Upgrade to remove ads
Only $35.99/year

Fetal heart rate monitoring (peri-facts)

Terms in this set (47)

Components of FHR tracings
- baseline
- variability
- accelerations
- decelerations
- contractions
FHR baseline
average HR over 10 min (rounded to 5)
- excludes variability >25 bpm
- at least 2 min baseline segments
Normal FHR baseline
110 - 160 bpm
FHR variability descriptors
- absent
- minimum
- moderate ("tops of picked fences")
- marked
Accelerations
- occur with fetal movement
- "reassuring" findings
- peak >/= 15 bpm for >/= 15 sec
- peak >/= 10 bpm for >/= 10 sec before 32 wks
Troubleshooting poor uterine contraction tracings
- change mother's position
- adjust monitoring device
Periodic patterns
associated with uterine contractions
Episodic patterns
NOT associated with uterine contractions
Baseline FHR variability
fluctuations in baseline FHR that have irregular amplitude and frequency
- determined in 10-min window
- excludes accelerations and decelerations
Absent FHR variability
amplitude range undetectable
Minimal FHR variability
amplitude range > undetectable and </= 5 bpm
Moderate FHR variability
amplitude range 6 - 25 bpm
- suggests adequate oxygenation and CNS function
Marked FHR variability
amplitude range > 6 - 25 bpm
(significance unclear)
Maternal causes of decreased baseline FHR variability
- CNS depressants
- morphine
- nalbuphine HCl
- butorphanol
- alcohol
- methadone
Fetal causes of decreased baseline FHR variability
- fetal sleep cycles
- fetal CNS anomalies (anencephaly/hydrocephaly, stroke)
- prolonged or severe fetal hypoxia
- cardiac anomalies
- persistent fetal tachycardia
- excessive/prolonged vagal stimulation
Change from moderate to minimal FHR variability
early sign of fetal acidosis (esp. with tachycardia and decelerations)
FHR bradycardia
baseline <110 bpm (over 10 min)
(no concern if present with moderate variability)
Deceleration
FHR decrease of at least 15 bpm for less than 2 min
Prolonged deceleration
FHR decrease of at least 15 bpm for longer than 2 min (but less than 10 min)
Fetal causes of baseline FHR bradycardia
- persistent increase in PNS/vagal stimulation
- umbilical cord occlusion/prolapse
- decompensating fetus
- cardiac conduction or anatomic defects
- congenital heart disease
- PNS maturity
Maternal causes of baseline FHR bradycardia
- maternal supine position
- maternal hypotension
- connective tissue disease
- prolonged maternal hypoglycemia
- maternal hypothermia
- drugs (i.e. inderal, atenolol, labetalol)
FHR tachycardia
> 160 bpm (over 10 min)
(premature FHR baseline slightly higher)
Fetal causes of baseline FHR tachycardia
- prolonged fetal activity/stimulation
- chronic fetal hypoxemia
- chorioamnionitis
- fetal cardiac abnormalities
- supraventricular tachycardia
- fetal anemia
- compensatory response to transient fetal hypoxemia
Maternal causes of baseline FHR tachycardia
- maternal fever/infection
- dehydration
- hyperthyroidism
- anemia
- maternal anxiety/endogenous adrenaline
- smoking
- drugs (i.e. illicits, parasympatholytic drugs, betasympathomimetic drugs)
Anterior shoulder of variable decleration
initial, brief compensatory fetal tachycardia
Posterior shoulder of variable decleration
brief fetal tachycardia once umbilical cord compression is relieved
Variable deceleration interventions
- first change maternal position
- O2 via facemask
Fetal behavioral states
- quiet sleep state
- active sleep state
(states alternate every 20 - 70 min)
Uterine contractions
number of contractions in 10 min averaged over 30 min
Normal contraction frequency
</= 5 in 10 min (averaged over 30 min)
Tachysystole ("camelbacking")
> 5 contractions in 5 min (averaged over 30 min)
- qualified by presence or absence of FHR decelerations
- applies to either spontaneous or stimulated labor
- decrease or d/c oxytocin if occurs during induction until normal pattern returns
Assessing uterine contractions by palpation
hand placed on abdomen and contraction timed from onset of tightening to resolution
Tocodynamometer
measures freq and duration of uterine contractions (not strength)
Intrauterine pressure catheter (IUPC)
measures (peak) contraction strength/intensity as well as frequency and baseline tone
- catheter inserted through cervix into amniotic cavity
- membranes must to ruptured for placement
- compared with external tocodynamometer for more accurate oxytocin titration during induction
- used with FHR tracings to evaluate fetal response to interventions
- can act as a port for amnioinfusion
- superior ability to monitor obese pts and those with uterine scar
IUPC limitations
- requires membrane rupture and adequate cervical dilation
- invasive
- risk of infection and uterine perforation
- meconium or blood can obstruct catheter
- catheter can become wedged against fetal part and distort, dampen, or truncate pressure wave
- contraindicated with herpes, HIV, or significant vaginal bleeding of unknown etiology
Recurrent decelerations
occur with >/= 50% contractions in any 20-min segment
Intermittent decelerations
occur with </= 50% contractions in any 20-min segment
Characteristics of early decelerations
- gradual decrease (>/= 30 sec) and return of FHR associated with contraction
- visually apparent
- usually symmetric
- onset, nadir, and recovery of deceleration coincides with onset, peak, and ending of contraction
- require no intervention
Early deceleration physiology
- occur with fetal head compression during contractions
- considered normal if coincides with contractions, baseline FHR is within normal range, and variability is moderate
- fetal CSF pressure increases --> vagal stimulation --> reflex fetal bradycardia
Characteristics of late decelerations
- onset, nadir, and recovery of deceleration occurs AFTER the onset, peak, and ending of contraction
- visually apparent
- usually symmetric
- "ominous" finding
- shallow deceleration
- subtle deceleration with decreased variability in severe cases
Late deceleration physiology
FHR response to hypoxemia (in the presence of already reduced fetal O2 reserves)
- umbilical cord compression during contraction --> stimulates fetal chemoreceptors --> increase in fetal BP --> FHR decreases
- lack of fetal heart response to hypoxemia indicates impending death
Variable deceleration
- most freq deceleration
- from umbilical cord compression (umbilical vein specifically)
- compression of umbilical vein --> transient reduction in fetal CO --> anterior shoulder (brief tachycardia)
- compression of umbilical arteries --> rise in fetal BP --> PNS activation --> reflexive drop in FHR
Characteristics of variable decelerations
- visually apparent abrupt decrease in FHR (onset to nadir < 30 sec)
- decrease in FHR >/= 15 bpm for >/= 15 sec (and for < 2 min)
- onset, depth, and duration vary with successive uterine contractions
Category I FHR tracings
- normal (indicate normal acid-base status)
- baseline 110 - 160 bpm
- moderate baseline variability (amplitude 6 - 25 bpm)
- no late or variable decelerations
- early decelerations present or absent
- accelerations present or absent
Category II tracings
- indeterminate (not predictive of fetal acid-base status)
- include all FHR tracings not categorized as I or III
- baseline bradycardia (without absent variability) or tachycardia
- minimal or moderate, absent (without recurrent declerations), or marked baseline variability
- absence of induced accelerations after fetal stimulation
- periodic or episodic decelerations (recurrent variable declerations with minimal to moderate variability, prolonged deceleration > 2 but < 10 min, recurrent late decelerations with moderate variability, or variable decelerations with slow return to baseline, "overshoots," or "shoulders")
- require close surveillance and continued evaluation
Category III tracings
- abnormal fetal acid-base status
- absent baseline variability with recurrent late decelerations, recurrent variable decelerations, or bradycardia OR sinusoidal pattern
Interventions for abnormal (category III) tracings
- maternal O2
- change maternal position
- d/c labor stimulation
- treat maternal hypotension
- expedient delivery if above measures fail
Sets with similar terms