Hypothermia in neonate

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Khushbu on Jul 25, 2012 Says :

nice presentaion on an exclusive topic.

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Slide 1 :

Temperature Control in the Neonate Dr. Jeetendra Prasad Sah Senior Resident BPKIHS

Slide 2 :

Introduction Hypothermia associated with increased morbidity/mortality in newborns of all birth weights/ages Now considered independent risk factor for mortality in preterm Western philosophy of conventional care – premature baby should be Placed under radiant warmer Uncovered for full visualization and to allow radiant heat to reach body More attention now focused on thermal care immediately after birth and during resuscitation

Slide 3 :

Premature Susceptibility to Heat Loss High surface area to volume ratio Thin non-keratinized skin Lack of insulating subQ fat Lack of thermogenic brown adipose tissue (BAT) Inability to shiver Poor vasomotor response

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Thermoregulation Metabolic rate of fetus per tissue wt. higher than adult Heat also transferred from mother to fetus via placenta/uterus Fetal temp consistently 0.3-0.5 deg C higher than mother’s (always in parallel) Even when mother’s temp elevates (eg fever) Despite BAT in utero, fetus cannot produce extra heat Exposed to adenosine and prostaglandin E2 ? inhibitors of non-shivering thermogenesis (NST) Metabolic adaptation for physiologically hypoxic fetus since NST requires oxygenation Inhibition of NST allows accumulation of BAT

Slide 5 :

Thermoregulation Heat gain/loss controlled by hypothalamus and limbic system Thermoregulatory system immature in newborns (esp premature newborn)

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Thermoregulation In term infant, response to cold stress relies on oxidation of brown fat (NST) Development begins 20th wk until shortly after birth (comprises 1% body wt at that time) High concentration stored TG’s Rich capillary network densely innervated by sympathetic nerve endings Temperature sensors on posterior hypothalamus stimulate pituitary to produce thyroxine (T4) and adrenals to produce norepinephrine Lipolysis stimulated ? energy produced in form of heat in mitochondria instead of phosphate bonds by uncoupling protein-1 (aka thermogenin)

Slide 7 :

Thermoneutral Environment Temp and environmental conditions at which metabolic rate and O2 consumption are lowest Silverman et al Maintaining constant abdominal skin temp b/w 36.2-36.5 deg C optimal WHO classification of hypothermia Mild: 36-36.4deg C Mod: 32-35.9deg C Severe: <32deg C

Slide 8 :

Risk Factors All neonates in 1st 8-12hrs of life Prematurity SGA CNS problems Prolonged resuscitation efforts Sepsis

Slide 9 :

Neonatal Energy Triangle

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Adverse Consequences of Hypothermia High O2 consumption ? hypoxia, bradycardia High glucose usage ? hypoglycemia / decreased glycogen stores High energy expenditure ? reduced growth rate, lethargy, hypotonia, poor suck/cry Low surfactant production ? RDS Vasoconstriction ? poor perfusion ? metabolic acidosis Delayed transition from fetal to newborn circulation Thermal shock ? DIC ? death

Slide 11 :

Modes of Heat Loss Conduction - direct heat transfer from skin to object (eg mattress) Convection - heat loss through air flow Also depends on air temp Radiation - direct transfer by electromagnetic radiation in infrared spectrum Heat gained by radiation from external radiant energy source Heat lost by radiation to cooler walls of incubator Evaporation - heat loss when water evaporates from skin and respiratory tract Depends on maximum relative humidity of surroundings ? less humidity = more evaporation

Slide 12 :

Heat Loss at Birth Hammarlund et al, 1980 Evaporative water loss 81-125 gm/m2/h when unwiped in ambient temp ~25.8deg C and 42% humidity Heat loss through Evaporation: 60-80 W/m2 Radiation: 50 W/m2 Convection: 25 W/m2 Conduction: negligible Total heat loss = 135-155 W/m2 All babies that were >3250g - body temp decreased 0.9deg C in 15min

Slide 13 :

Heat Loss at Birth Hammarlund et al, 1979 Naked infants <28wks need ambient temp ~40°C to maintain normal temp in 20% humidity Increasing humidity to 60% halved losses

Slide 14 :

Management Healthy newborn Dried & wrapped in prewarmed clothes Use of cap Examination should be done under radiant warmer If temp is stable the infant should be placed with blanket

Slide 15 :

Management Sick newborn Dried Transportation Radiant warmer Use of cling wrap

Slide 16 :

Management Sick newborn Incubator with maintenance of thermoneutral zone temp. Humidification of incubator

Slide 17 :

Management Newer devices Double walled incubators Limit radiant heat loss Decrease convective and evaporative losses Versalet incuwarmer Giraffe omnibed Hybrid devices

Slide 18 :

Kangaroo Mother Care (KMC) Introduced in 1983 by Rey and Martinez in Colombia LBW infants nursed naked (wearing only cloth diaper) between mothers’ breasts Data from other countries show infants nursed by KMC have Fewer apneic episodes Similar or better blood oxygenation Lower infection rates Are alert longer and cry less Are breastfed longer and have better bonding Improved survival in low-resource settings

Slide 19 :

Hazards of temp control methods Hyperthermia Undetected infections Volume depletion/ dehydration

Slide 20 :

Thank you

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