Intrapartum fetal surveillance chapter 17
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Translates fetal heart motion into electrical signals?
Cord around the fetal neck?
Reduced oxygen to the blood
Infusion of saline into the amniotic cavity to reduce cord compression to to wash out meconium
Muscle tension when the uterus is not contracting?
Uterine resting tone
Drug that reduces uterine muscle contractions?
List the five factors that affect fetal oxygenation?
adequacy of maternal blood volume and flow to the placenta
normal maternal blood oxygen saturation
adequate exchange of oxygen and carbon dioxide in the placenta
open circulatory path between the placenta and fetus through umbilical cord vessels
Normal fetal circulatory and oxygen carrying functions.
Explain how this factor influences the fetal heart rate : autonomic nervous system?
Sympathetic stimulatin increases the heart heart rate and strengthens the heart contractions to increase cardiac output by releasing epinephrine
Explain how this factor influences the fetal heart rate: Baroreceptors
Baroreceptors sense blood pressure changes in the carotid arch and major arteries to slow teh heart and reduce the blood pressure thus reducing cardiac output.
Explain how this factor influences the fetal heart rate: Chemoreceptors?
In the medulla oblongata aortic arch and carotid bodies sense changes in oxygen carbon dioxide and ph to increase the H/R
Explain how this factor influences the fetal heart rate: Adrenal Glands?
adrenal glands secrete epinephrin and norepinephrine in response to stress and release aldosterone to cause sodium and water thus increasing the blood volume
Explain how this factor influences the fetal heart rate: central nervous system?
the fetal cerebral cortex causes the fetal heart rate to increase during fetal movement and decrease during fetal sleep
the hypothalamus coordinates the branches of the autonomic nervous system.
The medulla oblongata maintains balance between forces that speed and slow the fetal heart rate.
Define the term that describe the fetal heart rate: NORMAL
Define the term that describe the fetal heart rate: BRADYCARDIA
rate less than 110 bpm that persists for at least 10 min
Define the term that describe the fetal heart rate: TACHYCARDIA
rate greater than 160 bpm that persists longer thatn 10 min
Define the term that describe the fetal heart rate: SHORT TERM VARIABILITY
changes of the fetal heart rate from one beat to the next.
Define the term that describe the fetal heart rate: LONG TERM VARIBILITY
Broader fluctuations in the FHR over 1-min intervals
List factors that may decrease short-term and long-term varibility?
decreased central nervous system oxygenation
abnormalities of the CNS, heart or both
Whys is varibility an important component of fetal heart pattern evaluation?
Variability reflects normal funtion of the autonomic nervous system which helps the fetus adapt to the stress of labor.
Describe methods that may be used during labor to clarify the fetal condition?
Fetal scalp stimulaion
fetal scalp blood sampling
fetal oxygen saturation monitoring
possible nursing interventions to identify and/or correct the cause of a nonreassuring fetal monitor pattern: IDENTIFYING THE CAUSE
- Check blood pressure to identify hypotension or hypertension,
- contractions to identifey uterine hyperactivtiy and recent maternal medicatons to identify sedative effects perform vaginal examination to identify prolapsed cord or initiate internal monitoring to provide more accuracy
possible nursing interventions to identify and/or correct the cause of a nonreassuring fetal monitor pattern: INCREASING PLACENTAL PERFUSION
- Change positon to displace uterus decreasing aortacaval compresssion
- discountinue oxytocin and /or administer tocoytics to reduce uterine activity
possible nursing interventions to identify and/or correct the cause of a nonreassuring fetal monitor pattern: INCREASING MATERNAL OXYGEN SATURATION
Administer oxygen at 8-10L/min through a snug facemask.
possible nursing interventions to identify and/or correct the cause of a nonreassuring fetal monitor pattern:REDUCING UMBILICAL CORD COMPRESSION.
Repositon or perform amnioinfusion to reduce umbilical cord compression.
List two uses from amnioinfusion.
Add fluid to create a cushion around the umbilical cord
dilute thick meconium to reduce the effects of possible aspiration at birth.
What is the purpose of vibroacoustic stimulation test (VST)
A vibroacoustic stimulation test (VST) identifies whether fetal heart rate accelerations occur in response to sound stimulation
it shortens the nonstress test (NST) or confirms a nonreactive NST
The basic principle of the contraction stress test is to observe the response of the _______to the stress of______?
Fetal heart rate
What two methods are used to cause uterine contractions when doing a contraction stress test?
Describe possible results and implications of a contraction of a contraction stress test?
Negative --normal (no late decelerations)
Positive--abnormal (late decelerations following 50% or more of the contractions)
Suspicious or equivocal--intermitent late or variable decelerations
equivocal hyperstimulation--late decelereations with excessive contractions
unsatisfactory--fewer than three contractions within 10 min of a poor quality tracing
Firm contractions that occur every 3 minutes and last 100 seconds ( 1 min 40 seconds) may reduce fetal oxygen supply because they?
Limit time for oxygen exchange in the placenta.
The expected response of the fetal heart rate to active fetal movement is?
Accelerations of at least 15 beats per min (BPM) for 15 seconds
The nurse notes a pattern of variable decelerations to 75 bpm on the fetal monitor. The initial nurse action is to?
Repostition the woman
The tocotransducer should be placed?
In the fundal area
Choose the important precaution when a fluid-filled catheter is used to monitor the uterine contractions during labor?
The tip of the catheter must be at the same level as transducer
The nurse notes a pattern of decelerations on the fetal monitor that begins shortly after the contraction and and returns to baseline just before the contraction is over the correct nursing response is to?
continue to observe and record the normal pattern.
What five related factors are required for adequate fetal oxygenation?
Normal maternal blood flow and volume to the placenta
Normal oxygen saturation in maternal blood
Adequate exchange of oxygen and carbon dioxide in the placenta
An open circulatory path between the placenta and the fetus through vessels in the umbilical cord.
Normal fetal cirulatory and oxygen-carrying functions
Maternal blood carrying fetal waste products drain from the intervillous spaces through endometrial veins and return to the mothers circulation for?
Elimination by her body
How much oxygen supply is available in the intervillous spaces during a contraction for the fetus?
about 1-2 mins worth.
As each contraction relaxes freshly oxygenated maternal blood re-renters teh intervillous spaces and waste laden blood drains out.
THe umbilical vein carries oxygentated blood to?
The two umbilical arteries carry deoxygenated blood From?
THe fetus to the placenta
Five fetal factors that interat to regulate FHR include the?
Autonomic nervous system
Central nervous system
What does sympathetic stimulation do?
Increases H/R and strengthens myocardial contractions through release of epinephrine and norepinephrin.
The result of sympahtetic stimulation is an increase in cardiac output
WHat does parasympathtic nervous system through stimulation of the vagus nerve do?
Reduces FHR and maintains variabiltiy
What do the baroreceptors Do?
Stimulate teh vagus nerve to slow FHR and decrease the blood pressure thus lowering cardiac output .
As fetal blood pressure falls the H/R accelerates to maintain normal cardiac output
WHere are chemoreceptors located?
in the medulla oblongata and in the aortic and carotid bodies.
Cells that respond to changes in oxygen carbon dioxide and ph are called?
What do the Adrenal medulla do?
Secrete epinephrine and norepinephrien in response to stress causing a response from teh sympathetic nervous system that accelertes FHR.
WHat does the adrenal cortex do?
respondes to decrease in fetal blood pressure with release of aldosterone and retentin of sodium and water resultin in an increase in ciculatin fetal blood volume.
What does the fetal cerebral cortex do?
Causes the H/R to increase during fetal movement and to decrease when the fetus sleeps
What does the hypothalamus do?
Coordinates the two branches of the autonomic nervous system
What does the medulla oblongata do?
Maintains the balance between stimuli taht speed and stimuli that slow H/R
What are hyertonic contractions?
contractions that are too long(>90 to 120 seconds)
Too frequent (closer than every 2 min or have an inadequate relaxation period ( less than 30 seconds of complete relaxation)
they will not allow optimal uteroplacental exhange
What may cause excessive uterine activity?
admin of prostaglandin and oxytocin
but may also occur with no external stimulation
What is the usual cause of interrupted blood flow though the umbilical cord?
What may cause a nuchal cord?
oligohydramnios because the amout of aminotic fluid is inadequate to cushion the cord.
in cord compression what is compressed intially?
the thin walled umbilcal vein reducing flow of more highly oxygenated blood in to the fetus.
results in hypoxia and hypotension, baro and chemoreceptors respond by accelerating the FHR.
What do you use for IA of FHR?
what is teh primary advantage of auscultation and palpation from intrapartum fetal monitoring of the fetus at low risk?
Mobility- the woman is free to change position and walk which is especially helpful during labor or with a fetal occiput posterior positon.
what is a disadvantage of IA and palpatation as teh primary method of fetal assessment is?
that FHR and uterin activity are assessed for a small part of the total labor.
Why may IA not be a realistic option as the primary method of intrapartum fetal surveillance?
it is staff intensive if teh nurse to patient ratio must be greater than 1:1 for patients in normal labor.
Whata can be used to identify FHR baseline rhythm and changes from the baseline?
Is the Doppler transducer or external fetal monitor reliable to detect fetal dysrhythmias?
advantage of the electronic fetal monitor?
Supplies more data about the fetus than auscultation and provides a permanent record that may be printed or stored electronically.
Gradual trends in FHR and uterine activity are more apparent because teh strip provides a graphic record for review.
Continuous EFM show the fetal respones befor during and after every contraction
ERM allows one nurse to observe two lavoring women primarily during uncomplicated early labor.
Limitations of EFM?
frequent maternal positon changes or active fetus may require constant adjustment of equipment to maintain a near-continuous trace.
the belt or stockinette used to keep sensors postitioned are uncomfortable.
a good trace is hard to find with fat girls.
woman may be concentrating on a good trace instead of comfort.
Equipment needed for EFM?
sensors for FHR and uterine activity
Telemetry (wireless trasmission of data to the base for observation and storage)
fetal monitor clocks
On the EFM paper grid where is FHR recorded?
on the upper grid. The range or rates is 30-240 bpm
WHere is uterine activity recorded on paper strip?
on the lower grid as bell-shaped curves with continuous smaller rises and falls that represent maternal breathin superimposed on the larger curve.
What is uterine resting tone?
contraction intensity and the degree of uterine muscle tension from 0-100 mmhg and are recorded on the lower grid.
What does a doppler ultrasound transducer do?
detects fetal heart movement for rate calculation. it is similar to the hand-held doppler unit. The transducer sends high-frequency sound wave into the uterus. The sound waves are reflected and the monitors computer continuoously calculates FHR based on the movement sensed as the heart beats.
What does a tocotransducer (toco) do?
with a pressure sensitive area detects changes in abdominal contour to measure uterine activity. The uterus pushes outward against the mother anterior abdominal wall with each contraction. The montior calculates changes in this singal and prints them as bell shapes on the lower grid of the strip
Factors that affect apparent intesity as printed on the strip include?
Abdominal fat thinkness
location of the transducer
What is the main advantage of using internal devices for EFM?
Accuracy- but they are invasive, slightly increasing the risk for infection
there use requires ruptured membranes and about 2 cm of cervical dilation.
The fetal heart rate monitoring with a scalp electrode?
detects electrical signal s from the fetal scalp
fetal or maternal movement interferes less with accuracy because teh rate is calculated from electrical events in the fetal heart
Areas to avoid for electrode application
Why is the scalp electrode easily displaced?
- because it barley penetrates the fetal skin (about 1 mm)
- the tracing then becomes erratic or stops if teh electrod is fully detached.
secure attachment of the electrode is often difficult if the fetus has thick hair
the electrode is removed by turning it counterclockwise about one and one half until it detaches.
Two kinds of intrauterine pressure catheters (IUPCs) can be used to measure uterine activity including contractin intensity and resting tone?
A solid catheter with a pressure transducer in its tip this catherter usually has an additonal lumen for amnioinfusion or infusin of sterile solution into the uterus
A hollow fluid filled catherter that connects to a pressure transducer on the bedside monitor.
Both types sense intraterine pressure an increases intraabdominal pressure such as with coughing or vomiting.
why should the fluid-filled catheter in the uterus should be at the level of the transducer on the outside?
for best accuracy.
if the tip is lower teh recorded pressure is lower than the acutal intrauterine pressure
if the tip is higher the pressure maybe higher.
The FHR baseline is the average heart rate rounded to ?
5 bpm measured over 2 min of clear tracing within a 10 min window during this 2 or more min the uterus must be at rest.
Normal Fetal heart rate
a rate that averages from 110 to 160 bpm
The preterm fetus at 26-28 weeks often averages a rate at teh upper end of this range because the parasypathetic nervous system which slow the rate, is immature some healthy full term fetuses have a rate that averages 100 to 110 bpm
Less than 110 bpm peristing for atleast 10 min
more than 160 bpm persisting for at least 10 min
What is variability?
the fluctuations in the baseline FHR that cause the printed line to have an irregular wavelike apperance rather than a smooth flat one.
Variabilty may be decreased by several nonpathologic and pathologic factors such as?
Narcotics or other sedative drugs such as magnesium sulfate given to the woman
alcohol illicit drugs
gestatin younger than 28 weeks
fetal anomalis that affect central nervous system regulation of the heart rate such as anencephaly
hypoxia that is sever enough to affect the central nervous system
abnormalities of the cns heart or both
maternal acidemia (low blood PH) or hypoxemia (reduced oxygen in blood)
Why does varibility occur?
because multiple factors constantly speed and slow the fetal heart rate in a push-pull manner
What does Evaluation of variability help do?
Clarify how a fetus is tolerating the stress of pregnancy compliation or labor including factors that cause hypoxia
Why is variablity a significant componet of FHR tracing on the electronic monitor Two reasons?
Adequte oxygenation promotes normal function of the autonomic nervous system and helps the fetus adapt to the stress of labor
Variability evaluates the function of the fetal autonomic nervous system especially the parasympathetic branch.
What are the 4 categories of variability in the NICHD
Absent - undetectable
Minimal - Undetectable to <_ 5 bpm
Moderate - 6 to 25 bpm
Marked - > 25 bpm
What are periodic patterns in HR?
temporary recurrent changes from the baseline rate that are associated with uterine contranctions the include accelerations and decelerations.
What is an acceleration?
a temporary increase in FHR that peaks at least 15 bpm above baseline and lasts at least 15 seconds.
WHen do accelerations often occur?
With fetal movement
they may also occur with vaginal exams uterine contractions and mild cord compression and when the fetus is in a breech presentation.
WHy are accelerations a reasurring sign?
reflects a fetus taht has a responsive Central nervous system and is not in acidosis.
Acceleration for a healty preterm fetus before 32 weeks?
FHR less that 15 bpm and peeks 10 bpm above baseline and lasts at least 10 seconds is considered an acceleration.
How does a fetus younger than 28 weeks accelerations appear?
flat because of autonomic nervous system immaturity.
What are prolonged accelerations?
lasting longer than 2 min but less than 10 min
may reflect a merging of several accelerations that later return to the previous baseline.
The three types of decelerations?
What is an early deceleration?
fetal head compression for any reason increases intracranial pressure, causing the vagus nerve to slow the H/R
Early decelerations are not associated with fetal compramise and require no intervention
Why do early decelerations occur?
occur during contractions as the fetal head is pressed against the womans pelvis or soft tissues such as the cervix and are common during the second stage.
Characteristics of early decelarations?
consistant in appearence they are uniform in that one looks simlar to others.
THEy mirror the contraction gradually falling from the baseline and gradually returing to the baseline at the end of contraction.
What is a nadir?
the low point of FHR
the rate is usually no lower than 30-40 bpm from the baseline.
What are late decelerations?
a late (delayed) decelerations that may result from impaired exchange of oxygen and waste products in the placenta.
what can happen with late decelerations?
the fetus may develop acidemia which can depress cardiac function because poor oxygen availibility in the placenta requires a shift to anaerobic metabolism
what is the cause of uteroplacental insufficiency?
may be acute and transient such as maternal hypotension or excessive uterine stimulation.
It may occur with chronic conditions that impair placental exchange such as maternal hypetension or diabetes
Although late decelerations are not reasurring other signs can suggest wheter the fetus is tolerating the uteroplacental insufficiency?
a normal baseline rate with moderate variability and presence of accelerations suggest that the fetus is tolerating the conditions.
However the fetal reserves eventually will be depleted if the cause not corrected and reassuring signs will disappear.
what is the diffrence between late and early decelerations.
Late look similar to early but are shifted to the right in relation to the contraction
Characteristic of late deceleration?
they have a consistent and often subtle appearance in that one late deceleration looks similar to others.
They gradually fall from the baseline and gradually return to the baseline after the contraction ends.
THe nadir of FHR in late decelerations
occur after the contraction and may not fall much below its baseline level.
The amount of rate decrease from the baseline does not indicate how much uteroplacental insufficiency exists.
What are variable decelerations?
do not have uniform appearance of early or late decelerations .
There shapes duration and degree of fall below baseline rate are variable.
THey fall and rise abruptly ( within 30 second) with the onset and relief of cord compression unlike the gradual fall and rise of early and late decelerations
varibale decelerations also may be noperiodic occuring at times unrelated to contraction.
What are the four components of uterine activity?
intesity of contractionS
uterine resting tone.
How is contraction intensity described?
WHat is a montevideo units (MVUs)
Maybe used to describe contraction intensity in millimeters of mercury when an IUPC is used.
How is the Montevideo Units calculated?
by noting the contraction intensity in millimeters of mercury above the resting tone and multiplying by the number of contractions in 10 min
Example if a woman three contractions in 10 min each of which has an intensity of 110 mm Hg and a resting tone of 15 mm Hg teh result is MVUs is 285. Excess uterine activity during labor would be 400 MVUs
The NICHD's three categories of significance of FHR patterns.
Category I- normal (reassuring)
Category II - Indeterminiate (often described as equivocal or ambiguous)
Category III - Abnormal (nonreassuring)
What are reassuring patterns?
often with fetal movement are associated with fetal well-being
What are indeterminate patterns?
do not clearly fall into reassuring or nonreassuring
indeterminate patterns often referred to as equivocal or ambiguous
category III is used for nonreasuing patterns or those in which favorable signs are abscent that are not associated with fetal hypoxia or acidosis are present
Do nonreasuring signs indicate that fetal hypoxia or acidosis has occured?
Not necesarily they indicate that steps should be taken to identify possible causes for the patterns that correct their causes
When are nonreasurring patterns more significant
when they occur together and are pesistent
Example bradycardia with varibility of less that 5 bpm and late decelerations suggest greater physiologic stress than bradycardia with normal varibility of the heart rate.
Nonreassuring patterns include but are not limited to?
Absent baseline varibility
recurrent late decelerations
recurrent varible decelerations
Sinusoidal pattern a visualy undulating pattern (rare)
What does fetal scalp stimulation do?
evalutates the fetus response to tactile stimulation during labor
how do you do fetal scalp stimuation?
the examiner applies pressure to teh scalp (or other presenting part) with a gloved finger or fingers sweeps the fingers in a circular motion
an acceleration in FHR of 15 bpm for at least 15 seconds is a reasurring response in the term fetus suggests normal oxygen and acid-base balance.
WHen would you not do fetal scalp stimulation?
Preterm fetus ( may cause or intesify contractions and rupture membranes
Prolonged rupture of membranes (higher risk of infection)
Chorioamnionitis (intrauterine infection)
Placenta previa (may cause hemorrhage)
maternal fever of unknown origin ( possiblility of introducing microorganisms into the uterus)
What is fetal scalp blood sampling?
more complex than other intrapartum techniques and requires rupture of the membranes
normal scalp pH is 7.25-7.35
acidocis is present if the ph is less than 7.20 and the clinician may hasten the birth by using forceps or cesarean delivery.
how to increase placental perfusion?
positon on the side to eliminate aortocaval compression
give a bolus of isotonic intravenous fluid such as LR.
give tocolytic drug.
What is a tocolytic?
such as terbutaine (0.125-0.25 mg intravenously or 0.25mg subq) and may be given to reduce uterine activity.
How to increase maternal blood oxygenation saturation?
admin 100% oxygen at 8-10 L/min through a snug facemask makes more oxygen available for transfer to the fetus.
What is an amnioinfusion?
an infusion of sterile isotonic solution into the uterus may be used to increase the fluid around the fetus and cushion the cord and reduce the likelihood of cesarean birth. LR or NS
Amnioinfusion has been used to wash out or dilute fluid heavily stained with meconium.
Intervals for assessing FHR?
active first stage labor 15-30 min shortly after a contraction
second stage labor 5-15 min
When shoud you take a women temp?
every 4 hours
and then every 2 hours after membranes rupture.
Assess the womans temp and fetal resp at least hourly or with fetal assessment
other times to document fetal heart rate?
before artificial rupture of the membranes
after rupture of the membranes
if contractions become too frequent or last to long or if there is an inadequate interval between them
before admin of oxytocin and when evaluating the dose for increase maintenace or decrease
before admin of sedatives or cns depressant and at time of peak action
before epidural analgesic is started and every 15 min for 1 hr after it is started.
The purpose of intrapartum fetal surveillance is to identify fetal well being and to identify the fetus who may be having hypoxic stress beyond teh ability to compenste for it.
the two approches to intraprtum fetal minitorin are intermittent auscultation with palpation of uterine activity and electronic fetal monitoring . Each type had distinct advantages advantages and limitaions. EFM has not been shown to be superior to auscultation with palpation but is recommeded for women with high risk conditions
Fetal oxygenation depends on a normal flow of oxygenated maternal blood into the placenta normal exchange within the placenta patent umbilical cord vessels and normal fetal ciculatory and oxygen carrying function
Stimulation of teh sympathetic nervous system increases FHR and strengths teh heart contractoin. Stimulation of teh parasympathertic nervous system slows the HR. The push-pull action of speeding and slowing the HR is evidenced by the wavy appearence of the baseline in the fetus who i monitored electronically
IA and palpation allow the greatest amount of maternal movement but also requires 1:1 nurse to patient ratio for best surveillance
External EFM is less accurate for FHR and uterine ativity patterns than internal monitoring but it is noninvasive and does not require ruptured membranes
Greater accuracy is the main advantage of internal EFM devices but these are invasive and require ruptured membranes
Nursing responsibilites related to intrpartum fetal surveilance by any mode include promoting fetal oxygenation identifying and reportin nonreassuring findings supporting parents communicating with the physician or nurse midwife and documenting all care.
What are the three goals of antepartum fetal surveillance?
to determine fetal health or compromise as accurately as possible to guide intervention by the obstetric and neonatal teams and to reduce perinatial morbidity and mortality.
The three common methods of fetal surveillance are?
the nonstress test
contraction stress (CST)
Biophysical profile (BPP)
What would you like to do?
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