ST Segment Analysis (STAN) for Intrapartum Electronic Fetal Monitoring

Presented By:Chukwuma I. Onyeije, M.D.Atlanta Perinatal AssociatesClinical Associate Professor, Morehouse School of Medicine

Specific FHR abnormalities are

related to cerebral palsy and neurologic injury in

the fetus

The 1970s

CLINICAL OBSTETRICS AND GYNECOLOGYVolume 54, Number 1, 56–65r 2011, Lippincott Williams & Wilkins

Intrapartum EFM associated with decreased perinatal

mortality due to fetal hypoxia but also with higher rates of

surgical intervention for suspected fetal distress.

Vintzeleos et al, Obstet Gynecol. 1993 Jun;81(6):899-907.

Compared to Auscultation, EFM

results in higher operative delivery rates

without significant lowering of perinatal

mortality.

Conclusion:Auscultation…. The winner!

Scalp pH Pulse Oximetry

Scalp pH largely abandoned in the United States 2 decades ago.

Fetal pulse oximetry did NOT reduce cesarean delivery rates for ‘nonreassuring’’ FHR patterns in NICHD trial.

The fetal ST interval changes in the fetus suffering from oxygen deficiency.

ST Analysis (STAN) consists of highlighting theses changes.

For a fetus, the birth is the treadmill.

STAN begins with conventional EFM (FHR + UCs) and adds automated ST Analysis

Comprehensive and mandatory education prior to introduction of STAN

Showed that hypoxia was associated with a significant elevation of the T-wave in the fECG.

Am J Obstet Gynecol.1984;149:190–195.

Increased myocardial glycogen breakdown

Liberation of potassium

Increased local catecholamines

The increase in T-wave height relative to the amplitude of the QRS complex was identified when the fetus transitions from aerobic to anaerobic metabolism.

The T:QRS ratio measures of myocardial metabolic status

Other changes in the ST-segment identified fetuses with chronic oxygen deprivation were subjected to acute hypoxic stress.

Baseline T :QRS ratio

Appearance of ST segment waveforms

Hypoxic fetuses Fetuses with

myocardial dysfunction

Chronically hypoxic fetuses with acute insults

BEFORE using STAN >36+0 gestational weeks Ruptured membranes No contraindication for scalp electrode or

STAN First stage, no active or involuntary pushing

At onset of STAN Classify the FHR. Check for FHR reactivity Confirm nondeteriorating fetal state Check for normal ECGwaveform Confirm sufficient signal quality Confirm baseline T:QRS ratio

Any contraindication to invasive monitoring◦ active maternal herpes ◦ HIV◦ Hepatitis

STAN determines

baseline T:QRS ratio over 20 T :QRS ratios and then tracks for changes over

time.

T:QRS Ratio

EVENT LOG

AVERAGE T:QRS

ST ALRETS

Episodic rise in T:QRS ratio ◦ (greater than 0.10 for less than 10 min);

Baseline rise in T :QRS ratio◦ (greater than 0.05 for more than 10 min); and

Recurrent biphasic ST segments

FHR CLASSIFICATION

BASELINE FHR VARIABILITY DECELERTIONS

GREEN110 - 160 MODERATE

(+)ACCELERATIONS

EARLY

VARIABLE (LESS THAN 60 x 60)

YELLOW

BRADY <110

TACHY > 160

> 150 WITH MINIMAL

VARIABILITY

MINIMAL FOR > 40 MIN

MARKED FOR > 40 MIN

VARIABLE GREATER THAN 60 x 60

RECURRENT LATE

PROLONGED

RED SINUSOIDAL OR ABSENT VARIABILITY REGARDLESS OF FHR PATTERN

STAN’s FHR Clinical Management Protocol

FHR CLASSIFICATION NO ST EVENTS ST EVENTS PRESENT

GREEN EXPECTANT MANAGEMENTCONTINUED OBSERVATION

YELLOW

EXPECTANT MANAGEMENT

DIRECT PHYSICIAN ASSESSMENT OF

FETAL STATE IF > 60 MINUTES

DIRECT PHYSICIAN ASSESSMENT

INTRAUTERINE RESUSCITATION

EXPEDITED DELIVERY IF NO IMPROVEMENT

RED EXPEDITIOUS DELIVERY / RESUSCITATION (?)

Main outcome of interest was a reduction in cord artery metabolic acidosis (pH <7.05 and base deficit >12 mmol/L) with the addition of STAN data.

U.K. – Am J Obstet Gynecol. 1993;169:1151–1160.Sweden - Lancet. 2001;358:534–538.

UNITED KINGDOM: 1993 SWEDEN: 2001

Significant reduction in fetal metabolic acidosis AND reduction in operative delivery.

Follow-up studies of the neonates showed a significant reduction in neonatal encephalopathy

Standard EFM is very good at detecting the very healthy and very sick fetus.

STAN allows us to grade fetuses between the extremes

STAN combined with EFM provides more accurate information about the fetus during labor than EFM alone.

STAN is automatic, continuous and has been proven to be effective in large randomized trials.

Information from STAN provides precise information about the fetal state during labor to detect fetuses at risk and avoid unnecessary interventions.

CLINICAL OBSTETRICS AND GYNECOLOGY Vol.54, Number 1, 56–65. 2011, Am J Obstet Gynecol. 1993;169:1151–1160. Lancet. 2001;358:534–538. Am J Obstet Gynecol.1984;149:190–195. Obstet Gynecol. 1993 Jun;81(6):899-907 http://www.neoventa.com/INT/Articles/Products/Goldtrace_INT.html