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Practice bulletins > #106 Intrapartum Fetal Heart Rate Monitoring: Nomenclature, Interpretation, and General Management Principles > Flashcards

#106 Intrapartum Fetal Heart Rate Monitoring: Nomenclature, Interpretation, and General Management Principles Flashcards

1
Q

What percentage of term pregnancies with fetal asphyxia had no known risk factors?

A

63%

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2
Q

How is the fetal heart rate modulated?

A

The fetal brain modulates FHR through interplay of sympathetic and parasympathetic forces

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3
Q

What are limitations of electronic fetal monitoring?

A

Poor interobserver and intraobserver reliability, uncertain efficacy, high false-positive rate

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4
Q

What components make up EFM?

A

Uterine contractions, baseline FHR, variability, presence of accelerations, periodic or episodic decelerations, and changes in these characteristics over time

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5
Q

What is the definition of uterine contraction frequency?

A

Number of contractions present in a 10-minute window, average over a 30-minute period

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6
Q

What factors are included in assessment of contractions?

A

Frequency, duration, intensity, relaxation time between contractions

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7
Q

What is the definition of the normal frequency of contractions?

A

Five contractions or less in 10 minutes, averaged over a 30-minute window

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8
Q

What is the definition of tachysystole?

A

More than five contractions in 10 minutes, averaged over a 30-minute window

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9
Q

What is normal FHR baseline?

A

110-160 bpm

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10
Q

Definition of FHR baseline?

A

Mean FHR rounded to increments of 5bpm during a 10 min segment. Must be for a minimum of 2 minutes

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11
Q

Definition of baseline variability regarding EFM?

A

Fluctuations in the baseline that are irregular in amplitude and frequency

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12
Q

How is baseline variability quantified (EFM)?

A

Visually as amplitude of peak to trough in bpm.

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13
Q

What are variability categories and definitions for these categories (EFM)?

A

Absent - undetectable amplitude range
Minimal - amplitude range detectable but 5bpm or fewer
Moderate (normal) - amplitude 6-25bpm
Marked - amplitude >25bpm

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14
Q

What is the definition of FHR acceleration?

A

Abrupt increase (<30s to peak) in FHR. 32wks or greater 15x15. Less than 32 10x10. Not lasting more than two minutes (then it is a prolonged acceleration)

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15
Q

What is a prolonged acceleration?

A

Lasts 2 mins or more, but less than 10 minutes (>10 min is baseline change)

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16
Q

What is an early deceleration?

A

Visually apparent usually symmetrical gradual decrease (>30s) and return associated with uterine contraction, nadir of decel at same time as peak of contraction

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17
Q

What is a late deceleration?

A

Visually apparent usually symmetrical gradual decrease (>30s) and return of FHR associated with uterine contraction where nadir of decel occurs after peak of contraction

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18
Q

What is a variable deceleration?

A

Visually apparent abrupt (<30s) decrease in FHR. At least 15x15, not lasting more than 2 minutes

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19
Q

What is a prolonged deceleration?

A

Visually apparent decrease in FHR below baseline (at least 15bpm) lasting 2 minutes or moe, but less than 10 minutes (change in baseline)

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20
Q

What is a sinusoidal pattern?

A

Visually apparent, smooth, sine wave-like undulating patter in FHR baseline with a cycle frequency of 3-5 per minute which persists for 20 minutes or more

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21
Q

What information does FHR tracing patterns provide?

A

Information on current acid-base status of the fetus

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22
Q

What are category I FHR tracings associated with?

A

Strongly predictive of normal fetal acid-base status at the time of observation.

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23
Q

What do category II FHR tracings predict?

A

Nothing. Require evaluation and continued surveillance and reevaluation taking into account the entire associated clinical circumstances

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24
Q

What are category III FHR tracings associated with?

A

Abnormal fetal acid-base status at the time of observation.

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25
Q

How do you manage a category III FHR tracing?

A

Depending on clinical situation, efforts to expeditiously resolve the abnormal FHR pattern may include (but not limited to) maternal oxygen, change in maternal position, discontinuation of labor stimulation, treatment of maternal hypotension, treatment of tachysystole with FHR changes. If not resolved with these measures, deliver.

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26
Q

What is definition of Category I FHR tracing.

A 
Baseline: 110-160
Variability: Moderate
Accelerations: present or absent
Early decelerations: present or absent 
Late or variable decelerations: absent
27
Q

What is the definition of category II FHR tracings?

A

Not category I or category III.

28
Q

What is the definition of category III FHR tracings?

A

Absent variability plus one of the following:

- recurrent late decels
- recurrent variable decels
- bradycardia

Or

Sinusoidal Pattern

29
Q

How often should FHR tracing be reviewed (in first and second stage of labor)?

A

Uncomplicated: q30 min first stage of labor and q15 min in the second stage.
Complicated (eg. FGR, PEC): q15 min in first stage, q5 min second stage

30
Q

Does use of EFM compared to intermittent auscultation increase or decrease cesarean rate?

A

Increase

31
Q

Does use of EFM compared to intermittent auscultation increase or decrease risk of operative vaginal deliveries?

A

Increase

32
Q

Does use of EFM compared to intermittent auscultation increase or decrease perinatal mortality?

A

No effect

33
Q

Does use of EFM compared to intermittent auscultation increase or decrease risk of neonatal seizure?

A

Decrease risk

34
Q

Does use of EFM compared to intermittent auscultation increase or decrease of cerebral palsy?

A

No effect

35
Q

What is the false-positive rate of EFM for predicting cerebral palsy?

A

> 99%

36
Q

Has the occurrence of cerebral palsy increased, decreased, or stayed the same over time?

A

Stayed stable

37
Q

What is the principal explanation as to why EFM has not decreased prevalence of cerebral palsy?

A

70% of cases occur before the onset of labor; only 4% of cases of encephalopathy can be attributed solely to intrapartum events

38
Q

How often is the protocol for intermittent auscultation successfully completed?

A

3%

39
Q

What is a proposed protocol for frequency of intermittent monitoring?

A

Evaluate and record FHR at least q15 min in active phase of first stage of labor and at least q5 min in second stage

40
Q

Who is not a candidate for intermittent FHR monitoring?

A

High risk pregnancies

41
Q

What percentage of preterm deliveries have variable decelerations?

A

55-70%

42
Q

What percentage of term deliveries has variable decelerations?

A

20-30%

43
Q

How does parenteral analgesia affect FHR tracing compared to regional?

A

Parenteral more associated with decreased variability and significantly less common accelerations

44
Q

Does an epidural increase the rate of cesarean delivery for nonreassuring FHR?

A

No

45
Q

Are FHR tracing abnormalities more common in women receiving epidurals or combined spinal-epidural anesthesia?

A

Combined spina-epidural anesthesia

46
Q

Is decrease in FHR variability related to serum magnesium level?

A

No

47
Q

What predicts a more profound decrease in variability of FHR for patients receiving magnesium?

A

Lower gestational age

48
Q

How do narcotics affect FHR tracings?

A

Decrease in variability, decrease in frequency of accelerations

49
Q

How does butorphanol (opioid) affect FHR tracing?

A

Transient sinusoidal FHR pattern (75%; not associated with adverse outcomes), slightly increased mean heart rate

50
Q

How does cocaine affect FHR tracing?

A

Decreased long-term variability. Frequent contractions even when labor unstimulated.

51
Q

How do corticosteroids affect FHR tracing?

A

Decrease in FHR variability with BMZ (returns to pretreatment status by 4-7 days), but not dexamethasone. Abolishment of diurnal fetal rhythms, increased effect at greater than 29wks

52
Q

How does magnesium sulfate affect FHR tracing?

A

Significant decrease in short-term variability, clinically insignificant decrease in FHR, inhibits the increase in accelerations with advancing GA

53
Q

How does terbutaline affect FHR tracing?

A

Increase in FHR baseline and incidence of fetal tachycardia

54
Q

How does zidovudine affect FHR tracing?

A

No difference in baseline, variability, number of accelerations, or decelerations

55
Q

What does moderate variability reassure us of, in most cases?

A

Reassurance of fetal status and absence of metabolic acidemia

56
Q

What are the four techniques to stimulate the fetus (in setting of tracing with minimal or absent variability and without spontaneous acceleration)?

A
  1. Fetal scal sampling
  2. Allis clamp scalp stimulation
  3. Vibroacoustic stimulation*
  4. Digital scalp stimulation*

*Preferred methods

57
Q

What are initial evaluation and treatment of Category II and III FHR tracing?

A
  • Discontinue any labor stimulating agent
  • Cervical exam to determine umbilical cord prolapse, rapid cervical dilation, or descent of the fetal head
  • Changing maternal position
  • Monitor maternal bp for evidence of hypotension
  • Assessment for uterine tachysystole
58
Q

How does supplemental maternal oxygen affect FHR tracing?

A

No data on the efficacy or safety of this therapy.

59
Q

What is the mechanism of action of terbutaline?

A

Beta2-adrenergic agonist

60
Q

What measure can be taken to help ameliorate recurrent variable decels?

A

Amnioinfusion

61
Q

Do amnioinfusions used for recurrent variable decelerations decrease the cesarean rate for suspected fetal distress?

A

Yes

62
Q

Does data support bolus or continuous infusion of amnioinfusion?

A

Randomized trial shows that both are similarly efficacious

63
Q

What intervention(s) can be used for category II or III tracing with maternal hypotension 2/2 regional anesthesia?

A

Volume expansion or IV ephedrine or both

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