1156Electronic Fetal Monitors

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ELECTRONICFETALMONITORS1

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MONITORINGTHEFETALHEARTRATE

External monitoring is performed using a

hand-held Doppler ultrasound probe to

auscultate and count the FHR during a

uterine contraction and for 30 secondsthereafter to identify fetal response.

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EXTERNALMONITORING

It may also be performed using an external

transducer, which is placed on the maternal

abdomen and held in place by an elastic belt or

girdle. The transducer uses Doppler ultrasound to

detect fetal heart motion and is connected to anFHR monitor. The monitor calculates and records

the FHR on a continuous strip of paper.

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INTERNALMONITORING

Is performed by attaching a screw-type electrode to

the fetal scalp with a connection to an FHR monitor.

The fetal membranes must be ruptured, and the

cervix must be at least partially dilated before the

electrode may be placed on the fetal scalp.

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INTERMITTENTVSCONTINUOUSAUSCULTATION

The American College of Obstetricians and Gynecologists(ACOG) states that with specific intervals, intermittentauscultation of the FHR is equivalent to continuous EFM indetecting fetal compromise.

ACOG has recommended a 1:1 nurse-patient ratio ifintermittent auscultation is used as the primary technique ofFHR surveillance.

The recommended intermittent auscultation protocol calls forauscultation every 30 minutes for low-risk patients in the activephase of labor and every 15 minutes in the second stage oflabor.

Continuous EFM is indicated when abnormalities occur withintermittent auscultation and for use in high-risk patients

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HIGH-RISKINDICATIONSFORCONTINUOUS

MONITORINGOFFETALHEARTRATE

Maternal medical illness:

Gestational diabetes

Hypertension

Asthma

Psychosocial risk factors

No prenatal care

Tobacco use and drug abuse

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HIGH-RISKINDICATIONSFORCONTINUOUS

MONITORINGOFFETALHEARTRATE

Obstetric complications

Multiple gestation

Post-date gestation

Previous cesarean section

Intrauterine growth restrictionPremature rupture of the membranes

Congenital malformations

Third-trimester bleeding

Oxytocin induction/augmentation of laborPreeclampsia

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BENEFITSANDRISKSOFEFM

Benefits:

1. to detect early fetal distress resulting from fetal

hypoxia and metabolic acidosis.

2. Closer assessment of high-risk mothers.Risks:

a) tendency to produce false-positive results.

b) fetal scalp infection and uterine perforation.

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NORMALPATTERNS

Normal rate: between 120 and 160 beats per

minute (bpm).

Short term variability (3-5 BPM)

Long term variability (15 BPM above baseline,lasting 10-20 seconds or longer)

Contractions every 2-3 minutes, lasting about 60

seconds

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FHR VARIABILITY

Loss of variability:

1. Prematurity: there is little rate fluctuation before 28weeks

Variability should be normal after 32 weeks

2. Fetal hypoxia

3. Congenital heart anomalies

4. Fetal tachycardia

5. May be uncomplicated and may be the result of

fetal quiescence (rest-activity cycle or behaviorstate), in which case the variability usuallyincreases spontaneously within 30 to 40 minutes

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Loss of variability:

Uncomplicated loss of variability may also be

caused by central nervous system depressants

such as morphine, diazepam (Valium) and

magnesium sulfate

Beta-adrenergic agonists used to inhibit labor, such

as ritodrine (Yutopar)

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TACHYCARDIA

>160 BPM

Most are not suggestive of fetal jeopardy

Associated with:

Fetal hypoxia Maternal fever

Hyperthyroidism

Maternal or fetal anemia

Drugs: Atropine ,Ritodrine (Yutopar) Chorioamnionitis

Fetal tachyarrhythmia

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BRADYCARDIA

Bradycardia in the range of 100 to 120 bpm ( mild)

1. not associated with fetal acidosis.

2. common in post-date gestations

3. in fetuses with occiput posterior or transverse presentations.

Bradycardia less than 100 bpm occurs in:

a) fetuses with congenital heart abnormalities

b) myocardial conduction defects

Moderate bradycardia of 80 to 100 bpm is a nonreassuring

pattern. Severe prolonged bradycardia of less than 80 bpm that lasts

for three minutes or longer is an ominous finding indicatingsevere hypoxia and is often a terminal event.

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CAUSESOFSEVEREFETALBRADYCARDIA

Prolonged cord

compression

Cord prolapse

Tetanic uterinecontractions

Paracervical block

Epidural and spinal

anesthesia

Maternal seizures

Rapid descent Vigorous vaginal

examination

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BRADYCARDIA

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LATEDECELERATIONS

Associated with uteroplacental insufficiency and areprovoked by uterine contractions.

Any decrease in uterine blood flow or placental

dysfunction Maternal hypotension

Uterine hyperstimulation may decrease uterine bloodflow.

Postdate gestation

Preeclampsia

Chronic hypertension and diabetes mellitus

Maternal conditions such as acidosis and hypovolemia(DKA) 18

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EARLYDECELERATIONS

Caused by fetal head compression during uterine

contraction, resulting in vagal stimulation and

slowing of the heart rate.

Has a uniform shape, with a slow onset that

coincides with the start of the contraction and a

slow return to the baseline that coincides with the

end of the contraction.

It has the characteristic mirror image of the

contraction

These decelerations are not associated with fetal

distress and thus are reassuring20

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VARIABLEDECELERATIONS

Variable in onset, duration and depth

May occur with contractions or between them

Sudden onset/recovery

Variable decelerations are shown by an acute fall inthe FHR with a rapid downslope and a variable

recovery phase.

They are variable in duration, intensity and timing.

They resemble the letter "U," "V" or "W" and maynot bear a constant relationship to uterine

contractions

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SEVEREVARIABLEDECELERATIONS

Most common pattern during labor

In patients who have experienced premature rupture of

membranes

and decreased amniotic fluid volume.

Variable decelerations are caused by compression of the

umbilical cord.

Pressure on the cord initially occludes the umbilical vein,

which results in an acceleration and indicates a healthyresponse. This is followed by occlusion of the umbilical

artery, which results in the sharp downslope.

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SIGNSOFNONREASSURINGVARIABLE

DECELERATIONSTHATINDICATEHYPOXEMIA

Increased severity of the deceleration

Late onset and gradual return phase

Loss of "shoulders" on FHR recording

A blunt acceleration or "overshoot" aftersevere deceleration

Unexplained tachycardia

Late decelerations or late return to baselineDecreased variability

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PROLONGEDDECELERATIONS

Last > 60 seconds

Occur in isolation

Associated with: Maternal hypotension

Epidural

Paracervical block

Tetanic contractions Umbilical cord prolapse

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NONREASSURINGANDOMINOUSPATTERNS

Fetal tachycardia

Fetal bradycardia

Saltatory variability

Variable decelerations

associated with a

nonreassuring pattern

Late decelerations with

preserved beat-to-beat

variability

Persistent late decelerationswith loss of beat-to-beatvariability

Nonreassuring variabledecelerations associated withloss of beat-to-beat variability

Prolonged severebradycardia Sinusoidalpattern

Confirmed loss of beat-to-beat variability not associatedwith fetal quiescence,medications or severeprematurity

Nonreassuring patterns Ominous patterns

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EMERGENCYINTERVENTIONSFOR

NONREASSURINGPATTERNS

Call for assistance

Administer oxygen through a tight-fitting face mask

Change maternal position (lateral or knee-chest)

Administer fluid bolus (lactated Ringer's solution)Perform a vaginal examination and fetal scalp

stimulation

When possible, determine and correct the cause of

the pattern Consider tocolysis (for uterine tetany or

hyperstimulation)

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EMERGENCYINTERVENTIONSFOR

NONREASSURINGPATTERNS

Discontinue oxytocin if used

Consider amnioinfusion (for variable

decelerations)

Determine whether operative intervention iswarranted and, if so, how urgently it is

needed

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1156Electronic Fetal Monitors

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