ECHOCARDIOGRAPHIC EVIDENCE OF IMPROVED HEMODYNAMICS DURING INHALED NITRIC-OXIDE THERAPY FOR PERSISTENT PULMONARY-HYPERTENSION OF THE NEWBORN

To evaluate the cardiovascular effects of inhaled nitric oxide (NO) on the systemic and pulmonary circulations, 25 consecutive infants with severe persistent pulmonary hypertension of the newborn (PPHN) underwe nt serial echocardiographic evaluations before and during inhaled NO t herapy. Estimation of the systolic pulmonary artery pressure (SPAP) wa s derived from measurement of a tricuspid regurgitant jet using Bernou lli's equation. We also derived a pulmonary/systemic pressure ratio to evaluate overall cardiopulmonary effects. Paired measurements of esti mated SPAP decreased from 62.0 +/- 3.8 mmHg to 44.7 +/- 4.3 mmHg (p < 0.01) during inhaled NO therapy. The pulmonary/systemic pressure ratio decreased from 0.98 +/- 0.06 to 0.59 +/- 0.04 during NO therapy (p < 0.01), indicating a significant decline in the vascular resistance bet ween the two circulations. These changes also correlated with changes in the extrapulmonary shunt patterns at the ductus arteriosus and fora men ovale seen during inhaled NO therapy. The decreased right-to-left shunting was accompanied by a parallel (64%) improvement in systemic o xygenation, with the alveolar-arterial oxygen gradient (A-a DO2) falli ng from 591 +/- 14 mmHg to 380 +/- 33 mmHg (p < 0.01). We found echoca rdiography to be a useful clinical tool for evaluating and monitoring pulmonary artery pressure in infants with PPHN. Measurement of the SPA P and the pulmonary/systemic pressure ratio gave a quantitative estima tion of the severity of PPHN, and the extrapulmonary shunt flow patter ns at the ductus arteriosus and foramen ovale gave qualitative estimat es of its severity. Inhaled NO increased pulmonary blood flow and oxyg enation and improved the systemic cardiopulmonary hemodynamics in this group of infants.