Foetal Monitoring Flashcards
What speed should the CTG paper be set at?
1cm/min
What are some adverse effects of using cEFM?
- High false positive rate
- Increased risk of instrumental delivery/CS
- Increased anxiety
What does mothers stand for?
Beware of: Meconium Oxytocin Temperature Hyperstimulation/haemorrhage Epidural Rate of progress Scar (VBAC)
What does DR C BRAVADO stand for?
DR = define risk C = contractions BRA = baseline rate V = variability A = accelerations D = decelerations O = overall
How is the overall CTG categorised?
Normal, Suspicious, Pathological
How are the individual elements categorised?
Reassuring, Non-reassuring, Abnormal
What makes a CTG suspicious?
1 non-reassuring feature
What makes a CTG pathological?
1 abnormal or 2 non-reassuring features
What are the categories for baseline rate?
Reassuring = 110-160 Non-reassuring = 100-109 or 161-180 Abnormal = >180 or <100
Give some causes of a bradycardic baseline
- Maternal hypotension
- Hypertonic uterus
- Placental abruption
- Cord prolapse
- Drugs (e.g. pethidine)
Give some causes of a tachycardic baseline
- Prematurity
- FM
- Hypoxia
- Anaemia/ hypovolaemia
- Maternal pyrexia/tachycardia
- Maternal dehydration
- Drugs (e.g. nicotine)
What causes variability?
Interplay between sympathetic and parasympathetic NS
What is cycling?
Periods of reduced variability, usually while the baby is sleeping - these are normal if under 30 mins
What are the categories for variability?
Reassuring = 5-25 or <5 for <30 mins Non-reassuring = <5 for 30-50 mins or >25 for 15-25 mins Abnormal = <5 for >50 mins or >25 for >25 mins
What factors may reduce variability?
- Cycling
- Opiates (e.g. pethidine, morphine)
- Hypoxia
- Brain damage
- Cardiac arrythmia
What kind of variability always has a pathological cause?
Sinusoidal (baseline 120-160 with regular sine waves)
What are the signs of foetal hypoxia?
Reduced variability + Tachycardia + Decelerations
What are accelerations?
Increase of at least 15 beats for at least 15 secs
What are decelerations?
Decrease of at least 15 beats for at least 15 secs
What are decelerations mediated by?
Baroreceptors and chemoreceptors
How do baroreceptors work?
- Detect raised BP
- Located in carotid artery and aortic arch
- Cause early/variable decels
How do chemoreceptors work?
- Detect change in pH of blood
- Located in carotid bodies, aortic arch and brain stem
- Cause late decels
Describe early decelerations
- Very rare (2% of decels)
- In line with contractions
- Head compression = raised BP = baroreceptors stimulate parasympathetic NS = vagus nerve releases acetylcholine = decreased FHR
How are late decelerations categorised?
> 50% for <30 mins = non-reassuring
>50% for >30 mins = abnormal
Describe late decelerations
- Mid to late contraction (finish after contraction)
- Nadir >20 secs after peak
- Chemoreceptor stimulation due to decreased pH
- Usually caused by placental insufficiency or hypoxia
How are variable decelerations categorised?
<50% for >30 mins or >50% for <30 mins = non-reassuring
>50% for >30 mins = abnormal
Describe variable decelerations
- Vary in size and shape
- Dependent on concerning characteristics
- Controlled by both chemoreceptors and baroreceptors
- Usually caused by cord compression
What are the concerning characteristics?
- > 60 secs
- reduced variability
- failure to return to baseline
- no shouldering
What is the management for a suspicious or pathological CTG?
- Correct underlying cause
- Observations
- Conservative measures
- Review by obstetrician
- Document and discuss
What are the conservative measures?
- Fluids
- Reduce/stop synto
- Change position
- Offer tocolytic drugs if appropriate
What is the most common tocolytic drug?
Terbutaline
What is shouldering?
Increase in heart rate before a deceleration, caused by cord compression
What is the first step of shouldering?
- Contraction occludes vein
- Decreased blood flow to foetus
- Blood flow to placenta unchanged
- Hypovolaemia in baby
- Decrease BP, Increase HR
What is the second step of shouldering?
- Contraction occludes arteries
- Blood flow equalises so BP increases
- HR decreases to prevent haemorrhagic stroke
What is the third step of shouldering?
- Arteries spring open
- Blood flow to placenta higher than to baby
- BP decreases, HR increases
What are the signs of respiratory acidosis?
Low pH, normal BE
What are the signs of metabolic acidosis?
Low pH, high BE
What is hypoxaemia?
Low oxygen tension in blood
What is hypoxia?
Low oxygen tension in blood and tissues
What is acidaemia?
Low pH in blood
What is acidosis?
Low pH in blood and tissues
What is the difference between base excess and base deficit?
They measure the same thing but base excess is -ve and base deficit is +ve
What is respiratory acidosis?
Decrease in pH due to the accumulation of carbon dioxide during anaerobic metabolism
What is metabolic acidosis?
Decrease in pH due to lactic acid produced during anaerobic metabolism
What is the difference between the vein and arteries?
Arteries have a lower pH, lower PO2 and higher PCO2 than the vein
When is continuous EFM required?
- Meconium
- RFM
- Medical comorbidities
- SGA/LGA
What is a bradycardia?
Deceleration >3 mins
How can the placental lakes change?
- Small baby = smaller placental lakes = less gas exchange between foetus and mother
- GDM = normal size villi but small placental lakes
What is the indication for foetal blood sampling?
Pathological CTG with no response to foetal scalp stimulation
What are the contraindications for FBS?
- Prolonged bradycardia
- 2nd stage
- Maternal pyrexia or sepsis
- Prematurity
