Inositol in preterm infants at risk for or having respiratory distress syndrome

Inositol is an essential nutrient required by human cells in culture for growth and survival. Inositol promotes maturation of several components of surfactant and may play a critical role in fetal and early neonatal life. A drop in inositol levels in infants with respiratory distress syndrome (RDS) can be a sign that their illness will be severe.

To assess the effectiveness and safety of supplementary inositol in preterm infants with or without respiratory distress syndrome (RDS) in reducing adverse neonatal outcomes including: death (neonatal and infant deaths), bronchopulmonary dysplasia (BPD), retinopathy of prematurity (ROP), intraventricular haemorrhage (IVH), periventricular leukomalacia (PVL), necrotizing enterocolitis (NEC) and sepsis.

We used the standard search strategy of Cochrane Neonatal to search the Cochrane Central Register of Controlled Trials (CENTRAL 2018, Issue 11), MEDLINE via PubMed (1966 to 5 November 2018), Embase (1980 to 5 November 2018), and CINAHL (1982 to 5 November 2018). We searched clinical trial databases, conference proceedings, and the reference lists of retrieved articles for randomised controlled trials (RCT) and quasi-randomised trials.

We included all randomised controlled trials of inositol supplementation of preterm infants compared with a control group that received a placebo or no intervention. Outcomes included neonatal death, infant death, bronchopulmonary dysplasia (BPD), retinopathy of prematurity (ROP), intraventricular haemorrhage (IVH), necrotizing enterocolitis (NEC) and sepsis.

The three review authors independently abstracted data on neonatal outcomes and resolved any disagreements through discussion and consensus. Outcomes were reported as typical risk ratio (RR), risk difference (RD) and number needed to treat for an additional beneficial outcome (NNTB) or number needed to treat for an additional harmful outcome (NNTH). We used the GRADE approach to assess the quality of evidence.

Six published randomised controlled trials were identified, with a total of 1177 infants. Study quality varied for the comparison 'Inositol supplementation to preterm infants (repeat doses in any amount and any duration of treatment) versus control' and interim analyses had occurred in several trials for the outcomes of interest. In this comparison, neonatal death was found to be significantly reduced (typical RR 0.53, 95% CI 0.31 to 0.91; typical RD -0.09, 95% CI -0.16 to -0.01; NNTB 11, 95% CI 6 to 100; 3 trials, 355 neonates). Infant deaths were not reduced (typical RR 0.89, 95% CI 0.71 to 1.13; typical RD -0.02, 95% CI -0.07 to 0.02; 5 trials, 1115 infants) (low-quality evidence). ROP stage 2 or higher or stage 3 or higher was not significantly reduced (typical RR 0.89, 95% CI 0.75 to 1.06; typical RD -0.04, 95% CI -0.10 to 0.02; 3 trials, 810 infants) (moderate-quality evidence). There were no significant findings for ROP (any stage), NEC (suspected or proven), sepsis, IVH grade greater than II (moderate-quality evidence). For the comparison 'Inositol supplementation IV initially followed by enteral administration (repeat doses of 80 mg/kg/day) in preterm infants born at less than 30 weeks' postmenstrual age (PMA) compared to placebo for preterm infants at risk for or having respiratory distress syndrome' the results from two studies of high quality were included (N = 760 neonates). Recruitment to the larger study (N = 638) was terminated because of a higher rate of deaths in the inositol group. We did not downgrade the quality of the study. The meta-analyses of the outcomes of 'Type 1 ROP or death before determination of ROP outcome using the adjudicated ROP outcome', 'Type 1 ROP including adjudicated ROP outcome', 'All-cause mortality (outcome collected through first event: death, hospital discharge, hospital transfer, or 120 days after birth)' and 'Severe IVH (grade 3 or 4)' did not show significant findings (moderate-quality evidence). There were no significant findings for the outcomes 'BPD or death by it prior to 37 weeks' postmenstrual age (outcomes collected through first event: death, hospital discharge, hospital transfer, or 120 days after birth)', 'Late onset sepsis (> 72 hours of age)', and 'Suspected or proven NEC' (high-quality evidence).

Based on the evidence from randomised controlled trials to date, inositol supplementation does not result in important reductions in the rates of infant deaths, ROP stage 3 or higher, type 1 ROP, IVH grades 3 or 4, BPD, NEC, or sepsis. These conclusions are based mainly on two recent randomised controlled trials in neonates less than 30 weeks' postmenstrual age (N = 760), the most vulnerable population. Currently inositol supplementation should not be routinely instituted as part of the nutritional management of preterm infants with or without RDS. It is important that infants who have been enrolled in the trials included in this review are followed to assess any effects of inositol supplementation on long-term outcomes in childhood. We do not recommend any additional trials in neonates.