PEDIATRICS Vol. 100 No. 5 November 1997, p. e7
Received Mar 7, 1997; accepted Jul 2, 1997.
, #,
,
From the Departments of * Cardiology,
Anesthesia, § Medicine,
Respiratory Care, and the ¶ Joint Program in Neonatology,
Children's Hospital, and the # Department of Pediatrics,
Harvard Medical School, Boston, Massachusetts.
Objective. To determine the effect of inhaled nitric oxide (NO) on clinical outcome in newborns with persistent pulmonary hypertension (PPHN).
Design. A prospective, randomized trial of patients referred to a level 3 nursery in a single large center. Clinicians were not masked to group assignment. Crossover of patients from control to NO treatment was not permitted.
Methods. We randomized 49 mechanically ventilated newborns, transferred to our center with clinical and echocardiographic evidence of severe PPHN (arterial oxygen tension [PaO2] <100; fractional inspired oxygen = 1) to treatment with or without NO. Patients with gestational age <34 weeks or with congenital heart disease or diaphragmatic hernia were excluded. High-frequency oscillatory ventilation was used but not allowed concomitantly with NO. Primary outcome variables were oxygenation, mortality, and use of extracorporeal membrane oxygenation (ECMO).
Results. Meconium aspiration syndrome and isolated PPHN
were the most common diagnoses (32/49) and were distributed equally between groups. The median age at the time of entry into the study was
similar between groups, 25 hours for control patients and 18 hours for
NO patients. Median baseline oxygenation index (OI) was similar in 23 control (OI = 29) and 26 NO (OI = 30) patients. Mortality
(8%), use of ECMO (33%), median days on mechanical ventilation (9 days), and duration of supplemental oxygen (13 days) were not different
between treatment groups. PaO2, oxygen
saturation, and OI improved in the NO group compared with baseline and
to control patients at 15 minutes. The median percent change in OI
(
31%) in the NO group was significantly different from baseline and from the control group. The difference in oxygenation between treatment
groups was still apparent 12 hours after baseline. Before cannulation
for ECMO, oxygenation was better in the NO group compared with control
patients. Among patients who were placed on ECMO, the median time from
baseline to ECMO cannulation was 2.4 hours (range, 1 to 12 hours) among
control patients and 3.3 hours (range, 2 to 68 hours) for those
randomized to receive NO. There was a tendency to observe fewer adverse
neurologic events (seizure and intracranial hemorrhage) in the NO group
(4/26 vs 8/23). One child with alveolar capillary dysplasia confirmed
by postmortem examination could not be weaned from 80 parts per million
of NO and transiently developed methemoglobinemia (peak methemoglobin
level = 17%). No other side effects were observed.
Conclusions. Although mortality and ECMO use were similar for both treatment groups using this study size and design, sustained improvement in oxygenation with NO and better oxygenation at initiation of ECMO may have important clinical benefits. We speculate that modification of treatment to include specific lung expansion strategies with NO treatment and recognition that early improvement of oxygenation may be sustained with NO may lead to reduced use of ECMO in NO treated patients compared with controls.
Key words: persistent fetal circulation, extracorporeal membrane oxygenation, high-frequency oscillatory ventilation, alveolar capillary dysplasia, methemoglobin.