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OBGYN 2023 > How to read a CTG - GM > Flashcards

How to read a CTG - GM Flashcards

1
Q

what is cardiotocography

A

used to monitor fetal HR and uterine contractions
most commonly used in the third trimester

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2
Q

the two transducers of CTG

A

one record fetal HR using US
the other monitors contractions of the uterus by measuring tension of the maternal abdominal wall (providing an indirect indication of intrauterine pressure)

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3
Q

DR C BRAVADO

A

DR - define risk
C - contractions
BRa - baseline rate
V - variability
A - accelerations
D - decelerations
O - overall impression

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4
Q

risk factors that may influence interpretation of a CTG

A

gestational diabetes
hypertension
asthma
multiple gestation
post date gestation
previous CS
intrauterine growth restriction
premature rupture of membranes
congenital malformations
oxytocin induction/augmentation of labour
pre-eclampsia
absense of prenatal care
smoking
drug abuse

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5
Q

contractions

A
  • record number of contractions in a 10 minute period
    individual contractions are seen as peaks on the uterine activity monitor
    each big square is equal to 1 minute
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6
Q

baseline rate of foetal heart

A

average HR of the fetus in a 10-minute window
ignore accelerations or decelerations

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7
Q

normal baseline foetal heart rate

A

110-160 bpm

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8
Q

fetal tahcycardia

A

baseline HR greater than 160
causes include
- fetal hypoxia
- chorioamnionitis
- hyperthyroidsim
- fetal or maternal anaemia
- fetal tachyarrythmia

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9
Q

fetal bradycardia

A

baseline HR less than 110

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10
Q

when might fetal bradycardia be normal

A

it is common to have a baseline HR of 100-120 during
- postdate gestation
- occipul posterior or transverse presentations

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11
Q

severe prolonged tachycardia

A

less than 80 bpm for more than 3 minutes
indicates severe hypoxia
causes include
- prolonged cord compression
- cord prolapse
- epidural and spinal anaesthesia
- maternal seixures
- rapid fetal descent

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12
Q

variability

A

variation in fetal HR from one beat to the next
a healthy fetus will constantly be adapting its heart rate in response to changes in its environment

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13
Q

normal level of variability

A

5-25 bpm
indicates intact neurological system in the fetus

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14
Q

categories of variability

A

reassuring, non-reassuring, abnormal

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15
Q

non reassuring variability

A

less than 5 bpm for between 30-50 minutes
more than 25 bpm for 15-25 minutes

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16
Q

abnormal variability

A

less than 5bpm for more than 50 minutes
more than 25 bpm for more than 25 minutes
sinusoidal

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17
Q

causes of reduced variability

A

fetal sleeping: most common cause, should last no longer than 40 minutes
fetal acidosis (due to hypoxia): more likley if late decelerations are also present
fetal tachycardia
drugs: opiates, benzodiazepines, methyldopa, and magnesium sulphate
prematurity: variability is lower at earlier gestations (< 28 weeks)
congenital heart abnormalities

18
Q

accelerations

A

an abrupt increase in baseline fetal heart rate of greater than 15 bpm for greater than 15 seconds
presence of accelerations is reassuring
accelerations occuring alongside uterine contractions is a sign of a healthy fetus

19
Q

absent accelerations

A

with an otherwise normal CTG, this is of uncertain significance

20
Q

decelerations

A

abrupt decrease in a baseline fetal heart rate of greater than 15 bpm for greater than 15 seconds

21
Q

cause of decelerations

A

in response to hypoxic stress, the fetus reduces its heart rate to preserve myocardial oxygenation and perfusion.
unlike an adult, a fetus cannot increase its respiration depth and rate

22
Q

types of decelerations

A

early deceleration
variable deceleration
late deceleration
prolonged deceleration
sinusoidal pattern

23
Q

early decelerations

A

start when uterine contractions begin and stop when uterine contractions stop
considered physiological

24
Q

are early decelerations pathological

A

they are physiological and not pathological

25
Q

why do early decelerations occur

A

due to increased fetal intracranial pressure caused increased vagal tone
will quickly resolve once the contraction ends and intracranial pressure reduces

26
Q

variable deceleration

A

rapid fall in baseline fetal heart rate with a variable recovery phase
may not have any relationship to uterine contractions

27
Q

variable decelerations are seen in

A

often seen during labour and in pateints with reduced amniotic fluid volume

28
Q

what causes variable deceleration

A

umbilical cord compression
initially there is compression on the umbilical vein which causes acceleration, the compression on the umbilical artery which causes deceleration, then pressure on the cord is reduced causing another acceleration

29
Q

shoulders of deceleration

A

the accelerations that occur before and after a variable deceleration
indicate that the fetus is not yet hypoxic and is ada[ting to the reduced blood flow

30
Q

variable decelerations without shoulders

A

more worrying as it suggests the fetus is hypoxic

31
Q

late deceleration

A

begin at the peak of uterine contraction and recover after the contraction ends

32
Q

are late decelerations worrying

A

yes
indicates there is insufficient blood flow to the uterus and placenta
blood flow to the fetus is significantly reduced causing fetal hypoxia and acidosis

33
Q

causes of reduced uteroplacental blood flow include

A

maternal hypotension
pre-eclampsia
uterine hyperstimulation

34
Q

prolonged deceleration

A

deceleration that lasts more than 2 minutes

35
Q

non-reasurraing deceleration

A

between 2-3 minutes

36
Q

abnormal deceleration

A

longer than 3 minutes

37
Q

sinusoidal pattern

A

sinusoidal CTG pattern is rare
very concerning, associated with high rates of fetal morbidity and mortality

38
Q

characteristics of a sinusoidal CTG pattern

A
  • a smooth, regular, wave like pattern
  • frequency of around 2-5 cycles a minute
  • stable baseline rate around 120-160bpm
  • no beat to beat variability
39
Q

a sinusoidal CTG pattern usually indicates

A

severe fetal hypoxia
severe fetal anaemia
fetal/maternal heamorrhage

40
Q

what qualitites should a reassuring CTG have

A

baseline fetal heart rate: 110-160bpm
baseline variability: 5-25bpm
decelerations: none or early, variable decelerations with no concerning characteristic for less than 90 minutes

41
Q
A

OBGYN 2023 (28 decks)

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