Postnatal dexamethasone in preterm infants

Is potentially lifesaving, but follow up studies are urgently needed

Clinical research must determine whether treatments enhance lives, make little difference, cause significant harm, or do several of these things. This is well illustrated by the epidemic of blindness due to retrolental fibroplasia that affected thousands of preterm babies in the 1950s.1 Although oxygen was accepted as lifesaving in severe respiratory distress syndrome, randomised controlled trials showed that its unrestricted use could also cause permanent visual impairment. The risk is minimised with modern oxygen therapy, which is strictly controlled. The lesson is that new treatments need to be tested with randomised trials that are large enough and with follow ups long enough to provide robust data on all clinically important endpoints 12 Dexamethasone for chronic lung disease in preterm infants may be a similar case where we need better data from larger trials with longer follow up.

In the past two decades dexamethasone has gained wide acceptance in routine practice for the postnatal treatment or prevention of chronic lung disease in preterm infants. Although dexamethasone is commonly associated with transient side effects, several randomised trials have shown that it rapidly reduces oxygen requirements and shortens the duration of ventilation.3 However, the longer term impact of postnatal dexamethasone on mortality and morbidity in survivors is less clear.

The table shows hospital mortality in all randomised studies of postnatal dexamethasone which have been identified and critically appraised according to the methods of the Cochrane Collaboration. These are arranged in groups, prespecified by the Cochrane reviewers, by onset of treatment: (a) early postnatal (<96 hours),4(b) moderately early postnatal (7-14 days),5 and (c) delayed (>3 weeks).6 There was a trend to lower mortality after moderately early dexamethasone, but not after early or delayed therapy. Of concern, however, is the suggestion of a risk of cerebral palsy.7^–9 The table summarises the best currently available evidence, including follow up data not yet available in the Cochrane Library.

Two trials suggest an increased risk of morbidity after 12 months, defined as cerebral palsy—one of them after early dexamethasone and one of them after delayed dexamethasone. Two further trials of delayed dexamethasone show a trend to increased risk and one of moderately early treatment shows no increased risk, though two of these trials were very small. As there is no evidence that early or delayed dexamethasone increases survival, any excess in cerebral palsy could not be attributed to increased salvage of prenatally impaired infants. Furthermore, the table may underestimate the true benefits and risks of dexamethasone, as in some studies control infants “crossed over” to receive open label dexamethasone, potentially blunting differences in outcome. The picture may be further complicated by publication bias, as so far only five studies have described neurodevelopmental outcome. We do not yet know whether these studies have been preferentially published because of the disquieting implications.

The paucity of follow up data is a major problem, however, and highlights the need to invest in better national and regional organisation of routine follow up, so perinatal studies can report follow up data as promptly as possible.10 Only then can we determine whether or not dexamethasone is a lifesaving therapy with potentially serious complications, like oxygen.

A definitive randomised controlled trial of dexamethasone, started in infants at high risk between 7 and 14 days at a lower dose than usual, now merits special priority, since these are the infants whom dexamethasone seems most likely to benefit. Until more follow up data are available clinicians who use dexamethasone liberally or in infants without life threatening lung disease would be wise to review their practice against the best currently available evidence. In any trial clinicians should discuss the need for longer term follow up when seeking initial consent and forge a continuing partnership with the parents to achieve this.

The “short termism” that is satisfied with surrogate measures as a substitute for longer term outcomes seems increasingly difficult to justify Clinicians may be pleased that dexamethasone allows babies to come off supplemental oxygen more quickly, but from the parents' perspective this is a minor issue. For parents the key question is,”Will this treatment increase the chances of survival, and its quality?” Clinical trials should assess all clinically relevant outcomes. We need randomised trials which report longer term follow up to be sure that patients are not paying a long term price for some relatively minor short term gains.