Review question/objective

What is the effectiveness of interventions to prevent heat loss at birth in premature and/or very low birth weight infants?

The objective of this review is to identify the effectiveness of interventions to prevent hypothermia at birth in premature and/or very low birth weight infants.

Specifically, the objective is to identify the effectiveness of interventions to prevent heat loss among this group of patients at admission to the Neonatal Intensive Care Unit (NICU). Interventions can include plastic wraps and/or plastic hats.

Background

In 1997 the World Health Organization (WHO) established criteria for assessing hypothermia and published a guidebook on the thermal protection of newborns which indicated that hypothermia at birth is a worldwide problem, even for term infants. The World Health Organization classifications of hypothermia are: (1) mild hypothermia: 36.0 to 36.4 degrees; (2) moderate hypothermia: 32.0 to 35.9 degrees; and (3) severe hypothermia: below 32 degrees1

There are four different ways through which infants may lose heat. In particular, infants' body heat is lost through evaporation.1,2 But loss of body heat can also occur by conduction when the infant is placed naked on a cold surface like a table or cold mattress, by convection if the infant is naked and exposed to air flow from cooler surroundings, and by radiation from the infant to cooler objects such as a cold wall even though the infant may not be in contact with these surfaces.1

Developments in the treatment and care of premature and very low birth weight (VLBW) infants have lowered neonatal morbidity and increased the survival rate of premature infants.3 In Europe, the average prevalence of preterm infants has increased from 5% in 1978 to approximately 7% today.4 Several studies have proven that temperature control is essential to reducing the mortality for newborns and especially for the premature and VLBW infants.5-7 At birth, heat is lost rapidly to the cold external environment. If measures are not initiated to reduce the heat loss, the body temperature drops.8 A study conducted by Adamsons & Towell in 1965 shows that the drop in core body temperature is about 0.1 degrees per minute and in skin temperature, about 0.3 degrees per minute.9 Environmental regulation is essential for premature and VLBW infants because, unlike adults and older children, they have reduced brown fat, immature epidermal barrier and increased surface area, providing the premature or VLBW infant with only a limited ability to regulate their temperature.10 Besides infants born preterm and with low birth weight, those with an open defect in the skin including omphalocoele and gastroschisis are also at an increased risk of heat loss.11

Hypothermia can lead to harmful side effects including hypoglycaemia, respiratory distress, hypoxia, metabolic acidosis, coagulation defects and fetal circulation.11-13 Despite the harmful side effects and risks of increased mortality for premature and VLBW infants, keeping the infant sufficiently warm after birth remains problematic.

In the delivery room, conventional practice for prevention of heat loss has been practiced since 1966.14 The standard care includes a warm delivery room at a minimum of 25 degrees, drying the infant quickly after birth, resuscitation under radiant warmers (if available), and skin-to-skin contact with the mother.1

In this review the area of interest is interventions to prevent hypothermia for preterm and low birth weight infants immediately after birth. The interventions in focus are barriers to heat loss, such as providing the infant plastic wraps or plastic hats. To assess the efficacy and safety of the interventions designed for prevention of hypothermia at birth for preterm and/or low birth weight infants, interventions should be applied within 10 minutes after birth in the delivery room, compared to standard care as described above.

A preliminary search identified a systematic review on the topic by McCall et al. from 201012 including seven studies identified in searches of electronic databases from 1950 through October 2009. Furthermore, we found new studies published after October 2009 in our search. Hence a new systematic review of the literature would be appropriate.

Definition:

Hypothermia: core temperature below 36.5 degrees1

Normothermia: core temperature between 36.5 and 37.5 degrees2

Plastic wrap: transparent plastic wraps and bags made of polyethylene, wrapped around the infant including the back of the head

Intraventricular hemorrhage (IVH): Bleeding into the ventricles inside of the brain.

VLBW: Birth weight < 1500g

Inclusion criteria

Types of participants

This review will consider studies that include premature and very low birth weight (VLBW) infants of any ethnic background within the following categories: gestational age (< 28 weeks, 28-32 weeks and 33-37 weeks) and birth weight (<1500g). In this review, infants with increased risk of heat loss related to omphalocoele and gastroschisis will be excluded.

Types of intervention(s)/phenomena of interest

This review will include studies of single or a combination of interventions that evaluate the effect of interventions to prevent hypothermia at birth in the preterm and low birth weight infant within 10 minutes after birth in the delivery room. These interventions will be compared with standard care, which includes wiping away amniotic fluid and swaddling the infant.

Types of outcomes

This review will consider studies that include the following outcome measures: infant temperature on admission to NICU. Rectal temperature will be accepted as equivalent core body temperature and axillary temperature will be accepted as equivalent skin temperature. If both core temperature and skin temperature are present, core temperature will be the priority. Risk of hypothermia is defined as body temp < 36.5 degrees or skin temp <36 degrees.

Types of studies

This review will consider any experimental study design including randomized controlled trials that meet the inclusion criteria; however in the absence of such studies other quantitative study designs will be considered. This may include non-randomized controlled trials, quasi-experimental studies, and case-controlled and cohort studies that assess the effectiveness of plastic wraps to reduce hypothermia after birth.

Search strategy

The search strategy aims to find both published and unpublished studies. A three-step search strategy will be utilized in this review. An initial limited search of PubMed/MEDLINE will be undertaken followed by an analysis of the text words contained in the title and abstract, and of the index terms used to describe the article. A second search using all identified keywords and index terms will then be undertaken across all included databases. Thirdly, the reference lists of all identified reports and articles will be searched for additional studies. Studies published in English, Danish, Norwegian and Swedish will be considered for inclusion in this review. The search will be conducted in all databases from their inception as the previous review12 on hypothermia only includes experimental studies. It will thus be too restrictive to search from the end-date of this review as it is the aim to include both experimental studies and observational studies.

The databases to be searched include:

PubMed/MEDLINE (from 1966)

The Cochrane Library (from 1993)

EMBASE (from 1974)

CINAHL (from 1982)

The search for unpublished studies will include:

Mednar

Initial keywords to be used will be:

plastic barrier*, plastic wrap*, polythylene*, plastic bag*, bubbleplast*, babybag*, plastic cap*, infant, newborn, intensiv neontal care, hypotermia*

Assessment of methodological quality

Papers selected for retrieval will be assessed by two independent reviewers for methodological validity prior to inclusion in the review using standardized critical appraisal instruments from the Joanna Briggs Institute Meta-Analysis of Statistics Assessment and Review Instrument (JBI-MAStARI) (Appendix I). Any disagreements that may arise between the reviewers will be resolved through discussion, or with a third reviewer.

Data extraction

Data will be extracted from papers included in the review using the standardized data extraction tool from JBI-MAStARI (Appendix II). The data extracted will include specific details about the interventions, populations, study methods and outcomes of significance to the review question and specific objectives.

Data synthesis

Quantitative data will, where possible, be pooled in statistical meta-analysis using JBI-MAStARI. All results will be subject to double data entry. Effect sizes expressed as odds ratio (for categorical data) and their 95% confidence intervals will be calculated for analysis. Heterogeneity will be assessed statistically using the standard Chi-square. Where statistical pooling is not possible findings will be presented in a narrative form, including tables and figures to aid in data presentation where appropriate.

Conflicts of interest

The authors have no conflict of interest to declare.

References