Perinatal Section, NCE, Boston Sunday October 16 2011
Transitional Neonatal Physiology:
How do we best prevent
hypothermia during resuscitation
Marilyn B Escobedo MD FAAP
Reba McEntire Endowed Chair in
Neonatology
University of Oklahoma
University of Oklahoma, Children’s Hospital
I have
nothing
to
disclose
Learning Objectives
 Recall the transitional physiology of thermal
regulation in the neonate
 Review the vulnerability of the ELGAN to
excessive morbidity and mortality of hypothermia
 Be updated on the multiple factors that may
threaten thermal integrity
 Become familiar with multiple methods to affect
better thermal outcomes in the vulnerable group.
Background
 About 10% of babies require some
resuscitation at birth
 1% need extensive resuscitation
 ALL need attention to thermal integrity
 ELGANs are the MOST vulnerable.
A few words
On the physiology
of
thermoregulation…
The relationship
between frogs
and humans
has long been
debated……
How is a baby not a
frog?
Homeotherms increase their metabolic rate
in response to cooling.
Poikilotherms decrease their metabolic rate
in response to cooling
How is a baby not a
frog?
This was an evolutionary LEAP
Poikiolotherms vs homeotherms
 Homeotherms have 2-3 times metabolic
rate
 Homeothermy demands that heat
production precisely compensates
losses to the environment
The human baby maintains his body temperature with energy –
The human baby maintains his body temperature with energy –
The human baby maintains his body temperature with energy –
What is the thermoneutral zone
in humans?
 Unclothed resting adult—23-28 C (73 F)
 Unclothed full term neonate—32-35 C (90 F)
 Unclothed 1 Kg preterm neonate– 35 C (95 F)
WHO, 1997, Safe Motherhood: Thermal Protection of the Newborn, a Practical Guide
PHYSICS OF HEAT TRANSFER
How does this apply to the DR?
LOSSES
 Radiation – Cold walls, all solid furnishings of
the theatre, poor muscle tone increasing
surface area exposed
 Conduction – cold blankets, instruments,
mattresses
 Convection-Vents from HVAC system,
Movement of personnel, Doors, Gases
 Evaporation- Amniotic fluid, no clothing
How does this apply to the DR?
INTERVENTIONS
 Radiation – Increase room temperature in
advance, use radiant warmer for care
 Conduction – warm blankets, exothermic
mattresses
 Convection-Design appropriate HVAC
system, Be aware of movement of personnel,
doors, gases, use transport incubator
 Evaporation- Dry or place barriers to
evaporation on body and head
WHEN do we need to intervene?
 How do we intervene?
 When do we intervene?
 To whom to we apply these techniques?
 Do they change outcome?
Is it just theoretically important?
Reduction in Mortality by
Reducing Hypothermia
 Budin, Pierre in The
Nursling
 Comparison of
Mortality in the
Maternite( the Usual
standard of care)
with
 The Tarnier ( the
preventive approach
to Hypothermia)
100
90
80
70
60
50
40
30
20
10
0
<32
3233.5
Silverman to Costeloe
 Survival significantly higher in incubators kept at 32
C. vs 29 C ( Silverman1958)
 Survival significantly higher in radiantly heated
incubators vs convectively heated due to stability of
the environmental temp ( Silverman1963)
 Survival improved in computer controlled SKIN
temperature environment (1976 Ahlgren)
 Hypothermia remains an independent risk factor
for mortality in very small preterm babies
(Costeloe 2000) Admission temps <35 C in 40% of
infants <26 wks
How do we best defend the tiny
baby’s thermal integrity?
McCall, Alderdice, Halliday Jenkins Vohra 2010 Cochrane Review
Barrier Methods to prevent
evaporative heat loss
 Polyethylene occlusive wrapping of ELGANs
immediately upon delivery (Vohra, et al J Pediatr 2004,
HeLP study
Decreases the incidence of hypothermia
Increases the NICU admission temperature
Fewer deaths (all hypothermic) but NS
Prevention of Evap Heat Loss
 ALL the RCTs of occlusive wrapping of the very
preterm baby with food grade plastic wrap

Showed improved temperatures on admission
to NICU of almost 1degree C

Reduced the incidence of hypothermia

Some have studied effects on







Acid base balance
RDS
IVH
NEC
O2 need
LOS
None have shown an effect on Mortality
Second barrier to reduction of evap loss of heat:
HATS
Second barrier to reduction of
evap loss of heat: HATS
 Stockinette Hat studies by Roberts ( >31 wks)
 Plastic hat study by Trevisunuto
 Plastic hat study in progress by Wyckoff
 Woolen hats studied in terms ( Coles 1979;
Stothers 1981; and Chaput de Saintonge
1979)
 NEEDS STUDY
Conductive heat transfer
 Exothermic warming mattressess
THERMAL MATTRESS vs PLASTIC WRAP
RCT < 28 week
 Thermal warming mattresses
Compared to plastic wrap
Reduced hypothermia ( <0.01)
 Raised NICU adm temp

Allowed more direct access
 Improved visualization
 Less cumbersome to apply

Thermal defense of extremely low gestational age newborns during resuscitation:
exothermic mattresses vs polyethylene wrap Simon Dannaway Escobedo et al
J Perinatology 2010
Various Studies of warming
mattresses—all positive
Brennan 1996 RCT
Singh 2009 Cohort, historical
Almeida 2009 RCT
Ibrahim 2010 Retrospective Review
Caveat!!
Positive transfer of radiant heat
 Manuel radiant warmer
International Standard requires power cut and
alarm if total output has been > 10mW/cm2 for
>15 minutes
 Most warmers will have shut off before the
usual 20- 30 minute resuscitation of VLBW

 Servo-controlled radiant warmer should
probably be used or team member should be
assigned to monitor temp to avoid highs and
lows (Rich, Leone, Finer in Clinics in Perinatology Mar 2010)
Reducing radiant heat losses
beyond the warmer
Delivery room temperature needs to be kept at
the WHO standard of 25 degrees C or higher
(mid 70s F)
Environmental Temps:
Birthing and Surgical Suite
 WHO recommendation for 25 C or greater

No references
 Knobel (2005) post hoc analysis

Subjects born in room temps > 26 had higher mean
admission temps than those in =<26
 Cramer (2005) Positive relationship between DR
temp and NICU admission temp
 Kent (2008) changed environmental temp from 20
to 25-28 C along with other interventions and
showed a positive effect on T.
Humidified and Heated Air during
Resuscitation
te Pas AB. Lopriore E. Dito I. Morley CJ. Walther FJ.
Pediatrics. 125(6):e1427-32, 2010 Jun.
 Prospective study of <33 wks
 "heated" cohort used heated and humidified gas
during resuscitation vs “cold” cohort
 Temperature at admission in the NICU 35.9 vs 36.4 (
P < .0001).
 Normothermia (36.5 degrees C-37.5 degrees C)
occurred less often in the cold cohort than in the
heated cohort (12% vs 43%; P < .0001).
 The use of heated and humidified air during
respiratory support in very preterm infants just after
birth reduced the postnatal decrease in temperature
What about hyperthermia?
 As core temperatures increase O2
consumption rises again.
 This is stressful for any neonate with ELGANs
more susceptible
 If preterms also have CNS injury, the
possibility of hyperthemia exacerbating the
injury may exist.
The evidence shows we should
be preventing hypothermia.
The VON report for 2010 shows a
rate of about ½ of VLBWs with
admission temps <36.5 C and
about ¼ < 36 C
Why aren’t we doing better?
TIPQC- Tennessee Initiative
Incidence of Hypothermia (< 36 C) on Admission to NICU
MUSC
2010 Robin L. Kissinger, PhD, APRN, NNP-BC; David J. Annabale, MD
Thermal Defense for Preterms
 Reasonable Evidence
Plastic bag with hats
 Thermal mattresses

 Emerging considerations
Hats
 Heated gases
 Radiant warmer
 The role of the delivery room temperature

 Effective and consistent application
HOME DELIVERY IS FOR PIZZA!!!!!!!
UNDERWATER BIRTH IS FOR WHALES!!!
questions?