Cardiotocograph (CTG)

Last updated 20.09.12

 

-  Review

-  Interpretation

-  Mx

 

Definition

-  Recording of fetal heart beat (FHR) & uterine contractions during pregnancy to identify fetal hypoxia & instigate measures to prevent harm to fetus

 

Features

-  2 separate transducers

-  1st for fetal heart

-  2nd for uterine contractions

-  Typically strapped to abdo wall

-  Continuous CTG monitoring reduces incidence of neonatal seizures

-  High negative predictive value

-  >98% foetuses w normal CTG do well

-  50% of foetuses w abnormal CTG are hypoxic but not acidotic, 50% do well

-  Typically not used <27/40 due to difficulty in finding fetal heart

 

Indications

-  Used in labour, esp 3rd trimester

-  On admission for labour

-   Screening test for placental function (how fetus coping with contractions)

-   20min+

-   In low risk pts chance of abnormal CTG for next 4hrs unlikely (excluding abruption, cord prolaspe..)

-  Continous in labour if

-   Previous LUSCS

-   Pre-eclampsia

-   Post dates

-   PROM, PPROM

-   IOL

-   DM

-   APH

-   IUGR

-   Prematurity

-   Oligohydramnios

-   Abnormal artery dopplers

-   Multiple pregnancy (twins..)

-   MSL

-   Breech

-   Oxytocin augmentation

-   Epidural

-   Vaginal bleeding in labour

-   Maternal fever

-  Montoring fetal wellbeing throughout pregnancy

-  Does not DDx fetal death as will pick up materal heart rate

 

Procedure

-  Paper speed at 1cm/min

-  Sensitivity at 20bpm/cm

-  FHR range 50-210bpm

-  Label: name, UR, date

-  Note relevant intrapartum events which may influence CTG

-   Change of position, VE, Epidural, Syntocinon, FSE, FBS, ARM

-  Uterine activity recorded at bottom of trace

-  Fetal activity recorded at top of trace

-  Need to endure FHR & not maternal

-  If continous CTG in labour should be R/V each 15-30min

 

 

 

CTG Review

<CTG>

 

-  Uterine activity

-  Baseline Heart Rate

-  Variability

-  Accelerations

-  Decelerations

 

Uterine Activity

-  Features

-  Lower trace on CTG

-  Low amplitude, frequent contractions: DDx placental abruption

-  Description

-  Duration: time from start to finish of one contraction

-  Interval: time from end of of one to start of next contraction

-  Frequency: time from start of one to start of next contraction

-   Noted as number of contractions in 10min (avg over 30min)

-   Normal: 5 or less contractions in 10min

-   Hyperstimulation/Tachysystole: >5 contractions in 10min OR >7 in 15min

 

Baseline fetal heart rate (FHR)

-  Definition

-  Estimated baseline heart rate over 10min+

-  Change for >10min = change in baseline

-  Features

-  Do not measure during periods of decels or accels or periods of marked variability (>25bpm)

-  Must have >2min readable baseline per 10min or unreadable

-  Rising baseline is suspicious esp if ass w reduced variability

-  Description

-  Rounded to 5bpm

-  Normal 110-160

-   Higher in preterm fetuses (still within range)

-  Bradycardia: FHR <110bpm

-  Tachycardia: FHR >160bpm

 

FHR Variability

-  Definition

-  Irregular fluctuations in baseline measured from peak to trough of the amplitude

-  Features

-  Most important feature of fetal wellbeing

-  Determined at baseline

-  Reflects PSNS & SNS activity

-  Description

-  Normal 5-25bpm

-  Absent: undetectable (<3bpm)

-  Reduced: variability of 3-5bpm

-   May indicate sleep phase but should not be >40min

-   Hypoxia

-   Preterm fetus w HR >180

-   Fetal infection/anaemia

-   Arythmia

-  Increased: variability >25bpm

-  Sinusoidal trace: fetal anaemia or hypoxia 2-5min

 

Accelerations

-  Definition

-  Abrupt (<30sec onset) increase in FHR

-  Must be >15bpm from baseline & >15sec duration

-  If <32/40 >10bpm for >10sec

-  x2 in 20min = reactive

-  Features

-  Ideally >2 per 15min

-  Reassuring when present

-  May be in response to fetal stimulation/movement

-  Presence of accelerations w contractions must DDx maternal trace

-  Beware in 2nd stage if valleys change to mountains

-  Description

-  Prolonged: >2min duration but <10min

-  If >10min = baseline change

-  Concerning if >90min wo accelerations unless in labour

-  Expected to see on antenatal trace

 

Decelerations

-  Definition

-  Decrease in FHR >15bpm for >15sec duration

-  Early

-  Usually symmetrical w gradual (>30sec onset) decrease & return to baseline

-  Associated w uterine contraction w peaks usually simultaneously

-  Likely related to head compression

-  Late

-  Similar in appearance to an early deceleration & associated w uterine contractions

-  Timing is delayed with lowest point of FHR >20sec later than peak contraction

-  Variable

-  Abrupt (<30sec onset) decrease in FHR >15bpm for >15sec but <2min

-  Likely related to cord compression

-  Increased likelihood of foetal hypoxia if

-   Rising baseline +/- reducing variability

-   Slow return to baseline

-   >60bpm change or down to 60bpm or >60sec

-  Prolonged

-   Decrease in FHR >15bpm for >90sec but <5min

-   If >10min = baseline change

 

CTG

 

 

 

CTG Interpretation

<CTG>

 

DR C BRAVADO

-  DR: define the risk

-  C: contractions

-  BRA: baseline rate

-  Reassuring: 110-160

-  Non-reassuring: 100-109 or 161-180

-  Abnormal: <100 (bradycardia) or >180

-  V: variability

-  Reassuring: >5

-  Non-reassuring: <5 for >40min (but <90min)

-  Abnormal: <5 for >90min

-  A: accelerations

-  Reassuring: present

-  D: decelerations

-  Reassuring: none

-  Non-reassuring: early decels, variable decels, single prolonged decel up to 3min

-  Abnormal: atypical variable decels, late decels, single prolonged decel >3min

-  O: overall

 

Changes unlikely related to Significant Fetal Compromise in Isolation

-  Baseline FHR 100-109

-  Absence of accelerations

-  Early decelerations

-  Variable decelerations

 

Indicators of Significant Fetal Compromise

-  Fetal tachycardia >160bpm

-  Prolonged bradycardia <100bpm for >5min

-  Reduced/absent baseline variability

-  Complicated variable decelerations

-  Late decelerations +/- reduced variability

-  Prolonged decelerations

 

Classification

-  Normal

-  Baseline 110-160bpm

-  Moderate variability

-  No late or variable decelerations

-  +/- early accelerations or decelerations

-  Suspicious: 1 non-reassuring feature

-  Pathological

-  2+ non-reassuring features or abnormal pattern

 

 

Trace

 

 

 

Management of the Abnormal CTG

<CTG>

 

-  Abnormal CTG

-  DDx maternal pulse

-  +/- maternal pulse oximtery

-  Consider FSE

-  Identify reversible causes

-   Cease oxytocin +/- tocolysis: alleviate contraction related compromise

-   Change maternal position: improve maternal hypotension (aortocaval compression) or cord compression

-   IV fluids: dehydration

-   Continuous CTG

-   Further fetal evaluation: FBS

-   OR Expediated delivery: Episiotomy, instrumental, LUSCS

 

 

 

References

 

Wikipaedia: Cardiotocography, October 2011

South Australian Perinatal Practive Guidelines: Chapter 2a Cardtocography, November 2010

Pic (Equip)

Pic (CTG)