Hemodynamics and oxygenation changes induced by the discontinuation of low-dose inhalational nitric oxide in newborn infants

Abstract

Objective: To assess changes associated with nitric oxide (NO) discontinuation in neonates receiving inhalational NO therapy as a treatment for pulmonary hypertension of the neonate (PPHN). Design: Prospective study. Setting: A pediatric PICU in a university hospital. Patients and methods: Ten neonates were included. NO discontinuation was attempted when the oxygenation index fell below 10. The mean NO concentration was 4.9 ± 0.8 ppm. Each infant was studied over three successive 5-min periods and was assigned to either group 1 (NO+1, NO+2, NO-) or group 2 (NO+1, NO-, NO+2). Measurements and results: Postductal transcutaneous PO2 (tcPO2), postductal oxygen saturation with pulse oxymetry (SpO2), systolic and diastolic blood pressure (BP), heart rate (HR), left ventricular shortening fraction (LVSF), cardiac output (CO), and ratio of pulmonary artery time to peak velocity and right ventricular ejection time (TPV/RVET) were similar during the two successive NO+ periods (group 1), thus demonstrating that the measurements were reproducible. NO removal (groups 1 and 2) did not modify systolic or diastolic BP, HR, CO, or LVSF but did induce a significant decline in SpO2, tcPO2 ( - 25 ± 5%) and TPV/RVET ratio ( - 25 ± 3%). No reinstitution reversed the effects of NO withdrawal on tcPO2, SpO2 and TPV/RVET ratio (group 2) without any changes in systemic hemodynamics. Conclusion: The shut-off of low-dose NO induced in each patient a decrease in oxygen delivery that may be due to increased pulmonary vascular resistances and or redistribution of pulmonary blood flow with ventilation-perfusion mismatching. The optimum weaning-off procedure of inhalational NO remains to be determined.