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FHR Descriptive Vocabulary:
1)
Baseline: Mean FHR over a 10min segment; must be
for minimum of 2min. Excludes variability, and accels/decels.
a.
Normal: 110-160bpm, Bradycardia <110,
Tachycardia >160
2)
Baseline Variability: Fluctuations in the
baseline FHR; irregular in amplitude and frequency.
a.
Absent: undetectable
b.
Minimal: detectable but <5bpm
c.
Moderate: (normal), 6-25bpm
d.
Marked: >25bpm
3)
Acceleration: Abrupt increase in FHR
a.
Prolonged: Lasts 2-10min; if >10min, is new
baseline
b.
>32wks GA, accel is >15bpm above baseline,
duration >15sec
c.
<32wks GA, accel is >10bpm above baseline,
duration >10sec
4)
Early Decel: Symmetrical, gradual decrease and
return of FHR, a/w uterine contraction. Gradual defined as onset of decel to
nadir of >30sec. Lasts 15sec-2min. Nadir occurs at same time as peak of
contraction. Usually onset and recovery coincide with beginning and end of
contraction.
5)
Late Decel: Symmetrical, gradual decrease and
return of FHR a/w uterine contraction. Gradual defined as onset of decel to
nadir of >30sec. Lasts 15sec-2min. Decel is delayed in timing with nadir
occurring after peak of contraction. Usually onset and recover occur after
beginning and end of contraction, respectively.
6)
Variable Decel: Abrupt decrease in FHR, with onset
of decel to nadir <30sec. Decrease in FHR is >15bpm, lasts 15sec-2min.
When a/w contractions, onset, depth, duration vary with success uterine
contractions.
7)
Prolonged Decel: Decel that is >15bpm, lasts
2min-10min.
8)
Sinusoidal Pattern: Smooth, sine wave-like
undulating pattern. Cycle frequency of 3-5/min, persists >20min
FHR Categorization:
1)
Category 1: Normal good and happy. Normal.
a.
Baseline rate wnl, moderate variability
b.
No variable or late decels
c.
+/-Early decels
d.
+/-Accels
2)
Category 3: Abnormal bad and unhappy. A/w fetal
acidemia. Shown to have érisk
for neonatal encephalopathy, CP, neonatal acidosis. However, predictive value
is poor.
a.
Absent baseline variability w/
i. Recurrent
late or variable decels
ii. Bradycardia
b.
Sinusoidal pattern
3)
Category 2: Anything not category 1 or 3
a.
Baseline rate
i. Tachycardia
ii. Bradycardia
w/out absent variability
b.
Variability
i. Minimal
or marked variability
ii. Absent
baseline variability w/out recurrent decels
c.
Accelerations
i. Absence
after fetal stimulation (scalp stim or echo)
d.
Decelerations
i. Prolonged
(2-10min)
ii. Recurrent
variable or late decels w/ mod variability
iii. Variable
decels w/ slow return to baseline
Management
1)
Category 1: Continue monitoring; should review
every 30 minutes in latent labor and every 15 minutes in second stage of labor.
2)
Category 2: Intrauterine resuscitation measures
a.
Intrauterine resuscitation measures: goal is to
increase O2 to fetus
i. Maternal
repositioning
ii. IVF
iii. Reduction
in Pitocin/Tocolytic
iv. Oxygen
v. Amnioinfusion
(limited evidence for improving outcomes)
vi. Can
be 2/2 maternal hypotension (ie s/p epidural)
b.
Management depends on specific tracing
i. Moderate
variability and accels are highly predictive of normal fetus acid-base status
(Category 2 but reassuring)
ii. Intermittent
variable decels do not require any treatment (Category 2 but reassuring)
iii. Recurrent
variable decels – intrauterine resuscitation
iv. Fetal
tachycardia – evaluate
1.
infection (chorio, pyelo)
2.
meds (terb, cocaine, stimulants)
3.
medical conditions (hyperthyroidism)
4.
obstetrical conditions (abruption, fetal bleed,
cord prolapse/occlusion, uterine rupture)
5.
fetal abnormality (fetal tachyarrhythmia)
v. Fetal
bradycardia and prolonged decel - evaluate
1.
Don’t wait around to differentiate the two
2.
Many of same causes of fetal tachycardia
vi. Minimal
FHR variability
1.
Fetal sleep cycle (20-60min): stimulate fetus
2.
Maternal meds (opioids [1-2hrs], mag)
3.
Fetal acidemia – if min variability cannot be
explained/resolved should be managed as such
3)
Category 3: Prompt delivery if intrauterine
resuscitation measures do not resolve tracing.
a.
30-min rule from decision to incision.
i. Studies
don’t show an increase in consequences for delay
ii. May
not improve outcome if fetus already suffered injury
b.
Valid factors may delay surgery
i. Stabilization
of mom: cardiopulm compromise, hemorrhage, eclampsia
ii. Preparation
of OR
iii. Notification
of NICU/Peds
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