Delivery Room Interventions for Hypothermia in Preterm Neonates: A Systematic Review and Network Meta-analysis | Neonatology | JAMA Pediatrics | JAMA Network
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Figure 1.  Network Plot, Surface Under the Cumulative Ranking Curve (SUCRA) Plot, and Forest Plot for Core Body Temperature at Admission or Within 2 Hours of Life
Network Plot, Surface Under the Cumulative Ranking Curve (SUCRA) Plot, and Forest Plot for Core Body Temperature at Admission or Within 2 Hours of Life

A, The size of nodes representing the interventions in network plots is proportional to the number of neonates receiving the intervention, and the width of the lines connecting the nodes is proportional to the number of trials evaluating the 2 interventions in a pairwise manner. The number of trials comparing any 2 interventions is indicated along the lines. B, SUCRA values for each intervention are as follows: plastic bag or wrap with thermal mattress (PBWrTM), 89.1%; plastic cap (PCAP), 71.6%; plastic bag or wrap with heated humidified respiratory gases (PBWrHHGAS), 66.5%; plastic bag or wrap with plastic cap (PBWrPCAP), 47.7%; thermal mattress (TM), 46.6%; plastic bag or wrap with incubator transport (INCUPBWr), 42.4%; plastic bag or wrap (PBWr), 35.5%; and routine care (RCARE), 4.7%. Higher rankings are associated with larger outcome values. C, Forest plot shows the mean difference (MD) in core temperature with 95% credible interval (CrI) of the different interventions with routine care as the common comparator.

Figure 2.  League Plot of the Network Estimates for Core Body Temperature at Admission or Within 2 Hours of Life
League Plot of the Network Estimates for Core Body Temperature at Admission or Within 2 Hours of Life

League plots compare the effect estimate for an intervention in the column with an intervention in a row. Network estimates are depicted as risk ratio (RR) with 95% credible interval (CrI). INCUPBWr indicates plastic bag or wrap with incubator transport; PBWr, plastic bag or wrap; PBWrHHGAS, plastic bag or wrap with heated humidified respiratory gases; PBWrPCAP, plastic bag or wrap with plastic cap; PBWrTM, plastic bag or wrap with thermal mattress; PCAP, plastic cap; RCARE, routine care; and TM, thermal mattress.

aRR is statistically significant.

Figure 3.  Network Plot, Surface Under the Cumulative Ranking Curve (SUCRA) Plot, and Forest Plot for Moderate to Severe Hypothermia at Admission or Within 2 Hours of Life
Network Plot, Surface Under the Cumulative Ranking Curve (SUCRA) Plot, and Forest Plot for Moderate to Severe Hypothermia at Admission or Within 2 Hours of Life

A, The size of nodes representing the interventions in network plots is proportional to the number of neonates receiving the intervention, and the width of the lines connecting the nodes is proportional to the number of trials evaluating the 2 interventions in a pairwise manner. The number of trials comparing any 2 interventions is indicated along the lines. B, SUCRA values are arranged from highest to lowest, as follows: thermal mattress (TM), 76.9%; plastic bag or wrap with heated humidified respiratory gases (PBWrHHGAS), 74.9%; skin-to-skin contact (SSC), 72.7%; plastic bag or wrap with thermal mattress (PBWrTM), 60.3%; plastic bag or wrap (PBWr), 44.8%; plastic bag or wrap with plastic cap (PBWrPCAP), 40.4%; plastic bag or wrap with incubator transport (INCUPBWr), 23.6%; and routine care (RCARE), 6.4%. Higher rankings are associated with better outcome values. C, Forest plot used the bayesian approach. D, Forest plot used the frequentist approach. CrI indicates credible interval; RR, risk ratio.

Table 1.  Characteristics of Included Studies
Characteristics of Included Studies
Table 2.  Certainty of Evidence for Different Comparisons for the Primary Outcomesa
Certainty of Evidence for Different Comparisons for the Primary Outcomesa
Supplement.

eFigure 1. PRISMA flow

eFigure 2. Mean gestational age of the enrolled neonates

eFigure 3. Mean birth weight of the enrolled neonates

eFigure 4. Risk of bias summary and graph of the included trials

eFigure 5. Direct evidence from the pair wise comparisons for the primary outcome: mean core body temperature (axillary or rectal) at admission or within first 2 hours of life

eFigure 6. Split between direct and indirect evidence for the primary outcome: mean core body temperature (axillary or rectal) at admission or within first 2 hours of life

eFigure 7. Sensitivity analysis by evaluating plastic bag and plastic wrap as separate interventions for the primary outcome: mean core body temperature (axillary or rectal) at admission or within first 2 hours of life. A. Network plot; B. SUCRA plot; C. Forest plot depicting the network estimates [MD (95% CrI)] of the various interventions with “Routine Care” as the common comparator

eFigure 8. League plot depicting the network estimate [MD (95% CrI)] for sensitivity analysis by evaluating plastic bag and plastic wrap as separate interventions for the primary outcome: mean core body temperature (axillary or rectal) at admission or within first 2 hours of life

eFigure 9. Split between direct and indirect evidence for sensitivity analysis by evaluating plastic bag and plastic wrap as separate interventions for the primary outcome: mean core body temperature (axillary or rectal) at admission or within first 2 hours of life

eFigure 10. Sensitivity analysis by evaluating studies in which the mean gestational age of the included neonates was</ = 30 weeks for the primary outcome: mean core body temperature (axillary or rectal) at admission or within first 2 hours of life. A. Network plot; B. SUCRA plot; C. Forest plot depicting the network estimates [MD (95% CrI)] of the various interventions with “Routine Care” as the common comparator

eFigure 11. League plot depicting the network estimate for sensitivity analysis by evaluating studies in which the mean gestational age of the included neonates was</ = 30 weeks for the primary outcome: mean core body temperature (axillary or rectal) at admission or within first 2 hours of life

eFigure 12. Split between direct and indirect evidence for sensitivity analysis by evaluating studies in which the mean gestational age of the included neonates was</ = 30 weeks for the primary outcome: mean core body temperature (axillary or rectal) at admission or within first 2 hours of life

eFigure 13. Meta-regression with gestational age as covariate

eFigure 14. Sensitivity analysis by evaluating drying versus no drying before wrapping in a plastic bag/wrap for the primary outcome: mean core body temperature (axillary or rectal) at admission or within first 2 hours of life. A. Network plot; B. SUCRA plot; C. Forest plot depicting the network estimates [MD (95% CrI)] of the various interventions with “Routine Care” as the common comparator

eFigure 15. League plot depicting the network estimate for sensitivity analysis - drying vs no drying before wrapping in a plastic bag/wrap for the primary outcome: mean core body temperature (axillary or rectal) at admission or within first 2 hours of life

eFigure 16. League plot depicting the network estimate [RR (95% CrI)] for primary outcome moderate or severe hypothermia [defined as core body temperature (axillary or rectal) less than 36 degree Celsius] at admission or within 2 hours of life

eFigure 17. Direct evidence from the pair wise comparisons for the primary outcome moderate or severe hypothermia [defined as core body temperature (axillary or rectal) less than 36 degree Celsius] at admission or within 2 hours of life

eFigure 18. Split between direct and indirect evidence for the primary outcome moderate or severe hypothermia [defined as core body temperature (axillary or rectal) less than 36 degree Celsius] at admission or within 2 hours of life

eFigure 19. Sensitivity analysis by evaluating any hypothermia (defined as core body temperature less than 36.5 °C at admission or within 1-2 hours of life). A. Network plot; B. SUCRA plot; C. Forest plot depicting the network estimates [MD (95% CrI)] of the various interventions with “Routine Care” as the common comparator

eFigure 20. League plot depicting the network estimate [RR (95% CrI)] for sensitivity analysis - any hypothermia (defined as core body temperature less than 36.5 degree Celsius at admission or within 1-2 hours of life)

eFigure 21. Split between direct and indirect evidence for sensitivity analysis - any hypothermia (defined as core body temperature less than 36.5 degree Celsius at admission or within 1-2 hours of life)

eFigure 22. Direct evidence from the pair wise comparisons for sensitivity analysis - any hypothermia (defined as core body temperature less than 36.5 degree Celsius at admission or within 1-2 hours of life)

eFigure 23. Mortality before discharge. A. Network plot; B. SUCRA plot; C. Forest plot depicting the network estimates [MD (95% CrI)] of the various interventions with “Routine Care” as the common comparator

eFigure 24. League plot depicting the network estimate [RR (95% CrI)] for mortality before discharge

eFigure 25. Split between direct and indirect evidence for mortality before discharge

eFigure 26. Direct evidence from the pair wise comparisons for mortality before discharge

eFigure 27. Hyperthermia [defined as core body temperature (axillary or rectal) more than 37.5 degree Celsius] at admission or within 2 hours of life A. Network plot; B. SUCRA plot; C. Forest plot depicting the network estimates [MD (95% CrI)] of the various interventions with “Routine Care” as the common comparator

eFigure 28. League plot depicting the network estimate [RR (95% CrI)] for hyperthermia [defined as core body temperature (axillary or rectal) more than 37.5 degree Celsius] at admission or within 2 hours of life

eFigure 29. Split between direct and indirect evidence for hyperthermia [defined as core body temperature (axillary or rectal) more than 37.5 °C] at admission or within 2 hours of life

eFigure 30. Direct evidence from the pair wise comparisons for hyperthermia [defined as core body temperature (axillary or rectal) more than 37.5 degree Celsius] at admission or within 2 hours of life

eFigure 31. Major brain injury (MBI) defined as grade III-IV intraventricular hemorrhage or periventricular leukomalacia A. Network plot; B. SUCRA plot; C. Forest plot depicting the network estimates [MD (95% CrI)] of the various interventions with “Routine Care” as the common comparator

eFigure 32. League plot depicting the network estimate [RR (95% CrI)] for MBI [defined as grade III-IV intraventricular hemorrhage or periventricular leukomalacia]

eFigure 33. Direct evidence from the pair wise comparisons for MBI [defined as grade III-IV intraventricular hemorrhage or periventricular leukomalacia]

eFigure 34. Funnel plots and trim plots for pairwise comparisons - 'PBWr' versus 'routine

care' for outcomes - mean core body temperature, mortality before discharge, hyperthermia

eTable 1. Literature search strategy for two electronic databases

eTable 2. Some of the studies that were excluded for valid reasons

eTable 3. Network characteristics for all the outcomes and sensitivity analysis

eTable 4. Certainty of evidence for different comparisons for the sensitivity analyses and secondary outcomes

eTable 5. Summary of results of the network meta-analysis

eReferences

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Linnér  A, Klemming  S, Sundberg  B,  et al.  Immediate skin-to-skin contact is feasible for very preterm infants but thermal control remains a challenge.   Acta Paediatr. 2020;109(4):697-704. doi:10.1111/apa.15062 PubMedGoogle ScholarCrossref
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Meyer  MP, Payton  MJ, Salmon  A, Hutchinson  C, de Klerk  A.  A clinical comparison of radiant warmer and incubator care for preterm infants from birth to 1800 grams.   Pediatrics. 2001;108(2):395-401. doi:10.1542/peds.108.2.395 PubMedGoogle ScholarCrossref
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Roberts  JR. Use of a Stockinette Cap on Premature Infants After Delivery. Dissertation. Texas Women’s University; 1981.
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Brignardello-Petersen  R, Murad  MH, Walter  SD,  et al; GRADE Working Group.  GRADE approach to rate the certainty from a network meta-analysis: avoiding spurious judgments of imprecision in sparse networks.   J Clin Epidemiol. 2019;105:60-67. doi:10.1016/j.jclinepi.2018.08.022 PubMedGoogle ScholarCrossref
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Rabe  H, Gyte  GM, Díaz-Rossello  JL, Duley  L.  Effect of timing of umbilical cord clamping and other strategies to influence placental transfusion at preterm birth on maternal and infant outcomes.   Cochrane Database Syst Rev. 2019;9(9):CD003248. doi:10.1002/14651858.CD003248.pub4 PubMedGoogle Scholar
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Hissink Muller  PC, van Berkel  LH, de Beaufort  AJ.  Axillary and rectal temperature measurements poorly agree in newborn infants.   Neonatology. 2008;94(1):31-34. doi:10.1159/000112840 PubMedGoogle ScholarCrossref
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Charafeddine  L, Tamim  H, Hassouna  H, Akel  R, Nabulsi  M.  Axillary and rectal thermometry in the newborn: do they agree?   BMC Res Notes. 2014;7:584. doi:10.1186/1756-0500-7-584 PubMedGoogle ScholarCrossref
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    Original Investigation
    May 24, 2021

    Delivery Room Interventions for Hypothermia in Preterm Neonates: A Systematic Review and Network Meta-analysis

    Author Affiliations
    • 1Department of Neonatology, Sri Ramachandra Institute of Higher Education and Research, Chennai, India
    • 2Department of Neonatology, Ankura Hospital for Women and Children, Hyderabad, India
    • 3Department of Neonatology, Dr Ram Manohar Lohia Hospital and Post Graduate Institute of Medical Education and Research, New Delhi, India
    • 4Division of Clinical Library, Sidra Hospital, Doha, Qatar
    • 5Department of Neonatology, All India Institute of Medical Sciences, Jodhpur, India
    • 6Department of Pediatrics, Medical School, University of Padua, Azienda Ospedaliera Padova, Padua, Italy
    • 7National Perinatal Epidemiology Unit, Nuffield Department of Population Health, Medical Sciences Division, University of Oxford, Oxford, United Kingdom
    JAMA Pediatr. 2021;175(9):e210775. doi:10.1001/jamapediatrics.2021.0775
    Key Points

    Question  Of the thermal care interventions available in the delivery room, which is the most appropriate for reducing hypothermia and improving clinical outcomes in preterm neonates?

    Findings  In this network meta-analysis of 34 trials involving 3688 newborns and 9 interventions, a combination of plastic bag or wrap with a plastic cap or with heated humidified respiratory gas was associated with reduced risk of mortality before discharge and major brain injury while stabilizing the core body temperature immediately after birth. Certainty of evidence for these interventions was moderate for temperature stabilization and low to moderate for other clinical outcomes.

    Meaning  In this study, delivery room use of a plastic bag or wrap with a plastic cap or with heated humidified gas appeared to be the appropriate thermal care intervention for preterm neonates.

    Abstract

    Importance  Prevention of hypothermia in the delivery room is a cost-effective, high-impact intervention to reduce neonatal mortality, especially in preterm neonates. Several interventions for preventing hypothermia in the delivery room exist, of which the most beneficial is currently unknown.

    Objective  To identify the delivery room thermal care intervention that can best reduce neonatal hypothermia and improve clinical outcomes for preterm neonates born at 36 weeks’ gestation or less.

    Data Sources  MEDLINE, the Cochrane Central Register of Controlled Trials, Embase, and CINAHL databases were searched from inception to November 5, 2020.

    Study Selection  Randomized and quasi-randomized clinical trials of thermal care interventions in the delivery room for preterm neonates were included. Peer-reviewed abstracts and studies published in non–English language were also included.

    Data Extraction and Synthesis  Data from the included trials were extracted in duplicate using a structured proforma. A network meta-analysis with bayesian random-effects model was used for data synthesis.

    Main Outcomes and Measures  Primary outcomes were core body temperature and incidence of moderate to severe hypothermia on admission or within the first 2 hours of life. Secondary outcomes were incidence of hyperthermia, major brain injury, and mortality before discharge. The 9 thermal interventions evaluated were (1) plastic bag or plastic wrap covering the torso and limbs with the head uncovered or covered with a cloth cap; (2) plastic cap covering the head; (3) skin-to-skin contact; (4) thermal mattress; (5) plastic bag or plastic wrap with a plastic cap; (6) plastic bag or plastic wrap along with use of a thermal mattress; (7) plastic bag or plastic wrap along with heated humidified gas for resuscitation or for initiating respiratory support in the delivery room; (8) plastic bag or plastic wrap along with an incubator for transporting from the delivery room; and (9) routine care, including drying and covering the body with warm blankets, with or without a cloth cap.

    Results  Of the 6154 titles and abstracts screened, 34 studies that enrolled 3688 neonates were analyzed. Compared with routine care alone, plastic bag or wrap with a thermal mattress (mean difference [MD], 0.98 °C; 95% credible interval [CrI], 0.60-1.36 °C), plastic cap (MD, 0.83 °C; 95% CrI, 0.28-1.38 °C), plastic bag or wrap with heated humidified respiratory gas (MD, 0.76 °C; 95% CrI, 0.38-1.15 °C), plastic bag or wrap with a plastic cap (MD, 0.62 °C; 95% CrI, 0.37-0.88 °C), thermal mattress (MD, 0.62 °C; 95% CrI, 0.33-0.93 °C), and plastic bag or wrap (MD, 0.56 °C; 95% CrI, 0.44-0.69 °C) were associated with greater core body temperature. Certainty of evidence was moderate for 5 interventions and low for plastic bag or wrap with a thermal mattress. When compared with routine care alone, a plastic bag or wrap with heated humidified respiratory gas was associated with less risk of major brain injury (risk ratio, 0.23; 95% CrI, 0.03-0.67; moderate certainty of evidence) and a plastic bag or wrap with a plastic cap was associated with decreased risk of mortality (risk ratio, 0.19; 95% CrI, 0.02-0.66; low certainty of evidence).

    Conclusions and Relevance  Results of this study indicate that most thermal care interventions in the delivery room for preterm neonates were associated with improved core body temperature (with moderate certainty of evidence). Specifically, use of a plastic bag or wrap with a plastic cap or with heated humidified gas was associated with lower risk of major brain injury and mortality (with low to moderate certainty of evidence).

    Introduction

    Neonatal hypothermia is a serious problem in both low- or middle-income and high-income countries.1-3 The dose-response association between the severity of neonatal hypothermia and the risk of mortality is well established.3-6 Hence, prevention of neonatal hypothermia in the delivery room is touted as a cost-effective, high-impact intervention to reduce neonatal mortality. The 2020 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations reiterated its previous advice to use additional thermal care interventions, such as maintaining delivery room temperature at 23 to 25 °C and using warm blankets, plastic wraps without drying, thermal mattresses, and caps for neonates born at less than 32 weeks’ gestation.7 However, authors of the 2020 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations stressed the weakness of the previous guidance on the basis of very low certainty of evidence and indicated the need for an updated systematic review.7 Apart from assessing the benefits of the interventions, establishing the safety of these interventions is also essential, given that some studies have shown an increased risk of hyperthermia with their use.8-10

    Previous systematic reviews have compared several thermal care interventions in pairwise meta-analyses.8-11 However, faced with a rapidly evolving evidence base and a choice of several competing interventions for which direct pairwise comparisons are not available, a systematic review based on network meta-analysis for data synthesis may be considered as an appropriate evaluation strategy.12 Hence, in the present study, we conducted a network meta-analysis to compare the outcomes and safety of different delivery room thermal care interventions. Our aim was to identify the delivery room intervention that can best reduce neonatal hypothermia and improve clinical outcomes for preterm neonates born at 36 weeks’ gestation or less.

    Methods

    The protocol was registered with PROSPERO.13 We followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guideline with a network meta-analysis extension.14

    Population, Interventions, and Outcomes

    We included randomized clinical trials (RCTs) and quasi-RCTs that evaluated thermal care interventions in the delivery room for preterm neonates born at 36 weeks’ gestation or less. Studies published as peer-reviewed abstracts or in non-English language were also included. Studies that included the term infants or infants with birth weight greater than 2500 g were excluded.

    The following 9 thermal care interventions were included: (1) plastic bag or plastic wrap covering the torso and limbs with the head uncovered or covered with a cloth cap; (2) plastic cap covering the head; (3) skin-to-skin contact; (4) thermal mattress; (5) plastic bag or plastic wrap covering the torso and limbs with the head covered with a plastic cap; (6) plastic bag or plastic wrap covering the torso and limbs along with use of a thermal mattress; (7) plastic bag or plastic wrap covering the torso and limbs along with heated humidified gas for resuscitation or for initiating invasive or noninvasive respiratory support in the delivery room; (8) plastic bag or plastic wrap covering the torso and limbs along with an incubator for transporting from the delivery room; and (9) routine care, including drying and covering the body with warm blankets, with or without a cloth cap.

    The primary outcomes were core body temperature (using axillary or rectal measurement) and incidence of moderate to severe hypothermia (defined as body temperature <36 °C) at admission or within the first 2 hours of life. Although incidence of hypothermia was the a priori decided primary outcome, moderate to severe hypothermia was reported as the primary outcome in this systematic review. The secondary outcomes were incidence of hyperthermia (defined as body temperature >37.5 °C), major brain injury (grade 3 or 4 intraventricular hemorrhage15 or periventricular leukomalacia), and mortality before discharge.

    Literature Search and Risk-of-Bias Assessment

    We searched MEDLINE, the Cochrane Central Register of Controlled Trials, Embase, and CINAHL from their inception to November 5, 2020. Reference lists of included trials and published systematic reviews were also searched to identify additional studies. Two of us (T.B. and S.T.) screened the title and abstract of all studies using Rayyan-QCRI software (Rayyan),16 and independently assessed the full-text articles for potentially relevant trials. The search strategy is provided in eTable 1 in the Supplement.

    Two of us (T.A. and V.V.R.) independently assessed the risk of bias (low, high, or unclear) in all included trials using the Cochrane risk-of-bias tool, version 1.0 (Cochrane).17 Discrepancies were resolved by consulting a third author (C.C.R.).

    Data Extraction and Data Synthesis

    Two of us (T.A. and V.V.R.) independently extracted data from the included trials and data in duplicate using a structured proforma. A network meta-analysis with bayesian random-effects model was used for data synthesis.18,19 Noninformative priors and generalized linear models with 4 chains, burn-in of 50 000 iterations, followed by 100 000 iterations and 10 000 adaptations, were used.19 Geometry of networks for all outcomes was evaluated using network plots. Model convergence was assessed with the Gelman-Rubin statistic trace and density plots.20 Fit of the model was analyzed with leverage plots, total residual deviance, and deviance information criterion. Node splitting was used to detect inconsistency.21 I2 statistic and Cochran Q test were used to evaluate heterogeneity in a pairwise meta-analysis for direct evidence. Publication bias was identified using a funnel plot when a meta-analysis included 10 or more trials.

    Statistical Analysis

    Statistical analysis was performed with R (R Foundation for Statistical Computing). Network estimates were expressed as risk ratio (RR) or mean difference (MD), with respective 95% credible interval (CrI), and were illustrated with league plots and forest plots. Ranking of interventions for all outcomes was done with surface under the cumulative ranking curve (SUCRA) plots.22 SUCRA values when expressed as a percentage can range from 0% to 100%. The higher the SUCRA value, the better the ranking of the intervention. SUCRA values are prone to misinterpretation; the value needs to be interpreted along with the certainty of evidence for any intervention. In addition, SUCRA can vary for an intervention for different outcomes. Although an intervention may be ranked higher for its improved outcomes, it could be ranked down for its adverse effect profile. These factors need to be considered by the clinician while interpreting SUCRA and before adopting any intervention to practice. Meta-regression with gestational age as a covariate was performed for the primary outcome. Certainty of evidence for all of the estimates was ascertained according to the GRADE Working Group recommendations for a network meta-analysis.23

    We also conducted sensitivity analyses for the following: (1) neonates born at 30 weeks’ gestation or less; (2) plastic bag and plastic wrap as separate interventions; (3) drying vs no drying before application of plastic bag or wrap; and (4) incidence of any hypothermia defined as a core body temperature <36.5 °C at admission or within the first 2 hours of life.

    Results

    A total of 6154 titles and abstracts were screened, of which 34 studies that enrolled 3688 neonates were included (eFigure 1 in the Supplement).24-57 Among the 34 studies were 4 three-armed RCTs.30,51,54,55 The mean gestational age of the neonates was 29 weeks, and their mean birth weight was 1200 g (eFigures 2 and 3 in the Supplement). The characteristics of the included trials are given in Table 1. The characteristics of some of the excluded studies are shown in eTable 2 in the Supplement along with the reasons for exclusion.58-64

    Risk of Bias

    Among the 34 included trials, 4 (12%) had high risk and 8 (24%) had unclear risk of selection bias.24-26,28,30-32,34-36,50,54 Masking of the interventions was not performed in most studies, except in 2 (6%) in which only the outcome assessors were masked.26,50 One trial (3%) had high risk of attrition bias,30 and 6 studies (18%) had high risk of other biases.26,27,30,40,43,50 The risk-of-bias assessment of individual trials is shown in eFigure 4 in the Supplement.

    Primary Outcomes

    Thirty-two studies (94%), which involved 3568 neonates, reported the primary outcome of core body (axillary or rectal) temperature at admission or within 2 hours of life.24,25,27-43,45-57 Eight interventions, including routine care, were evaluated in these 32 studies. Figure 1 shows the network plot, SUCRA plot, and forest plot with routine care as the common comparator. Figure 2 shows the league plot that depicts the network estimates for various comparisons. Forest plots for the direct evidence are provided in eFigure 5 in the Supplement. No inconsistency was found on node-splitting analysis (eFigure 6 in the Supplement). Certainty of evidence assessment for primary outcomes is listed in Table 2. The characteristics of the networks for all of the outcomes can be found in eTable 3 in the Supplement.

    Compared with routine care alone, plastic bag or wrap with a thermal mattress (MD, 0.98 °C; 95% CrI, 0.60-1.36 °C), plastic cap (MD, 0.83 °C; 95% CrI, 0.28-1.38 °C), plastic bag or wrap with heated humidified respiratory gas (MD, 0.76 °C; 95% CrI, 0.38-1.15 °C), plastic bag or wrap with a plastic cap (MD, 0.62 °C; 95% CrI, 0.37-0.88 °C), thermal mattress (MD, 0.62 °C; 95% CrI, 0.33-0.93 °C), and plastic bag or wrap alone (MD, 0.56 °C; 95% CrI, 0.44-0.69 °C) were associated with greater core body temperature. Certainty of evidence was moderate for 5 interventions and was low for plastic bag or wrap with a thermal mattress. Plastic bag or wrap with a thermal mattress was ranked as the most beneficial intervention (SUCRA value, 89.1%).

    In a sensitivity analysis of plastic bag and plastic wrap as separate interventions, both plastic bag and plastic wrap were found to be equally good at maintaining core body temperature (MD, 0.06 °C; 95% CrI, −0.19 to 0.30 °C). Certainty of evidence was moderate (eFigures 7 and 8 in the Supplement). Inconsistency was detected in the network for the plastic bag vs routine care comparison (eFigure 9 in the Supplement). Certainty of evidence assessment for sensitivity analyses and secondary outcomes is listed in eTable 4 in the Supplement.

    In a sensitivity analysis of studies in which the mean gestational age of the newborns was 30 weeks or less, the results were similar to those of the primary analysis. However, incubator transport was also associated with greater core body temperature compared with routine care (MD, 0.68 °C; 95% CrI, 0.16-1.22 °C) (eFigures 10-12 in the Supplement).

    Core body temperature was evaluated at 3 gestational ages: 24, 30, and 34 weeks. Although all of the interventions were associated with significantly greater core body temperatures for neonates at 24 weeks of gestation, some interventions (ie, plastic cap, incubator transport, and plastic bag or wrap with heated humidified gas) had imprecise estimates for those at 30 and 34 weeks of gestation (eFigure 13 in the Supplement).

    In a sensitivity analysis of drying vs no drying before application of plastic bag or wrap, the core body temperature was comparable between drying vs no drying for both plastic bag or wrap alone (MD, −0.09 °C; 95% CrI, −0.38 to 0.19 °C; moderate certainty of evidence) and plastic bag or wrap with plastic cap (MD, −0.37 °C; 95% CrI, −0.90 to 0.15 °C; very low certainty of evidence) (eFigures 14 and 15 in the Supplement).

    Eight interventions, including routine care, were evaluated for the other primary outcome of incidence of moderate to severe hypothermia at admission or within 2 hours of life. Figure 3 shows the network, SUCRA, and forest plots for these interventions. Plastic bag or wrap alone (RR, 0.23; 95% CrI, 0.04-0.55), thermal mattress (RR, 0.12; 95% CrI, 0.00-0.62), and plastic bag or wrap with heated humidified gas (RR, 0.12; 95% CrI, 0.00-0.47) were associated with reduced risk of moderate to severe hypothermia compared with routine care. These findings are depicted in a league plot in eFigure 16 in the Supplement. Certainty of evidence was moderate for plastic bag or wrap alone and was low for thermal mattress and plastic bag or wrap with heated humidified gas. Thermal mattress (SUCRA value, 76.9%) and plastic bag or wrap with heated humidified gas (SUCRA value, 74.9%) were ranked as the 2 best interventions. However, certainty of evidence was low for both. Direct estimates are depicted in eFigure 17 in the Supplement, and no inconsistency was found in the network (eFigure 18 in the Supplement).

    The CrIs of network estimates were wider for many comparisons when assessed against the direct evidence from pairwise comparisons. Hence, a sensitivity analysis was performed using the frequentist method of the random-effects model. The results were similar, and the estimates were more precise for plastic bag or wrap with a plastic cap (RR, 0.37; 95% CI, 0.19-0.75), plastic bag or wrap with a thermal mattress (RR, 0.21; 95% CI, 0.07-0.63), and skin-to-skin contact (RR, 0.09; 95% CI, 0.01-0.76) (Figure 3D).

    In a sensitivity analysis of incidence of any hypothermia, interventions such as skin-to-skin contact, plastic bag or wrap with heated humidified gas, plastic bag or wrap with a thermal mattress, plastic bag or wrap with a plastic cap, thermal mattress, and plastic bag or wrap were associated with lower risk of any hypothermia compared with routine care alone (eFigures 19-22 in the Supplement).

    Secondary Outcomes

    Plastic bag or wrap with a plastic cap was associated with decreased risk of mortality before discharge when compared with plastic bag or wrap alone (RR, 0.26; 95% CrI, 0.02-0.86) and routine care (RR, 0.19; 95% CrI, 0.02-0.66; low certainty of evidence) (eFigures 23-26 in the Supplement).

    Only direct evidence from pairwise meta-analysis revealed an increased risk of hyperthermia for plastic bag or wrap alone vs routine care (RR, 3.39; 95% CrI, 1.84-6.25) as well as for plastic bag or wrap with a thermal mattress vs plastic bag or wrap alone (RR, 2.25; 95% CrI, 1.13-4.50) (eFigures 27-30 in the Supplement).

    Plastic bag or wrap with heated humidified gas was associated with decreased risk of major brain injury compared with routine care (RR, 0.23; 95% CrI, 0.03-0.67) and showed a pattern toward less risk for major brain injury compared with plastic bag or wrap alone (RR, 0.38; 95% CrI, 0.08-1.08; moderate certainty of evidence) (eFigures 31-33 in the Supplement). All of the results are summarized in eTable 5 in the Supplement.

    Discussion

    This systematic review and network meta-analysis included 34 trials of 9 thermal care interventions in 3688 preterm neonates to prevent hypothermia immediately after birth in the delivery room. Most of the interventions showed better performance compared with routine care alone in stabilizing the core body temperature and reducing the risk of moderate to severe hypothermia. However, there were distinct differences between the interventions for the secondary outcomes of hyperthermia, mortality, and major brain injury.

    A systematic review and meta-analysis by McCall et al8 showed that plastic bag or wrap was associated with improved core body temperature at admission or within 2 hours of life with moderate certainty of evidence. The data for other interventions were small, and the evidence was not graded.8 In the present study, we found moderate certainty of evidence that 5 interventions (plastic bag or wrap, thermal mattress, plastic bag or wrap with heated humidified gas, and thermal mattress and plastic cap) were associated with greater core body temperature. This finding could be attributed to an increase in statistical power by the addition of evidence from the indirect fraction as well as the inclusion of 9 additional studies in this network meta-analysis.24,25,36,37,43-46,48,51

    Because the various thermal care interventions have different mechanisms of action for preventing heat loss, using a combination of interventions might be beneficial for the most vulnerable neonates. SUCRA ranked plastic bag or wrap with a thermal mattress as the best intervention for improving core body temperature at admission or within 2 hours of life. However, direct evidence indicated that plastic bag or wrap with a thermal mattress might be associated with higher risk of hyperthermia. Although these findings were not reflected in the final network estimates, these estimates were derived from a sparse network in which bayesian analysis with a random-effects approach is known to present imprecise results when compared with the direct evidence.65 Hence, plastic bag or wrap with a thermal mattress might not be recommended as the first choice until more adequately powered studies on hyperthermia are available.

    The mean differences in the core temperature between the different thermal adjuncts and routine care varied from 0.56 °C to 0.98 °C. Although these differences were statistically significant, it is important to ponder whether they translated into clinical benefits. Observational studies and quality improvement projects have indicated that better temperature profiles at admission to the neonatal intensive care unit are associated with decreased mortality and morbidity, but meta-analyses of RCTs have failed to show the clinical benefits of these thermal care interventions.4,7,8 On the contrary, in this network meta-analysis, we found important clinical benefits for plastic bag or wrap with heated humidified gas, which decreased the risk of major brain injury (with moderate certainty of evidence), and for plastic bag or wrap with a plastic cap, which decreased the risk of mortality (with low certainty of evidence). In addition, plastic bag or wrap and plastic bag or wrap with a thermal mattress showed a pattern toward lower mortality (with low certainty of evidence) compared with routine care.

    We conducted a meta-regression for core body temperature with gestational age as a covariate. Although the meta-regression showed that the benefit of thermal care adjuncts was greater at lower gestational ages, some of the interventions were still beneficial at 34 weeks of gestation. The results of individual trials that were conducted in more mature newborns were also in agreement with this finding.26,30,51 We suggest further research in this group of neonates, especially in resource-limited settings in which radiant warmers and transport incubators might not be available and low-cost interventions such as plastic bag or wrap and plastic cap may play an important role in reducing hypothermia and neonatal mortality. Furthermore, presterilized plastic bag or wrap and plastic cap might be the most feasible interventions during delayed cord clamping, which is now considered the standard of care in term and preterm neonates.66 None of the included studies had examined thermal care interventions during delayed cord clamping, which potentially represents a period of rapid heat loss in preterm newborns.

    Plastic bags and wraps work by the same principle of reducing evaporative and convective heat loss and seem to be technically similar; however, they may differ in thickness of the plastic material, ease of application, extent of body coverage, and risk of displacement, among other factors. A systematic review on plastic bag or wrap suggested possible differences between plastic bags and wraps and recommended further studies to evaluate the advantages of plastic bags vs wraps.10 However, we found that plastic bags and wraps were equally beneficial. The 2020 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations suggested applying a plastic bag or wrap to the newborn immediately after birth without prior drying.7 This advice is based on the understanding that extremely preterm neonates have high transepidermal water loss; keeping the newborn wet inside the plastic bag or wrap creates a high-humidity microenvironment and reduces evaporative heat loss. However, this recommendation does not have a high level of evidence. We found that drying vs no drying before applying a plastic bag or wrap may not make a difference in maintaining core body temperature, with moderate certainty of evidence.

    To define hypothermia, the included studies used a cutoff temperature of less than 36.5 °C or less than 36 °C for rectal or axillary temperature. Although we considered both rectal and axillary temperature as core body temperature, as followed in the systematic review and meta-analysis by McCall et al,8 a difference of 0.5 °C or higher between rectal and axillary temperature has been reported in neonates.67,68 Hence, to avoid this variability and the risk of inconsistency secondary to intransivity, we analyzed the incidence of moderate to severe hypothermia (temperature <36 °C) as a primary outcome rather than any hypothermia. Plastic bag or wrap was associated with decreased risk of moderate to severe hypothermia at admission or within 2 hours of life (with moderate certainty of evidence) compared with routine care. Two other recent systematic reviews on plastic bag or wrap also found substantial reduction in hypothermia with use of this intervention.9,10 The frequentist analysis showed that most thermal care interventions were successful in reducing the risk of moderate to severe hypothermia.

    Limitations

    This study has several limitations. First, the variation among demographic and other characteristics, such as gestational age, diverse delivery room care practices, and the underlying sickness profile of the neonates, in the included trials might have introduced intransitivity in this network meta-analysis. Second, wide differences were observed in the way temperature was measured (axillary vs rectal) in the included trials. Third, we did not analyze some a priori decided secondary outcomes because limited data were available. Fourth, many of the included RCTs were single-center trials with small sample size and low event rates, making the effect estimates prone to selective reporting and publication bias. Fifth, we were unable to access unpublished data from the included studies and relied instead on the systematic review by McCall et al.8

    Conclusions

    Most of the thermal care interventions used in the delivery room were associated with better core body temperature (with moderate certainty of evidence) and decreased risk of moderate to severe hypothermia (with moderate certainty of evidence for plastic bag or wrap, but low to very low certainty of evidence for other interventions) at admission or within the first 2 hours of life compared with routine care alone. Use of a plastic bag or wrap with heated humidified gas was associated with reduced risk of major brain injury (with moderate certainty of evidence) and a plastic bag or wrap with a plastic cap was associated with lower risk of mortality (with low certainty of evidence). Future RCTs that are adequately powered to assess important clinical outcomes are warranted.

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    Article Information

    Accepted for Publication: February 26, 2021.

    Published Online: May 24, 2021. doi:10.1001/jamapediatrics.2021.0775

    Corresponding Author: Viraraghavan Vadakkencherry Ramaswamy, DM, Department of Neonatology, Ankura Hospital for Women and Children, KPHB 7th Phase, Hyderabad 500072, India (19.vira@gmail.com).

    Author Contributions: Dr Ramaswamy had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

    Concept and design: Abiramalatha, Ramaswamy, Pullattayil, Roehr.

    Acquisition, analysis, or interpretation of data: All authors.

    Drafting of the manuscript: Abiramalatha, Ramaswamy, Roehr.

    Critical revision of the manuscript for important intellectual content: All authors.

    Statistical analysis: Abiramalatha, Ramaswamy, Bandyopadhyay.

    Administrative, technical, or material support: Abiramalatha, Pullattayil.

    Supervision: Abiramalatha, Trevisanuto, Roehr.

    Other - derive search strategy, literature search, collecting articles: Pullattayil.

    Conflict of Interest Disclosures: Dr Roehr reported being the scientific co-chair of the European Resuscitation Council and Neonatal Life Support guideline writing group and a member of the International Liaison Committee on Resuscitation guideline writing group. No other disclosures were reported.

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