VARIABLE OXYGENATION RESPONSE TO INHALED NITRIC-OXIDE IN SEVERE PERSISTENT PULMONARY-HYPERTENSION OF THE NEWBORN

The causes of variable responsiveness to inhaled nitric oxide (NO) in Persistent Pulmonary Hypertension of the Newborn (PPHN) are unknown. T he changes in the severity of respiratory failure after the onset of i nhaled NO (maximal dose 20 ppm) were studied in 13 consecutive neonate s with severe PPHN. Response was defined as a sustained decrease of al veolar-arterial oxygen gradient (AaDO(2)) by > 20%, or a decrease in o xygenation index (OI) by > 40%. Six neonates had a rapid response with in 30 min, three had an intermediate response within 8 h, and three ha d a delayed response within 12 h after the onset of NO. Three infants with birth asphyxia responded rapidly to inhaled NO. One infant with s epsis did not respond, and two with suspected sepsis had a delayed res ponse. The infants with Meconium Aspiration Syndrome and idiopathic PP HN had a variable response time. Twelve neonates required 4 to 14 days of mechanical ventilation and survived. Infants with PPHN may benefit from a trial of inhaled NO therapy that exceeds 30 min. The variabili ty of the response time to inhaled NO is likely to be multifactorial a nd dependent on the disease process associated with PPHN.