JOURNAL ARTICLE
REVIEW

Interventions to prevent hypothermia at birth in preterm and/or low birth weight infants

Emma M McCall, Fiona Alderdice, Henry L Halliday, Sunita Vohra, Linda Johnston
Cochrane Database of Systematic Reviews 2018 February 12, 2: CD004210
29431872

BACKGROUND: Newborn admission temperature is a strong predictor of outcomes across all gestations. Hypothermia immediately after birth remains a worldwide issue and, if prolonged, is associated with harm. Keeping preterm infants warm is difficult even when recommended routine thermal care guidelines are followed in the delivery room.

OBJECTIVES: To assess the efficacy and safety of interventions designed for prevention of hypothermia in preterm and/or low birth weight infants applied within 10 minutes after birth in the delivery room, compared with routine thermal care or any other single/combination of intervention(s) also designed for prevention of hypothermia in preterm and/or low birth weight infants applied within 10 minutes after birth in the delivery room.

SEARCH METHODS: We used the standard search strategy of Cochrane Neonatal to search the Cochrane Central Register of Controlled Trials (CENTRAL; 2016, Issue 5), MEDLINE via PubMed (1966 to 30 June 2016), Embase (1980 to 30 June 2016), and CINAHL (1982 to 30 June 2016). We also searched clinical trials databases, conference proceedings, and reference lists of retrieved articles for randomised controlled trials and quasi-randomised trials.

SELECTION CRITERIA: Trials using randomised or quasi-randomised allocations to test interventions designed to prevent hypothermia (apart from 'routine' thermal care) applied within 10 minutes after birth in the delivery room for infants at < 37 weeks' gestation and/or birth weight ≤ 2500 grams.

DATA COLLECTION AND ANALYSIS: We used Cochrane Neonatal methods when performing data collection and analysis.

MAIN RESULTS: Twenty-five studies across 15 comparison groups met the inclusion criteria, categorised as: barriers to heat loss (18 studies); external heat sources (three studies); and combinations of interventions (four studies).Barriers to heat loss Plastic wrap or bag versus routine carePlastic wraps improved core body temperature on admission to the neonatal intensive care unit (NICU) or up to two hours after birth (mean difference (MD) 0.58°C, 95% confidence interval (CI) 0.50 to 0.66; 13 studies; 1633 infants), and fewer infants had hypothermia on admission to the NICU or up to two hours after birth (typical risk ratio (RR) 0.67, 95% CI 0.62 to 0.72; typical risk reduction (RD) -0.25, 95% CI -0.29 to -0.20; number needed to treat for an additional beneficial outcome (NNTB) 4, 95% CI 4 to 5; 10 studies; 1417 infants). Risk of hyperthermia on admission to the NICU or up to two hours after birth was increased in infants in the wrapped group (typical RR 3.91, 95% CI 2.05 to 7.44; typical RD 0.04, 95% CI 0.02 to 0.06; number needed to treat for an additional harmful outcome (NNTH) 25, 95% CI 17 to 50; 12 studies; 1523 infants), but overall, fewer infants receiving plastic wrap were outside the normothermic range (typical RR 0.75, 95% CI 0.69 to 0.81; typical RD -0.20, 95% CI -0.26 to -0.15; NNTH 5, 95% CI 4 to 7; five studies; 1048 infants).Evidence was insufficient to suggest that plastic wraps or bags significantly reduce risk of death during hospital stay or other major morbidities, with the exception of reducing risk of pulmonary haemorrhage.Evidence of practices regarding permutations on this general approach is still emerging and has been based on the findings of only one or two small studies.External heat sourcesEvidence is emerging on the efficacy of external heat sources, including skin-to-skin care (SSC) versus routine care (one study; 31 infants) and thermal mattress versus routine care (two studies; 126 infants).SSC was shown to be effective in reducing risk of hypothermia when compared with conventional incubator care for infants with birth weight ≥ 1200 and ≤ 2199 grams (RR 0.09, 95% CI 0.01 to 0.64; RD -0.56, 95% CI -0.84 to -0.27; NNTB 2, 95% CI 1 to 4). Thermal (transwarmer) mattress significantly kept infants ≤ 1500 grams warmer (MD 0.65°C, 95% CI 0.36 to 0.94) and reduced the incidence of hypothermia on admission to the NICU, with no significant difference in hyperthermia risk.Combinations of interventionsTwo studies (77 infants) compared thermal mattresses versus plastic wraps or bags for infants at ≤ 28 weeks' gestation. Investigators reported no significant differences in core body temperature nor in the incidence of hypothermia, hyperthermia, or core body temperature outside the normothermic range on admission to the NICU.Two additional studies (119 infants) compared plastic bags and thermal mattresses versus plastic bags alone for infants at < 31 weeks' gestation. Meta-analysis of these two studies showed improvement in core body temperature on admission to the NICU or up to two hours after birth, but an increase in hyperthermia. Data show no significant difference in the risk of having a core body temperature outside the normothermic range on admission to the NICU nor in the risk of other reported morbidities.

AUTHORS' CONCLUSIONS: Evidence of moderate quality shows that use of plastic wraps or bags compared with routine care led to higher temperatures on admission to NICUs with less hypothermia, particularly for extremely preterm infants. Thermal mattresses and SSC also reduced hypothermia risk when compared with routine care, but findings are based on two or fewer small studies. Caution must be taken to avoid iatrogenic hyperthermia, particularly when multiple interventions are used simultaneously. Limited evidence suggests benefit and no evidence of harm for most short-term morbidity outcomes known to be associated with hypothermia, including major brain injury, bronchopulmonary dysplasia, retinopathy of prematurity, necrotising enterocolitis, and nosocomial infection. Many observational studies have shown increased mortality among preterm hypothermic infants compared with those who maintain normothermia, yet evidence is insufficient to suggest that these interventions reduce risk of in-hospital mortality across all comparison groups. Hypothermia may be a marker for illness and poorer outcomes by association rather than by causality. Limitations of this review include small numbers of identified studies; small sample sizes; and variations in methods and definitions used for hypothermia, hyperthermia, normothermia, routine care, and morbidity, along with lack of power to detect effects on morbidity and mortality across most comparison groups. Future studies should: be adequately powered to detect rarer outcomes; apply standardised morbidity definitions; focus on longer-term outcomes, particularly neurodevelopmental outcomes.

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