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Chapter 17 Intrapartum Fetal Surveillance
Terms in this set (38)
Adequate fetal oxygenation requires five related factors:
•Normal maternal blood flow and volume to the placenta
•Normal oxygen saturation in maternal blood
•Adequate exchange of oxygen and carbon dioxide in the placenta
•An open circulatory path between the placenta and the fetus through vessels in the umbilical cord
•Normal fetal circulatory and oxygen-carrying functions
During contractions, the fetus depends on the oxygen
supply already present in body cells, fetal erythrocytes, and the intervillous spaces. The oxygen supply in these areas is enough for about 1 to 2 minutes.
increases the heart rate and strengthens myocardial contractions through release of epinephrine and norepinephrine. The net result of sympathetic stimulation is an increase in cardiac output.
The parasympathetic nervous system
through stimulation of the vagus nerve, reduces FHR and maintains variability. The parasympathetic branch gradually exerts greater influence as the fetus matures, beginning between 28 and 32 weeks of gestation.
Vagal response, hold breath and bare down
that are too long (≥90 to 120 seconds), too frequent (closer than every 2 minutes, or have an inadequate relaxation period (less than 30 seconds of complete relaxation) will not allow optimal uteroplacental exchange.
-(around the fetal neck), one that is wrapped around the fetal body, or a knot in the cord. It may occur with oligohydramnios, because the amount of amniotic fluid is inadequate to cushion the cord. The umbilical cord may become tangled around fetal body parts.
-results in initial hypoxia with hypotension.
-most common because of its ease of use, ability to adjust the volume, and compact size.
- Many devices have a digital or paper display of the rate, and some may be used under water.
-creates an electronic sound based on movements of the fetal heart and may be the only way to use auscultation if a woman has a thick abdominal fat pad.
useful in cases of fetal cardiac dysrhythmias because its sound is that of actual opening and closing of heart valves, similar to the amplified sounds one hears with a stethoscope.
fetoscope and Doppler transducer
can be used to identify FHR baseline, rhythm, and changes from the baseline
using two horizontal grids—one for FHR and another for the uterine activity
recorded on the upper grid. The range of recorded rates is from 30 to 240 beats per minute (bpm).
-recorded on the lower grid as bell-shaped curves with continuous smaller rises and falls that represent maternal breathing superimposed on the larger curve.
-Fetal movements, maternal coughing, vomiting, or position changes cause erratic curves or spikes on the uterine activity line.
-Contraction intensity and the degree of uterine muscle tension, or uterine resting tone (from 0 to 100 mm Hg)
dark vertical lines
1 minute apart
subdivide the 1-minute divisions into six 10-second segments.
A Doppler ultrasound transducer
detects fetal heart movement for rate calculation.
A tocotransducer ("toco") with a pressure-sensitive area
detects changes in abdominal contour to measure uterine activity.
Devices for Internal Fetal Monitoring
-Accuracy is the main advantage
-slightly increasing the risk for infection
- requires ruptured membranes and about 2 cm of cervical dilation.
The fetal scalp electrode (FSE)
-detects electrical signals from the fetal heart
-calculated from electrical events in the fetal heart.
-avoid the fetal face, fontanels, and genitals.
- penetrates the fetal skin (about 1 mm)
intrauterine pressure catheters (IUPCs)
1.A solid catheter with a pressure transducer in its tip
This catheter usually has an additional lumen for amnioinfusion, or infusion of sterile solution into the uterus
intrauterine pressure catheters (IUPCs)
2.A hollow, fluid-filled catheter
connects to a pressure transducer on the bedside monitor unit.
The FHR baseline
is the average heart rate, rounded to 5 bpm, measured over 2 minutes of clear tracing within a 10-minute window.
A rate that averages from 110 to 160 bpm. The preterm fetus at 26 to 28 weeks often averages a rate at the upper end of this range because the parasympathetic nervous system, which slows the rate, is immature. Some healthy full-term fetuses have a rate that averages 100 to 110 bpm.
Less than 110 bpm, persisting for at least 10 minutes.
More than 160 bpm, persisting for at least 10 minutes.
-describes the fluctuations in the baseline FHR that cause the printed line to have an irregular wavelike appearance rather than a smooth, flat one
Variability may be decreased by
•Narcotics or other sedative drugs, such as magnesium sulfate, given to the woman
•Alcohol, illicit drugs
•Gestation younger than 28 weeks
•Fetal anomalies that affect central nervous system regulation of the heart rate, such as anencephaly
•Hypoxia that is severe enough to affect the central nervous system
•Abnormalities of the central nervous system, heart, or both
•Maternal acidemia (low blood pH) or hypoxemia (reduced oxygen in blood)
Evaluation of variability
helps clarify how a fetus is tolerating the stress of a pregnancy complication or labor, including factors that cause hypoxia.
Variability is a significant component of FHR tracing on the electronic monitor, for two reasons:
•Adequate oxygenation promotes normal function of the autonomic nervous system and helps the fetus adapt to the stress of labor.
•Variability evaluates the function of the fetal autonomic nervous system, especially the parasympathetic branch.
four categories of variability:
Minimal: Undetectable to ≤5 bpm
Moderate: 6 to 25 bpm
Marked: >25 bpm
Cord Compression- Reposition
• Are mirror images of the contraction
Left Lateral Recumbent position
Right Lateral Recumbent position
-Prep for Delivery
Reassuring 15 bpm by 15 seconds
fetus younger than 28 weeks may appear relatively flat because of autonomic nervous system immaturity.
• Look similar to early decelerations but begin after the contraction begins
Poor placental profusion
GIVE O2 FIRST@8 to 10L by mask
Increase LR fluids(bolus)
Lower or stop Pitocin
(low point) of FHR occurs at the same time the contraction peaks. The rate at the nadir is usually no lower than 30 to 40 bpm from the baseline.
Interventions for non reassuring patterns
Fetal Scalp Stimulation
Acoustic stimulation, or VAS
-evaluates the fetus's response to tactile stimulation during labor
-An acceleration in FHR of 15 bpm for at least 15 seconds is a reassuring response in the term fetus, suggesting normal oxygen and acid-base balance
Acoustic stimulation, or VAS
-A stimulator that uses a combination of sound and vibration is applied to the mother's lower abdomen, and it is turned on for up to 3 seconds.
-The reassuring response is the same as with fetal scalp stimulation: an acceleration in FHR of 15 bpm for 15 seconds or more.
Feeling for FHR
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