Fetal monitoring Flashcards
sleeping fetus CTG
Less variability and higher baseline as decreased parasympathetic activation
sleep wake cycle or 20-40 minutes
How does gestation affect baseline
premature - sympathetically dominant - higher baseline
term /post term - more parasympathetic so lower baseline
variability definition
3 to 5 cycles per minute fluctuations in the range of 6-25 bpm in amplitude
Reflects the balance between sympathetic and parasympathetic stimulation
Accelerations vs reactivity
Fetal response to stimulation and are transient increase in FHR of 15 bpm above the baseline for 15 seconds or more
Reactivity is the presence of two or more accelerations in twenty minutes
Intrapartum does not have to have reactivity
features that we are monitoring maternal HR
poor quality recording, sudden change in baseline, change in recording style, accelerations with contractions
Usually taken from the uterine artery
Acceleration with contraction as increased preload from redistribution of blood from the myometrium
Conservative management of abnormal CTG
Continue the monitoring Consider the complete clinical picture Identify reversible causes - positioning, hyperstimulation, hypotension Give time for management to work Escalation of care Consider further evaluation
tachysystole definition + management
more then 5 active labour contractions over 10 minutes without fetal heart rate abnormalities
continuous CTG, reduce or stop oxytocin, 1:1 care, notify snr, consider tocolysis
Uterine hypertonus definition + management
contractions lasting more then 2 minutes or occuring within 60 seconds of each other without FHR abnormalities
continuous CTG, reduce or stop oxytocin, 1:1 care, notify snr, consider tocolysis
Uterine hyperstimulation definition + management
tachysystole or hypertonus with FHR abnormalities
continuous CTG, reduce or stop oxytocin, 1:1 care, notify snr, consider tocolysis / urgent delivery
tocolysis options
250 mcg terbutaline IV or SC
IV salbutamol 100 mcg
Sublingual GTN 400 mcg
what affects variability
Sleep
Sedation -medications pethidine, morphine, fentanyl, MgSO4
Prematurity
Hypoxia
What causes a low baseline
postdates
Profound hypoxia eg cord compression and bradycardia
drugs - high dose B Blockers suppress sympathetic innervation so have a lower baseline
fetal conduction defects / heart block
What causes baseline tachycardia
Maternal fever Drugs - terbutaline or salbutamol Fetal infection eg chorio Premature fetus hypoxia fetal tachyarrhythmias
Decelerations - definition
Early
normal physiological response to mild increases in intracranial pressure from head compression, and reflex drp in FHR - uniform in shape and finish with the contraction
occur in sleep phase, 4-8 cm, mimic the contraction
Variable decelerations
Caused by cord compression
Vary in depth, duration timing
cord compression -> fall in oxygen -> reflex parasympathetic response -> Acetylcholine released -> fall in FHR
Thought is to reduce myocardial workload to reduce ischemia
Shouldering physiology
As the compression starts, thin walled veins compress first, therefore reduction of blood to the heart, reduced oxygenation, so sympathetic response increases FHR
As it compresses the umbilical artery, O2 drops, detected by chemoreceptors ACH released, though vagal nerve (parasynpathetic) and rapid fall in FHR.
The artery opens first as the contraction eases, (thicker wall) withdrawn of vagus nerve as now low pressures, and if there is still venous compression the reduced R atrial pressures trigger a sympathetic response - shouldering
Shouldering is a normal physiologica lresponse and represents a well oxygenated fetus
When are variable complicated
Rising baseline
reduced variability
Persistent large amplitude >60 bpm OR to 60 bpm and long duration > 60 seconds
Smooth post deceleration overshoot - completely sympathetic dominant as no oxygen left after contraction, so is smooth
Slow return to baseline
Loss of shouldering (no longer in guideline)
Prolonged deceleration definition and causes
between 90 seconds and 5 minutes
Caused by hypoxia
- maternal hypotension, hypertonus / tachysystole / supine / abruption / rupture
Late decelerations
Contractions in the presence of hypoxia
Start after the start of the contraction and the peak is 20 seconds after the peak of the contraction
Uniform and repetitive
Sinusoidal pattern
Smooth and regular oscillating pattern - not necessarily regular in amplitude but in timing of oscillations
rate 2-5 cycles per minute at an amplitude of 5-15 bpm from baseline
Sign of anaemia
Loss of autonomic control
pseudosinusoidal - not as smooth or regular, prior normal trace, ? thumb sucking
How to perform intermittent auscultation
at least every 30 minutes in first stage (from 4 cm)
and After each contraction in second stage or at least every 5 minutes in second stage
Indications for intrapartum CTG
abnormal dopplers IUGR RFM within 1 week of labour APH intrapartum bleed Abnormal antenatal CTG Oligo or polyhydramnios / no liquor at ARM >37 or <42 weeks IOL / augmentation Abnormal contractions Abnormal progress Maternal pyrexia, HTN, PET VBAC BMI over 40 Abn fetal screening PAPP A diabetes + macrosomia OR medicated OR poor control Epidural Breech Multiple pregnancy Fetal abnormality
Contraindications to FBS include?
Contraindications to FBS include:
- Evidence of serious, sustained fetal compromise.
- Risk of fetal bleeding disorders (e.g. fetal thrombocytopenia,
haemophilia).
- Non-vertex presentation.
- Maternal infection
* (e.g. HIV, hepatitis B, hepatitis C, active
primary herpes and suspected fetal sepsis).
*Group B
Streptococcus carrier status does not preclude FBS.
Not recommended <34 weeks
When should paired umbilical cord lactates be performed?
Paired umbilical cord blood gas or lactate analysis should be taken at delivery either routinely or where any of the following are
present:
- Apgar score < 4 at 1 minute.
- Apgar score < 7 at 5 minutes.
- Fetal scalp sampling performed in labour.
- Operative delivery undertaken for fetal compromise
