Fetal HR Monitoring and Antenatal Surveillance Flashcards
HISTORICAL FACTS MY FRIENDS
- Fetal heart first heard in 17th century by a physician in France named Marsac.
- Evory Kennedy published a book in 1833 in Dublin “Observations on Obstetric Auscultation.”
- The head stethoscope (fetoscope) was first reported in 1917 by David Hillis an Obstetrician in Chicago.
- The first commercially available monitor was produced by Hewlett-Packard in 1968.
What are the 2 external monitoring instruments?
- Tocodynamometer
2. Doppler
What are the 2 internal monitoring instruments?
- Intrauterine pressure catheter
2. Fetal scalp electrode
What does a tocodynamometer measure?
External contraction monitor…so it measures frequency and duration (NOT STRENGTH)
-This is the belt thing with the button on it
What does an intrauterine pressure catheter measure?
Strength, frequency, and duration
-This is inside the uterus
What does a doppler do?
US through abdomen that measures HR
What does a fetal scalp electrode measure?
It monitors the R-R of QRS complex and extrapolates HR…This is very accurate
What develops first, S or PS nervous system?
Sympatetic
What does the sympathetic nervous system give a base HR of?
150-160 bpm
-Remember, normal is 110-160 bpm
What does the development of the PS nervous system do?
Lowers the rate and gives variability…
Flat rates aren’t good… variability shows that the baby is neurologically intact
What is the PS nervous system mediated through?
The Vagus nerve
A normal FHR pattern indicates what?
Greater than 95% probability of well-being
True or False: FHR has a high false positive rate
TRUE- Good Apgar scores and normal pH in the presence of abnormal FHR patterns is 80%
So what kind of tool is FHR monitoring?
Screening (not diagnostic)
What is a normal fetal heart rate?
110-160 bpm
What constitutes tachycardia in a fetus?
Over 160 bpm
What constitutes bradycardia in a fetus?
Under 110 bpm
What are baseline characteristics with FHR monitoring?
FHR and variability
What are periodic and episodic changes seen with FHR monitoring?
Accelerations and decelerations
What are causes of tachycardia?
- MATERNAL FEVER
- INFECTION- maternal or fetal
- Hypoxemia
- Prematurity
- Dehydration
- Thyrotoxicosis
- Pharmacological Agents
What are causes of bradycardia?
- HYPOXEMIA
- Pharmacological Agents
- Fetal Arrhythmia’s (heart block)
- Maternal Hypotension.
What changes over time of the fetal heart rate?
Variability
True or False: The more variability the better
TRUE.. More variability, baby is well
What are 2 types of variability?
Short term and long term
What is short term variability?
Beat to beat changes in FHR
What is normal short term variability?
Between 5-25 bpm
What is long term variability?
Undulations of fetal HR around baseline
How many undulations per minute is normal?
3-5
True or Fase: A good baby will have an increase over baseline of 15bpm lasting at least 15 seconds
TRUE- This ensures the absence of fetal acidosis
Changes in baseline FHR can be related to what?
Uterine contractions
What are 2 types of changes in baseline FHR related to uterine contractions?
- Accelerations
2. Decelerations
What are accelerations?
FHR increase in response to uterine contractions
What are decelerations?
FHR decreases in response to uterine contractions
-Decelerations can be early, late, variable, or mixed
Describe early decelerations
Has an onset, maximum fall and recovery that coincides with the onset, peak and end of the uterine contraction
What do early decelerations result from?
Fetal head compression (Vagal response)
Are early decelerations gradual?
Yes… onset to nadir >/= 30 seconds decrease in with return to baseline
-This coincides with the peak of contraction like a mirror image
Are early decelerations associated with fetal distress?
No
Describe late decelerations
Onset, e maximal decrease and recovery that is shifted to the right in relation to the contraction
What are late decelerations associated with?
Uteroplacental insufficiency
WHat is more pronounced with severe decelerations?
Fetal hypoxia and acidosis
What are late decelerations associated with?
Low scalp pH values and high base deficits (indicating metabolic acidosis)
What is the severity of a late deceleration graded by?
The magnitude of the decrease in FHR at the nadir
What is most frequently encountered abnormal FHR pattern?
Variable decelerations
What causes variable decelerations?
Umbilical cord compression
Describe variable decelerations
Variable time of onset, variable form and may be nonrepetitive
If cord compression is prolonged, what can happen?
Hypoxia can be present and show a combined respiratory and metabolic acidosis
Hos is severity of a variable deceleration graded?
By their duration
More detailed description of variable deceleration?
-Visually Apparent, abrupt (onset to nadir or = to 5bpm below the baseline and lasts > or = 15 sec but < 2 minutes.
What is a prolonged variable deceleration?
> or = to 15bpm below baseline lasting > or = to 2min but < 10 min
What are 5 strategies for intervention in variable decelerations?
- STOP PITOCIN !!!!!!
- Change in maternal position left to right.
- 100% O2.
- Amnioinfusion
- Delivery