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Keywords:

  • Administration, Inhalation;
  • Bronchopulmonary Dysplasia [mortality; prevention & control];
  • Cerebral Hemorrhage [epidemiology];
  • Incidence;
  • Infant, Newborn;
  • Infant, Premature;
  • Infant, Premature, Diseases [*therapy];
  • Nitric Oxide [*administration & dosage];
  • Randomized Controlled Trials as Topic;
  • Respiratory Insufficiency [*therapy];
  • Salvage Therapy;
  • Vasodilator Agents [*administration & dosage];
  • Humans

Abstract

Background

Inhaled nitric oxide (iNO) has been proven to be effective in term infants with hypoxic respiratory failure. The pathophysiology of respiratory failure, and the potential risks, differ substantially in preterm infants. Therefore, analysis of the efficacy and toxicities of iNO in infants born before 35 weeks is necessary.

Objectives

To determine the effect of treatment with iNO on the rates of death, bronchopulmonary dysplasia (BPD), intraventricular haemorrhage (IVH), or neurodevelopmental disability in preterm newborn infants (< 35 weeks gestation) with respiratory disease.

Search strategy

Standard methods of the Cochrane Neonatal Review Group were used. MEDLINE, EMBASE, Healthstar and the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library) were searched, using the following keywords: nitric oxide, clinical trial, and newborn covering the years from 1985 to 2006. In addition, the abstracts of the Pediatric Academic Societies were also searched.

Selection criteria

Randomised and quasi-randomised studies in preterm infants with respiratory disease that compared the effects of administration of iNO gas compared to control, with or without placebo are included in this review.

Data collection and analysis

Data regarding clinical outcomes including death, BPD (defined as oxygen dependence at 36 weeks postmenstrual age), IVH, periventricular leukomalacia (PVL), long term neurodevelopmental outcome and short term effects on oxygenation were excerpted from the trial reports by the investigators. Standard methods of the Cochrane Neonatal Review Group were used. Two investigators extracted, assessed and coded separately all data for each study. Any disagreement was resolved by discussion.

Main results

Eleven randomised controlled trials of inhaled nitric oxide therapy in preterm infants were found. The trials have been grouped post hoc into three categories depending on the entry criteria; entry in the first three days of life based on oxygenation criteria (Kinsella 1999; Hascoet 2004; INNOVO 2005; Van Meurs 2004; Mercier 1999; Dani 2006), routine use in intubated preterm babies (Schreiber 2003; Kinsella 2006) and later enrolment based on an increased risk of BPD (Subhedar 1997; Ballard 2006). The usefulness of the overall analyses was considered limited by the differing characteristics of the studies, and only subgroup analyses were performed.

Trials of early rescue treatment of infants based on oxygenation criteria demonstrated no significant effect of iNO on mortality or BPD. The subgroup of studies with routine use of iNO in intubated preterm infants demonstrated a marginally significant reduction in the combined outcome of death or BPD [typical RR 0.91 (95% CI 0.84, 0.99); typical RD -0.06 (95% CI -0.12, -0.01)]. Later treatment with iNO based on the risk of BPD demonstrated no significant benefit for this outcome in our analysis.

Studies of early rescue treatment with iNO demonstrated a trend toward increased risk of severe IVH, whereas the subgroup of studies with routine use in intubated preterm infants seems to show a reduction in the risk of having either a severe IVH or PVL [typical RR 0.70 (95% CI 0.53, 0.91); typical RD -0.07 (95% CI -0.12, -0.02)].

Later iNO treatment of infants at risk of BPD is given after the major risk period for IVH, and does not appear to lead to progression of old lesions.

Two studies (Schreiber 2003; INNOVO 2005) presented data on long term neurodevelopmental outcome. The early routine treatment study (Schreiber 2003) showed an improved outcome at two years corrected age, while the rescue treatment study (INNOVO 2005) showed no effect of iNO.

Authors' conclusions

iNO as rescue therapy for the very ill ventilated preterm infant does not appear to be effective and may increase the risk of severe IVH. Later use of iNO to prevent BPD also does not appear to be effective. Early routine use of iNO in mildly sick preterm infants may decrease serious brain injury and may improve survival without BPD. Further studies are needed to confirm these findings, to define groups most likely to benefit, and to describe long term outcomes.

Plain Language Summary

Inhaled nitric oxide for respiratory failure in preterm infants

The use of inhaled nitric oxide (iNO) may help reduce breathing failure in preterm babies.Breathing failure in premature newborn babies may be complicated by raised pressure within the vessels that carry blood to the lung (pulmonary hypertension). Medications that cause sedation or muscle relaxation and mechanically assisted breathing (mechanical or assisted ventilation) are used to treat pulmonary hypertension. Nitric oxide is believed to help regulate muscle tone in the arteries of the lungs and, thereby lessen pulmonary hypertension; however, iNO may also cause excessive bleeding (haemorrhage). This review of studies found that nitric oxide therapy may improve the chances of the baby having an improved outcome, but only when used in babies who were mildly ill. These studies indicated that there may be a decrease in serious bleeding in the brain (intracranial hemorrhage). When given to babies who were very ill, iNO did not seem to help, and may have contributed to an increase in intracranial hemorrhage.