 11 patients postoperatively. NO treatment was started if PAPs/SAPs rose to 0.8 or the pulmonary oximetry fell below 40%. Postoperatively, eight of 11 patients, including 6 patients with Down's syndrome, needed NO. PAPs/SAPs decreased more than preoperatively: 48.5% vs 11.2, p = 0.0045. Pulmonary oximetry increased by 15.7%, p = 0.02. The degree of preoperative response to NO did not differ between the patients with postoperative pulmonary hypertension and the other children. Patients with early pulmonary hypertensive crisis (first 24 h; n = 6) had a higher PVRI (7.6 vs 4.4 Um2; p = 0.003) and PVR/SVR (0.34 VS 0.17; p = 0.02) preoperatively. Two patients died in pulmonary hypertensive crisis.
Subject(s)
Heart Defects, Congenital/surgery , Hypertension, Pulmonary/drug therapy , Nitric Oxide/administration & dosage , Vasodilator Agents/administration & dosage , Administration, Inhalation , Cardiac Catheterization , Child, Preschool , Female , Heart Defects, Congenital/complications , Heart Defects, Congenital/physiopathology , Humans , Hypertension, Pulmonary/etiology , Hypertension, Pulmonary/physiopathology , Infant , Male , Oximetry , Postoperative Care/methods , Preoperative Care/methods , Pulmonary Wedge Pressure/drug effects , Treatment Outcome , Vascular Resistance/drug effectsABSTRACT
OBJECTIVE: To test the vasodilatory response of the pulmonary vascular bed in children with pulmonary hypertension. DESIGN: Prospective dose response study in which the effects of inhaled nitric oxide (NO) are compared with those of oxygen and intravenous prostacyclin. PATIENTS AND INTERVENTIONS: The vasodilator test was performed in 20 patients in whom mean pulmonary artery pressure (PAPm) was > or = 40 mm Hg and /or pulmonary vascular resistance index was > or = 4 Um2. Haemodynamic effects of inhaled NO (20, 40, and 80 ppm) at a fractional inspired oxygen (FiO2) value of 0.3, pure oxygen, oxygen at FiO2 0.9-1.0 combined with NO as above or with intravenous prostacyclin at 10 and 20 ng/kg/min were measured. RESULT: NO decreased PAPm with a dose response from 20 to 40 ppm (mean change at 40 ppm-5.50, 95% confidence interval (CI) -7.98 to -3.02 mm Hg. Maximal decrease in the ratio of pulmonary to systemic vascular resistance was achieved with a combination of NO 80 ppm and oxygen (-0.18, 95% CI -0.26 to -0.10). Increase in the pulmonary flow index was greatest with pure oxygen in those with an intracardiac shunt (8.52, 95% CI -0.15 to 17.20 l/min/m2). Neither NO nor oxygen altered systemic arterial pressure but intravenous prostacyclin lowered systemic arterial pressure and resistance. CONCLUSIONS: NO selectively reduces pulmonary vascular resistance and pressure maximally at 40 ppm. Oxygen reduces pulmonary vascular resistance and NO potentiates this reduction without affecting the systemic circulation. Prostacyclin vasodilates the pulmonary and the systemic circulations.
