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Fetal Monitoring Interpretation Essentials

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Author:    Patricia Hartley (RNC, MSN)

Objectives

Upon completion of this module the learner will be able to:

  • Identify the basic elements of the fetal monitor strip
  • Define the key terms of fetal monitoring
  • Identify essential documentation
  • Describe the limitations of fetal heart rate (FHR) monitoring

Introduction

This module provides concepts for nursing process interpretation of the FHR (fetal heart rate) characteristics. Interpretation includes the systematic analysis of collected assessment data necessary for collaborative diagnosis and intervention. Emphasis is placed on the physiologic basis of FHR characteristics found on electronic fetal monitoring tracings.

Much of the technology developed to improve perinatal outcomes focuses on indirect measures of fetal status because a direct examination of the fetus is difficult. Whether auscultated or electronically monitored, the fetal heart is the element that is most easily and frequently observed in fetal evaluation. Practitioners involved with interpreting FHR monitoring tracings agree on one aspect, that there is a lack of agreed upon reproducible definitions or terminology in clinical trails and clinical practice. That inconsistency challenges even the fetal monitoring experts.

Regardless of practice settings documentation whether on the tracing or in the medical record, reflects the standard of care provided. The more complete the documentation the higher the standard of care. The healthcare provider must be able to identify what is seen; understand the physiology of what is displayed and describe in consistent terms to other members of the healthcare team.

Documenting Key Elements

A. Uterine Activity – Clinicians should use consistent terms which have clearly defined meanings in order to “speak the same language” when communicating the interpretations of the FHR and uterine activity (UA) tracings.

  1. Definition of UA terms:
    1. Frequency: the time from the beginning of one contraction to the beginning of the next, some define it as the number of contractions over a period of time, e.g. 10 minutes. If the contractions are bell shaped and not skewed, frequency may be timed from the peak of one contraction to the peak of the next contraction.
    2.  Duration: measured in seconds, it is the time from the beginning to the end of the contraction. Some calculate a mean or average duration over a specific period of time.
    3. Intensity; by palpation it is mild moderate or strong; by intrauterine pressure catheter (IUPC) it is calculated as the difference between the peak pressure and the resting tone (peak minus tonus) this difference is also known as the amplitude or active pressure.
    4. Peak Intrauterine Pressure (IUP): the acme of the contraction in mm Hg, determined only when an IUPC is in place, also known as the quality or strength of the contraction.
    5. Interval: the time from the end of one contraction to the beginning of the next, also known as the rest interval.
    6.  Hyper stimulation:also known as Tachystole or hyper contractility, abnormal contraction frequency (closer together than every 2 minutes) with the contraction interval less than 60 seconds. Hyper stimulation may or may not be accompanied by hyper tonus.
    7. Hyper tonus: abnormally high resting tone (above 30 mm Hg).
  2. Documentation of UA.

Doubling: sometimes called “camel backs” is two contractions with the first contraction being longer and stronger than the second. The uterus rarely returns to resting tone and the interval between is usually less than 20 seconds. The interval between each set of contractions will be greater than 60 seconds.

Contractions are displayed in the UA channel on the tracing. Documentation of contractions may include frequency, duration, intensity and relaxation. Documentation should include the method of monitoring. More information can be obtained by a toco or IUPC than by palpation. The tracing is only one small but important part of the entire medical record. Although it was once thought that the tracing should be able to stand alone as evidence of labor events, thinking has changed. The tracing or strip provides limited evidence of events related to a woman’s care and the standard of practice. The nurse’s notes reflect assessment and observation, action, fetal and maternal responses and communications. Evidence of the standard of care provided should be found in the nurses' notes and need not be double-charted on the fetal monitor tracing. The nurses’ notes should provide enough information about the UA and FHR patterns that the tracing could be drawn if the strip were lost.

Assessment of UA might be documented in the nurses’ notes as follows:

Method of Assessment

Sample Documentation

Palpation

UCs palpated q3 min X 60 sec, strong, uterus, soft between UCs.

Tocotransducer

Toco, UCs q 3-31/2 min X 60-80 Sec, strong, uterus soft between UCs

IUPC

IUPC, UCs q 3-31/2 min X 60-80 sec, ­ 75-85 mm Hg, rest, tone 20-25 mm Hg. (The ¯ reflects the peak IUP).

 

B. The Fetal Heart Rate

  1. Baseline - the FHR over a period of time, not including accelerations or decelerations. The baseline may be recorded as a range, e.g. 120-130 bpm or an average rate, e.g. 125 bpm.
    1. Tachycardia is a baseline greater than 160 bpm for 10 or more minutes. Moderate tachycardia is baseline 160-180. Marked tachycardia is greater than 180 bpm or more. Tachycardia is abnormal and increases the risk of chorioamnionitis and sepsis, meconium aspiration, asphyxia, neonatal respiratory distress and neonatal pneumonia.
    2. Bradycardia is a baseline less than 100 bpm in term or post term and less than 120 bpm in a preterm fetus. Duration that separates a prolonged decel from bradycardia is 10 or more minutes. A prolonged decel has a duration form 2-10 minutes if the decel persists more than 10 minutes it is labeled bradycardia.

End-stage bradycardia or second stage bradycardia is a sustained drop of 15 to 30 bpm during the second stage of labor.It occurs in as many as 91% of fetuses. If end-stage bradycardia was preceded by a lack of accelerations, decreased variability or late decelerations, the fetus was Hypoxic. If there was thick meconium in the amniotic fluid prior to the second stage of labor, there is an increased risk of decreased variability, late decels, bradycardia and meconium aspiration syndrome. Therefore it is important to be prepared to intervene to improve fetal oxygenation or expedite delivery if hypoxia exists prior to the second stage of delivery.

Agonal pattern is the FHR of a decompensating fetus with a surge of catecholamines. The baseline is less than 100 beats per minute (bpm) with upward and downward swings that last 20 or more seconds and often precedes terminal bradycardia.

Terminal bradycardia is the FHR of a decompensated fetus with sinus node depression. The baseline is near 60 bpm and falling.

Stability - a well-oxygenated fetus should have short-term variability (STV), long-term variability (LTV), accels and a baseline level that fluctuates within a 25-bpm range. The baseline may flatten and rise over a period of minutes or hours. A rising baseline is abnormal and is usually a fetal response to infection or hypoxia. The baseline may abruptly or slowly drop. This happens in direct vagal response or in response to hypoxia. Abruption may cause an abrupt drop in the baseline. A smooth meandering baseline with absent STV and LTV is called wandering or unstable. It is ominous.

 

  1. Variabilityis present when the baseline is chaotic, irregular and fluctuating. It is absent when the baseline is regular, non-chaotic or smooth.
    1. Short-term variability is the beat-to-beat fluctuation of the pulse intervals. It is instantaneous rhythmic fluctuations of the FHR exclusive of accels or decels. STV is documented as present or absent.
    2. Saw-toothed respiratory sinus arrhythmia is a baseline with instantaneous rhythmic FHR fluctuations that increase during inspiratory fetal breathing movements and decrease during expiratory fetal breathing movements. It is a sign of fetal well-being.
    3. Long-term variability is irregular, crude sine waves, which create a wave appearance of the baseline. It is oscillations of the FHR around an average level. It is the sum of many small changes in the R-R interval and calculated FHR. LTV has two dimensions – cycle and amplitude. Cycles are horizontal dimensions of the baseline and are counted during each minute of the baseline. Cycle frequency is determined by counting every time the Heart rate crosses the baseline. LTV is classified based on the amplitude. Amplitude is the vertical dimension of the baseline and refers to the bandwidth of most of the cycles it is the BPM between the top and bottom of most of the oscillations or cycles of the baseline. LTV is documented as absent if there is 0-2 bpm. It is marked or salutatory if bandwidth is more than 25 bpm with less than 6 cycles per minute.
    4. Sinusoidal is a series of sine waves with similar but not always identical duration and amplitude. They may be either benign or pathological. Benign require no treatment. Accels are present before and after. Usually they have sudden onset after administration of some meds like stadol. Pathologic patterns are associated with fetal anemia, hypoxia and acidosis.
  2. Accelerations are transient increases in FHR above the baseline.
    1. Spontaneous accels are an abrupt transient increase in the FHR with an abrupt return to the baseline.
    2. Uniform accels are transient increases in the FHR in response to stimulation of chemoreceptors and baroreceptors when the umbilical cord is mildly compressed. They have a gradual onset and usually a gradual offset or return to baseline.
    3. Lambda patterns are a transient increase in the FHR preceded and/or followed by a dip in the FHR. Avoid the use of “periodic” and “non-periodic” when describing accels. Spontaneous accels are response to a stimulus.
  3.  Decelerations are periodic decreases in the FHR in response to stimuli.
    1. Early decelerations are periodic decreases in the FHR due to intense fetal head compression. It has gradual onset, begins shortly after onset of contraction and returns to baseline shortly after the contraction ends. It has uniform shape.
    2. Late decelerations are periodic decelerations due to uteroplacental insufficiency. This transient decrease in FHR is in response to the contraction and hypoxia. It begins after the contraction begins and returns to the baseline after the contraction ends. It has uniform shape. There are 4 types based on their shape, depth and the presence of STV: subtle, reflex, hypoxic myocardial failure and late variables but it is not recommended to use these terms in documentation.
    3. Variables are transient decreases in FHR that last at least 15 seconds and decrease 15 or more bpm. The onset is abrupt. The depth varies and the return to baseline is usually abrupt.
    4. Shoulders are defined as an increase of FHR before and/or after a variable decel. It is not an accel. Document these as “variable decel with shoulders”
    5. Overshoots look like a rebound accel but is not an accel. An overshoot is attached to a variable as part of the decel pattern. The increase is 20 or more bpm above baseline for more than 20 seconds.

 

Essential Documentation

Early and late decels have clear physiologic implications: early decels are not related to hypoxia; late decels are related to hypoxia. Because of their clear significance, it is common to document “early decels” and “late decels” in addition to the rest of the systematic review.

Since variable decels vary in configuration, duration and depth, it is more common to use abbreviations to document a range of duration and depth. The duration and depth of variables should be described. For example, one variable decel might be documented as “variable decel X 25 sec. ¯ 90 bpm.”

It is appropriate to write on the tracing unless the tracing is copied onto an optical disk, in which case a computer keyboard is needed to make entries on the tracing. Circling or initialing heart rate changes such as decels is discouraged. If it is done it is essential that the interventions, which were immediately taken following the noted pattern, are also promptly recorded on the tracing or in the notes.

By circling a pattern, all eyes will focus on that aspect of the tracing particularly during retrospective review. This increases the potential of ignoring other important aspects of the tracing and makes it hard to be objective. JCAHO has suggested guidelines for charting in nurse’s notes should include the woman and/or her fetus’s needs, problems, capabilities and limitations; the nursing interventions and patient responses; and patient status at the time of transfer or discharge.

Below is a suggested list of items that may be documented on the strip:

  • Woman’s name
  • Physician’s name
  • Date and time monitoring initiated
  • Gravida/parity
  • High-risk conditions
  • EDC
  • Vaginal exams-include as much data as possible
  • Woman’s position in bed
  • Anesthesia and/or med administration
  • Vital signs
  • Oxygen with liters per minute
  • Pushing
  • Fetal movement
  • Procedures
  • Auscultated FHR
  • Time of birth, sex and apgars

In addition the notes should include the systematic review of FHR pattern and uterine activity; intake and output; and communications with the physician.

The importance of documentation on the patient’s medical record cannot be over emphasized. Adherence to standards of practice is essential and appropriate assessment; intervention and evaluation should be clearly documented. Nurses are cautioned against the use of terms such as “fetal distress,” ”fetal hypoxia,” or “uteroplacental insufficiency” in their charting because these terms are medical diagnosis.

Nurses should avoid the use of empty and meaningless charting phrases such as “physician notified of patient’s condition.” The chart should explain of what the physician was specifically notified (e.g. notified of ¯ B/P)

The overall goal of narrative medical record charting is to be accurate objective and free from editorial comment. A properly documented monitor strip should be able to stand alone with the information contained on it. However the medical record should also be able to stand alone.

Limitations

Second-generation fetal monitors and some hand held Doppler devices use autocorrelation. It was determined that these ultrasound records “very closely” approach that of beat-to-beat variability (STV) generated from the scalp electrode. As long as you are using one of these second generation monitors you may document STV with an external toco.

When auscultation is used, the practitioner’s assessment is the sole source of information about the FHR. Careful listening and precise descriptions of auscultation findings can provide useful information of the status of the fetus. Auscultation detects:

  • FHR baseline
  • FHR rhythms
  • Increases and Decreases of FHR
  • Differentiation of fetal and maternal heart rates eliminating errors that are due to misplacement of a monitor device or fetal demise.
  • Verification of fetal heart dysrhythmias visualized on EFM tracing (this is only possible with a fetoscope).
  • Clarification of halving or doubling on the EFM tracing.

Limitations exist with the auscultation method despite careful listening and descriptions of the FHR by practitioners. Auscultation does not:        

  • Detect LTV or STV
  • Is not continuous and may miss or delay detection of decreases and increases of FHR.
  • Does not generate a graphic record for assistance in decision-making or future review.
  • Requires education, practice, skill and a 1:1 nurse: fetus ratio.
  • May be disrupted by uterine contractions
  • May be limited by position and movement of the mother or fetus as well as maternal size.

Regardless of the practice setting all practitioners who work with fetal monitoring must know how their equipment works, what the information they receive means and how to convey that information to the rest of the healthcare team.

REFERENCES

AWHONN Fetal Heart Monitoring Principles and Practice 2nd Edition

 Kendall/Hunt Publishing Company. Dubuque (1993)

Murray, Michelle, Antepartal and Intrapartal Fetal Monitoring 4th Edition,

            Learning Resources International Inc. Albuquerque (1997)

Tucker, Susan, Mosby’s Fetal Monitoring and Assessment 4th Edition,

            St. Louis (2000)