Module 2: Vinod Flashcards
What are the 4 newborn physiological adaptations required at birth?
- respiratory system
- cardiovascular system
- thermal adaptation
- metabolic adaptation
What factors can influence effective ventilation (4)?
- The infant must clear amniotic fluid from the lungs.
- Surfactant must be adequate.
- Respiratory musculature must be sufficient.
- The infant must establish a regular pattern of breathing.
- Pulmonary perfusion must match ventilation (VQ matching).
- Increased pulmonary blood flow must occur.
What 4 factors are included for establishment of effective respiration at prior/during birth?
- catecholamine surge that occurs prior to the onset of labour,
- the postnatal decrease in 02 concentration,
-the increase in C02 concentration and - decrease in pH that trigger the respiratory centre,
- the mechanical squeeze on the chest as the infant moves through the vaginal canal, and
- further expansion of the lungs as the infant cries
What are the profound changes that occur in the cardiovascular system during transition from fetal to neonatal life?
fetal circulation:
- high pulmonary vascular resistance (PVR) and
- low systemic vascular resistance (SVR),
- three shunts: ductus venosus, ductus arteriosus, foramen ovale
At birth:
- the umbilical cord is clamped and the placenta is removed as the organ of gas exchange (along with the ductus venosus), and therefore the lungs must take over this role.
- Fetal fluid must be absorbed and alveoli expanded in order for the lungs to effectively take over oxygenation.
- Mechanical compression of the chest during birth creates negative pressure, drawing air into the lungs, and positive intrathoracic pressure created when the newborn cries keeps alveoli open and forces remaining fetal fluid out of the lungs.
- As oxygen enters the lungs, the pulmonary vascular bed dilates, allowing for increased blood flow to the lungs and decreased pressure in the right atrium.
- The left atrial pressure exceeds the right atrial pressure due to increased pulmonary venous return to the left atrium and less blood flow to the right atrium, which leads to functional closure of the foramen ovale.
- Blood is now following the path of right atrium to right ventricle to lungs
After birth:
- SVR rises and PVR falls, causing a reversal of blood flow through the ductus arteriosus.
-Instead of bypassing the lungs, blood is now sent to the lungs.
- Closure of the ductus arteriosus is due to a rise in P02 concentration after birth and a decrease in circulating prostaglandin levels (from removal of the placenta).
- Closure of the ductus arteriosus happens gradually, with 90% of infants having full closure by 48 hours of age; therefore, in the first days of life, there may be some bidirectional shunting of blood, depending on the levels of PVR and SVR
How is oxygenated blood delivered from placenta to fetus via umbilical vein in the fetal circulation?
- Some of this blood perfuses the liver and some of it bypasses the hepatic system through the ductus venous, a connection between the umbilical vein and the inferior vena cava (IVC).
- Once this oxygenated blood enters the IVC, it is mixed with de-oxygenated blood from the lower body and sent to the right atrium.
- Approximately half of this blood is sent directly to the left atrium through the foramen ovale, while the rest enters the right ventricle.
- The blood flow across the foramen ovale is due to high PVR, ensuring the pressure in the right atrium is higher than the left.
- Most of the blood that makes its way to the right ventricle is shunted across the ductus arteriosus directly into the aorta (again this is due to increased resistance in the pulmonary vessels).
- The remaining approximately 10% of the blood coming from the right ventricle perfuses the lung tissue.
What makes newborns predisposed to heat loss (3)?
- they have a large surface area in relation to their body weight,
- limited body fat, and
- decreased ability to shiver to stay warm
What are 3 of the processes that term infants have available to stay warm?
- increased muscle activity,
- non-shivering thermogenesis (burning brown fat),
- peripheral vasoconstriction
Newborn still rely on caregiver to maintain thermoregulation, what happens if there were no caregiver support?
- infants will use up oxygen and glucose in an effort to produce heat;
- this yields lactic acid and
- can lead to metabolic acidosis, hypoglycemia, decreased surfactant production and poor growth.
Where is Glycogen is stored for use after birth?
- liver
Use of brown fat for heat production is called?
- non-shivering thermogenesis
The use of glucose and oxygen to produce heat produces?
- lactic acid
The connection between the umbilical vein and the inferior vena cava is called the?
- ductus venosus
What signals the ductus arteriosus to close (2)?
- An increase in p02 and a
- decrease in prostaglandin signals the ductus arteriosus to close
What is perinatal asphyxia or intrapartum hypoxia-ischemia?
- When organ of gas exchange fails (placenta or lungs)
- used to describe impaired gas exchange or inadequate blood flow to the fetus/newborn that occurs during labour and delivery
- hypoxia (↓pO2) and hypercapnia (↑pCO2)
- perinatal asphyxia puts all of infants organ systems at risk for damage due to hypoxia and decreased perfusion
What are causes of asphyxia to occur prenatally (3)?
- pregnancy-induced hypertension (PIH), leading to poor placental function
- placental abruption
- compression of the umbilical cord
- low maternal 02 levels
- low maternal blood pressure
- inadequate relaxation of the uterus during labour
What 2 cues might suggest presence of asphyxia in an infant in utero?
- Fetal heart rate decelerations
- Passage of meconium is also a clue to the presence of asphyxia.
What disorders affect gas exchange in a newborn leading to asphyxia (3)?
- congenital diaphragmatic hernia
- sepsis
- congenital heart defects
- severe anemia
- low blood pressure
- respiratory problems that limit oxygen intake (meconium aspiration, severe RDS)
What are 2 ways infant response to hypoxia to provide their organs with oxygen?
Alteration of blood flow:
- to provide those organs necessary for immediate survival—the brain and the heart—with as much oxygen as possible at the cost of non-vital organs (diving reflex).
- blood is shunted away from non-vital organs such as the lungs, intestines, kidneys, and peripheral vessels.
Tachycardia:
- increase in heart rate is a reflection of the heart’s effort to increase cardiac output in response to the decrease in blood oxygen levels.
- When the heart rate increases, the cardiac output and blood pressure are improved, therefore increasing perfusion and oxygenation
When does infant switch from aerobic to anaerobic metabolism?
- when oxygen availability is compromised
- Hypoxia and asphyxia alter glucose production and utilization by requiring an increase in glycogeolysis to meet the increased metabolic and energy demands
What is anaerobic metabolism?
- is less efficient than aerobic metabolism and requires significantly more glucose to create energy.
- This rapidly depletes the glucose reserves; this decreased energy production is often inadequate to maintain normal cell processes and leads to the accumulation of lactic acid, which causes metabolic acidosis
- Hypoxia will also lead to hypercapnia (↑CO2) due to the body’s attempt to bring in more oxygen and will result in respiratory acidosis
How is asphyxia characterized?
- Asphyxia is a process characterized by inadequate/insufficinent gas exchange, leading to progressive hypoxia, hypercapnia, and acidosis, which may occur in utero or shortly after an infant is born.
What causes inadequate gas exchange in utero (3)?
- pregnancy-induced hypertension
- abruptio placenta
- cord compression
- apnea at birth
- meconium aspiration
What negative response to the pulmonary system as a result of infant having been asphyxiated (3)?
- Respiratory distress,
- meconium aspiration,
- persistent pulmonary hypertension,
- atelectasis,
- pneumonia
What are 3 negative response to the cardiovascular system as a result of infant having been asphyxiated?
- Congestive heart failure,
- cardiogenic shock,
- hypotension,
- disseminated intravascular coagulation (DIC)
What are 2 negative response to the GI system as a result of infant having been asphyxiated?
- Feeding intolerance,
- necrotizing enterocolitis (NEC)
What are 2 negative response to the renal system as a result of infant having been asphyxiated?
- Decreased urine output,
- hyperkalemia,
- renal failure
What are 3 negative response to the central nervous system as a result of infant having been asphyxiated?
- Hypoxic-ischemic encephalopathy (HIE),
- periventricular leukomalacia (PVL)
- seizures,
- sometimes long-term neurological problems such as cerebral palsy and cognitive deficits
What nursing measures could you implement in order to prevent further asphyxia and to prevent the complications associated with asphyxia (3)?
- Immediate effective resuscitation with provision of warmth, ventilatory support, and maintenance of adequate circulation. Establishing spontaneous respirations, a normal heart rate, and correcting acidosis will prevent further brain injury.
- Assess for the effects of asphyxia: hypoxia, hypercapnia, acidosis, and hypoglycemia, which may show up in many ways, such as seizures, apnea, respiratory distress, intolerance of feeds (when started), and temperature instability.
- Closely monitor the infant’s vital signs (including blood pressure), oxygen saturation, blood work results, and urine output.
- Maintain the infant’s warmth—prevent cold stress.
- Ensure sufficient glucose intake—usually the infant is NPO, so an IV is initiated. Fluid intake may be restricted to 50–70 mL/kg/hr to prevent fluid overload (since renal function may be impaired due to hypoxia) and to prevent cerebral edema.
- Keeping the infant NPO will give the gut an opportunity to recover.
- Developmentally supportive and family-centred care is key!
What is meconium composed of?
- the first stool of the infant, is composed of material ingested in utero such as amniotic fluid, bile, mucous, and epithelial cells.
- Meconium is very thick and sticky, like tar
What is the difference in meconium aspiration in preterm (less than 32 weeks) vs full term infants?
- Preterm infants, particularly those less than 32 weeks gestation, rarely experience meconium aspiration as their guts contain very little meconium.
- Meconium aspiration is a common feature of perinatal asphyxia for full- and post-term infants
- Full- and post-term infants, in contrast, have large amounts of meconium in their colons.
What are 2 reasons that post-term infants are at risk for meconium aspiration?
- They have large amounts of meconium in their gut.
- These infants can be quite large (if they continue to grow in utero) and consequently suffer second stage problems arising from their larger size.
- If they have not been growing—because the placenta has been deteriorating—they will likely be stressed and may already be experiencing hypoxia, causing meconium passage
What is the steps when meconium is expelled into amniotic fluid?
meconium expelled into amniotic fluid -> hypoxia causes infant to gasp -> delivery -> first breath -> meconium aspiration -> hypoxia
- When full- and post-term fetuses experience hypoxia, their gastrointestinal wall relaxes and meconium is expelled into the amniotic fluid
- if the hypoxia is severe, the infant can gasp (even in utero), causing the meconium to be aspirated into the airways.
- When the infant begins breathing at birth, the meconium is further aspirated, leading to severe respiratory distress, hypoxia and hypercapnia
What are 4 ways meconium aspiration causes hypoxia in the neonate?
- airway obstruction: The glottis, trachea, and smaller airways are physically obstructed, resulting in atelectasis, air trapping and alveolar collapse.
- surfactant dysfunction: Meconium deactivates surfactant and may inhibit surfactant synthesis, which results in atelectasis throughout the lungs.
- increased pulmonary vascular resistance: This occurs as a result of the hypoxia/asphyxia, which can result in the ductus arteriosus staying open (right-to-left shunting) and the maintenance of fetal circulation.
- chemical pneumonitis: The contents of the meconium can irritate the airways and parenchyma, causing the release of cytokines, which results in inflammation of the airways.
What is the comparison of normal and impaired pulmonary blood flow (4)?
Normal pulmonary blood flow:
- closure of ductus arteriosus
- closure of foramen ovale
- pulmonary vasodialtion
- increase PO2
Impaired Pulmonary blood flow:
- patent ductus ateriosus
- (+/-) patient foramen ovale
- pulmonary vasoconstriction
- decrease PO2
Why are full term infant more vulnerable to persistent pulmonary hypertension of the newborn (PPHN) than preterm infant?
- because the muscles in the walls of their pulmonary vessels are well developed and are highly sensitive to hypoxia
- Preterm infants, while they can and do experience asphyxia, are less likely to develop PPHN because their pulmonary vessels are less muscularized and less sensitive to hypoxia
Why is the development of PPHN adds to infants vulnerability?
- a rising blood oxygen level is critical to successful transition.
- Recall that in utero, low pO2 levels help to keep the ductus arteriosus open and cause pulmonary vasoconstriction.
- Together, a patent ductus arteriosus and pulmonary vasoconstriction shunt blood away from the lungs (right-to-left shunting).
- During transition, rising pO2 begins to close the duct and causes pulmonary vasodilation, lung fluid is absorbed, and the lungs take over the process of gas exchange (which was previously done by the placenta).
- In the presence of hypoxia, pulmonary vasoconstriction continues, which in turn will maintain a patent ductus arteriosus that can lead to pulmonary hypoperfusion
What are the ABCs of resuscitation as per NRP?
A - airway - position and clear
B - breathing - stimulate to breath
C- circulation - assess heart rate and colour
What is the APGAR score and when is it done?
Appearance: colour
Pulse: heart rate
Grimace: reflex irritability
Activity: muscle tone
Respiration: breathing
- An infant is given a score in each category at 1 and 5 minutes (and sometimes at 10 minutes).
- The highest score possible would be 10 (a score of 2 in each category)
- Apgar score quantifies the infant’s response to extrauterine life and resuscitative measures.
What are the normal range for capillary blood gas?
- pH: 7.35–7.45
- bicarb: HCO3- 20–26
- pCO2: 35–45
- PaO2: 50–80: aterial
-PcO2: - bases excess: BE -4 –+4
high CO2: respiratory acidosis: hypoventilation
low bicarb and low base excess: metabolic acidosis
Why is management of perinatal asphyxia involves every organ system?
- Management of perinatal asphyxia involves every organ system because perinatal asphyxia has multiple organ system sequelae.
- Every organ system is vulnerable to damage from hypoxia as a result of perinatal asphyxia and must, therefore, be supported.
How would you advise Meagan to proceed with her assessment of Vinod? What does she need to pay attention to?
- Assessment during resuscitation is based on the NRP sequences of airway, breathing, and circulation.
- In these sequences, position, colour, HR, respiratory rate, and effort and oxygen saturation are important parameters.
- Assessment must also be multi-system. Once an infant is resuscitated and stabilized, a baseline assessment must be done with a view to collecting key information in each system. This can be done by a systems approach or from a head-to-toe approach
What are the 3 interrelated but separate processes that blood gas analysis assesses?
- oxygenation
- ventilation
- acid-base homeostasis
