Sudden unexpected deaths after discharge from the neonatal intensive care unit
Introduction
Infants of low birthweight, short gestation, or both, are at significantly increased risk of sudden death during infancy.1, 2, 3 This increased risk applies to deaths that are sudden, unexpected and remain unexplained after full investigation (i.e. sudden infant death syndrome—SIDS)4 and those deaths that, although sudden and unexpected, are subsequently fully explained as being due for instance to infection, or previously unrecognised congenital anomalies.1, 4 Most published studies have concentrated on SIDS, and in the remainder of this paper we will deal primarily with this group, but it is important to remember that infants of low birthweight or short gestation are also at increased risk of sudden unexpected but explained deaths, particularly from unrecognised infections.1, 3, 4
Many of the epidemiological factors shown to be of significance in the prediction of high risk for SIDS are also significantly associated with the risk of preterm delivery or low birthweight—e.g. socio-economic deprivation, maternal smoking, young maternal age, maternal infection during pregnancy.1, 2, 5 It is thus difficult to separate the effects of preterm delivery from the effects of the factors that may have contributed to such delivery, and may also affect the risk of SIDS directly.
Thus, although it has been known for over 30 years that neonatal intensive care unit (NICU) graduates are at increased risk of SIDS, the nature of the factors contributing to that risk has not been cleared, and the value or importance of risk-reduction measures for this vulnerable group of infants has not been widely appreciated by those providing their neonatal care—commonly infants are discharged from NICUs after weeks or months of high technology intensive care, with the parents having been given very little or highly inaccurate information on how to minimise the risk of SIDS for their infant.3, 6, 7
The undoubted value of the prone position in improving oxygenation in small infants withrespiratory distress has led some neonatologists to worry about the validity of the ‘back to sleep’ message for SIDS prevention in ex-preterm infants. The frequency of gastro-oesophageal reflux in otherwise healthy preterm infants, and concern that this may be exacerbated by the supine sleep position has also led to concern about this position for preterm infants. The frequency of apnoea and bradycardia in preterm infants, and the concern that such episodes could contribute to the risk of SIDS has further confused the issue.
In this article we will review the evidence on the risk of SIDS for infants of low birthweight and short gestation, and present an evidence-based approach to reducing the risk of SIDS for such infants.
Section snippets
What is the risk of SIDS for infants of short gestation or low birthweight?
Studies conducted before back to sleep campaigns showed significantly increased risk of SIDS for infants of short gestation, and for those of very low birthweight. In the Oxford Record Linkage study from the UK, Golding et al.5 showed that the risk of SIDS increased with decreasing gestation at birth, and in a prospective population based study in the late 1980s in the Netherlands, Wieringa8 showed a SIDS rate of 15% for infants of less than 1500 g, though no other studies have identified such a
Sleeping position in the NICU and after discharge
Several studies in the late 1970s and early 1980s showed the potential benefits of the prone sleeping position for preterm infants in terms of oxygenation, reduction in apnoea, and reduction in the work of breathing.16, 17 The reported lower incidence and lesser severity of gastro-oesophagealreflux in preterm infants in the prone position has been seen by many neonatologists as a further reason for using this position for infants in the NICU.18, 19 The relationship between episodes of
Neonatal apnoea and the risk of SIDS
Episodes of apnoea or bradycardia on the neonatal period are very common in preterm infants, and in most neonatal units an apnoea-free period is included as part of the criteria for stopping apnoea monitoring and preparing for discharge. Several studies have addressed the question of whether the persistence of asymptomatic episodes of apnoea or bradycardia is predictive of subsequent adverse outcomes including apparent life-threatening events (ALTE) or SIDS. Southall et al.33, 34 showed in a
Identification of infants at particular risk of SIDS or apparent life-threatening events and the use of apnoea, cardiorespiratory or oxygenation monitors after discharge
Despite the widespread use, in Europe and North America of recordings of respiration, ECG and possibly oxygen saturation to identify infants reputedly at particular risk of SIDS or ALTE, the evidence upon which such assessments are based is unconvincing.1, 33, 34, 35, 40, 41
As noted above, the large studies by Southall et al.33, 34 showed that episodes of apnoea or bradycardia recorded at the time of discharge from hospital were of no value in predicting unexpected deaths in preterm or term
Evidence-based recommendations
All of the recommendations on reducing the risk of SIDS contained within the recent report of the CESDI SUDI study1 are clearly applicable to preterm, low birthweight or other infants with adverse perinatal histories (Table 1). A careful review of the published literature shows no evidence to treat such infants differently from low risk infants, and shows that the consequences of not following the recommendations—particularly with regard to sleeping position—may be more severe for high-risk
Acknowledgments
P.S.B. is supported by research grants from Babes in Arms, the Wellcome Trust and the Foundation for the Study of Infant Deaths.
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