Week 5 - A - Adaptations at birth - Circulation, PPHN, TTN, hypothermia, glucose, jaundice/haem

Question 1

What is abnormal about this scan of the foetus?

Answer 1

Can see that the baby has an NG tube inserted and s on an ECG scan Also lungs should be black and full of air whereas these lungs have white patchy infiltrates throughout

Question 2

In patients with life threatening respiratory or cardiac failure, what is the alternative to cardiopulmonary bypass so that you dont require open heart surgery?

Answer 2

This would be extracorporeal life support - maintains tissue oxygenation for a short while (days)

Question 3

What is the function of the placenta?

Answer 3

Removal of CO2 for the baby and providal of O2 for the baby Transrts waste from baby to mother Involved in hormone production Transports IgG from mother to foetus

Question 4

When does the transport IgG from mother to foetus mainly happen? What hormone is mainly involved in foetal growth? How does this happen?

Answer 4

The transport of IgG mainly happens during the third trimester of pregnancy - especially near delivery and continues a little post delivery - IgG is a monomer

The main antibody in breast milk is IgA - dimer

Insulin (maternal insulin cannot cross over the placenta) is the hormone mainly involved in foetal growth - it regulates the maternal glucose levels which foetal glucose levels are directionally proportional to - foetal gluocse control its own insulin levels which promote foetal growth

Question 5

What hormone promotes uterine and placental growth during pregnancy? What hormone promtoes childhood development?

Answer 5

IGF2- insulin like growth factor 2 promotes uterine and placental growth

Question 6

Where is oxytocin mainly produced?

Answer 6

Oxytocin is mainly produced in the hypothalamus (then stored in the posterior pituitary gland) and a little in the placenta

Question 7

What effect does oxytocin have on GABA? It ensures the foetal brain is less vulnerable to hypoxic injury at birth WHat is GABA?

Answer 7

Oxytcin cause the gamma-aminobutryic acid to switch from an excitatory neurotransmitter to an inhibitory neurotransmitter slightly before delivery Preparing fetal neurons for delivery: Crossing the placenta, maternal oxytocin reaches the fetal brain and induces a switch in the action of neurotransmitter GABA from excitatory to inhibitory on fetal cortical neurons. This silences the fetal brain for the period of delivery and reduces its vulnerability to hypoxic damage.

Question 8

What are the three shunts in the foetal circulation? What percentage of the foetal blood goes to the lungs?

Answer 8

Three shunts Ductus venosus Foramen ovale Ductus arteriosus Only 7% of the foetal blood actually goes to the lungs - the foetal lungs are immature

Question 9

The lungs in utero are gorwing and therefore the placenta is the main place for gas exchange The lungs (alveoli) Is fluid filled before birth and pulmonary vascular resistance is really high so foetal circulation doesn’t go through the lungs really Only 7% just to keep the lungs growing Talk through the foetal blood circulation, starting and finishing with the placenta?

Answer 9

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Question 10

How is that the brain still receives oxygenated blood even though the blood entering the right atrium from the IVC (the only one which will contain any oxygenated blood), SVC and coronary sinus will all contain deoxygenated blood?

Answer 10

This is due to a tissue flap in the right atrium known as the Eustachian Valve - this would direct the incoming oxygenated blood from the IVC into the foramen ovale, so it can go to LA then LV then ascending aorta and away from the right atrium. The majority of the LV blood is delivered to the brain and coronary circulation thus ensuring that blood with the highest possible oxygen concentration is delivered to these vital structures.

Question 11

What joins the umbilical vein to IVC? What joins the pulmonary trunk to the descending aorta? What joins the right atrium to left atrium? What directs oxygenated blood from IVC heading to right atrium to the left atrium?

Answer 11

Umbilical vein to IVC - ductus venosus Pulmonary trunk to ascending aorta - Ductus arteriosus Right atrium to left atrium - foramen ovale Directs oxygenated blood from IVC going to the right atrium through the foreman ovale and into the left atrium - this is the Eustachian valve

Question 12

In preparation for birth, in the third trimester there is the production of several things eg IgG poduction increases, surfactant production, accumulation of brown fat, accumulation of subcutaneous fat, also amniotic fluid is swallowed What produced the surfactant? What is the function of surfactant?

Answer 12

Surfactant is produced by Type II pneumocytes (aka as alveolar cells) (also produced by a type of cell known as Club cells - previosuly known as Clara cells) The function of surfactant is to help keep alveoli open and to increase pulmonary compliance to prevent collapse of the lung

Question 13

How does the pulmonary surfactant increase the pulmonary compliance of the lung? Lung compliance, or pulmonary compliance, is a measure of the lung’s ability to stretch and expand

Answer 13

The pulmonary surfactant increases the pulmonary compliance of the lung by decreasing the alveolar surface tension - The internal surface of the alveolus is covered with a thin coat of fluid. The water in this fluid has a high surface tension, and provides a force that could collapse the alveolus. The presence of surfactant in this fluid breaks up the surface tension of water, making it less likely that the alveolus can collapse inward.

Question 14

What is the law where pressure is proportonal to the surface tension of the alveoli?

Answer 14

The Law of LaPlace

• P= 2T/r
• P = pressure in alveolus
• T = Surface tension
• R = Radius

Question 15

How does the brown fat in the foetus differ from white fat? (brown fat is also found in smaller quantities in adults) Where does the brown fat accumulate?

Answer 15

Brown fat is produced in the foetus accumulates between the scapulae and around internal organs - Unlike regular white fat which store calories - the brown fat are mitochondria packed and therefore can burn energy and produce heat

Question 16

Why does the baby begin to swallow amniotic fluid in the third trimester?

Answer 16

Amniotic fluid also helps your baby develop his lungs. While in the womb your baby practices breathing by breathing in and out the water in the amniotic sac.

Question 17

During delivery, what changes with the lungs?

Answer 17

The lungs stop producing fluid to enable the foetus to breathe once delivered Vaginal delivery also limitedly helps squeeze the fludi out of the lungs

Question 18

During labor, your baby’s body releases chemicals to help their lungs push out the fluid. The pressure of the birth canal on your baby’s chest also releases fluid. After birth, your baby’s cough, as well as air filling their lungs, should expel the remaining amniotic fluid. If the babys lungs do not expel the fluid ass quickly and completely as it should, this can make it difficult for the baby’s lungs to function properly. What is this condition known as?

Answer 18

This condition is known as Transient Tachpnoea of the Newborn (TTN) - due to excess lung fluid

Question 19

What is a risk factor for TTN? How long does it usually tae to resolve?

Answer 19

Risk factor is giving pre-term birth via C-Section Usually resolves within 24 hours

Question 20

the baby is born blue usually then gradullay starts to go pink from centre to periphery and the cord is cut Why is the cord not cut immediately after birth? Why is the baby rubbed vigorously at birth also?

Answer 20

The cord pulses for a minute or so after birth providing the baby with oxygen and nutrients hence why it is not cut immediately The baby is rubbed vigorously at birth to dry the baby - prevents hypothermia

Question 21

What are the changes in the circulatory system that occur with the first foetal breaths?

Answer 21

The pulmonary vascular resistance decrease The systemic vascular resistance increases Oxygen tension rises Circulating prostoglandins drop The duct constricts Foramen ovale closes

Question 22

What causes the foramen ovale to close?

Answer 22

The foramen ovale closes - in utero the pressure in the right atrium is greater than in the left atrium but as the pulmonary vascular resistance decreases and the systemic vascular resistance increases - the pressure in the left atrium becomes greater than the right atrium closing the shunt

Question 23

What is the remnant of the fossa ovale known as?

Answer 23

The remnant of the foramen ovale is known as the fossa ovalis

Question 24

What does the drop in circulating prostoglandins cause?

Answer 24

The E series of prostoglandins are responsible for keeping the ductus arteriosus patient by causing dilation of vascular smooth muscle Therefore when the circulating levels drop after birth the ductus arteriosus closes

Question 25

What two main prostoglandins are responsible for keeping the ductus arteriosus patent? Which is the main?

Answer 25

PGE2 (Prostaglandin E2) and PGE1 (Prostoglandin E1) are the two main prostoglandins responsible for keeping the ductus arteriosus open during pregnancy PGE2 is the main one

Question 26

WHen may prostoglandins be given to a baby if the hope is to keep the ductus arteriosus open? The ductus arteriosus connect the pulmnary trun to what part of the aorta?

Answer 26

Prostoglandins may be given to the foetus in transposition of the great arteries - this keeps the DA open and means oxygenated entering the left atrium and going into the pulmonary trunk due to the condition can travel into the aorta

The DA connects pulmonary trunk to the descending aorta

Question 27

What can be given to a mother in preterm labour to promote closure of the DA in the foetus? When a baby is born and the ductus arteriosus remains patent, what can be given?

Answer 27

Dexamethasone can be given in preterm labour to help close the ductus arteriosus If a baby is born with a PDAS - can try giving a non-steroidal anti-inflammatory as these inhibit the prostoglandin pathway - indomethacin is usally the recommended (can give ibuprofen however)

Question 28

NSAIDs taken late in pregnancy can cross the placenta and cause the ductus arteriosus to close WHat painkillers are therefore recommended during pregnnacy? What are symptoms of a patent ductus arteriosus in the child? Why shouldnt aspirin be used as a painkiller in children under 12 years of age?lp-

Answer 28

Recommended that paracetamol is taken as the painkiller Symptoms of PDA -Continuous machine like murmur heard over the pulmonary area, failure to thrive, pneumonia Aspirin is not recommended for children under 12 years of age due to the increase in the risk of Reye’s syndrome Reye’s syndrome is a very rare disorder that can cause serious liver and brain damage. If it’s not treated promptly, it may lead to permanent brain injury or death.

Question 29

What do the foetal shunts become?

Answer 29

Formane ovale - closes and becomes the fossa ovalis Ductus arterios - becomes ligamentum arteriosum Ductus venosus - this becomes the ligamentum venosum

Question 30

When the ductus venosus becomes the ligamentum vensoum, what is this continous with?

Answer 30

This is continuous with the round ligament of the liver (ligamentum teres) which is the remnant of the umbiical vein

Question 31

What babies are at risk of failure of cardiorespiratory adaptations?

Answer 31

Premature babies Babies who pass meconium before birth Babies who get cold post labour Babies with infections - group B strep most common One of the biggest problems is if the baby doesnt take a first breath - this prevents the cardiorespiratory adaptations from occuring

Question 32

Again, state which babies are more likely to suffer from cardiorespiratory maladaptions?

Answer 32

Babies who are premature Babies who pass meconium before birth - meconium aspiration can cause pneumonia Babies who get cold post labour Babies who have infections - group B strep most common as it colonises the vaginal flora

Question 33

What causes persistent pulmonary hypertension of the newborn?

Answer 33

PPHN is caused when two shunts in the foetus fail to close - these shunts being the foramen ovale and the ductus arteriosus

Question 34

This means unoxygenated blood gets into the left atrium and the aorta and due to the pulmonary hypertension, there is very little blood getting oxygenated in the blood What part of the baby will receive at least partly oxygenated blood in this condition?

Answer 34

The right arm, head and neck vessels will recieve at least partly oxgenated blood (due to the eustachian valve sending oxygenated blood to the left atrium and then out the LV to head and neck) - this means however in PPHN the rest of the body will receive relatively unoxygenated blood

Question 35

If there is a problem around the time of birth which interferes with this process, the blood vessels may not open up properly so the pressure inside them remains high. This is called persistent pulmonary hypertension of the newborn (PPHN). What are some things that predispose to PPHN?

Answer 35

Meconium aspiration - the baby passes meconium in utero resulting in aspiration of the meconium causing the foetus to struggle to breathe Infections such as pneumonia (lung or chest infection) and bloodstream infections can make PPHN more likely Also a diaphragmatic hernia can cause the condition

Question 36

When the right arm and head remain pink, while the left arm and lower body are cyanotic, a clinical condition with differential cyanosis occurs. This condition is due to the difference in oxygen content in preductal and postductal blood, and is relatively specific for PFC (persistent foetal circulation is the same as PPHN). However, not all cases of PFC present with this picture. What can be done to diagnose PPHN?

Answer 36

To diagnose PPHN

Can measure the preductal and postductal oxygen saturations by placing a pulse oximeter on the right hand (preductal) and on the left foot (post ductal) - the sat difference will usually be greater than 10% in this condiiton with the preductal sats being greater

Question 37

In contrast to adult primary pulmonary hypertension, the newborn syndrome is not defined by a specific pressure of the pulmonary circulation. What pressure of pulmonary circulation is used to diagnose adult primary pulmonaryg hypertension?

Answer 37

The pressure in adult primary hypertension has to be a pulmonary arterial pressure of =/> 25mmHg

Question 38

What are the management options for PPHN? If all else fails, what is the finl step for trying to treat PPHN?

Answer 38

Management Ventilation - provides baby with oxygen Surfactant Inotropes Nitric oxide ExtraCorporeal Life support (ECLS) - final line - provides oxygen and a mechanical pump to help continue with perfusion and oxygen of the foetal tissues

Question 39

How do inotropes help to treat ECLS? What is the difference between inotropes and chronotropes? How does nitric oxide help to treat PPHN?

Answer 39

Inotropes increase contraction of the heart - hopes to increase the blood flow into pulmonary vessels Chronotropic drugs increase the heart rate - not used in PPHN Nitric oxide is used to treat PPHN - Given to the baby through the breathing machine, straight into the lungs. Opens up the closed blood vessels so that more blood flows into the lungs, and the high pressures are reduced.

Question 40

What causes Transient Tachypnoea of the Newborn? (TTN) What is the main risk factor for this?

Answer 40

During labor, your baby’s body releases chemicals to help their lungs push out the fluid. The pressure of the birth canal on your baby’s chest also releases fluid. After birth, your baby’s cough, as well as air filling their lungs, should expel the remaining amniotic fluid. However, sometimes the fluid doesn’t leave the lungs as quickly and completely as it should. This excess fluid in the lungs can make it difficult for the baby’s lungs to function properly Main risk factor for the condition is having a C-section

Question 41

Thermoregulation Glucose homeostasis Nutrition Very important in the first few hours of the babies life Why is the baby likely to lose heat when born? What are the 4 mehtods by which heat loss occurs?

Answer 41

Likely to lose heat when born because it is wet and the baby has a large surface area to lose heat from 4 methods by which heat loss occurs: * Radation * Conduction * Convection * Evaporation

Question 42

Describe each of the 4 ways in which heat is lost from the body

Answer 42

• Radiation - Heat lost from body due to surrounding air being colder
• Conduction - loss of heat through direct contact with an object - ie putting body on a cold surface
• Convection - heat is lost through air movement - ie wind
• Evaporation - loss of heat through water turning into gas

Question 43

Thermoregualtion is important in the nenoates as hypothermia can predispose the neonates to many other problems Non-shivering thermogenesis is the main way in which the neonate produces heat What happens here? What controlls the non-shivering thermogenesis activty?

Answer 43

Research shows it to be a metabolic process located primarily in brown adipose tissue and controlled by the activity of the sympathetic nervous supply of this tissue. The brown adipose tissue accumualtes mainly between scapula and around internal organs - brown fat is mitcohdnria packed to burn energy and produce heat

Question 44

The main source of heat production, albeit the non shivering thermogenesis, is not actually fully effective in the first 12 hours of life an therefore the baby needs help with maintaining temperature Why are small for dates/pre-term babies particularly susceptible to hypothermia?

Answer 44

This is becuase they have low brown fat stores Little subcutaneous fat And a large surface area : volume ratio

Question 45

What ways are used to help the baby maintain its temperature?

Answer 45

• Dry the baby
• Give the baby a hat
• Direct skin to skin contact with mother
• Blanket
• Heated mattress
• Incubator if necessary

Question 46

It is important to keep the glucose levels up - the glucose homeostasis which was due to the placenta (mothers insulin levels dictated mother glucose levels which dictated foetal glucose and insulin levels) has now been interrupted - baby needs its own glucose supply Natural breast feeding is important for a newborn baby if mum is willing What is the oral milk intake of the baby in first 24 hours? What is this milk known as/

Answer 46

Oral milk intake of the bbay in the 1st 24 hours is only about 5mls This is the colostrum - changes to breast milk after baout 3/4 days post-gestation Due to the baby only receiving only about 5mls colostrum per day for the first few days - the baby needs to use its internal fuel reserves to provide adequate glucose

Question 47

How does the baby acquire gluocse in the first few days of life other than the colostrum?

Answer 47

There is a drop in inuslin levels and an increase in glucagon levels allowing the baby to increase extracellular glucose by converting the stored glyocgen into glucose - this mobilises the haptic gycogen stores The brain is also able to use ketones as fuel

Question 48

Hypoglycaemia can be caused by the increased energy demands, low glyocgen stores, maternal diabetes/hyperinsulinism or some drogs can cause it How can maternal diabetes cause hypoglycaemia? Name a drug that can cause hyperglycaemia?

Answer 48

Maternal diabetes can cause a large glucose level which cause the foetus to have a large glucose level which cause a large foetal insulin level When the baby is born, the insulin levels should drop but stay at a higher than normal after dropping and as the glucose levels decrease - the baby goes into hypoglycaemia Beta blockers ca cause hypoglycaemia

Question 49

What is the reflex called when the baby starts to suckle? What does the composition of breast milk known as colostrum change to? How much weight does the baby normally lose in the first few days after birth?

Answer 49

The reflex is known as the Suckling reflex - the baby suckling will cause a positive feedback to increase milk production Colostrum changes to foremilk and hindmilk after 3/4 days Baby normally loses up 10% birth weight first few days postnatally

Question 50

Why does foetal haemoglobin have a greater affinity for oxygen that adult haemoglobin? When does foetal hameoglobin change so that the blood transport is fully adult haemoglobin?

Answer 50

Foetal haemoglobin - 2alpha, 2gamma subints Adult haemoglobin - 2alpha, 2beta subunits The acid - 2,3 BPG (biphosphoglycerate) binds more strongly to the beta subunits than gamma subunits and this shifts the oygen dissociation curve to the right in adults - therefore in foetus - oxygen will have a greater affintiy for the foetal hameoglobin Foetal haemoglobin changes fully to adult haemoglobin by approx 6 months

Question 51

The disdvantage with foetal hameoglobin is that adult hameoglobin is synthesised more slowly than foetal haemgolobin is broken down Nadir - he lowest or most unsuccessful point in a situation. When is the nadir of haemoglobin levels reached during the change from foetal to adult haemoglobin? Apart from anaemia, what can the breakdown of foetal haemoglobin cause?

Answer 51

The nadir haemoglobin is reached at ~8-10 weeks The breakdown of foetal haemoglobin can cause a major increase in bilirubin levels and as the liver is too immature to process this - can lead to physiological jaundice 60% of terms will get jaundice and usually is physiological

Question 52

Liver enzyme pathways present but immature * Physiological Jaundice * Breakdown of fetal haemoglobin * Conjugating pathways immature * Rise in circulating unconjugated bilirubin * Generally not harmful unless very high levels When is jaundice in the foetus said to be physiological?

Answer 52

Physiological if between 2and14 days after birth

Question 53

The treatment options if the bilirubin levels do rise too high are phototherapy or exhange transfusion How do both work?

Answer 53

Photherapy changes the bilirubin isomers from the trans-bilirubin into the water soluble cis-bilirubin so the bilirubin can be excreted in the urine and faces Exchnage transfusion is where we take out and replace twice the babies blood volume removing the excess bilirubin

Question 54

Providing phototherapy and exchange transfusion come under different bilirubin levels on a graph basically If bilirubin levels are above what level, is photherapy always given to the neonate given? Same for exchange transfusion?

Answer 54

Bilirubin levels >350micromoles/litre - always give phototherapy

Bilirubin levels >450micromoles/litre - always give exhange transfusion