Transcript Document

“FETAL HEART MONITORING”
Dr Seyed Asadollah Kalantari
OB & Gynecologist
Isfahan Fertility & Infertility Center
FETAL MONITORING
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Non Stress Tests
• Contraction Stress Tests
Non stress test
Non stress test
A nonstress test determines the response of the fetal
heart rate to fetal movements.
• “running a strip.” During a nonstress test, an
external monitor is placed around the mother's
abdomen to record the fetal heart rate.
• Each time ,the fetal movement is noted on the
recording chart.
• If the fetus is asleep, the mother press on her
abdomen or make a loud noise to awake the fetus.
Cont OB/GYN 2005;50:38-48
Cont OB/GYN 2005;50:38-48
Non stress test
• The NST is derived from observations that a
fetus that is not acidotic and has an intact
normally functioning autonomic nervous
system will have periodic accelerations of the
FHR.
Non-stress test physiology
• Afferent signals:
– Baroreceptors: aorta, atrium, carotids
– Proprioceptors: joints
– Pain fibers: skin
• When stimulated, send afferent impulses to brain to increase FHR
• Efferent signals increase FHR
• If movement and accelerations observed, reasonable to conclude th
afferent and efferent limbs intact and cardioregulatory neurons
adequately oxygenated
Indications for the NST
• Suspected post-maturity
• Maternal diabetes
• Maternal hypertension: chronic and
pregnancy-related disorders
• Suspected or documented IUGR
• History of previous stillbirth
• Isoimmunization
Indications for the NST
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Older gravida
Decreasing fetal movement
Sever maternal anemia
Multiple gestation
High-risk antepartal conditions: PROM, PTL,
bleeding
• Chronic renal diseases
Factors that can interfere with NST
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Fetal positions
Being unable to lie still throughout the procedure
Being overweight
An infection in either you or your baby.
Low (hypoglycemia) or high (hyperglycemia) blood
sugar levels.
Medications, such as magnesium sulfate.
Alcohol.
Illegal drugs, such as cocaine.
stool (feces) or air in the intestines or rectum
interfering with the fetal ultrasound
NST: How to do it
• Patient in lateral tilt position
• Tracing observed for 40 minutes
• Accelerations peak (but do not
necessarily remain) at least 15 BPM
above baseline
• Last for 15 seconds
• Reactive: 2 or more accelerations
within 20 m period
• Nonreactive: one that lacks
sufficient accelerations over 40
minute period
• No contraindications
The preterm fetus
• Frequently nonreactive
– 24-28 weeks,
up to 50% of NST nonreactive
– 28-32 weeks,
15% nonreactive
Reactive NST (Acceleration)
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Non Reactive NST (Lack of Acceleration )
Fetal sleep
Medication
Hypoxia
Contraction stress test
• (CST) measures the fetus''s ability to tolerate
the stress of uterine contractions started
(induced) before true labor begins.
• during a contraction stress test ,evaluate the
fetus''s heart rate during contractions.
• helps evaluate the placenta''s ability to
provide enough oxygen to the fetus.
• For determine the safest method of delivery .
• A contraction stress test is also called an
oxytocin challenge test.
Contraction stress test
• the hormone oxytocin is given to cause labor
contractions.
• you may massage your nipples to prompt
your body to release oxytocin.
• (decelerates) instead of (accelerates) after a
contraction, baby not be able to tolerate the
stress of normal labor.
• A contraction stress test is often done if a
baby''s heart rate is abnormal during
(nonstress test).
• This test may be used in rare cases for
women who have had an abnormal nonstress
test or biophysical profile
CST interpretation
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Interpreted as to the presence or absence of late
decelerations
Negative: no late or significant variable
decelerations
Positive: Late decels following 50% or more of
contractions
Equivocal: intermittent late decels or significant
variable decels
Equivocal-hyperstimulatory: FHR decels in
presence of contractions occurring more than
every 2 minutes or lasting longer than 90 seconds
Unsatisfactory: fewer than 3 contractions in ten
minutes
Contraction stress test
• Contraindications:
– Preterm labor patients at high risk of
preterm labor
– PROM
– History of extensive uterine surgery or
classical cesarean
– Known placenta previa
• Positive contraction stress test
• Fetal heart rate decceleration
• Fetal hypoxia (uteroplacental insufficiency)
• Negative contraction stress test
• Fetal heart rate decceleration
FHR Variability
• Increased Variability: marked variability from a
previous average variability.
– Causes:
-early mild hypoxia
- fetal stimulation
- uterine palpation
- contractions
- fetal activity
- maternal activity
- illicit drugs
• Saltatory ( Increased Variability) pattern with wide variability. The
oscillations of the fetal heart rate above and below the baseline
exceed 25 bpm .
FHR Variability
• Decreased Variability: marked decrease in
variability from a previous average
variability.
– Causes: hypoxia / acidosis; CNS depressants;
analgesics / narcotics; barbiturates;
tranquilizers, anaractics; parasympatholytics;
general anesthetics; prematurity (<24 wks);
fetal sleep cycles; congenital abnormalities;
fetal cardiac dysrhythmias.
FHR Variability
• Decreased Variability (continued):
– Significance: benign when associated with fetal
sleep cycles; if drugs, variability usually increases
as drugs are excreted; when associated with
uncorrectable late decelerations indicates
presence of fetal acidosis and can result in low
APGARs.
– Nsg.Interventions: none, if fetal sleep cycle, or
CNS depressants; consider fetal scalp stimulation
or apply a spiral electrode; monitor fetal oxygen
saturation; prepare for birth if indicated.
Selected High-Risk Indications for Continuous Monitoring
of Fetal Heart Rate
• Maternal medical illness
- Gestational diabetes
- Hypertension
- Asthma
• Obstetric complications
- Multiple gestation
- Post-date gestation
- Previous cesarean section
- Intrauterine growth restriction
- Premature rupture of the membranes
- Congenital malformations
- Third-trimester bleeding
- Oxytocin induction/augmentation of labor
- Preeclampsia
• Psychosocial risk factors
- No prenatal care
- Tobacco use and drug abuse
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Factors that can interfere with
Electronic fetal monitoring
Nicotine or caffeine which can falsely raise your
baby's heart rate and produce inaccurate test
results.
Extra noises such as your heartbeat or your
stomach rumbling.
baby is sleeping during a nonstress test.
Fetal movement during the test. If your baby is
moving a lot, it may be difficult to correctly
position the external montioring device.
Being overweight, or pregnant with multiple
babies. In these cases it may be difficult to
correctly position the external monitoring device.
INDICATION
Electronic fetal monitoring
• diabetes
• high Blood Pressure
• small baby or baby not growing properly
• past your due date
• too much or too little fluid around the baby
• Baseline fetal heart rate is 130 to 140 beats per minute (bpm), preserved beatto-beat and long-term variability. Accelerations last for 15 or more seconds
above baseline and peak at 15 or more bpm. (Small square=10 seconds; large
square=one minute)
Increase the baseline fetal heart
• Prematurity
• maternal anxiety
• fever rate
Decreases the baseline fetal heart
• fetal maturity
Periodic FHR Changes
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Accelerations
Early Decelerations
Late Decelerations
Variable Decelerations
Sinusoidal Pattern
Accelerations
• fetal movement.
• Partial umbilical cord compression
This occurs with normal autonomic
function, which acts to preserve
cardiac output by increasing heart
rate in response to decreased blood
return to the fetal heart.
Decelerations
• 50% of NST
• Non repetitive and less than 30 seconds in duration,
obstetric intervention is not needed
• repetitive decelerations or decelerations that last longer
than 60 seconds are associated with an increased risk of
fetal demise and cesarean delivery for the diagnosis of
nonreassuring FHR pattern
Early Decelerations
• Definition: a transitory gradual decrease
and return to baseline FHR in response to
fetal head compression.
• Generally starts before the peak of the
uterine contractions.
• Returns to the baseline at the same time
as the contraction returns to its baseline.
• Considered benign. No interventions.
• Early deceleration in a patient with an unremarkable course
of labor. Notice that the onset and the return of the
deceleration coincide with the start and the end of the
contraction, giving the characteristic mirror image .
• Late deceleration with loss of variability. This is an ominous
pattern, and immediate delivery is indicated .
• Nonreassuring pattern of late decelerations with preserved beat-tobeat variability. Note the onset at the peak of the uterine
contractions and the return to baseline after the contraction has
ended. The second uterine contraction is associated with a shallow
and subtle late deceleration .
Late Decelerations
• Definition: a transitory gradual decrease in and return to
baseline of FHR associated with contractions.
• Begins after the contraction has started, and the lowest
part of the decel occurs after the peak of the contraction.
• Usually does NOT return to baseline until after the
contraction is over.
• Indicates uteroplacental insufficiency. Interventions
required!
• Considered ominous sign when they’re uncorrectable,
especially when associated with decreased variability
and tachycardia.
Late Decelerations
• Interventions:
– Change maternal position (lateral)
– Correct maternal hypotension (elevate legs)
– Increase rate of maintenance IV
– D/C oxytocin if infusing
– Administer O2 at 8-10 L/min (face mask)
– Fetal scalp or acoustic stimulation
– Assist with fetal O2 saturation if ordered
– Assist with birth if pattern cannot be corrected.
• Late deceleration with loss of variability. This is an ominous
pattern, and immediate delivery is indicated .
Late deceleration
Variable Decelerations
• Definition: an abrupt decrease in FHR that is
variable in duration, intensity,and timing
related to onset of contractions; caused by
umbilical cord compression.
• Onset to the beginning of the nadir is <30
seconds; decrease in > 15 bpm, lating >15
seconds; variable times in contracting phase;
often preceded by transitory acceleration.
• Return to baseline is rapid and <2 min from
onset; sometimes with transitory acceleration
immediately before and after decel.
• Described as: mild, moderate, or severe.
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Variable Decelerations
Interventions:
– Change maternal position (side to side).
• If severe:
– D/C oxytocin if infusing
– Administer O2 at 8-10 L/min (face mask)
– Assist with vag or speculum exam
– If cord is prolapsed, examiner will elevate fetal
presenting part with cord between gloved
fingers until c/s is accomplished
– Assist with amnioinfusion if ordered
– Assist with fetal O2 saturation monitoring if
ordered
– Assist with fetal O2 saturation if ordered
• Variable deceleration with pre- and postaccelerations ("shoulders"). Fetal heart rate is 150 to
160 beats per minute, and beat-to-beat variability is
preserved .
• Severe variable deceleration with overshoot.
However, variability is preserved
Prolonged Decelerations
• Definition: a visually apparent decrease in
FHR below the baseline 15 bpm or more
and lasting more than 2 minutes but less
than 10 minutes.
• Benign causes: pelvic exam, application of
spiral electrode, rapid fetal descent &
sustained maternal valsalva maneuver.
• Other causes (severe): progressive severe
variable decels, sudden umbilical cord
prolapse, hypotension, paracervical
anesthesia, tetanic contraction & maternal
hypoxia (may occur with seizure).
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Signs of Nonreassuring Variable
Decelerations that Indicate
Hypoxemia
Increased severity of the deceleration
Late onset and gradual return phase
Loss of "shoulders" on FHR recording
A blunt acceleration or "overshoot" after
severe deceleration
Unexplained tachycardia
Saltatory variability
Late decelerations or late return to baseline
Decreased variability
Interference
• Hypoxemia
• Acidemia
• oligohydramnios
interfere with measures of central
nervous system (CNS) performance,
such as
• FHR patterns
• Fetal movement
• Tone
Other DEFINITIONS
• Tachycardia: a baseline FHR >160 bpm for
a duration of 10 minutes or longer.
• Bradycardia: a baseline FHR <110 bpm for
a duration of 10 minutes or longer.
Fetal Monitoring
Bradycardia
Fetal heart rate less than 120 bpm
If longer than 5 minutes, consider delivery
Can tolerate 80-90's for about 20 minutes
Can tolerate 60-70's for only about 6-10 minutes
Common etiologies:
Maternal hypotension
Maternal hypoxia
Hypothermia
Placental abruption
Uterine tetany
Bradycardia
• Baroreceptors influence the FHR through the
vagus nerve in response to change in fetal
blood pressure
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Hypoxia
uterine contractions
fetal head compression
fetal grunting
Causes of Severe Fetal Bradycardia
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Prolonged cord
compression Cord
prolapse Tetanic
uterine contractions
Paracervical block
 Epidural and spinal
anesthesia
 Maternal seizures
 Rapid descent
 Vigorous vaginal
examination
Tachycardia
• Chemoreceptors located in the aortic
and carotid bodies respond to
hypoxia, excess carbon dioxide and
acidosis, producing tachycardia and
hypertension.
Fetal Monitoring
Tachycardia
Fetal heart rate greater than 160 bpm
Usually tolerated well
Common etiologies:
• maternal fever
• chorioamnionitis
• Beta-agonists
• Fetal tachycardia with possible onset of decreased variability( right )during
the second stage of labor. Fetal heart rate is 170 to 180 bpm. Mild variable
decelerations are present .
Fetal Monitoring
Sinusoidal Pattern
Fetal heart rate exhibits a sinusoidal wave form
Common etiologies :
• Fetal anemia
• Fetal hypoxia
• Breech presentation
• True sinusoidal pattern Note the decreased regularity
and the preserved beat-to-beat variability,
• Pseudosinusoidal pattern
• Note the decreased regularity and the
preserved beat-to-beat variability
“ THE END “