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Yr 4 - GOSH > CTG: Interpretation > Flashcards

CTG: Interpretation Flashcards

1
Q

What is a CTG?

A

A device known as a cardiotocograph.

This involves the placement of 2 transducers onto the abdomen of a pregnant woman.

One transducer records the FETAL HEART RATE using US.

The other transducer monitors the CONTRACTIONS of the uterus.

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2
Q

How does the transducer monitor the contractions?

A

By measuring the tension of the maternal abdominal wall using US (providing an indirect indication of intrauterine pressure).

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3
Q

What is the normal contraction rate?

A

3-5 in a 10 minute window, typically lasting 30-40 seconds each.

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4
Q

Give some indications for continuous CTG monitoring

A
  • Sepsis
  • Pre-eclampsia (particularly blood pressure > 160 / 110)
  • Maternal tachycardia (> 120)
  • Significant meconium
  • Fresh antepartum haemorrhage
  • Delay in labour
  • Use of oxytocin
  • Disproportionate maternal pain
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5
Q

Structure for interpreting a CTG?

A

DR C BRaVADO

DR: Define risk

C: Contractions

BRa: Baseline rate

V: Variability

A: Accelerations

D: Decelerations

O: Overall impression

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6
Q

Purpose of ‘defining risk’ when intrepreting a CTG?

A

When performing CTG interpretation, you first need to determine if the pregnancy is high or low risk.

This is important as it gives more context to the CTG reading (e.g. if the pregnancy categorised as high-risk, the threshold for intervention may be lower).

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7
Q

What are 3 maternal medical illnesses that may cause a pregnancy to be considered as high risk?

A

1) Gestational diabetes

2) HTN

3) Asthma

Other risk factors:
- absence of prenatal care
- smoking
- drug abuse

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8
Q

What are some obstetric complications that may cause a pregnancy to be considered as high risk?

A
  • Multiple gestation
  • Post-date gestation
  • Previous cesarean section
  • Intrauterine growth restriction
  • Premature rupture of membranes
  • Congenital malformations
  • Oxytocin induction/augmentation of labour
  • Pre-eclampsia
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9
Q

Variable decelerations –> may indicate fetal distress –> what would you want to do about it?

A
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10
Q

How do you assess contractions?

A

1) Record the number of contractions present in a 10 minute period.

2) Assess duration: how long do they last?

3) Intensity: how strong are they?

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11
Q

What is each big square on a CTG equal to?

A

1 minute: so look at how many contractions occurred within 10 big squares.

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12
Q

How are individual contractions seen on a CTG?

A

As peaks on the part of the CTG monitoring uterine activity.

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13
Q

How is intensity of contractions assessed?

A

Using palpation

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14
Q

What is the baseline rate?

A

The average HR of the fetus within a 10 minute window.

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15
Q

What is a normal fetal HR?

A

110-160 bpm

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16
Q

How to assess baseline rate on a CTG?

A

Look at the CTG and assess what the average HR has been over the last 10 minutes, ignoring any accelerations or decelerations.

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17
Q

Define fetal tachycardia

A

Baseline heart rate greater than 160 bpm.

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18
Q

What are some causes of fetal tachycardia?

A
  • Fetal hypoxia
  • Chorioamnionitis
  • Hyperthyroidism
  • Fetal or maternal anaemia
  • Fetal tachyarrhythmia
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19
Q

Define fetal bradycardia

A

Baseline heart rate of less than 110 bpm

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20
Q

In what 2 situations is it common to have a baseline fetal heart rate of between 100-120 bpm?

A

1) Postdate gestation

2) Occiput posterior or transverse presentations

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21
Q

What does severe prolonged fetal bradycardia (less than 80 bpm for more than 3 minutes) indicate?

A

Severe hypoxia

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22
Q

What are 5 causes of prolonged severe bradycardia?

A
  • Prolonged cord compression
  • Cord prolapse
  • Epidural and spinal anaesthesia
  • Maternal seizures
  • Rapid fetal descent
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23
Q

Define baseline variability

A

The variation of fetal heart rate from one beat to the next.

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24
Q

Why is variability a good indicator of fetal health at that particular time?

A

As a healthy fetus will constantly be adapting its heart rate in response to changes in its environment.

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25
Q

What is normal variability?

A

Between 5-25 bpm

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26
Q

What does normal variability indicate?

A

An intact neurological system in the fetus.

Variability occurs as a result of the interaction between the nervous system, chemoreceptors, baroreceptors and cardiac responsiveness.

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27
Q

How to calculate variability?

A

To calculate variability you need to assess how much the peaks and troughs of the heart rate deviate from the baseline rate (in bpm).

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28
Q

What 3 categories can variability be?

A

1) Reassuring
2) Non-reassuring
3) Abnormal

29
Q

Define reassuring variability

A

5-25 bpm

30
Q

Define non-reassuring variability

A

There is less than 5 bpm for between 30-50 minutes.

or

There is more than 25 bpm for 15-25 minutes.

31
Q

Define abnormal variability

A

There is less than 5bpm for more than 50 mins

or

There is more than 25bpm for more than 25 minutes.

or

Sinusoidal

32
Q

What is the most common cause of reduced variability?

A

Fetal sleeping: this should last no longer than 40 minutes

33
Q

Give some causes of reduced variability

A

1) Fetal sleeping (most common)

2) Fetal acidosis (due to hypoxia)

3) Fetal tachycardia

4) Drugs: opiates, benzodiazepines, methyldopa and magnesium sulphate

5) Prematurity: variability is reduced at earlier gestation (<28 weeks)

6) Congenital heart abnormalities

34
Q

Reduced variability due to fetal acidosis is more likely if what other feature is present?

A

Late decelerations

35
Q

Define accelerations

A

An abrupt increase in the baseline fetal heart rate of greater than 15 bpm for greater than 15 seconds.

36
Q

Is the presence of accelerations reassuring or not?

A

Yes - reassuring

37
Q

What are accelerations occurring alongside uterine contractions a sign of?

A

A healthy fetus

38
Q

What does the absence of accelerations with an otherwise normal CTG indicate?

A

uncertain significance.

39
Q

Define a deceleration?

A

An abrupt decrease in the baseline fetal heart rate of greater than 15 bpm for greater than 15 seconds.

40
Q

What is the foetal HR controlled by?

A

the autonomic and somatic nervous system.

41
Q

Why does foetal HR decrease in response to hypoxic stress?

A

In response to hypoxic stress, the fetus reduces its HR (deceleration) to preserve myocardial oxygenation and perfusion (i.e. reduce myocardial demand).

42
Q

What are the 4 types of deceleration?

A

1) Early deceleration

2) Variable deceleration (MOST COMMON)

3) Late deceleration

4) Prolonged deceleration

43
Q

What are early decelerations?

A

These start when the uterine contraction begins and recover when uterine contraction stops (i.e. deceleration & contraction align on CTG).

This is due to increased fetal intracranial pressure caused increased vagal tone.

It therefore quickly resolves once the uterine contraction ends and intracranial pressure reduces.

44
Q

Are early decelerations physiological or pathological?

A

Physiological

45
Q

What are variable decelerations?

A

Observed as a RAPID FALL in baseline fetal HR with a variable recovery phase.

They are variable in their duration and may not have any relationship to uterine contractions.

46
Q

When are variable decelerations most often seen?

A

1) During labour

2) In patient’s with reduced amniotic fluid volume

47
Q

What are variable decelerations caused by?

A

usually caused by umbilical cord compression.

48
Q

Mechanism of umbilical cord compression cause variable decelerations?

A

1) The umbilical VEIN is often occluded first causing an ACCELERATION of the fetal heart rate in response.

2) Then the umbilical ARTERY is occluded causing a subsequent rapid DECELERATION.

3) When pressure on the cord is reduced another acceleration occurs and then the baseline rate returns.

49
Q

What are the accelerations before and after a variable deceleration known as?

A

The shoulders of deceleration

50
Q

What does the presence of accelerations before and after a variable deceleration indicate?

A

Indicates that the fetus is not yet hypoxic, and is adapting to the reduced blood flow.

51
Q

What can sometimes cause variable decelerations to resolve?

A

If mother changes position

52
Q

What does the presence of persistent variable decelerations indicate the need for?

A

Close monitoring

53
Q

Why are variable decelerations without the shoulders more worrying?

A

As it suggests the fetus is becoming hypoxic

54
Q

What are late decelerations?

A

These begin at the PEAK of the uterine contraction and recover after the contraction ends.

55
Q

What do late decelerations indicate?

A

There is INSUFFICIENT blood flow to the uterus and placenta.

As a result, blood flow to the fetus is significantly reduced causing fetal hypoxia and acidosis.

56
Q

Give 3 causes of reduced uteroplacental blood flow (causing late decelerations)?

A

1) Maternal hypotension

2) Pre-eclampsia

3) Uterine hyperstimulation

57
Q

Early vs late decelerations?

A

Late –> begin at the peak of the uterine contraction and recover after the contraction ends.

Early –> start when the uterine contraction begins and recover when uterine contraction stops.

58
Q

Define a prolonged deceleration

A

Deceleration that lasts >2 minutes:

  • If between 2-3 minutes: non-reassuring
  • If >3 minutes: abnormal
59
Q

How long does a ‘non-reassuring’ prolonged deceleration last?

A

2-3 mins

60
Q

How long does an ‘abnormal’ prolonged deceleration last?

A

> 3 mins

61
Q

What is a sinusoidal CTG pattern? What are the characteristics?

A

Rare, however, if present it is very concerning as it is associated with high rates of fetal morbidity and mortality.

1) A smooth, regular, wave-like pattern
2) Frequency of around 2-5 cycles a minute
3) Stable baseline rate around 120-160bpm
4) No beat to beat variability

62
Q

What does a sinusoidal pattern usually indicate?

A

1 or more of the following:

1) severe fetal hypoxia
2) severe fetal anaemia
3) fetal/maternal haemorrhage

63
Q

Once you have assessed all aspects of the CTG you need to determine your overall impression.

What can the overall impression be described as?

A

Reassuring, suspicious or abnormal.

This is determined by how many of the CTG features were either reassuring, non-reassuring or abnormal.

64
Q

Reassuring CTG features?

A

Baseline HR: 110-160 bpm

Baseline variability: 5-25 bpm

Decelerations:
- None or early
- Variable decelerations with no concerning characteristics for <90 minutes

65
Q

Non -reassuring CTG features?

A

Baseline HR:
- 100 to 109 bpm
- 161 to 180 bpm

Baseline variability:
- Less than 5 for 30 to 50 minutes
- More than 25 for 15 to 25 minutes

Decelerations:
- Variable decelerations with no concerning characteristics for ≥90 mins.
- Variable decelerations with any concerning characteristics in up to 50% of contractions for ≥30 mins.
- Variable decelerations with any concerning characteristics in over 50% of contractions for <30 mins.
- Late decelerations in over 50% of contractions for <30 mins, with no maternal or fetal clinical risk factors such as vaginal bleeding or significant meconium.

66
Q

Features of an abnormal CTG?

A

Baseline HR:
- Below 100 bpm
- Above 180 bpm

Baseline variability:
- Less than 5 for more than 50 minutes
- More than 25 for more than 25 minutes
- Sinusoidal

Decelerations:
- Variable decelerations with any concerning characteristics in over 50% of contractions for 30 minutes (or less if any maternal or fetal clinical risk factors).
- Late decelerations for 30 minutes (or less if any maternal or fetal clinical risk factors).
- Acute bradycardia, or a single prolonged deceleration lasting 3 minutes or more.

67
Q

What are the concerning characteristics of variable decelerations?

A
  • Lasting >60 seconds
  • Reduced baseline variability within the deceleration
  • Failure to return to baseline
  • Biphasic (W) shape
  • No shouldering
68
Q
A

Yr 4 - GOSH (45 decks)

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