Monitoring Complex Labour Flashcards
What does MOTHERS stand for and what does it relate to?
The indications for continuous monitoring M = meconium O = oxytocin T = temperature H = hyperstimulation E = epidural R = rate of progress
What does Dr C Bravado stand for?
DR - define risk C - contractions Bra - baseline rate V - variability A - accelerations D - decelerations O - overall
Define complex labour
Anyone who doesn’t meet the criteria for labouring in a midwifery-led unit/ homebirth
What does CTG stand for?
Cardiotocograph - monitors the foetal HR and uterine contractions
What does STAN stand for?
ST wave analysis - combines CTG monitoring with analysis of a foetal ECG
What are the 3 classifications of a CTG trace?
Normal - all features reassuring
Suspicious - 1 feature non-reassuring and 2 features reassuring
Pathological - 1 feature pathological OR 2 features non-reassuring
What are the 3 classification of the Dr C Bravado characteristics?
Reassuring, Non-reassuring, Abnormal
What is the different between the 2 types of nervous system?
Somatic - voluntary
Autonomic - involuntary
Describe the autonomic NS
Split into:
Sympathetic - fight or flight, increases HR, releases catecholamines
Parasympathetic - decreases HR, RR etc, releases acetylcholine
What is a reassuring baseline rate?
100-160bpm
What is a non-reassuring baseline rate?
100-109bpm
160-180bpm
What is an abnormal baseline rate?
<100 or >180bpm
What is a baseline bradycardia?
Baseline <110bpm for >10 mins
What is a baseline tachycardia?
Baseline >160bpm for >10 mins
What are 4 possible causes of abnormal baselines?
- Gestation
- Drugs
- Infection
- Hypoxia
What effect can the release of catecholamines have on the baseline?
Increases baseline (in absence of maternal temp) Caused by decreased oxygen levels in tissues and blood
What is a reassuring variability?
5-25bpm
What is a non-reassuring variability?
<5 for >30 mins but <50 mins
>25 for >15 mins but <25 mins
What is an abnormal variability?
<5 for >50 mins
>25 for >25 mins
What is cycling?
Periods of reduced variability while the baby is asleep
What are some factors that affect variability?
- Maternal opiates
- Foetal hypoxia
- Pre-existing foetal brain damage
- Cardiac arrhythmia
What 3 signs, when combines, are a sign of foetal hypoxia?
Reduced variability
Tachycardia
Decelerations
What are the features of a sinusoidal pattern?
- Baseline of 120-160bpm with regular sine-wave oscillations
- Amplitude of 5-15 beats
- 2-5 cycles per minute
- Reduced/absent baseline variability
- No accelerations
Which is different about an atypical/ jagged sinusoidal pattern?
It always has a pathological cause (hypoxia/ foeto-maternal haemorrhage)
What are accelerations?
- Increase of >15 beats for >15 secs
- Related to the somatic NS
- Occur most frequently during foetal activity
- Sign that the baby is healthy
What is a deceleration?
- A drop in FHR of >15 beats for >15 secs
- Drop of <15 beats with reduced variability may also be a concern
What is an early deceleration?
- Reassuring
- Nadir of deceleration in line with peak of contraction
What usually causes early decelerations?
- Head compression causes increase in BP
- High BP detected by baroreceptors which stimulate the parasympathetic NS
- Vagus nerve releases acetylcholine which decreases FHR
What is a late deceleration?
- Mid to late contraction
- Nadir >20 secs after peak of contraction
- Similar to shape of contractions
How are late decelerations classified?
> 50% contractions in <30 mins = non-reassuring
>50% contractions in >30 mins = abnormal
What are variable decelerations and how are they classified?
- Vary in shape, form and timing
- Classified by the presence/ absence of concerning characteristics (CC)
What are the characteristics of variable decelerations without concerning characteristics?
- Last <60 secs
- > 60 bpm
- Classified by the presence of shouldering
What are the characteristics of variable decelerations with concerning characteristics?
- Last >60 secs
- Reduced variability with deceleration
- Failure to return to baseline
- No shouldering
What is shouldering?
FHR increases just before a deceleration
How does blood flow between the placenta and the baby?
- Oxygenated foetal blood flows from placenta to baby via thin walled veins
- Deoxygenated foetal blood flows from placenta to baby via thick walled veins
How does hypovolaemia affect FHR?
- Increases FHR
- Increased FHR in presence of normalising BP causes decreased FHR
What is hypovolaemia?
Decreased blood volume
How does shouldering occur?
- Contraction occludes the vein
- Contraction occludes arteries
- Arteries spring open
- Vein opens
What happens when the contraction occludes the vein?
- Reduces blood flow to foetus
- Blood flow to placenta is unchanged
- Decreases BP and increases FHR (baroreceptors stimulate sympathetic NS)
What happens when the contraction occludes the arteries?
- Blood flow to and from baby equalises
- Increased FHR and increased BP may cause haemorrhagic stroke so FHR is decreased (baroreceptors stimulate parasympathetic NS)
What happens when the arteries spring open?
- Blood flow to placenta is greater than the blood flow to the baby
- BP decreases and FHR increases (baroreceptors stimulate sympathetic NS)
What happens when the vein opens?
- Blood flow to and from placenta equalises
- BP and FHR normalise
How are variable decelerations classified?
<50% contractions for >30 mins = non-reassuring
>50% contractions for <30 mins = non-reassuring
>50% contractions for >30 mins = abnormal
How likely is it that contractions will recover after prolonged decelerations?
- 90% recover within 6 mins
- 95% recover within 9 mins
What are the possible causes of prolonged decelerations?
- Cord compression/ prolapse
- Anaesthesia
- Uterine rupture
- Respiratory depression
- Prolonged contractions/ hypercontractility
What may indicate an OP position?
Coupling contractions
What should be done if the CTG is suspicious or pathological?
Start conservative measures (fluids, reduce/stop synto, change position, offer tocolytic drugs)
When is cEFM necessary?
- P 2 x >120bpm or temp >38
- Significant meconium
- PV bleeding in labour
- Hypertension
- Delay in 1st/2nd stage
- Oxytocin
When is cEFM not necessary?
Women who have an epidural but no other risk factors
How can subacute hypoxia be detected?
When the HR spends more time decelerating than at the baseline (baby’s pH drops by 0.01 every 2 mins during subacute hypoxia)
What is the gradual evolution of hypoxia?
Normal CTG -> Decelerations -> Loss of accelerations -> Catecholamines released -> Raising baseline -> Reduced variability -> Baseline instability -> Terminal bradycardia -> Foetal demise
What is aerobic metabolism?
Glucose/Fat/Protein + Oxygen -> CO2 + Water + ATP
CO2 + Water -> H+ + HCO3-
How is pH measured?
The concentration of free H+ ions; most are buffered by Hb
What is anaerobic metabolism?
Glycogen -> Glucose -> Energy (lactic acid produced as a by-product)
What do significant and insignificant meconium look like?
Significant = Dark green waters with lumps Insignificant = Stained waters but not very thick
If waters turn from clear to stained, what can this mean?
- Sign that baby is stressed
BUT - Can be normal with term babies as their vagus nerve is more developed
How are placental lakes different in SGA babies?
- Small baby = small placenta
- Smaller placental lakes around villi
- Less gaseous exchange between foetal and maternal blood
How are placental lakes different in GDM babies?
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 some contraindications of FBS?
- Prolonged bradycardia
- 2nd stage
- Not technically possible
- Certain maternal/foetal conditions
- Significant maternal pyrexia or sepsis
- Prematurity
What is the procedure for FBS?
- Position woman in left lateral to avoid aortocaval compression
- 2 samples optimum = use lowest result
- Consider result, prev. results and whole clinical picture
- If abnormal, seek consultant support
What is the normal lactate and pH?
Lactate = <4.1mmol/l
pH = >7.25
Repeat in 1hr unless CTG abnormalities resolve or worsen
What is borderline lactate and pH?
Lactate = 4.2-4.8mmol/l
pH = 7.21-7.24
Repeat in 30 mins
What is abnormal lactate and pH?
Lactate = >4.9mmol/l
pH = <7.20
Deliver baby
What are the issues with performing FBS?
- Never been validated in humans
- No evidence that is reduce the number of LSCS, instrumental deliveries or long-term neonatal outcome
- Caput
- Contamination with amniotic fluid/ mec
- Lack of consistency in results
Describe the process of paired cord sampling
- Double clamp cord
- 2 heparinised syringes
- Sample artery and then vein at 45 degree angle
- Expel excess air
- Sample should be taken within 30 mins of delivery
- Sample should be processed as soon as taken (within 10 mins)
What is a normal arterial and venous pH?
A = 7.04-7.39 V = 7.16-7.47
What is a normal arterial and venous base deficit?
A = -2.8 - 9.4mmol/l V = -1.4 - 8.8mmol/l
What is a normal arterial and venous pCO2?
A = 37-80 V = 26-59
What do levels of pH and base excess indicate?
Low pH, normal BE = respiratory acidaemia
Low pH, abnormal BE = combined respiratory and metabolic acidaemia
What is respiratory acidaemia?
Accumulation of carbon dioxide through impaired gas exchange = low pH
What is combined respiratory and metabolic acidaemia?
Accumulation of carbon dioxide through impaired gas exchange and the build up of lactate and H+ ions through anaerobic metabolism
What is indicated if there’s a difference in pH acidaemia?
Large arterial-venous difference = likely to have occurred in 2nd stage, acute event or cord compression
Small arterial-venous difference = likely to be longstanding acidaemia
What is a significant base excess?
Arterial = >-12.0mmol/l Venous = >-10.0mmol/l
What is acidaemia?
Low blood pH
What is acidosis?
Low blood and tissue pH
What is base excess/deficit?
Measure of how much buffer has been used
What is hypoxaemia?
Low oxygen tension in blood (low pO2)
What is hypoxia?
Low oxygen levels in tissues
What is metabolic acidosis?
Low blood pH and high BE due to accumulation of CO2 and H+ ions using up buffers
