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NM704 - M3 - Study Guide
Terms in this set (37)
The approximate mean fetal Heart rate rounded to increments of 5 BPM during a 10 min window-excluding accelerations and decelerations, and periods of marked variability. Must have 2 mins of identifiable baseline. 110-160.
Baseline less than 110. Must last for at least 10 mins to be considered baseline change.
Baseline greater than 160.
Baseline FHR variability:
Fluctuations in the baseline FHR that are irregular in amplitude and frequency. Amplitude is a range that is visually quantified.
minimal= undetectable to 5 bpm,
moderate= 6pm to 25 bpm, marked= >25 bpm.
An abrupt (<30sec from onset to peak) increase in the FHR above baseline.
Gradual onset, >30secs from onset to nadir; nadir simultaneous with peak of contraction.
Gradual onset, >30 secs from onset to the nadir; nadir is delayed in timing to the peak of the contraction.
Abrupt onset, <30 secs from onset to nadir, lasting > or = 15 secs but < 2mins; at least 15 beats down.
Decrease of > or = 15 bpm lasting > or = 2 mins but less than 10 mins (> or = 10 mins is a baseline change.
Understand the following physiologic mechanisms responsible for normal fetal heart rate patterns.
Made of nerve fibers in the myocardium.
Stimulation causes increase in FHR.
Vagus nerve, stimulation causes decrease in fetal heart rate. Parasympathetic tone increase with gestation causing the decrease in FHR baseline and increase in variability.
Interplay between sympathetic and parasympathetic nervous systems establishes baseline and variability.
Respond to changes in oxygen and carbon dioxide in fetal blood stream, stimulates the sympathetic and parasympathetic in response.
Respond to changes in pressure in the aorta and carotid vessels of fetus.
Increase in pressure - triggers parasympathetic system = decrease in HR.
Decrease in pressure- triggers sympathetic system = increase in HR.
Identify the proposed cause(s), physiologic and/or pathophysiologic mechanism, and clinical significance of the following variant fetal heart rate patterns:
Stimulation of vagus nerve with rapid decent, vaginal exam.
Maternal fever, stress response.
Late deceleration with and without variability:
Deficiency of uteroplacental perfusion.
Decrease in oxygen reserve, immature parasympathetic system.
Lose of fetal oxygen reserve, neurological insult.
Severe fetal anemia, neurologic defect, thumb sucking.
Define the following terminology recommended by NICHD for a three tier fetal heart rate interpretation system:
Category I (normal):
BL - 110 to 160, moderate variability, no late or variable decels, may have early decels, may have accelerations (not required).
Category II (indeterminate):
All tracings not meeting criteria for cat I or Cat III. Wide range.
Category III (abnormal):
Absent baseline variability WITH recurrent late decels OR recurrent late decels OR bradycardia.
Any Sinusoidal pattern.
Know how to evaluate and manage the following:
Category I tracing:
Category 1 is normal:
- Normal baseline, moderate variability, early decels okay, no variables or lates, accelerations present or absent.
- Normal fetal acid-base balance
- No specific actions needed.
Category II tracing:
Category II FHR tracings require evaluation and continued surveillance and reevaluation, taking into account the entire associated clinical circumstances.
Ex. Recurrent variables with moderate variability:
Fluids, O2, position change, amnioinfusion.
1. Intermittent and recurrent variables.
2. Recurrent late decelerations.
3. Fetal tachycardia.
4. Bradycardia and prolonged decelerations.
5. Minimal FHR variability.
6. Tachysystole with and without FHR changes.
Category III (abnormal):
Category III is abnormal! Prompt Evaluation is needed!!
Indicates abnormal fetal acid-base balance.
Discontinuation of labor induction meds (pitocin).
IV fluid bolus/medications to treat suspected maternal hypotension.
What are the recommendations for frequency of fetal heart rate assessment during labor (distinguishing between review of the EFM tracing when continuous monitoring is used and frequency of intermittent auscultation)?
What are the conclusions in the ACOG Practice Bulletin on the use of fetal scalp pH for assessment of fetal well being during labor?
- Can be used in the case of persistent cat III tracing.
- Scalp stimulation is less invasive and provides similar information.
- Positive predictive value of low umbilical arterial pH = 9%.
- Sensitivity of low umbilical arterial pH = 36%.
- Positive predictive value of IDing newborn with HIE = 3%.
- Sensitivity of IDing newborn with HIE = 50%.
- Negative predictive value = 97-99%.
- If available, may provide additional information.
What are the conclusions in the ACOG Practice Bulletin on the use of fetal pulse-oximetry for assessment of fetal well being in labor?
Not demonstrated to be clinically useful in evaluating fetal status.
Compare the information on use of maternal oxygen administration for non-reassuring fetal heart tones as presented in the ACOG bulletin (2009, p. 199), the Simpson article (2007), and Varney's Midwifery (2015, p. 866).
ACOG: No data on efficacy or safety of this therapy. FHR often persist despite O2.
Simpson: Appears to be beneficial in improving fetal oxygen status during labor and resolving nonreassuirng FHR patterns and reducing/eliminating late decelerations; improve FHR variability and reactivity; increases fetal O2 sat; recommended 15-30 mins as there was one study that showed that there was a deterioration in umbilical cord blood values when maternal oxygen was administered for more than 10 mins.
Varney: Increases fetal oxygenation, up to 30 mins after O2 is stopped. Relieves late decels. It may produce free oxygen radicals that could harm fetus, so should be stopped once FHR pattern improves.
Compare continuous electronic fetal heart rate monitoring and intermittent auscultation in terms of rates of cerebral palsy, neonatal seizures, perinatal mortality, and cesarean sections.
- Cerebral Palsy: False high positive rate of >99%; does not reduce rates of CP
- Neonatal Seizures: Decreases rates of neonatal seizures (but does not reflect in decreased rates of CP)
- Perinatal Mortality: No significant difference from IA
- C-Section: Increase by 1/3-1/2, depending on the study
- Similar rates of CP & perinatal mortality to CEFM
- Reduced c-section rates
- Slightly increased rates of neonatal seizures
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