Temperature Temperature Control in the Control in the
NeonateNeonatePearl S. Park, D.O.Pearl S. Park, D.O.
PGY-2PGY-2
August 30, 2007August 30, 2007
IntroductionIntroduction Hypothermia associated w/ increased Hypothermia associated w/ increased
morbidity/mortality in newborns of all birth morbidity/mortality in newborns of all birth weights/agesweights/ages Now considered independent risk factor for Now considered independent risk factor for
mortality in pretermmortality in preterm Western philosophy of conventional care – Western philosophy of conventional care –
premature baby should bepremature baby should be Placed under radiant warmerPlaced under radiant warmer Uncovered for full visualization and to allow radiant Uncovered for full visualization and to allow radiant
heat to reach bodyheat to reach body More attn now focused on thermal care More attn now focused on thermal care
immediately after birth and during immediately after birth and during resuscitationresuscitation
Premature Susceptibility to Premature Susceptibility to Heat LossHeat Loss
High surface area to volume ratioHigh surface area to volume ratio Thin non-keratinized skinThin non-keratinized skin Lack of insulating subQ fatLack of insulating subQ fat Lack of thermogenic brown adipose Lack of thermogenic brown adipose
tissue (BAT)tissue (BAT) Inability to shiverInability to shiver Poor vasomotor responsePoor vasomotor response
ThermoregulationThermoregulation Metabolic rate of fetus per tissue wt. higher than Metabolic rate of fetus per tissue wt. higher than
adultadult Heat also transferred from mother to fetus via Heat also transferred from mother to fetus via
placenta/uterusplacenta/uterus Fetal temp consistently 0.3-0.5 deg C higher than Fetal temp consistently 0.3-0.5 deg C higher than
mother’s (always in parallel)mother’s (always in parallel) Even when mother’s temp elevates (eg fever)Even when mother’s temp elevates (eg fever)
Despite BAT in utero, fetus cannot produce extra Despite BAT in utero, fetus cannot produce extra heatheat Exposed to adenosine and prostaglandin E2 Exposed to adenosine and prostaglandin E2 inhibitors inhibitors
of non-shivering thermogenesis (NST)of non-shivering thermogenesis (NST) Metabolic adaptation for physiologically hypoxic fetus Metabolic adaptation for physiologically hypoxic fetus
since NST requires oxygenationsince NST requires oxygenation Inhibition of NST allows accumulation of BATInhibition of NST allows accumulation of BAT
ThermoregulationThermoregulation Heat gain/loss controlled by hypothalamus and Heat gain/loss controlled by hypothalamus and
limbic systemlimbic system Thermoregulatory system immature in newborns Thermoregulatory system immature in newborns
(esp premature newborn)(esp premature newborn) In term infant, response to cold stress relies on In term infant, response to cold stress relies on
oxidation of brown fat (NST)oxidation of brown fat (NST) Development begins 20th wk until shortly after Development begins 20th wk until shortly after
birth (comprises 1% body wt at that time)birth (comprises 1% body wt at that time) High concentration stored TG’sHigh concentration stored TG’s Rich capillary network densely innervated by Rich capillary network densely innervated by
sympathetic nerve endingssympathetic nerve endings Temperature sensors on posterior hypothalamus Temperature sensors on posterior hypothalamus
stimulate pituitary to produce thyroxine (T4) and stimulate pituitary to produce thyroxine (T4) and adrenals to produce norepinephrineadrenals to produce norepinephrine
Lipolysis stimulated Lipolysis stimulated energy produced in form of energy produced in form of heat in mitochondria instead of phosphate bonds by heat in mitochondria instead of phosphate bonds by uncoupling protein-1 (aka thermogenin)uncoupling protein-1 (aka thermogenin)
Risk FactorsRisk Factors
All neonates in 1st 8-12hrs of lifeAll neonates in 1st 8-12hrs of life PrematurityPrematurity SGASGA CNS problemsCNS problems Prolonged resuscitation effortsProlonged resuscitation efforts Sepsis Sepsis
Adverse Consequences of Adverse Consequences of HypothermiaHypothermia
High O2 consumption High O2 consumption hypoxia, bradycardia hypoxia, bradycardia High glucose usage High glucose usage hypoglycemia / hypoglycemia /
decreased glycogen storesdecreased glycogen stores High energy expenditure High energy expenditure reduced growth reduced growth
rate, lethargy, hypotonia, poor suck/cryrate, lethargy, hypotonia, poor suck/cry Low surfactant production Low surfactant production RDS RDS Vasoconstriction Vasoconstriction poor perfusion poor perfusion
metabolic acidosismetabolic acidosis Delayed transition from fetal to newborn Delayed transition from fetal to newborn
circulationcirculation Thermal shock Thermal shock DIC DIC death death
Modes of Heat LossModes of Heat Loss Conduction - direct heat transfer from skin to Conduction - direct heat transfer from skin to
object (eg mattress)object (eg mattress) Convection - heat loss through air flowConvection - heat loss through air flow
Also depends on air tempAlso depends on air temp Radiation - direct transfer by electromagnetic Radiation - direct transfer by electromagnetic
radiation in infrared spectrumradiation in infrared spectrum Heat gained by radiation from external radiant energy Heat gained by radiation from external radiant energy
sourcesource Heat lost by radiation to cooler walls of incubatorHeat lost by radiation to cooler walls of incubator
Evaporation - heat loss when water evaporates Evaporation - heat loss when water evaporates from skin and respiratory tractfrom skin and respiratory tract Depends on maximum relative humidity of surroundings Depends on maximum relative humidity of surroundings
less humidity = more evaporation less humidity = more evaporation
Heat Loss at BirthHeat Loss at Birth Hammarlund et al, 1980Hammarlund et al, 1980 Evaporative H20 lossEvaporative H20 loss
81-125 gm/m81-125 gm/m22/h when unwiped in ambient temp /h when unwiped in ambient temp ~25.8deg C and 42% humidity~25.8deg C and 42% humidity
Heat loss throughHeat loss through Evaporation: 60-80 W/mEvaporation: 60-80 W/m22
Radiation: 50 W/mRadiation: 50 W/m22
Convection: 25 W/mConvection: 25 W/m22
Conduction: negligibleConduction: negligible Total heat loss = 135-155 W/mTotal heat loss = 135-155 W/m22
All babies that were >3250g - body temp All babies that were >3250g - body temp decreased 0.9deg C in 15mindecreased 0.9deg C in 15min
Heat Loss at BirthHeat Loss at Birth
Hammarlund et al, 1979Hammarlund et al, 1979
Naked infants <28wks need ambient Naked infants <28wks need ambient temp ~40deg C to maintain nl temp in temp ~40deg C to maintain nl temp in 20% humidity20% humidity
Increasing humidity to 60% halved Increasing humidity to 60% halved losseslosses
Attempt to Overcome Attempt to Overcome LossesLosses
Radiant heaters insufficient to warm Radiant heaters insufficient to warm preterm babypreterm baby Esp during resuscitationEsp during resuscitation 750g baby w/ surface area of ~ 0.06m750g baby w/ surface area of ~ 0.06m22
requires at least 9.3W to compensate requires at least 9.3W to compensate for losses at birthfor losses at birth
At mattress lvl, max of 9W absorbed by At mattress lvl, max of 9W absorbed by baby if radiant heat absorbed by, at baby if radiant heat absorbed by, at least, 50% of mattressleast, 50% of mattress
Thermoneutral Thermoneutral EnvironmentEnvironment
Temp and environmental conditions Temp and environmental conditions at which metabolic rate and O2 at which metabolic rate and O2 consumption are lowestconsumption are lowest
Silverman et alSilverman et al Maintaining constant abdominal skin Maintaining constant abdominal skin
temp b/w 36.2-36.5 deg C optimaltemp b/w 36.2-36.5 deg C optimal WHO classification of hypothermiaWHO classification of hypothermia
Mild: 36-36.4deg CMild: 36-36.4deg C Mod: 32-35.9deg CMod: 32-35.9deg C Severe: <32deg CSevere: <32deg C
Kangaroo Mother Care Kangaroo Mother Care (KMC)(KMC)
Introduced in 1983 by Rey and Martinez Introduced in 1983 by Rey and Martinez in Colombiain Colombia LBW infants nursed naked (wearing only cloth LBW infants nursed naked (wearing only cloth
diaper) between mothers’ breastsdiaper) between mothers’ breasts Data from other countries show infants nursed Data from other countries show infants nursed
by KMC haveby KMC have Fewer apneic episodesFewer apneic episodes Similar or better blood oxygenationSimilar or better blood oxygenation Lower infxn rtesLower infxn rtes Are alert longer and cry lessAre alert longer and cry less Are breastfed longer and have better bondingAre breastfed longer and have better bonding Improved survival in low-resource settingsImproved survival in low-resource settings
KMCKMC Bergman et al, 2004Bergman et al, 2004
Randomized controlled trial comparing KMC to Randomized controlled trial comparing KMC to pre-warmed servo-controlled closed incubator pre-warmed servo-controlled closed incubator after birthafter birth
20 infants b/w 1200-2199g using KMC vs 14 20 infants b/w 1200-2199g using KMC vs 14 controlscontrols
Excluded if C-sec, mother too ill to look after self/infant, Excluded if C-sec, mother too ill to look after self/infant, known HIV, BW outside 1200-2199g, 5min Apgar <6, known HIV, BW outside 1200-2199g, 5min Apgar <6, congenital malformationscongenital malformations
1/20 subjects vs 8/14 controls had initial temps < 1/20 subjects vs 8/14 controls had initial temps < 35.5deg C (P = 0.006)35.5deg C (P = 0.006)
1/20 subjects vs 3/14 controls had bl glucoses < 1/20 subjects vs 3/14 controls had bl glucoses < 2.6 mmol/L (though 40mg/dL = 2.2mmol/L)2.6 mmol/L (though 40mg/dL = 2.2mmol/L)
Stability of cardio-respiratory system in preterm Stability of cardio-respiratory system in preterm infants (SCRIP) score was 2.88 points higher w/in infants (SCRIP) score was 2.88 points higher w/in 1st 6hrs in KMC group (95% CI 0.3-5.46)1st 6hrs in KMC group (95% CI 0.3-5.46)
SCRIP ScoreSCRIP Score
SCRIPSCRIP 22 11 00
HRHR RegularRegular Decel to 80-Decel to 80-100100
Rte <80 or Rte <80 or >200 bpm>200 bpm
RRRR RegularRegular Apnea <10s Apnea <10s or periodic or periodic breathingbreathing
Apnea >10s Apnea >10s or or
tachypnea tachypnea >80 >80
OO22 sat sat >89%>89% 80-89%80-89% <80%<80%
Barriers to Heat LossBarriers to Heat Loss Cochrane database reviewCochrane database review 4 studies compared barriers to heat loss vs. no 4 studies compared barriers to heat loss vs. no
barriersbarriers 2 comparison subgroups2 comparison subgroups
Plastic wrap/bag vs routine carePlastic wrap/bag vs routine care Stockinet cap vs routine careStockinet cap vs routine care
Plastic wrap/bag vs routine carePlastic wrap/bag vs routine care 3 studies involving 200 infants all <36wks3 studies involving 200 infants all <36wks All placed under radiant warmer, wrapped to shoulders All placed under radiant warmer, wrapped to shoulders
while still wet, heads dried and resuscitated according while still wet, heads dried and resuscitated according to guidelines to guidelines
GA <28wks: wrap group had temps 0.76deg C higher GA <28wks: wrap group had temps 0.76deg C higher than controls (95% CI 0.49-1.03)than controls (95% CI 0.49-1.03)
GA 28-31wks: no statistical difference GA 28-31wks: no statistical difference
Barriers to Heat LossBarriers to Heat Loss
Plastic wrap/bag vs routine care (cont)Plastic wrap/bag vs routine care (cont) 1hr after admission for GA <28wks, no 1hr after admission for GA <28wks, no
statistical difference (though direction was in statistical difference (though direction was in favor of intervention)favor of intervention)
Plastic wrap significantly reduced risk of Plastic wrap significantly reduced risk of hypothermia (core temp <36.5deg C) on hypothermia (core temp <36.5deg C) on admission to NICUadmission to NICU
RR 0.63 (95% CI 0.42-0.93)RR 0.63 (95% CI 0.42-0.93) NNT found to be 4 (95% CI 3-17) - so 4 infants would NNT found to be 4 (95% CI 3-17) - so 4 infants would
need to be wrapped in plastic to prevent 1 from need to be wrapped in plastic to prevent 1 from becoming hypothermicbecoming hypothermic
No significant differences found in duration of No significant differences found in duration of OO22 therapy, major brain injury, duration of therapy, major brain injury, duration of hospitalization, or deathhospitalization, or death
Barriers to Heat LossBarriers to Heat Loss Stockinet cap vs routine careStockinet cap vs routine care
1 study involving 40 AGA infants w/ GA’s 32-36wks1 study involving 40 AGA infants w/ GA’s 32-36wks Exclusion critera: 5min Apgar <7, SSx CNS Exclusion critera: 5min Apgar <7, SSx CNS
defect, sepsis, or maternal temp >37.8deg C defect, sepsis, or maternal temp >37.8deg C during laborduring labor
Cap group had caps placed ASAP after drying Cap group had caps placed ASAP after drying under radiant warmer and infants <2500g were under radiant warmer and infants <2500g were transported in incubatortransported in incubator
BW <2000g: Cap group had core temps 0.7deg C BW <2000g: Cap group had core temps 0.7deg C higher than control (95% CI -0.01-1.41) - higher than control (95% CI -0.01-1.41) - borderline statistical differenceborderline statistical difference
BW >/= 2000g: no sig difBW >/= 2000g: no sig dif No sig dif in preventing hypothermiaNo sig dif in preventing hypothermia
External Heat SourcesExternal Heat Sources
Cochrane database reviewCochrane database review 2 studies compared external heat 2 studies compared external heat
sources to routine caresources to routine care 2 comparison subgroups2 comparison subgroups
Skin-to-skin vs routine care (already Skin-to-skin vs routine care (already mentioned)mentioned)
Transwarmer mattress vs routine careTranswarmer mattress vs routine care
External Heat SourcesExternal Heat Sources Brennan et al, 1996Brennan et al, 1996 24 infants w/ BW </= 1500g24 infants w/ BW </= 1500g Transport Mattress (TM) - made of sodium Transport Mattress (TM) - made of sodium
acetate - activated to ~40deg C when delivery acetate - activated to ~40deg C when delivery imminentimminent Infant placed upon blankets covering mattress, Infant placed upon blankets covering mattress,
dried, then placed on TM directlydried, then placed on TM directly Control group = same intervention but w/o Control group = same intervention but w/o
TMTM Both groups resuscitated according to Both groups resuscitated according to
guidelines then transferred to NICU on guidelines then transferred to NICU on radiant warmer surface radiant warmer surface
External Heat SourcesExternal Heat Sources
Brennan et al, contBrennan et al, cont Increase of 1.6deg C in TM group Increase of 1.6deg C in TM group
(95% CI 0.83-2.37)(95% CI 0.83-2.37) Evidence suggests that TM Evidence suggests that TM
significantly reduces risk of significantly reduces risk of hypothermia w/ RR 0.3 (95% CI 0.11-hypothermia w/ RR 0.3 (95% CI 0.11-0.83)0.83) NNT = 2 (95% CI 1-4)NNT = 2 (95% CI 1-4)
No adverse occurrences reported in No adverse occurrences reported in this study, though other studies have this study, though other studies have had infants sustain 3rd deg burnshad infants sustain 3rd deg burns
In ConclusionIn Conclusion Plastic barriers effective in reducing heat loss in Plastic barriers effective in reducing heat loss in
newborns <28wks newborns <28wks No evidence yet to suggest plastic barriers No evidence yet to suggest plastic barriers
decrease duration of Odecrease duration of O22 therapy, hospitalization, or therapy, hospitalization, or incidence of major brain injury/deathincidence of major brain injury/death
Stockinet caps effective in reducing hypothermia in Stockinet caps effective in reducing hypothermia in newborns <2000g, but not >/= 2000gnewborns <2000g, but not >/= 2000g
KMC shown to be effective in stable newborns KMC shown to be effective in stable newborns down to 1200g in reducing risk of hypothermiadown to 1200g in reducing risk of hypothermia
TM decreases incidence of hypothermia </= 1500gTM decreases incidence of hypothermia </= 1500g In the end, the smaller the baby, the more likely In the end, the smaller the baby, the more likely
any intervention will be of benefitany intervention will be of benefit
Areas of Further StudyAreas of Further Study Need more studies w/ larger Need more studies w/ larger
population basespopulation bases Short- and long-term outcomes need Short- and long-term outcomes need
to be studied further (especially w/ to be studied further (especially w/ neurdevelopmental F/U)neurdevelopmental F/U)
Secondary outcomes that need Secondary outcomes that need further study:further study:HypoglycemiaHypoglycemia RDSRDS Intubation/Intubation/
ve-ntilationve-ntilationLength of Length of staystay
Metabolic Metabolic acidosisacidosis
ARFARF GrowthGrowth Adverse Adverse eventsevents
Neonatal Energy Neonatal Energy TriangleTriangle
ReferencesReferences Laroia, N. “Double wall versus single wall incubator for reducing heat loss in very Laroia, N. “Double wall versus single wall incubator for reducing heat loss in very
low birth weight infants in incubators.” Cochrane Database of Systematic Reviews. low birth weight infants in incubators.” Cochrane Database of Systematic Reviews. Vol (3) 2007.Vol (3) 2007.
Fienady, V. “Radiant warmers versus incubators for regulating body temperature Fienady, V. “Radiant warmers versus incubators for regulating body temperature in newborn infants” Cochrane Database of Systematic Reviews. Vol (3) 2007.in newborn infants” Cochrane Database of Systematic Reviews. Vol (3) 2007.
Asakura, H. “Fetal and Neonatal Thermoregulation.” Journal of Nippon Medical Asakura, H. “Fetal and Neonatal Thermoregulation.” Journal of Nippon Medical School. Vol. 71 (2004) , No. 6.School. Vol. 71 (2004) , No. 6.
Ibe, O.E. “A comparison of kangaroo mother care and conventional incubator care Ibe, O.E. “A comparison of kangaroo mother care and conventional incubator care for thermal regulation of infants <200 g in Nigeria using continuous ambulatory for thermal regulation of infants <200 g in Nigeria using continuous ambulatory temperature monitoring.” Annals of Tropical Paediatrics (2004) 24, 245-251.temperature monitoring.” Annals of Tropical Paediatrics (2004) 24, 245-251.
Bergman, N.J. “Randomized controlled trial of skin-to-skin contract from birth Bergman, N.J. “Randomized controlled trial of skin-to-skin contract from birth versus conventional incubator for physiological stabilization in 1200- to 2199-gram versus conventional incubator for physiological stabilization in 1200- to 2199-gram newborns.” Acta Paediatrica (2004) 93: 779-785.newborns.” Acta Paediatrica (2004) 93: 779-785.
McCall, E.M. “Interventions to prevent hypothermia at birth in preterm and/or low McCall, E.M. “Interventions to prevent hypothermia at birth in preterm and/or low birthweight babies.” Cochrane Database of Systematic Reviews. Vol (3), 2007. birthweight babies.” Cochrane Database of Systematic Reviews. Vol (3), 2007.
Watkinson, M.A. “Temperature Control of Premature Infants in the Delivery Watkinson, M.A. “Temperature Control of Premature Infants in the Delivery Room.” Clin Perinaol 33 (2006) 43-53.Room.” Clin Perinaol 33 (2006) 43-53.
““Knobel, R.B. “Heat Loss Prevention for Preterm Infants in the Delivery Room.” J Knobel, R.B. “Heat Loss Prevention for Preterm Infants in the Delivery Room.” J Perinaol 25 (2005) 304-308.Perinaol 25 (2005) 304-308.
The neonatal energy triangle Part 2: Thermoregulatory and respiratory adaptation.” The neonatal energy triangle Part 2: Thermoregulatory and respiratory adaptation.” Paediatric Nursing. Sept. Vol 18 no 7. Paediatric Nursing. Sept. Vol 18 no 7.
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