Thermoregulation in the Neonate Presented by Fred Hill, MA, RRT

Minimize Cold Stress

Heat Production and Metabolism Heat production is byproduct of normal metabolismHeat production is byproduct of normal metabolism To maintain constant body temperature: heat of metabolism = heat lossTo maintain constant body temperature: heat of metabolism = heat loss Homeotherm: An organism that can increase heat production in a cool environmentHomeotherm: An organism that can increase heat production in a cool environment Poikilotherm: snake, lizard, frog, etc.Poikilotherm: snake, lizard, frog, etc.

Response to Cooling: Adult Voluntary Muscle ActivityVoluntary Muscle Activity Shivering (involuntary muscle activity)Shivering (involuntary muscle activity) Nonshivering thermogenesis (involuntary)Nonshivering thermogenesis (involuntary)

Response to Cooling: Baby Nonshivering thermogenesis (involuntary) – primarily brown fat metabolismNonshivering thermogenesis (involuntary) – primarily brown fat metabolism Brown fatBrown fat Nape of the neckNape of the neck Between scapulaeBetween scapulae MediastinumMediastinum Surrounding kidneys and adrenalsSurrounding kidneys and adrenals

Brown Fat Characteristics Rich in mitachondriaRich in mitachondria Numerous fat vacuolesNumerous fat vacuoles Dense capillary networkDense capillary network Highly innervated with sympathetic nerve endingsHighly innervated with sympathetic nerve endings Oxidation to heat as opposed to ATPOxidation to heat as opposed to ATP

Why babies lose heat easily Large surface-to-volume ratioLarge surface-to-volume ratio Thin, more permeable skinThin, more permeable skin Less insulating subcutaneous fatLess insulating subcutaneous fat Unable to shiverUnable to shiver

Mechanisms of Heat Loss RadiationRadiation ConductionConduction ConvectionConvection EvaporationEvaporation

Vicious Cycle of Cooling

Neutral Thermal Environment

Reduces insensible water lossReduces insensible water loss Reduces caloric needs for growthReduces caloric needs for growth Comparison studyComparison study Neutral thermal environment (36.5 O ): grew fasterNeutral thermal environment (36.5 O ): grew faster Standard group (35 O ): Better cold resistanceStandard group (35 O ): Better cold resistance Comparable growth achieved with standard conditions by increasing caloriesComparable growth achieved with standard conditions by increasing calories

Strategies for Reducing Heat Loss Radiant warmersRadiant warmers Double-walled isoletsDouble-walled isolets Cover with blanketCover with blanket HatsHats Plastic wrapPlastic wrap Heated water-filled mattressHeated water-filled mattress Keep away from air conditioning ductsKeep away from air conditioning ducts

Strategies for Resuscitation Dry infant - reduce evaporative heat lossDry infant - reduce evaporative heat loss Place on a blanket - reduce conductive heat lossPlace on a blanket - reduce conductive heat loss Radient warmer - counteracts radiant heat lossRadient warmer - counteracts radiant heat loss Protect from air currents - reduces convective heat lossProtect from air currents - reduces convective heat loss