Electronic Fetal Monitoring

ELECTRONIC FETAL MONITORING FALL 2009 NURSING 2111

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Electronic Fetal Monitoring The electronic fetal monitor (EFM) is a device that provides a graphic display of the fetal heart rate (FHR) and monitoring of uterine activity by digital readout and tracing. EFM can be either external, which is noninvasive or internal, which requires the attachment of an electrode to the presenting fetal part. Nursing staff may routinely initiate external monitoring; initiating the internal route is generally performed by a physician or midwife. A nurse may also be certified in this skill. Monitoring of uterine contractile activity can also be executed by an external or internal method. Continuous fetal monitoring is indicated when abnormalities occur with intermittent auscultation and for use in high-risk clients. A.

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External 1. Noninvasive 2. Two devices are secured to the maternal abdomen by belts and connected to the monitoring machine. a. Ultrasound Transducer 1. Detects fetal heart sounds i. Water soluble conducting gel is placed on the surface to the transducer. ii. Transducer is placed on the maternal abdomen where the fetal heart tones (FHT) are heard loudest iii. Ultrasound waves generated from this device bounce back from the fetus. iv. The ultrasound waves are then displayed on the monitor paper and by digital readout. b. Tocotransducer 1. Detects the relative strength of uterine contractions. i. Placed over the uterine fundus and secured by a belt. ii. As the uterus contracts, pressure is exerted against the transducer and is recorded. iii. FHT and contractions pressure (intensity) cannot be accurately recorded on obese clients or if there are problems securing the belt. B. Internal 1. Invasive 2. Provides the most accurate fetal heart monitoring and monitoring of uterine pressure. 3. Two devices

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Fetal scalp electrode (FSE) is secured to the fetal scalp by a small electrode and records FHR.

b. Intrauterine pressure catheter (IUPC) is inserted directly into the uterine cavity and records the intensity of contractions.

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Prerequisites for a. b. c. d.

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internal monitoring Membranes must be ruptured. Cervix must be at least 2-3 centimeters dilated. Careful insertion of FSE to avoid fetal face, fontanels and genitals Presenting part must be engaged.

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5 Both external and internal monitoring is accomplished by the same electronic monitoring machine.

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Uterine contractions occur about every 3-5 minutes with a duration of 30-60 seconds and an intensity of 40-60 mm HG (contraction intensity is measured by mm HG only when the internal method is utilized). Uterine contractions are assessed in the following manner A.

Frequency-measured from the beginning on one contraction to the beginning o the next contraction.

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Duration-measured from the beginning of one contraction to the end of the same contraction.

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Intensity-pressure of a contraction (called contraction pressure). Resting pressure-pressure between contractions. Average resting pressure is 5-15 mm Hg.

An example of FHR and uterine activity on chart paper. The upper section of the chart paper is used to record the FHR by both the external and internal modes of monitoring. The vertical scale is related to FHR, which can be recorded between 30 and 240 beats/min (bpm). The horizontal scale is divided into 1 millimeter sections, which are subdivided by six sections representing 10 seconds of time. The lower section is used to record uterine activity. BASELINE FETAL HEART RATE The baseline heart rate is the average rate when no contractions are occurring. Note the baseline on the strip below. Also, note the variability of the heart rate.

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The normal FHR is between 110 and 160 bpm. The baseline FHR is the mean (average) FHR rounded to increments of 5-10 bpm in a 10 minute segment. Need 2 minutes total over the entire 10 minute period to determine FHRB. These 2 minutes do not need to be consecutive minutes! The evaluation also must exclude periodic segments with periodic or episodic changes or periods of marked FHR variability. Accelerations are transient increases in FHR greater than 15 bpm for at least 15 seconds. Two accelerations in 20 minutes are considered to be a reactive trace. Accelerations are reassuring patterns as they indicate fetal responsiveness and the integrity of the mechanisms controlling the heart. Beat to beat variability is the normal irregularity of the cardiac rhythm, caused by continuous balancing interaction of the sympathetic (cardioacceleration) and parasympathetic (cardiodeceleration) divisions of the autonomic nervous system. Slowing is mediated by the vagus nerve. The vagal stimulation becomes dominant as the fetus reaches term. After birth, the vagus nerve also leads to a gradual slowing in the baseline of the newborn’s heart rate. Good variability is demonstrated by cyclic fluctuations and changes of heart rate from the baseline. Decreases in variability indicate central nervous system (CNS) depression. Causes of CNS include: A. Medications (analgesics MgSO4) B. Fetal sleep cycles (usually last no longer than 15-20 minutes) C. Congenital anomalies D. Preterm fetus (less than 28 weeks, usually normal after 32 weeks) E. Fetal hypoxia and acidosis

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Fetal tachycardia Fetal brain damage

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10 The cause of increased beat-to-beat variability is unknown; however, this usually signifies fetal well being. Baseline beat should vary 10-15 beats over a 60 second period. Variability is described as long or short term. Shortterm variability is the variation from beat to beat and is difficult to detect without internal monitoring to read the exact FHR during a minute period. Long-term variability is the rhythmic fluctuation of the FHR from baseline over a minute (usually 5-6 waves). Variability is usually classified in the following manner: No variability (0-2 bpm) Minimal (3-5 bpm) Average (6-10 bpm) Moderate (11-25 bpm) Marked (> 25 bpm)

Decreased variability in combination with late or variable decelerations indicates and increased risk of fetal pre-acidosis (pH 7.20-7.25) or acidosis (pH < 7.20) signifying the infant will be depressed at birth. The combination of late or variable decelerations with loss of variability is particularly ominous. Late or worsening variable decelerations in the presence of normal variability indicate a nonreassuring pattern indicating the fetal distress is of recent origin or mild degree.

Baseline of 110-150 bpm with average variability

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Note the decreased variability of the above strip. If lasts for longer than 10 minutes this reflects a change in baseline FHR.

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12 FETAL TACHYCARDIA Fetal tachycardia is usually considered to be a baseline FHR greater than 160 bpm. Suspicious tachycardia is between 150-170 bpm. A pathological pattern is tachycardia is greater than 170 bpm. Causes of fetal tachycardia include: A. Fetal hypoxia B. Prematurity C. Fetal or maternal infection (chorioamnionitis) D. Maternal anxiety E. Stimulation and activity F. Maternal or fetal anemia G. Paraysmpatholytic medications (atropine or Atarax {hydroxyzine}) H. Sypathomimetic medications (Yutopar, {ritodrine }, Brecanyl, {terbutaline} I. Maternal hyperthyroidism J. Idiopathic FETAL BRADYCARDIA Fetal bradycardia is considered to be a baseline of less than 100 bpm. A FHR of 100-120 with normal variability is not associated with fetal difficulty. If lasts longer than 10 minutes reflects a change in the baseline FHR.

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13 Causes of fetal bradycardia include the following: A. Fetal hypoxia B. Medications (anesthesics, analgesics) C. Maternal hypotension or seizures D. Rapid descent E. Vigorous vaginal examination F. Tetanic uterine contraction G. Prolapse or prolonged compression of the umbilical cord H. Fetal cardiac dysrhythmias I. Hypothermia J. Paracervial block K. Epidural and spinal anesthesia DECELERATIONS Decelerations (decals) are distinguished based on their waveforms. A prolonged deceleration is greater than 15 bpm, lasting longer than 2 minutes and with duration greater than 15 seconds but less than 2 minutes. Recurrent decelerations occur with at least 50% of uterine contractions in any 20 minute segment.

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14 Early Decelerations A. Begins at the onset of the contraction and ends at the end of the contraction. B. Cause of this type of deceleration is head compression and is caused by vagal stimulation; may be prevented by avoiding early rupture of membranes. C. Is a reassuring pattern that is usually seen late in labor and reinforces the fetus is moving downward in the birth canal. D. No nursing intervention is necessary.

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A. B.

C. D. E.

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Late Decelerations Occurs after the peak of the contraction or late in the contraction Transitory decreases in FHR caused by uteroplacental insufficiency; compromised blood flow to the fetus does not deliver the amount of oxygen necessary for the fetus to withstand the stress of labor. Regardless of the depth of the deceleration, all late decals are considered potentially ominous. Persistent late decals with decreased variability lead to an ominous pattern (fetal hypoxia). Also associated with fetal acidosis and low Apgar scores. Nursing Intervetions: 1. Place in lateral position, preferably left side. 2. Administer O2 by tight face mask 3. Discontinue oxytocin, if hyperstimulation present consider using terbutaline 0.25 mg SC 4. Correct maternal hypotension 5. Hydrate by bolus infusion of fluid 6. If persist > 30 minutes despite above, consider fetal scalp pH and/or emergency procedure

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A. B. C. D. E. F. G.

Variable Decelerations Shown by an acute fall in the FHR with a rapid downslope and a variable recovery phase. Variable in duration, intensity and timing. They may not bear a constant relationship to uterine contractions. Are caused by umbilical cord compression Resemble letter “U”, “V” or “W” Occur frequently in women who have PROM and decreased amniotic fluid volume. As many as 50% of all monitored fetus experience variable decels during labor. If baseline FHR remains stable and variability remains good, these decels are not associated with poor fetal outcome. Nursing Interventions: 1. Change maternal position 2. Discontinue oxytocin if associated with poor variability 3. Assist with amnioinfusion

FHR patterns are called reassuring, non-reassuring and ominous. A. Reassuring patterns are those associated with fetal well-being and positive outcomes. -normal baseline rate -presence of accelerations

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Non-reassuring patterns, “warning patterns”, suggest decreasing fetal capacity to cope with the stress of labor. -absence of reassuring characteristics *recurrent late or variable decelerations with absent variability *substantial bradycardia with absent variablity Assessment of Fetal Monitoring Strips Suggested Approach

Baseline Fetal Heart Rate (FHRB) 1. What is FHRB? 2. Assess if it is average (110-160), tachycardia ( > 160), bradycardia (<110). a. Tachycardia or bradycardia-what could be some possible causes Baseline Variability a. Absent, minimal, moderate, marked Accelerations 1. Present or absent 2. Periodic (with fetal movement or stimulation) 3. Episodic (with uterine contractions) 4. Regular (30 seconds-2 minutes) or Prolonged (2-10 minutes) 5. Gestational age criteria ≥ 32 weeks ≥ 15 bpm x ≥ 15 seconds ≤ 32 weeks ≥ 10 bpm x ≥ 10 seconds Decelerations 1. Early associated cause: 2. Late associated cause: 3. Variable associated cause: 4. Prolonged deceleration associated causes: 5. Periodic (with uterine contractions) or Episodic (not associated with uterine contractions) 6. Recurrent decelerations: with 50% of uterine contractions in a 20 minute segment 7. Combination decelerations: choose one closet to definition to label Uterine Activity 1. Frequency 2. Duration 3. Intensity 4. Resting tone 5. Resting time 6. Hyperstimulation-6 or more contractions in a 10 minute strip Reassuring features present…..or non-reassuring??? EFM

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