FHR Flashcards
Rate of fetal blood flow in placenta and 4 things it’s dependent on
500ml/min
Cardiac activity, BP, R to L shunts, systemic and pulmonary vascular resistance
Factors that reduce UBF
Umbilical cord compression Maternal hypotension & hypertension Aortocaval syndrome Vasoconstriction in uterine vessels (predominantly alpha) Hypertonic uterine contractions
What is the main determinant of fetal pO2
Maternal uterine venous pO2
Fetal metabolic acidosis ABG
Ph <7.2, HCO3 < 20 BE -6
Reliability is poor while sensitivity is high
FHR monitoring
FHR at 20 weeks and at term
155bpm then slows down to 140 bpm as PNS matures
What determines baseline fetal HR
Tonic effects on the SA node
What are some causes of fetal bradycardia (<110 BPM for >10 minutes)
Maternal hypoxia, drugs decreasing UPP, hypotension, vagal stimuli
Fetal acidosis, asphyxia, cord compression
What are some causes of fetal tachycardia (>160bpm for >10 min)
Maternal fever, chorioamnioitis, Drugs (terbutaline, ephedrine, atropine)
Fetal hypoxia, arrythmias
Most reliable sign of fetal compromise d/t fewer false alarms
Baseline variability
How is variability reduced
CNS depressants (opioids, sedatives, anesthetic agents, barbs, magnesium) Hypoxemia Fetal sleep Acidosis Anencephaly Cardiac anomalies
Absent variability is indicative of
Metabolic acidosis and depression of fetal brain stem and heart
Periodic accelerations related to fetal movements and uterine pressure
Long term variability
Normal is 15-40 an hour
R to R variability
Short term
3-6 bpm
Measured by fetal scalp electrode
Treatment of Early decelerations
LUD & oxygen
D/t fetal head compression
Benign with contraction & well tolerated by healthy fetus
No risk for fetal hypoxemia
Early decelerations
Treatment of late decelerations
LUD, O2, IVF, vasopressors, poss C/S
Ominous type of deceleration, indicator of UP insufficiency
Risk for fetal hypoxemia
Gradual decrease of FHR below baseline
Caused by: maternal hypotension, hypovolemia, acidosis, pre-eclampsia
Late deceleration
This type of deceleration indicates cord compression
Risk for fetal hypoxemia
Abrupt decrease in FHR below baseline
No consistent pattern between FHR and contraction
Variable deceleration
Treatment of variable deceleration
LUD, O2, IVF, amnioinfusion - urgent assessment of fetal status
Treatment for prolonged decelerations
LUD, O2, IVF, vasopressors, stat c section
This type of deceleration is a visually apparent sustained decrease in FHR
Caused by asphyxia, hyperstimulation, examination, supine hypotension
Can be a terminal fetal rhythm
Prolonged deceleration
Level 1 emergent CS is usually for what type of NRFHR
Late decelerations without variability or bradycardia sustained below 70
Treatment for NRFHR
LUD O2 Treat hypotension - fluids and pressors D/c pitocin Treat uterine hypertony - terbutaline 0.25mg sc Pelvic exam for cord prolapse Internal monitoring Amnioinfusion
FHR tracings in category III
Absent variability plus Bradycardia or Variable decels or Late decels or Sinusoidal pattern
FHR tracings in Category II
Recurrent variable decels
Tachycardia
Bradycardia without absence of FHR variability
What is normal fetal scalp blood gas
Ph <7.25, pco2 <50 po2 >20
Fetus maintains normal aerobic metabolism until
O2 falls to 50% of normal
What happens with acute hypoxemia
PRIMARY
Maintain BF and O2 in major organs with increased CO and HR
Then FHR slows decreasing o2 consumption
SECONDARY
O2 uptake by fetal hgb becomes less efficient as pH decreases- go to anaerobic metabolism
Will lead to fetal asphyxia
Chronic hypoxia is d/t
Chronic decreased UPP
- pre eclampsia
Maternal hypertension
Maternal DM
What happens to the fetus with chonic hypoxia
IUGR and delay in neural development
What leads to hypoxic ischemic encephalopathy
Surviving severe asphyxia
- adaptive mechanisms fail
- arterial O2 falls
- myocardial depression
- loss of autoregulation with CBF
FHR tracing methods
Continuous electronic
Intermittent ausculation
Which FHR tracing method is required for neuraxial
Continuous electronic
Indicators of overall well being
Short and long term variability
Accelerations
Short term variability represents a
Normal functioning autonomic system and reassuring for fetal o2
Decrease of long term variability is d/t
Fetal sleep, drug effects (opioids, mag, atropine), fetal hypoxia
Onset to nadir is >30
Onset to nadir is < 30 seconds
Late decelerations
Prolonged and variable
Stat C/S indicated with
Prolonged & late variability without variability
Sustained brady <70bpm
Neonatal resuscitation med doses
Epi
Naloxone
Crystalloid
Crystalloid 10ml/kg over 5-10 min
Epi 0.01. To 0.03 mg
Nalaxone 0.1 mg/kg
Part A of neonatal resuscitation
Term gestation?
Amniotic fluid clear?
Breathing crying?
Good muscle tone?
Provide warmth
Position clear airway
Dry stimulate resposition
Apneic or HR <100 for neonatal?
PPV
HR < 60
Provide PPV, chest compressions
And if still HR < 60 give epi and IVF
