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Check Pattern Variability First in Fetal Heart Rate Monitoring


 

SAN FRANCISCO — The first and most important thing to look for in a fetal heart rate pattern is variability, Michael D. Fox, R.N., said at a meeting on antepartum and intrapartum management sponsored by the University of California, San Francisco.

Pattern recognition is the key. Is the heart rate pattern jagged and unpredictable? That's a sign of moderate variability, which nearly guarantees that the fetus is sufficiently oxygenated. Is the pattern smooth, round, blunted, and flat? That loss of variability, when combined with recurrent heart rate decelerations, flags a baby who may be getting asphyxiated, said Mr. Fox, director of the perinatal resource group at the university.

The conventional method of assessing fetal heart rate-monitoring strips starts with drawing an arbitrary line that the clinician designates as the baseline heart rate, so that everything above it is considered accelerations and everything below it is thought to be decelerations. “I would argue that [the conventional method] is fraught with peril” because it employs the wrong interpretive construct and the wrong cues, he said.

Clinicians get into trouble by focusing too much on various methods to measure the height of the variability complexes on the fetal heart rate-monitoring strip. “It's not just the height of the variability complexes that are important, but the way they look,” he added.

A jagged and unpredictable pattern on the heart rate-monitoring strip is good: It's a visual representation of an intact neurologic pathway in the fetus. A progressively smooth, round, blunted and flat pattern is bad: This is a pattern that every baby who dies of asphyxia develops, even if the height of the heart rate oscillations meets previous definitions for moderate variability. A common mistake is to consider smooth, round, blunted oscillations to be moderate variability if they have enough height in the pattern.

Because heart rate accelerations usually occur in association with moderate variability, they are typically jagged and unpredictable in both appearance and timing. Rarely are accelerations regular, rhythmic, or occurring with each contraction.

Recurrent decelerations that get deeper and deeper as labor progresses are no cause for immediate delivery, so long as moderate variability remains present. “These are tracings that we traditionally called nonreassuring,” yet 98% of fetuses with this pattern will be free of asphyxia and 99% will have no morbidities, he noted.

That doesn't mean clinicians needn't be alert. If you see recurrent decelerations in the presence of moderate variability, then be sure a physician or nurse-midwife is managing the patient at the bedside, prepare the patient for delivery, and notify the rest of the obstetric and neonatal team. “Once you have the capacity to rescue this fetus, these are tracings that can continue to be observed,” he said.

The timing of decelerations in relation to uterine activity may tell the clinician something about the underlying physiology “but it does not tell you what to do in most circumstances,” Mr. Fox added. “Variability always trumps timing.”

He teaches a four-step process of evaluating a fetal heart rate strip. First, ask if variability is absent, minimal, moderate, or marked. Second, look for decelerations. Third, consider the baseline fetal heart rate. Finally, sum up the evolution of the tracing. Babies with asphyxia don't regain variability; they continue to lose it over time in association with deeper decelerations.

Video Teaches Pattern Recognition

A free video that teaches recognition of variability and other signs of fetal health on heart rate-monitoring tracings is available to clinicians who “commit to interdisciplinary education”—meaning it will be used to train doctors, nurses, midwives, and anyone else involved in monitoring fetal heart rates, Mr. Fox said.

Funded by Kaiser Permanente, the video “Situational Awareness in Fetal Heart Rate Monitoring” features four 27-minute segments with cases and tracings presented by Mr. Fox, Dr. Julian (“Bill”) Parer, professor of obstetrics, gynecology, and reproductive sciences at the University of California, San Francisco, and other faculty members.

A small shipping and handling fee is charged for each order. Mr. Fox is the distributor. To request a copy, contact him at

perinatal@consultant.com

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