Fetal Monitoring Flashcards
What is a normal Fetal Heart Rate Range?
110-160 bpm
What is classified as fetal tachycardia?
> 160 bpm
What are causes of fetal tachycardia?
Maternal:
-fever
-infection
-Beta-Synpathomimetic drugs (terb and epi)
-Parasympatholytic drugs (scopolamine, atropine, phenothiazines, hydroxyzines)
-Dehydration
-Hyperthyroidism
-Cocaine
Fetal:
-increased metabolic rate
-Anemia
-Acute blood loss
-Hyperthyroidism
-Heart Failure
-Hypoxemia
-infection/sepsis
-tachyarrhythmia
What is classified as Bradycardia?
<110 bpm
What are causes of fetal bradycardia?
Maternal:
- acute drop in oxygenation (respiratory depression, apnea, seizure)
-acute impairment of uteroplacental exchange (maternal hypotension, excessive uterine activity, loss of placental area with uterine rupture or placental abruption)
-prolonged occlusion of the umbilical cord
-profound vagal stimulation
Fetal:
-bradyarrhythmia
-head compression related to increased vagal tone
What is variability in the fetal heart rate?
this is the fluctuations in the fetal heart rate over time and is considered the most important predictor of adequate fetal oxygenation during labor
The pull between the sympathetic and parasympathetic
What is classified as Moderate variability?
This is variability with an amplitude of 6-25 bpm.
Which part of the nervous system is the most important for variability?
Parasympathetic Nervous System
True or False: does a decrease in variability and lack of accelerations mean there is fetal hypoxemia?
False: fetal sleep cycles, some maternal medications or substance use, congenital neurologic abnormalities, and cardiac conduction can also depress variability
What is classified as Minimal variability?
This is variability with an amplitude greater than undetectable but less than 5 bpm.
What are some causes of minimal variability?
centrally acting medications (opioids, tranquilizers, and other analgesics), premature gestations, and fetal sleep cycles
What is classified as Absent variability?
Absent variability has an undetectable amplitude.
this is smooth, blunted, and flat.
What is classified as Marked variability?
Marked variability has an amplitude range greater than 25 bpm.
What are periodic changes from the baseline?
These are occurring in association with uterine contractions.
What are episodic changes from the baseline?
These are not associated with uterine contractions.
What is an abrupt onset?
This is whether the onset to nadir or peak of the fetal heart rate change occurs in less than 30 seconds.
What is a gradual onset?
This is whether the onset to nadir or peak of the fetal heart rate change takes 30 seconds or longer.
Define Accelerations
These are ABRUPT increases from the fetal heart rate baseline.
-At 32 weeks and older: accelerations have to peak at least 15 beats above the baseline and last at least 15 seconds but less than 2 minutes (15x15’s)
-At less than 32 weeks: accelerations have to peak at least 10 beats above the baseline and last at least 10 seconds but less than 2 minutes (10x10’s)
True or False: Accelerations are predictive of adequate central fetal oxygenation
True: This is also an accurate predictor if a fetal pH of at least 7.19 and they rule out acidemia AT THE TIME THEY ARE OBSERVED.
Define Early Decelerations
These are GRADUAL PERIODIC decreases in the fetal heart rate.
-the onset, nadir, and recovery generally coincide with the onset, peak, and recovery of uterine contractions.
-vagal response
Explain how early decelerations represent a vagal response.
This is caused by a cerebral redistribution of blood flow caused by compression of the fetal head.
When the contraction occurs, the fetal head is subjected to pressure, stimulating the vagus nerve.
Define Late Decelerations
These are GRADUAL PERIODIC decreases in the fetal heart rate.
-the onset, nadir, and recovery occur after the respective onset, peak, and resolution of the contraction.
-Response to transient or chronic uteroplacental insufficiency.
Late Decelerations with three types of variability.
Lates with moderate variability:
- this is believed to reflect a chemoreceptor-mediated response to a transient hypoxemic event
Lates with minimal variability:
-this may be associated with acidemia
Lates with absent variability:
-this is associated with abnormal fetal acid-base status.
Define Variable Decelerations
These are ABRUPT PERIODIC or EPISODIC decreases in the fetal heart rate.
-decrease at least 12 beats below the baseline and last for at least 15 seconds and less than 2 minutes.
-this is commonly caused by interruption of umbilical blood flow (oligo, cord prolapse, knots in the cord, nuchal cord)
