Temperature Control In Neonates

One of the most crucial components of neonatal care is temperature control. Restoring a newborn's vital signs begins with TABC, or temperature, airway, breathing, and circulation.

There are numerous approaches that can be used to prevent or lessen the risk of hypothermia in infants, such as the use of radiant warmers, incubators, specific polyethylene wraps, and care for kangaroo mothers, among other things. To avoid hypothermia, adopt kangaroo mother care (KMC) techniques.

Benefits Of KMC

• Practice kangaroo care (KMC) to prevent hypothermia 
• Benefits of KMC 
• Improving breastmilk feeding 
• Better weight gain 
• Less infections 
• Early discharge from hospital.

Introduction

Intrauterine temperature is maintained by maternal processes during pregnancy.  Newborns must generate heat through their metabolism in order to adjust to their comparatively cold surroundings outside of their body.  It is a disadvantage that they are unable to produce a sufficient shivering response; as a result, they must rely on their metabolic regulation.

Brown Fat

 Sympathetic, not parasympathetic, neurons innervate brown fat, which is highly vascularized.  When these babies experience cold stress, their blood levels of norepinephrine rise. This causes the brown fat tissue to undergo lipolysis, which releases free fatty acids.

Therefore, when it comes to brown fat, norepinephrine levels are elevated and linked to thermogenesis.  The majority of free fatty acids (FFAs) undergo oxidation or re-esterification, both of which result in the production of heat.

Also Read: Skull Fractures And Traumatic Intracranial Hemorrhage

Temperature Maintenance In Preterms

Infants born before their due date are more likely to lose heat than to produce it.  Premature infants have larger skin surface area to weight ratios than term infants. They also have highly porous skin, which increases transdermal water loss.

Reduced subcutaneous fat with a lower ability to act as insulation.  Decreased glycogen levels and less developed brown fat stores, Poor vasomotor control, Challenges with enough caloric intake to give nutrients for thermogenesis. Restricted oxygen supply in the event that pulmonary disorders coexist. These are all potential causes of hypothermia in preterm infants.

The “low Reading” Thermometers

Q. What Are The Low Reading Thermometers?

 It is advised to use low-reading thermometers (below 29.4°C or 85.0°F) as standard thermometers may miss temperature readings below 34.4°C (94.0°F). Even the tiniest neonates can experience extremely low temperatures.

It is therefore advised to use the low-reading thermometers, which should be the first choice. Their readings should be at or below 29.4°C (85.0°F), which is 5°C or roughly 9°F lower than the routine thermometers.

Thermistor probes that are compatible with radiant heaters or incubators can detect and notify a doctor of hypothermia (by setting off alarms whenever skin temperature falls 0.5°C to 1°C below the set temperature).

Neonatal Cold Injury – Features

Neonatal cold damage is an uncommon and severe type of hypothermia that can affect both term newborns with central nervous system problems and low birth weight (LBW) infants.

The classical temperature in newborn cold damage will be less than 32.2 °C (90 °F).  Because oxyhemoglobin does not dissociate at low temperatures, these infants may seem extremely red.  As a result of the cold injury, they may have central pallor cyanosis and exhibit edema and sclerema on the skin.

There may be signs of neonatal cold injury, such as metabolic acidosis, hypoglycemia, hyperkalemia, azotemia, and oliguria.

Generalized bleeding, including pulmonary hemorrhage, can occur occasionally.  There is actually debate over how quickly or slowly to rewarm a child whose temperature has dropped to such a low degree because rapid warming presents its own set of hemodynamic problems.

Neonatal Cold Injury - Management

Slow rewarming will result from managing a newborn's cold injury by heating the skin on the abdomen to a temperature 1°C above the core temperature or to 36.5°C using a radiant warmer. Correction of hypoglycemia should be done in addition to rewarming.

The baby might gain from more oxygen, a standard saline bolus (10 to 20 ml/kg), and metabolic acidosis correction.

These newborns are not normally sick; instead, they may be experiencing hypotension and have impaired blood supply to the gut. As a result, food should not be administered to any infant.

It needs to be thoroughly examined and treated in case there is any bleeding, infection, or damage. Infants suffering from sepsis, on the other hand, frequently exhibit vasoconstriction and have cooler extremities than the trunk.

Dehydration fever, which manifests as significant weight loss and hypernatremia, is common in hot settings, particularly if feeding is not established.

Frequent nursing, expressed breast milk, formula milk, and taking off extra layers of clothes are all part of the management of dehydration fever. Verify that the infant is free of infections. Thus, in these situations, the newborns' body temperatures rise. The baby's temperature will drop when they have neonatal cold damage, and they shouldn't be fed if this condition is discovered.

Induced Hypothermia

The desired temperature span is between 33°C and 34°C. Every fifteen minutes, the core temperature (usually taken rectally at the referring hospital and during transport) should be checked.

Mechanism of Heat Loss 

 The way that neonates, or preterm babies, lose heat. One such mechanism is radiation, which transfers heat from the baby to a colder object in the surroundings.

Radiation is the transfer of heat from the infants to a colder item in their surroundings; both do not need to come into contact with one another.

Convection: The skin loses heat to moving air. Temperature and air speed affect how much is lost.

Evaporation: Water turns into gas, which results in the loss of heat. The two main factors influencing the amount of loss are relative humidity and air velocity. Infants that are wet during birth are particularly vulnerable to heat loss through evaporation.

Conducting: Heat loss occurs from the baby's body heat transferring to the surface they are lying on. Thus, radiation does not require an object to be in direct contact with the infant, whereas conduction is essentially heat loss from an object that is in contact with the baby.

Neutral Thermal Environments

 The settings that reduce heat loss are known as thermally neutral or neutrally neutral environments.  When core temperature is within the normal range and heat production (as determined by oxygen consumption) is negligible, thermoneutral circumstances are present.

Temperature Maintenance at Birth

MCQ

Q. What are the standard thermal care guidelines as per WHO for maintaining the delivery room?

According to AAP/WHO standard thermal care guidelines, the delivery room temperature should be kept at 75 °F or 25 °C.
During the first one to two hours of life, skin-to-skin care is a useful and efficient way to create a neutral thermal environment; also, this strategy encourages early breastfeeding.

Warm Chain

A warm chain is basically a set of ten interlinked steps that should be followed to avoid hypothermia in neonates. This includes

1.  Warm delivery room: 25 to 28 °C with no draughts.

2.  Warm resuscitation

3.  Immediate drying with warm linen

4.  Skin-to-skin contact.

5.  Breastfeeding

6.  Postpone bath.

7.  Appropriate clothing and bedding

8.  Rooming in mother and baby together

9.  Warm transportation,

10. Training of health personnel and awareness-raising

Preterm Baby (As Per Cloherty 2021) 

Very helpful thermal care bundles will comprise plastic wrap, a prewarmed warmer, room temperature, and maintenance (25 to 28 °C for the first two days).  Infants born very prematurely should have barriers installed to stop heat loss.

Infants delivered at 32 weeks (as opposed to "29 weeks" in Cloherty 2018) can benefit from plastic wraps and caps. • Severe preterm babies should be put in a polyethylene bag right away, without drying.  When doing stabilization and resuscitation, a radiant warmer should be employed.

For transportation, a hot incubator ought to be utilized. Using plastic wrap and an external heat source, like temporary warmer beds, in combination has shown to lower the risk of hypothermia in extremely preterm infants (28 weeks).

Humidification  

It has been demonstrated that humidifying incubators lowers sensible water loss and evaporative heat loss.  It is primarily used for the first 10–14 days following birth in patients weighing 1,200 g or 30–32 weeks gestation.

Regardless of gestation, most infants will have comparatively thicker and more mature skin by the time they are 14 days old.  The present incubator design addresses risks and concerns regarding potential bacterial contamination with humidification.

In the past, people used to worry that turning on the humidification continuously for 10–14 days would increase the risk of bacterial infection. However, more recent incubator designs have addressed this issue, and there is very little chance of bacterial infection when humidity is used correctly.

These incorporate heating elements that raise the water's temperature to a point where the majority of organisms are destroyed. Interestingly, the water turns into a gaseous vapor rather than a mist, removing the possibility of airborne water droplets spreading illness in these situations.

When frequent access to the baby is crucial, a severely controlled open warmer bed may be used for really unwell infants.  Owing to the possible infectious risk, these creams and oils should be used sparingly and not for more than 72 hours after birth. Convection heat loss and insensible water loss can be prevented by using barrier creams like Aquaphor [sunflower seed oil or coconut oil in resource-limited settings] or tent-made plastic wrap.

Advantage Of Incubators

Q. What type of heat loss is prevented by the use of incubators?

The four types of heat loss that incubators are intended to reduce are radiation, convection, conduction, and evaporation.
Incubators with double walls also reduce heat loss, which is mostly caused by radiation and, to a lesser extent, conduction.

Hazards of Temperature Control Methods

If the methods are done properly, the hazards are not much, However, hyperthermia can occur if a servo-controlled warmer produces excessive heat, if the temperature probe comes loose or is not affixed to the baby's skin correctly, or if other factors provide the machine with incorrect feedback, causing the machine to overproduce heat, which then causes the baby to become hyperthermic.

The hypothermia, hyperthermia, or temperature instability linked to undetected illnesses may be concealed by servo-controlled temperature.  Volume depletion: Babies wearing radiant warmers may occasionally lose 10–20 ml/kg of fluids daily in addition to experiencing insensible water loss. Considerations include sodium levels, predicted weight loss, and urine production.

A Few Unrelated Miscellaneous Points  

Routine newborn examinations involve checking each newborn's pulse oximetry before releasing them from the hospital.Usually, it entails employing later-generation technology, making sure staff members are appropriately trained in pulse oximetry measurement, and evaluating the infants at 24 and 48 hours of age. pulse oximeters, which are less affected by irregularities in motion

Q. All the babies before discharge should be screened for CHD with the help of ……?

Pulse oximetry should be used to screen all newborns for congestive heart failure prior to discharge. Following screening, the following criteria must be met in order for a positive screening test to indicate that critical congenital heart disease [CCHD] has to be further investigated clinically:

Any oxygen saturation reading below 90% that is not getting better.  Three measurements, separated by an hour, showing oxygen saturation levels in the right hand and either foot less than 95%, or the right hand and foot have oxygen saturation differences of more than 3% on three different examinations, each separated by one hour.

Therefore, newborns should also be encouraged to be checked for congenital cyanotic heart disease if they have persistent oxygen saturation of 90% and 95% in the right hand and either foot on three measures, as well as a difference of more than 3% between the preductal and postductal saturation in routine.

The Routine Newborn Examination

The most common type of arrhythmia is ducto-premature atrial contractions, which can occasionally be detected during a standard newborn screening.

Q. What is the most common type of arrhythmia in neonates?

 Early atrial contractions are the most common cause of arrhythmia in newborns.  The penis nearly invariably has pronounced phimosis from birth, thus attempting to retract the foreskin is not advised.  A normal newborn's stretched penile length should be greater than 2.5 cm at birth; if it is less than 2.5 cm, this is abnormal and has to be evaluated.

A newborn's normal testicle dimensions range from 1.6 cm in length by 10 cm in width to 2.9 cm by 1.8 cm.  If there is typically no pain or redness, a larger, harder testis with no transillumination might be suspected of being a torsion. Surgery and an urgent ultrasonography may be necessary.

It is important to take attention of the clitoris, which becomes less noticeable as gestational age increases.  A mean clitoral length of 4 mm is considered normal; however, if it is greater, it may be linked to specific genetic abnormalities or hormonal problems such congenital adrenal hyperplasia.

 The mean clitoral length in term newborns is 4.0 ± 1.24 mm ± 1 SD. It is normal for young babies to have palpable lymph nodes measuring 12 mm in diameter. These nodes are typically located in the inframammary, cervical, and occasionally axillary locations. About one-third of normal neonates have palpable lymph nodes.

Extra caution should be used while searching for skin abnormalities, pilonidal sinus tracts, or tiny, soft midline swellings that could be signs of a minor meningocele or another anomaly.  Unless they meet strict criteria for spinal dysraphism, simple, blind-ending midline sacral dimples, a common occurrence, may not require additional assessment.

The following are high-risk factors for spinal dysraphism:  Being more than 0.5 cm deep.  It is connected to other cutaneous signs like hypertrichosis, a subcutaneous mass, or a caudal appendage;  Its location is more than 2.5 cm from the anal margin.

Also Read: Hearing Loss in Nicu Graduates

Hope you found this blog helpful for your NEET SS Pediatrics Neonatology Preparation. For more informative and interesting posts like these, keep reading PrepLadder’s blogs.