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ACOG Pub Review > PB#106: Intrapartum Fetal Heart Rate Monitoring: Nomenclature, Interpretation, and General Management Principles > Flashcards

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

1
Q

Percentage of term pregnancies w/ fetal asphyxia w/o any known risk factors

A

63%

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2
Q

General principle behind FHR for monitoring fetal oxygenation

A

Fetal brain modulates FHR through sympathetic and parasympathetic factors

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3
Q

Limitations of EFM (3)

A

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

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4
Q

Calculation of ctxs when analyzing FHT

A

Number present in 10 min window averaged over 30 min period

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5
Q

Definition of normal contractility

A

5 or fewer ctxs in 10 mins averaged over 30 min period

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6
Q

Definition of tachysystole

A

> 5 ctxs in 10 mins averaged over 30 min period

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7
Q

How should tachysystole always be qualified?

A

In the presence/absence of decels

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8
Q

Does tachysystole apply to spontaneous labor or induced/augmented labor?

A

Both

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9
Q

When are decels considered recurrent?

A

If they occur w/ >50% of ctxs

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10
Q

Definition of FHR baseline

A

Mean FHR rounded to increments of 5 bpm over 10 min segment, excluding periodic/episodic changes, periods of marked variability, and/or segments of baseline that differ by >25 bpm

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11
Q

Minimum time requirement for FHT to be considered a baseline

A

2 mins in any 10 min segment, or else baseline for that period is indeterminate (in which case one may refer to prior 10 min window for determining baseline)

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12
Q

Normal baseline

A

110-160 bpm

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13
Q

Fetal tachycardia

A

> 160 bpm

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14
Q

Fetal bradycardia

A

<110 bpm

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15
Q

Definition of FHR variability

A

Fluctuations in baseline FHR that are irregular in amplitude and frequency, visually quantitated as amplitude of peak-to-trough in bpm

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16
Q

Absent variability

A

Undetectable amplitude range

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17
Q

Minimal variability

A

Amplitude range detectable but <5 bpm

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18
Q

Moderate variability

A

Amplitude range 6-25 bpm

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19
Q

Marked variability

A

Amplitude range >25 bpm

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20
Q

Definition of accels

A

Visually apparent abrupt increase (onset to peak <30 secs) in FHR

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21
Q

Criteria for accels at 32+wga; criteria for accels at <32wga

A

Peak >15 bpm above baseline, w/ duration of >15 secs but <2 mins from onset to return; peak >10 bpm above baseline, w/ duration of >10 secs but <2 mins from onset to return

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22
Q

Definition of prolonged accel

A

Lasting >2 mins but <10 mins in duration

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23
Q

What is it considered if an accel lasts >10 mins?

A

Baseline change

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24
Q

Definition of early decels

A

Visually apparent usually symmetrical gradual decrease and return of FHR associated w/ ctx, wherein onset to nadir is >30 secs, and nadir of decel occurs at same time as ctx peak

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25
Q

Timing of onset/nadir/recovery of early decel as it relates to ctx (in most cases)

A

Coincident w/ beginning/peak/ending of ctx, respectively

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26
Q

Definition of late decels

A

Visually apparent usually symmetrical gradual decrease and return of FHR associated w/ ctx, wherein onset to nadir is >30 secs, and nadir of decel occurring after peak of ctx

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27
Q

Timing of onset/nadir/recovery of late decel as it relates to ctx (in most cases)

A

Occur after beginning/peak/ending of ctx, respectively

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28
Q

Definition of variable decels

A

Visually apparent abrupt decrease in FHR, wherein onset to nadir is <30 secs, decrease is >15 bpm, and lasts >15 secs but <2 mins in duration

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29
Q

Are onset/depth/duration of variable decels consistent across ctxs?

A

No, they commonly vary w/ successive ctxs

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30
Q

How is decrease in FHR calculated when evaluating decels?

A

From onset to nadir

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31
Q

Definition of prolonged decels

A

Visually apparent decrease in FHR, wherein decrease is >15 bpm, and lasts >2 mins but <10 mins in duration

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32
Q

What is it considered if a decel lasts >10 mins?

A

Baseline change

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33
Q

Definition of sinusoidal pattern

A

Visually apparent, smooth, sine wave-like undulating pattern in FHR baseline w/ cycle frequency of 3-5 per min, which persists for >20 mins

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34
Q

Info that FHTs can provide on acid-base status of fetus

A

ONLY current acid-base status

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35
Q

General classification, acid-base status prediction, and recommended monitoring for Cat 1 FHTs

A

Normal, strongly predictive of normal fetal acid-base status at time of obs, can be monitored in routine manner (no specific action required)

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36
Q

Criteria for Cat 1 FHTs

A

Include all of the following: normal baseline, mod variability, absent late/variable decels, present/absent early decels, present/absent accels

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37
Q

General classification, recommended monitoring, potential considerations for Cat 2 FHTs

A

Indeterminate, require evaluation and continued surveillance/reevaluation, may require ancillary testing of fetal wellbeing and/or intrauterine resuscitative measures

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38
Q

Acid-base status prediction of Cat 2 FHTs

A

Not predictive of abnormal fetal acid-base status, but not enough evidence to classify as Cat 1 or Cat 3

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39
Q

Criteria for Cat 2 FHTs

A

Brady not accompanied by absent variability; tachy; min variability; absent variability w/o recurrent decels; marked variability; absence of induced accels after fetal stim; recurrent variable decels accompanied by min/mod variability; prolonged decel; recurrent late decels w/ mod variability; variable decels w/ other characteristics (ie slow return to baseline, overshoots, “shoulders”)

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40
Q

General classification, acid-base status prediction, and recommended monitoring for Cat 3 FHTs

A

Abnormal, associated w/ abnormal fetal acid-base status at time of obs, require prompt evaluation

41
Q

Possible measures to provide expeditious resolution of Cat 3 FHTs (5)

A

Provision of maternal O2 (if indicated), position change, discontinuation of induction/augmentation measures, management of maternal hypotension, tx of tachysystole w/ FHT changes

42
Q

Next step if Cat 3 FHT does not resolve w/ resuscitation measures

A

Delivery

43
Q

Criteria for Cat 3 FHTs

A

Include either: absent variability + recurrent late decels/recurrent variable decels/brady, or sinusoidal pattern

44
Q

How often should FHT be reviewed in a pt w/o complications in first stage of labor, in second stage of labor?

A

q30mins, q15mins

45
Q

How often should FHT be reviewed in a pt w/ complications (ie FGR, pre-E) in first stage of labor, in second stage of labor?

A

q15mins, q5mins

46
Q

How is efficacy of intrapartum EFM judged?

A

By ability to decrease complications (ie neonatal seizures, CP, intrapartum demise) while minimizing need for unnecessary OB interventions (ie OVD, C/S)

47
Q

Effect of EFM on overall C/S rate (and RR); effect of EFM on C/S rate for abnormal FHT and/or acidosis (and RR), compared to intermittent auscultation

A

Increased overall C/S rate (RR = 1.66); increased C/S rate for abnormal FHT and/or acidosis (RR = 2.37)

48
Q

Effect of EFM on OVD (and RR)

A

Increased risk for both vacuum and forceps OVD (RR = 1.16)

49
Q

Effect of EFM on perinatal mortality (and RR w/ 95% CI)

A

No reduction (RR = 0.85, 95% CI = 0.59-1.23)

50
Q

Effect of EFM on neonatal seizures (and RR)

A

Reduced risk (RR = 0.50)

51
Q

Effect of EFM on CP (and RR w/ 95% CI)

A

No reduction (RR = 1.74, 95% CI = 0.97-3.11)

52
Q

PPV of NRFHT pattern to predict CP among singleton newborns w/ birth weights >2500g

A

0.14% (meaning out of 1,000 fetuses w/ NRFHT pattern, 1-2 will develop CP)

53
Q

False positive rate of EFM for predicting CP

A

> 99%

54
Q

Principal explanation for why prevalence of CP has not diminished despite use of EFM

A

Because 70% of cases occur before labor onset

55
Q

Percentage of cases of encephalopathy that can be attributed solely to intrapartum events

A

4%

56
Q

Rec for cEFM or intermittent auscultation in pt w/o complications

A

Either is acceptable

57
Q

Rec for cEFM or intermittent auscultation in pt w/ complications (ie FGR, pre-E, DM1)

A

cEFM

58
Q

Guideline recs regarding frequency of intermittent auscultation during active phase of first stage of labor, during second stage of labor

A

q15mins, q5mins

59
Q

In interpretation of FHTs, is interobserver variability high or low; is intraobserver variability high or low?

A

High; high

60
Q

Under what circumstances is FHT interpretation more consistent?

A

When tracing is normal

61
Q

When is a reviewer more likely to find evidence of fetal hypoxia (and criticize management) while reviewing an intrapartum FHT?

A

If outcome was poor (vs good)

62
Q

Is reinterpretation of FHT (especially if neonatal outcome is known) reliable?

A

No

63
Q

Rec for cEFM or intermittent auscultation for pt undergoing C/S for indications related to preterm fetus

A

cEFM

64
Q

Percentage of pts w/ PTL that exhibit NRFHTs; most common FHT abnormalities in pts w/ PTL

A

60%; decels and brady, followed by tachy and min/absent variability

65
Q

Are variable decels more common among preterm or term deliveries?

A

Preterm (55-70% vs 20-30%)

66
Q

Measures if FHT abnormalities are persistent in setting of preterm fetus (3)

A

Resuscitative measures, ancillary tests of fetal well-being, poss delivery

67
Q

Poss effects of epidural analgesia w/ local anesthetic agents (ie lidocaine, bupivacaine) on maternal/fetal physiology (4)

A

Sympathetic blockade, maternal hypotension, transient uteroplacental insufficiency, alterations to FHR

68
Q

Effects of parenteral narcotics w/ or w/o added antiemetics on FHT (2)

A

Decreased variability, decreased frequency of accels

69
Q

Equivalent of meperidine, morphine, fentanyl, nalbuphine

A

75mg meperidine = 10mg morphine = 0.1mg fentanyl = 10mg nalbuphine

70
Q

Effects of IV meperidine, compared to epidural anesthesia w/ 0.25% bupivacaine, on FHT (2)

A

Decreased variability, and significantly less common accels w/ IV meperidine

71
Q

Is rate of brady, emergent C/S for NRFHTs, and adverse neonatal outcomes higher for pts w/ combined spinal-epidural anesthesia or w/ IV meperidine?

A

Rate of brady and emergent C/S for NRFHTs is significantly higher for pts w/ combined spinal-epidural anesthesia; not significantly different neonatal outcomes between two both groups

72
Q

Effects of mag sulfate on FHT (2)

A

Decreased short-term variability (related to early gestational age, not serum mag level), inhibition of accels w/ advancing gestational age

73
Q

Poss effect of butorphanol on FHT in pts in labor (2); associated neonatal outcomes

A

Transient sinusoidal pattern (in 75% of pts), slightly increased FHR (compared to meperidine); not associated w/ adverse outcomes

74
Q

Poss effects of cocaine exposure on FHT (2)

A

Decreased long-term variability, frequent ctxs (even when labor unstimulated)

75
Q

Effects of morphine on fetal BPP and on FHT in antepartum pts

A

Decreased fetal breathing movements, decreased number of accels

76
Q

Effects of BTMZ on FHT (2); duration until return of FHT to pre-tx status; effect on OB interventions/adverse outcomes

A

Transient decrease in variability, decrease in rate of accels (and diurnal fetal rhythms); 4-7 days; no effect

77
Q

Effects of terb on FHT (2)

A

Increased FHR baseline, increased incidence of fetal tachy

78
Q

Effects of zidovudine on FHT

A

No effects

79
Q

What does presence of accels indicate?

A

Fetus is not acidemic

80
Q

Predicted umbilical artery pH if mod variability is observed

A

Strongly associated w/ pH >7.15

81
Q

Predicted umbilical artery pH if late/variable decels are observed in setting of mod variability

A

> 7.00 in 97% of cases

82
Q

Prediction of mod variability re fetal status and acidemia

A

Reassuring fetal status, absence of metabolic acidemia

83
Q

Techniques to elicit accel if EFM has min/absent variability w/o spontaneous accels (4); methods that are preferred (2)

A

Fetal scalp sampling, Allis clamp scalp stim, vibroacoustic stim, digital scalp stim; less invasive methods (vibroacoustic stim, digital scalp stim) preferred

84
Q

Between scalp stim and scalp pH sampling, method that provides more info about likelihood of fetal acidemia

A

Similar info between two methods

85
Q

What does it mean if an accel follows stim?

A

Acidemia unlikely and labor may proceed

86
Q

Poss technique in setting of persistent Cat 3 FHT

A

Fetal scalp blood sampling for determination of pH or lactate (though use of technique is decreasing)

87
Q

Sensitivity of scalp pH <7.21 (75%ile) to predict umbilical artery pH <7.00; PPV of scalp pH <7.21 (75%ile) to predict umbilical artery pH <7.00

A

36%, 9%

88
Q

Sensitivity of low scalp pH to identify newborn w/ HIE; PPV of low scalp pH to identify newborn w/ HIE; NPV of scalp pH to identify newborn w/o HIE

A

50%; 3%; 97-99%

89
Q

Effect of intrapartum scalp sampling for pH vs lactate level on rates of acidemia at birth/APGARs/NICU admissions

A

No difference demonstrated

90
Q

Is pulse ox clinically useful in evaluating fetal status?

A

No

91
Q

Initial evaluation/tx of Cat 2-3 FHT (5)

A

Discontinuation of labor stim agent; SVE to determine cord prolapse/rapid cervical dilation/descent of fetal head; changing maternal position to L/R lateral recumbent, reducing compression of IVC and improving uteroplacental blood flow; monitoring maternal BPs for evidence of hypotension (especially in pts w/ regional anesthesia); assessment for tachysystole by evaluating ctx frequency/duration

92
Q

Recommended tx for Cat 2-3 FHT if maternal hypotension present and suspected 2/2 regional anesthesia (2)

A

Volume expansion and/or ephedrine, or phenylephrine

93
Q

Has supp O2 been shown to improve FHT?

A

No

94
Q

Options for tocolytic therapy to stop ctxs and poss avoid cord compression (3)

A

Terb, hexoprenaline, mag sulfate

95
Q

Comparison of using tocolytic therapy over no therapy re rates of perinatal mortality, low 5-min APGAR, NICU admission

A

No differences

96
Q

Class of med used for managing tachysystole w/ associated FHT changes; two meds in this class; percentage of cases that respond to tx

A

Beta-2 adrenergic meds; hexoprenaline, terb; 98%

97
Q

Technique that can be used to relieve cord compression in case of recurrent variable decels

A

Amnioinfusion

98
Q

RR in rates of decels w/ amnioinfusion; RR in rates of C/S for suspected fetal distress w/ amnioinfusion; general effect of amnioninfusion on pt/newborn hospital stay >3 days

A

RR = 0.54; RR = 0.35; decreased

99
Q

Between bolus and continuous infusion technique for amnioinfusion, which method has better ability to relieve recurrent variable decels?

A

Similar ability

ACOG Pub Review (12 decks)

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