prevention of hypothermia.ppt

hypothermia is one of the major causes of neonatal death

1. By DrAbdurahmanS.
Moderator DrHana A.(pediatric surgeon)

2. INTRODUCTION
THERMOREGULATION
◦HEAT PRODUCTION
◦HEAT LOSS
◦Thermoregulation and Anesthesia
HYPOTHERMIA
PERIOPERATIVE HYPOTHERMIA PREVENTIVE MEASURES
COMPLICATION OF PERIOPERATIVE HYPOTHERMIA
REFERENCES

3. Maintaining a neutral thermal environment is one of
the key physiologic challenges that a newborn must
face after delivery
In early 1900s
◦Realized warm environment is essential
Last decades
◦Improved care of newborns in developed world
◦Still common problem in developing countries
Thermal care is central to reducing morbidity and
mortality in newborns.

4. Thermoregulation
◦The ability to balance heat production and heat loss in
order to maintain body temperature within a certain
normal range(36.5-37.5ºc)
Goals
◦Maximize metabolic efficiency
◦Reduce oxygen use
◦Protect enzyme function
◦Reduce calorie expenditure

5. Thermoneutral zone:
◦The range of ambient temperature required for the
infant (for each gestational age and weight) to keep a
normal body temperature and a minimal basal
metabolic rate
Extreme environmental temperature variations
◦overcome this effective thermoregulatory function
lead to heat-or cold-related illnesses

6. Radiation
convection
Evaporation
Conduction

7. Heat loss occurs from
energy needed to vaporize
liquids
◦skin,lung,mucosa and serosa
Accounts major heat
loss…50%
Depends on
◦The exposed body surface area
◦Relative humidity of the
ambient air
◦The speed of the wind

8. Heat loss to the nearby cold
objects with out physical
contact
Major source of heat loss in
most surgical patients(60%)
Depends on
◦The T differences
◦The body exposed to the
environment
◦Distance between two surfaces
◦The skin blood flow

9. Heat transfer from warm to
cool objects with direct contact
Accounts 5%
Depends on
◦Area of body exposed
◦Relative difference in temperature
◦Thermal conductivity

10. Special type of conduction heat
loss through moving gases
Accounts 15%
Second most common heat loss
in anesthetized pt
Depends on
◦The temperature difference
◦The speed of air
Proportional to the square root of air
speed

11. Cold Items on Bed
Cold Walls
Cold Room Temp.
Radiation
Cold Blankets
Cold X-ray plates
Cold Scale
Conduction
Passing Traffic
Oxygen left on
Bed Near Air Vent
Convection
Tachypnea
Bath
Wet Diaper
Evaporation
Baby d

12. During pregnancy
◦Maternal mechanisms maintain the intrauterine
temperature
After birth
◦The newborn must adapt to their environment by the
metabolic production of heat
Primary source of heat in the newborn
◦Non -shivering thermogenesis
◦Metabolic processes
◦Voluntary muscle activity
◦Involuntary muscle activity (shivering thermogenesis)??
◦Peripheral vasoconstriction

13. Metabolism of brown adipose tissue
◦Initiated in hypothalamus
◦Sympathetic nervous system
◦Norepinephrine release at the site of brown fat
◦Non-shivering thermogenesis is initiated and brown
fat is burned for energy to keep the body temperature
stable
This is the infant’s initial response
3

14. Brown fat is an
energy source for
infants
It can be found:
◦Near Kidneys and
adrenals
◦Neck, mediastinum,
scapular, and the
axilla areas.
Can not be replaced
once used

15. In full term infants
◦4 % -10% of adipose deposits
In preterm infants
◦Not be found until 26-30 weeks gestation
◦Then only in small amounts
Disappears 3-6 months after birth
◦In cold stressed infants
Disappears sooner
Hypoxia causes impairment of brown fat
metabolism
5

17. A large surface area-to-body mass ratio
Decreased subcutaneous fat
Greater body water content
Immature skin leading to increased evaporative
water and heat losses
Poorly developed metabolic mechanism for
responding to thermal stress (e.g. no shivering)

18. Premature
SGA
Neuro problems
Endocrine
Cardiac / respiratory problems
Large open areas in the skin
Sedated Infants
Drug exposure
8

19. Anesthesia-induced inhibition of central
thermoregulation
Internal redistribution of heat from the central
to the peripheral compartment
Reduction in metabolic heat production
Increased exposure to the environment
◦up to 90% of heat loss occurs via skin mainly by radiation and convection

20. Patterns of body temperature
after general anesthesia
1.Internal redistribution of heat
2.Thermal imbalance
3.Thermal steady state (plateau or
rewarming)

22. Definition:
It is a condition characterized by lowering of
body temperature than 36.5°C.
Could be classified based on:
◦Causes:
Primary and secondary
◦Severity:
Mild( 35-36.4ºc)
Moderate(32-34.9ºc)
Severe (<32ºc)

23. Hypoxemia
Hypoglycemia
Respiratory & metabolic acidosis
Inhibition of surfactant production
pulmonary blood flow
pulmonary vascular resistance compromises the
delivery of oxygen at the cell level
risk of developing PPHN

24. Mild hypothermia
◦Skin-to-skin contact
In a warm room
At least 25°C
◦Covering of head with
cap
◦Cover mother and
newborn with warm
blankets
Moderate hypothermia
◦Under a radiant heater
◦In a warmed incubator
◦In a heated water-filled
mattress
◦skin-to-skin contact with the
mother
Severe
◦Warm incubator
◦Skin to skin contact in warm room

25. Warm chain
1)Warm delivery room
2)Immediate drying
3)Skin-to-skin contact
4)Breast-feeding
5)Bathing and weighing postponed
6)Appropriate clothing/bedding
7)Mother and baby together
8)Warm transportation
9)Warm resuscitation
10)Training and awareness raising


26. RADIANT HEAT LOSS
◦Avoiding placement of incubators,
warming tables and bassinets near cold
windows, walls, air conditioners, etc..
◦Placing a knit hat on the infant’s head
◦Wrapping tiny babies in saran or “bubble”
wrap
◦environmental temperature
6

27. EVAPORATIVE HEAT LOSS
◦Keeping the neonate and his/her
environment dry
◦Drying the baby immediately after
delivery
◦Placing preterm or SGA infant in
occlusive wrap/bag at delivery
◦Delay bath until temperature is
stable
7

28. CONDUCTIVE HEAT LOSS
◦Placing a warm diaper or blanket
between the neonate and cold surfaces
◦Placing infant on pre-warmed table at
time of delivery
◦Warming all objects that come in
contact with the neonate
◦Admitting infant to a pre-warmed
room
◦Skin to skin contact
8

29. CONVECTIVE HEAT LOSS
◦Providing warm ambient air temperature
Placing infants less than 1500 grams in
incubators
Keeping portholes of the incubator closed
Warming all inspired oxygen
On open warmers keeping sides up and
covering infant if possible
Using Infant Servo Temperature Control
9

30. Preoperative warming
◦To keep a patient comfortably warm
◦To prevent phase I hypothermia
◦Techniques
Active-with forced air warming
Passive-with passive insulation
Warm blanket
Socks
Warm circulating water mattress
Head covering
◦Duration ???
30’ to 1hr

31. Operating room warming
◦Reduces the temp. gradient
◦Ideally
For preterm …minimum 29ºc
Term…..27ºc
Adult……21ºc
◦Relative humidity
40-60%
Using warm fluids
◦Both IV and irrigations
Humidified and warm inspired gases
◦With HME device.

32. Appropriately covered during any transport
◦Older children and adults
A warm blanket may be sufficient
◦Neonates and premature babies
Transport in a prewarmed incubator, or
Chemical heating pads

33. Most commonly used to warm patients in post
anesthesia recovery room
◦Forced air blankets
◦Radiant heaters

35. Increased intraoperative blood loss and
transfusion
Adverse cardiac events
Prolonged stay in RR and hospital
Delayed surgical wound healing and high rate of
infection
Cold induced coagulation dysfunction
Prolonged drug metabolism

37. CORAN PEDIATRICS SURGERY 7TH EDITION
Atlas procedures in neonatology
Pediatric Anesthesia : Bruno Bissonnette
Thermal protection of the newborn: a practical
guide. WHO/RHT /MSM/97
Uptodate

38. 