APGAR Scoring and Transition Flashcards
Define resistance to flow.
a force that must be overcome to push blood through the circulatory system
How does vasodilation affect vascular resistance?
dilation causes an increase in blood vessel diameter and subsequent decrease in vascular resistance; very little resistance = easy work for the heart
How does vasoconstriction affect vascular resistance?
decrease in blood vessel diameter increases vascular resistance
Define SVR.
the resistance offered by the vasculature of the peripheral circulation (that the LV has to pump against); increases post birth r/t cord clamping
Define PVR.
the resistance offered by the vasculature of the lungs
What is reverse end diastolic flow?
the placenta is the low resistance organ in utero; in diastole there should be no trouble for blood to travel through the descending aorta to return to the placenta; with PIH, the placenta is high resistance, not permitting blood to return for exchange easily
What is the function of the placenta in fetal circulation?
exchange organ for O2, CO2, nutrients and waste
What is the function of the ductus venosus in fetal circulation?
blood from the placenta by-passes the liver to enter the IVC
What is the function of the foramen ovale in fetal circulation?
blood from the IVC by-passes the lungs to the LA
What is the function of the ductus arteriosus in fetal circulation?
blood from the pulmonary artery by-passes fetal lungs to the aorta
Where is the highest O2 content in fetal circulation?
umbilical vein; 35 mmHg or 70% SpO2
Where is the lowest O2 content in fetal circulation?
right atrium from SVC; 16mmHg of 40% SpO2; blood is then to go through the PA and be shunted away from the lungs by the DA and return to the placenta for exchange
When does transition occur?
begins at stabilization and lasts about 6-12h
How does the catecholamine surge prior to labor facilitate elimination of fetal lung fluid?
the surge just before or during labor changes Na channel transport in the lung from secretions to absorption
What percentage of fetal lung fluid is absorbed prior to a normal term birth?
75%
What effect does the fist breath have on carotid chemo receptors and aortic baro receptors?
hypercarbia stimulates chemo receptors to have spontaneous breathing effort; stimulating baroreceptors will help to maintain independent homeostasis of BP
How does the first breath affect the pulmonary tissue?
replaces fluid with air; first breath = Tv 12-67mL; pressures needed 20-60 cm/H2O
How does lung expansion affect the pulmonary system?
release of surfactant, decreases alveolar tension, creates a stable FRC (~30mL/kg)
When is near normal FRC established?
within the first 15 min
What is the affect of increased blood flow to the lungs?
1) increase pH, decrease CO2, increase O2
2) decrease PVR
3) simultaneous decrease R side heart pressures and increase L side
4) increase blood return to the L side of the heart
5) when L>R; functional closure of FO
6) increase pulmonary metabolism of PGE
7) increasing O2 stimulates closure of DA
What is the biggest supplier of PGE in utero?
the placenta; also metabolized in the lungs
What is the effect of the DA when exposed to oxygen?
remains open in utero r/t high levels of PGE from the placenta and relative pulmonary hypoxia; response post birth with increasing O2 is to constrict
What is the effect of a clamped cord (no blood flow FROM the placenta) on SVR post birth?
decrease in R atrium pressures
What mechanisms facilitate a decrease in RV pressure post birth?
Increasing pH, decreasing CO2 & increasing O2 causes a decrease in PVR
What is the effect of a clamped cord (no blood flow TO the placenta) on SVR post birth?
1) increase SVR
2) increase aortic pressure
3) increase pressure in the L atrium, then L ventricle
4) pressure in L>R; functional closure of FO
What is the effect of the loss of the placenta have on SVR post birth?
1) means loss of a large source of prostaglandins
2) closure of DA (fx closure at 15-24h; structural @ 3-4wks)
What is the effect of blood no longer flowing through the DV?
closure; structurally closed @ 1-2wks
What is the results if transitional changes do not occur?
hypoxia (low pH, high CO2, low O2)
- causes high PVR
- persistent PDA and PFO
- R>L shunting
- PPHN
When does the transfer of blood occur post birth from the placenta to the infant?
during the first 3 minutes after birth
How does the volume of blood transfer from the placenta vary with timing?
30-60sec after delivery (15-20%), 60-90 sec (25%), 3 min (50-60%)
What is the effect of a 2 min cord clamping delay in a term infant as it pertains to volume and Fe?
delivers an additional 40mL/kg of blood and an additional 75mg of Fe
Where should the preterm infant be positioned for a delayed cord clamping?
needs to stay in lap or at maternal thigh level
What infant health outcomes have been improved by the practice of delayed cord clamping in preterm newborns?
a delay of 30-120 secs improved cerebral oxygenation, BP, less anemia requiring blood transfusion and less IVH
What infant health outcomes have been improved by the practice of delayed cord clamping in term newborns?
improved blood volume and hct, decreased anemia in first 6mo of life
What infant health outcomes have been improved by the practice of milking the cord x3 over <30 secs in preterm newborns?
improved BO, high hct, less transfusion; no difference in IVH, NEC or death
What comprises the APGAR score?
A (appearance, color) P (pulse, HR) G (grimace, reflex irritability) A (activity, muscle tone) R (respirations)
Why was the Apgar score created?
to facilitate clinical assessment of the newborn and guide resuscitation efforts
What is the Apgar score?
a cursory assessment of the cardiopulmonary and neurological status of the newborn
What action should be taken if the score is < 7 at 5min?
repeat the scoring every 5 min until 20 min has passed or the infant earns 2 consecutive scores > 7
What do the scores at 1 and 5 min indicate?
1: how they tolerated labor; 5: how they tolerated resuscitation
What are the factors that influence the Apgar score?
- GA
- maternal meds: narcotics, general anesthesia
- infection: chorio, GBS, TORCH
- congenital disorders: CDH, CHD
- cardiopulmonary conditions: PPHN
- neurologic conditions
What are the new NRP questions to guide resuscitation?
term gestation? breathing or crying? good tone?
if yes, baby stays with MOB, warm & dry, sx ONLY if evidence of obstruction
Why should deep sx be avoided?
vagal stimulation to decrease HR
What should be the focus of resuscitation?
respirations> HR > oxygenation
What are the target Sat ranges for a term infant post delivery?
1 min: 60%; 5 min: 90%; term CSX without labor 90% at 7 min
The majority of evidence suggests that it takes what length of time for healthy late preterm infants to ‘pink up’?
5-10 min; sats >90%
When is pulse oximetry monitoring indicated post birth?
1) supplemental O2 is used
2) PPV is required for more than a few breaths
3) central cyanosis is persistent or need to confirm perception of central cyanosis
4) resuscitation is anticipated
What is the danger of giving babies unnecessary supplemental oxygen?
newborns are relatively deficient in anti-oxidants and too much oxygen may damage tissues
What is the significance of touch during a resuscitation?
how you touch a baby during resuscitation can alter adaptations to extrauterine life
What is the type of touch an infant is subjected to during a resuscitation?
human touch- used to evaluate the baby; mechanical touch- PPV & sx; protective touch- gentle, soothing, caring
What are the implications of a low Apgar score?
not necessarily markers of later neurologic dysfunction, somewhat prognostic
What are the implications of a low Apgar score at 1 min?
not predictive of survival and long-term neurologic status
What are the implications of a low Apgar score at 5 min?
more predictive of survival and neuro status
What are the implications of a persistently low Apgar score?
at 10 min may provide useful prognostic data; risk for CP increases with severely depressed Apgar scores
What percentage of infants who later develop CP have normal Apgar scores at birth?
75%
What is asphyxia?
a severe deprivation of oxygen derived from a failure to establish normal respirations; duration is critical to outcome
When can asphyxia occur in the newborn?
prior to birth (r/t maternal/fetal conditions), during L&D, due to conditions that occur after birth
What are maternal causes of asphyxia?
infection and asthma
What are placental causes of asphyxia?
severe PIH, abruption
What are fetal causes of asphyxia?
anemia, cord compression
What is placenta accreta?
chorionic villi attach to the myometrium, rather than being restricted within the decidua basalis
What is placenta increta?
chorionic villi invade into the myometrium
What is placenta percreta?
chorionic villi invade through the myometrium and potentially into surrounding organs
How does asphyxia present in the newborn?
1) combination of hypoxemia, hypercapnea and metabolic acidosis
2) PVR remains high
3) DA remains open R>L shunt
4) FO remains open R>L shunt
What is characteristic of asphyxia just prior to birth?
should respond to ventilation & resusc; if poor response, probably d/t prolonged, severe acidemia
What will happen if the process of asphyxia is not quickly reversed?
it is self perpetuating and may result in severe hypoxemia, ischemia, acidosis and irreversible organ damage
What should be suspected if an infant is vigorous at birth, then develops apnea, cyanosis and bradycardia?
1) wrong steps in resusc
2) baby has an airway/lung disorder/anomaly
What are possible causes of airway obstruction after delivery?
1) mec aspiration or severe pneumonia
2) intrathoracic malformations that interfere with ventilation- CDH, CAM
3) congenital anomalies of airway- laryngeal web, vascular ring
4) pneumo
How frequently does mec appear in the amniotic fluid of normal term deliveries?
10-15%; mec in term infant as an isolated finding is not considered significant for CP
When will an umbilical cord appear yellow or green?
if mec has been passed 6-12h prior to delivery
What are characteristic markers of birth asphyxia?
1) mec in amniotic fluid
2) fetal HR
3) Apgar scores
4) pH and other acid/base measures
What are the current recommendations of the AAP for the use of Apgar scores and the determination of perinatal asphyxia?
should not be used alone to establish a diagnosis of asphyxia
What is the best marker to identify asphyxia during L & D?
low pH; recent research is not conclusive that pH correlates to neuro outcomes
What is the only clinical predictor of later neurologic outcome?
neonatal encephalopathy with early seizures
What is HIE?
H: hypoxemia- decreased oxygen to the brain
I: ischemic- decreased blood perfusing the brain
E: encephalopathy- any dysfunction of the brain
What are the 4 factors necessary for diagnosis of HIE?
1) low Apgar scores (0-3 for >5min)
2) cord gas pH < 7
3) Evidence of neurologic manifestations in 1st 24h of life such as hypotonia, coma or sz
4) evidence of other organ damage (brain will be protected as long as it can)
In the pathophysiology of HIE, following termination of the insult, what can occur?
a cascade of deleterious events resulting in cell death (necrosis and cell death)
What are the 2 main areas of the brain affected by HIE?
basal ganglia and thalamus, resulting in: hearing loss, learning disability, mild motor dysfunction, CP, severe motor dysfx and death
What is the effect of mild thermal stress?
can help to establish respirations, thyroid and catecholamine surge
What is the effect of severe thermal stress?
acidosis, hypoxia, hypoglycemia, DIC, IVH, shock, death
What is the effect after birth of temp stability?
temp falls 2-3 degrees C, triggers metabolic processes and increases heat production
What is the effect of a decreasing core temperature on the newborn’s metabolism?
increases 100% by 15-30 min; 170% by 1 week of age (term infants)
What is the thermic response mounted by the newborn?
non-shivering thermogenesis of brown fate
When does brown fat develop in the fetus?
~ 26 weeks through 3-5 weeks post birth; accounts for 1/10th adipose tissue in the full-term infant
Describe the appearance of brown fat.
smaller vacuoles, high in glucose, mitochondria, sympathetic nerves and blood supply
Where is brown fat located?
- mid scapula
- back of the neck
- under clavicles
- abdominal aorta
- kidneys
- mediastinum
- trachea
- heart
- liver
- esophagus
- adrenal glands
What is the mechanism of convective heat loss?
skin > air; depends on air temp, air flow, relative humidity, clothes and hat; head is 21% surface area and brain produces 44% of body heat
What is the mechanism of radiant heat loss?
skin > environment; heat lost to walls, windows, objects NOT in direct contact
What is the mechanism of conductive heat loss?
skin > surface; direct contact of baby with blankets, scale, diapers, etc
What is the mechanism of evaporative heat loss?
- biggest source of heat loss* 58 calories are lost for every gram of H2O evaporated; depends on air flow and humidity
How quickly should an infant be rewarmed?
term: no faster than 1 degreeC/hr; if t rewarm faster than 0.5 degreeC/hr
