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EndoRepro 2 Exam 1 > Clin: Fetal Heart Monitoring - Moulton > Flashcards

Clin: Fetal Heart Monitoring - Moulton Flashcards

1
Q

how often do you monitor an uncomplicated pregnancy in the first and second stages of labor?

A

1st: q 30 minutes
2nd: q 15 minutes

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2
Q

how often do you monitor a complicated pregnancy in the first and second stages of labor?

A

1st: q 15 minutes in active phase (following contraction)
2nd: q 5 minutes

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3
Q

what does a pressure sensitive tocodynanmometer transducer measure?

A

detects and records the frequency of contractions, NOT strength

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4
Q

does internal or external monitoring give the most accurate readings?

A

internal

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5
Q

internal electronic fetal monitoring:

  • rate computed from the R wave peaks of fetal echocardiogram
  • maternal and fetal movement will not alter quality of signal
A

fetal scalp electrode (FSE)

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6
Q

when should you avoid internal fetal monitoring?

A

HIV patients

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7
Q

internal electronic fetal monitoring

  • soft plastic catheter placed transcervically
  • gives precise measurement of intensity of the uterine contractions in mmHg
A

intrauterine pressure catheter (IUPC)

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8
Q

fetal oxygen reserve is only enough to meet it’s metabolic needs for how long?

A

1-2 minutes

  • blood flow from maternal circulation, which supplies the fetus with oxygen thru placental exchange of respiratory gases, is momentarily interrupted during contractions
  • normal fetus can tolerate temporary reduction in blood flow without suffering because adequate oxygen exchange occurs between contractions
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9
Q

what determines fetal heart rate?

A

atrial pacemaker

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10
Q

what modulates fetal heart rate?

A

innervation via vagus (decelerator) and sympathetic (accelerator) nerves

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11
Q

if fetus is not getting adequate blood supply between contractions, what happens?

A

will beome hypoxic
- chemoreceptors and baroreceptors in peripheral arterial circulation of the fetus influence FHR by giving rise to contraction related or periodic FHR changes

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12
Q

what happens if hypoxia becomes severe?

A

anaerobic metabolism -> accumulation of pyruvic and lactic acid -> fetal acidosis

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13
Q

what is the normal pH of fetal scalp blood?

A

7.25-7.3

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14
Q

what is considered fetal acidosis?

A

< 7.2

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15
Q

with each contraciton, blood flow from mom to baby ceases as what are compressed?

A

uterine myometrial vessels

- at this point, mom and baby are physiologically separated

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16
Q

what happens as the contraction begins to subside?

A
  • uterine myometrial ARTERIES reopen, allowing oxygenated blood/nutrients to flow from mom to baby
  • uterine myometrial VEINS reopen, allowing blood carrying fetal waste products to flow from baby to mother
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17
Q

what does the upper tracing on fetal monitoring strip measure?

A

FHR (BPM)

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18
Q

what does the lower tracing on fetal monitoring strip measure?

A

uterine contractions (mmHg)

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19
Q

what is considered normal uterine activity in active labor?

A

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

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20
Q

what is considered tachysystole?

A

> 5 contractions in 10 minutes, averaged over 30 minute window (LOWER STRIP)
- may or may not be associated FHR decelerations (UPPER STRIP)

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21
Q

how are contractions measured?

A

from peak to peak

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22
Q

3 contractions in 8 minutes, occurring every 2-3 minutes

A

normal

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23
Q

a measure of uterine contraction intensity (LOWER STRIP) during labor

  • units are calculated via INTERNAL pressure monitor
  • subtract baseline resting tone from the peak pressure of uterine contraction (done over 10 minute interval)
A

Montevideo units (mmHg)

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24
Q

what is the threshold number that is considered necessary for adequate labor to bring about dilation and effacement during the active phase of labor

A

> 200 MVUs

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25
Q

what is the normal range of FHR?

A

110-160 bpm

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26
Q

what is considered tachycardia?

A

> 160 bpm

27
Q

what is considered bradycardia?

A

< 110 bpm

28
Q

when do you measure baseline FHR?

A

BETWEEN uterine contractions, NOT during

29
Q
  • fetal hypoxia (late sign of hypoxia)
  • obstetric anesthesia
  • pitocin
  • maternal hypotension
  • prolapsed or prolonged compression of umbilical cord
  • heart block
A

causes of fetal bradycardia

30
Q
  • fetal hypoxia (early sign of hypoxia)
  • medications (excessive oxytocin augmentation)
  • arrhythmias
  • prematurity
  • maternal fever
  • fetal infection (chorioamnionitis is MCC)
A

causes of fetal tachycardia

31
Q

chemoreceptors produce tachycardia in response to what?

A

hypoxia

32
Q

baroreceptors influence FHR via vagus n. in response to what?

A

changes in fetal blood pressure

33
Q

how is baseline variability quantified?

A

amplitude of peak to trough (bpm) change in baseline rate

34
Q

no detectable variability around baseline (line doesn’t really change)

A

absent variability

persistently minimal or absent FHR variability appears to be the most significant intrapartum sign of fetal compromise

35
Q

amplitude range detectable, but < 5 bpm

A

minimal variability

36
Q

what is the normal variability range?

A

moderate variability = 6-25 bpm

37
Q

amplitude range > 25 bpm

A

marked variability

38
Q

Reasons for absent variability

A
  • inadequate oxygenation
  • fetal central nervous system or cardiovascular anomaly
  • pre-existing fetal brain injury
  • effects of maternal medication administration (MgSO4 or narcotics)
  • OR might just indicate normal fetal sleep patterns!
39
Q

Reasons for marked variability

A
  • early stages of fetal hypoxemia
  • OR may be a normal finding. Therefore,

why baseline variability is a key assessment

40
Q

Reasons for moderate variability

A
  • intact neurological modulation of fetal heart rate
  • normal cardiac responsiveness, and fetal reserve
  • reliably predicts the absence of fetal metabolic acidemia and usually indicates that the fetus is well-oxygenated at that point in time
41
Q

why are NST’s only performed after 28 weeks?

A

fetal ANS does not finish developing until 30 weeks, so measuring FHR before then will not give an accurate reading

42
Q

indicator of possible fetal stress

  • is ominous if associated with persistent late delerations
  • is associated with hypoxia and acidemia (lack of oxygen build up of acid in the fetus depresses FHR and CNS)
A

decreased variability

43
Q
  • prematurity
  • sleep cycle
  • maternal fever
  • fetal tachycardia (chorioamnionitis)
  • fetal congenital anomalies
  • maternal hyperthyroidism
  • maternal drugs (caffeine nicotine, cocaine, narcotics)
A

cases of decreased baseline variability

44
Q

what are the 4 types of FHR decelerations?

A
  • early
  • variable
  • late
  • prolonged
45
Q
  • an abrupt increase in FHR is a normal, reassuring response
  • if >32 weeks: HR > 15bpm above baseline for 15 seconds or more
  • if <32 weeks: HR > 10bpm above baseline for 10 seconds or more
A

accelerations

46
Q

what is considered a prolonged acceleration?

A

last more than 2 minutes

47
Q

what is considered a change in baseline?

A

if acceleration last more than 10 minutes

48
Q

what are the main causes of accelerations?

A
  • spontaneous fetal movement
  • scalp stimulation or vibro-acoustic stimulation
  • vaginal exam
49
Q

what are the 3 types of decelerations?

A
  • early
  • variable
  • late
50
Q

secondary to fetal head compression

  • fetal ANS response (vagus) to increased intracranial pressure caused by transient compression of fetal head -> decreases HR
  • NOT associated with fetal distress
  • nadir of decel (lowest point/trough of FHR) occurs at the same time as the peak of contraction -> MIRROR IMAGE
A

early deceleration

51
Q

secondary to umbilical cord compression

  • abrupt decrease in FHR d/t fetal hypovolemia -> activates baroreceptors and chemoreceptors (stimulates vagus)
  • can occur before, during, or after the contraction starts
  • decrease in FHR > 15 bpm, lasting >15 seconds and more than 2mins in duration
  • onset, depth and duration can vary
A

variable deceleration

- V is variable! looks like a wide V

52
Q

what happens if the umbilical cord is only slightly compressed?

A

it will obstruct the umbilical VEIN (low pressure system), which returns re-oxygenated blood to fetal heart

  • normal fetal response is slight increase in FHR to compensate for lack of blood return and the slowly diminishing oxygen supplies
  • increase in FHR is followed by major drop in FHR -> called a “shoulder”
53
Q

secondary to uterine placental insufficiency (UPI)

  • OMINOUS
  • repetitive decels usually indicate fetal metabolic acidosis and low arterial pH
  • nadir of the decel occurs AFTER the peak of contraction
A

late decelerations

54
Q

what are two potential causes of late decelerations?

A
  • excessive uterine activity

- maternal supine hypotension

55
Q

decrease in FHR from baseline that is > 15 bpm last more than 2 mins, but less than 10

  • disruption of oxygen transfer from environment to the fetus at one or more points along oxygen pathway
  • commonly seen during maternal pushing
A

prolonged deceleration

56
Q

smooth, sine wave-like undulating pattern in FHR baseline with a cycle frequency of 3-5 per minute
- seen with fetal anemia

A

sinusoidal pattern

- very bad sign :((

57
Q

instillation of normal saline, can alleviate cord compression (can help resolve some variables)

  • initially 250-1000cc infused 15cc/min
  • followed by continuous infusion 100-200cc/hour
  • infused thru transcervical IUPC
A

amnioinfusion

58
Q
  • minimal or absent variability
  • recurrent late decelerations
  • prolonged decelerations
  • tachycardia
  • bradycardia
  • variable, late or prolonged decelerations occurring with maternal pushing
A 
category II (indeterminate)
- not predictive of abnormal acid-base status, but insufficient data to classify as category I or III
59
Q

category II, INTERMITTENT variable decelerations (<50% of contractions)

A

common finding usually associated with normal outcomes

- no intervention required

60
Q

category II, RECURRENT variable decelerations (>50% of contractions)

A

umbilical cord compression with impending acidemia
- moderate variability and/or accelerations suggest fetus is not acidemic

GOAL: to alleviate cord compression (promote fetal oxygenation) -> repositioning, amnioinfusion (in 1st stage), modification of pushing efforts (push w/every other contraction)

61
Q

what is the goal/management of tachysystole?

A

reduce uterine activity

  • lateral positioning
  • IV bolus
  • decrease oxytocin rate
  • removal of cervadil insert
  • if no response, give uterine tocolytic (tertbutaline)
62
Q

absent baseline variability (increased risk fetal acidemia)

  • recurrent late decels
  • recurrent variable decels
  • bradycardia

sinusoidal pattern (increased risk hypoxemia and acidemia)

A

category III -> prepare for delivery

  • reposition mom
  • IV bolus
  • oxygen supplementation
  • scalp stimulation test
  • if no improvement, delivery is advisable
63
Q

used to differentiate fetal sleep from acidosis, when the fetal tracing shows reduced variability but no decelerations

A

fetal scalp stimulation

64
Q

what is the expected pH value when an acceleration of 15bpm lasts 15 seconds?

A

fetal pH almost always 7.22 or greater (good sign, baby just sleeping)

EndoRepro 2 Exam 1 (25 decks)

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