Electronic Fetal Monitor Flashcards
Category I or Normal FHR
Rules out fetal metabolic acidemia
Fetal Oxygen Pathway: Extrinsic
- Maternal oxygenation
- Uterine blood flow
- Placental exchange
- Umbilical blood flow
Fetal Oxygen Pathway: Intrinsic
- Fetal circulation
- Oxygenation of tissues
- FHR reguation
What is well-oxygenated blood dependent upon?
- Adequate hemoglobin concentration and saturation (O2 carrying capacity)
- Adequate arterial oxygen tension (PaO2) (immediately available O2 for exchange.
What is intervillous space perfusion dependent upon?
Adequate uterine blood flow
What substances are transferred across the placenta by simple diffusion?
O2
CO2
Narcotics
What substances are transferred across the placenta by facilitated diffusion?
Glucose
What substances are transferred across the placenta by active transport?
Amino acids Ca P Fe I
What substances are transferred across the placenta by pinocytosis?
IgG
phospholipids
What substances are transferred across the placenta by bulk flow?
H2O
Electrolytes
What substances are transferred across the placenta by breaks or leaks?
Intact blood cells
What substances are transferred across the placenta by independent movement?
Treponema pallidum
What substances are transferred across the placenta by infection?
Toxoplasma gondii
What uteroplacental perfusion factors may decrease?
- Excessive uterine activity (tachysystole, hypertonus, abruptio placenta)
- Maternal hypotension (supine, analgesia)
- Maternal hypertension
- Placental changes (decreased surface area, edema, degenerative, calcifications, infarcts, infection
- Vasoconstriction (exogenous – most sympathomimetics, except ephedrine)
How does the fetus survive in an environment with a pO2 value equal to adult venous blood (fetal oxygenation)?
- Fetal hemoglobin concentration is higher than the adult - Ave Hct at term 51-56%
- Fetal hemoglobin has increased O2 affinity than adult - oxyhemoglobin dissociation curve
- Fetus has increased CO and HR than the adult resulting in rapid circulation
How does fetal oxygenation compensate with abrupt decrease in pO2 normoxic fetus?
- Redistribution of blood to vital organs
- 2-3x increase to heart, brain, adrenal glands
- decrease to gut, spleen, kidneys, limbs - with severe acidemia
- decrease CO, BP, blood flow to brain and heart
- tissue damage or fetal death
Sympathetic Innervation Action and Effect
Action: Releases norepinephrine and epinephrine
Effect: Increase HR
Parasympathetic innervation Action and Effect
Action: Releases acetylcholine
Effect: Decrease HR and transmits variability
Baroreceptors (peripheral) Action and Effect
Action: Regulate BP
Effect: Decrease FHR, BP, and CO
Fetal chemoreceptors action and effect
Action: Increase PCO2, Decrease PO2, pH
Effect: Bradycardia, hypertension
Does fetal stroke volume fluctuation significantly?
No, CO = HR
FHR and Fetal Sleep-Wake Cycles: State 2F Active REM Sleep
Active body movement: frequent
Associated FHR: Moderate variability, accelerations with FM, Reactive NST
FHR and Fetal Sleep-Wake Cycles: State 1F Quiet Sleep
Active body movement: Infrequent
Associated FHR: minimal variability, non-reactive NST
What is required for normal fetal acid base status on EFM Category I?
Moderate variability Baseline rate: 110-160 bpm Late or variable decels: absent Early decels: present or absent Accels: present or absent
What is required for normal fetal acid base status on EFM Category III? ( options)
- Absent variability with recurrent late decels, or recurrent variable decels, or bradycardia
- Sinusoidal pattern
What is normal FHR?
110-160 bpm
What is FHR tachycardia?
> 160 bpm
What is FHR bradycardia?
<110 bpm
What is moderate variability
6-25 bpm
What is minimal variability
> 0 and = 5 bpm
What is marked variability (saltatory)?
> 25 bpm
What is the oxygen depletion cascade?
Aerobic metabolism -> hypoxemia -> tissue hypoxia -> anaerobic metabolism -> lactic acid build up -> Metabolic Acidosis
What is prolonged acceleration?
Lasts >/=2 min and <10 min duration
What is the pH that correlates with acceleration of FHR in response to scalp or acoustic stimulation?
pH > 7.19
What are recurrent decels?
Occur >/= 50% of contractions in any 20-min window
What are intermittent decels?
Occur with <50% of contractions in any 20-min window
Describe early deceleration
- Symmetric, gradual, a/w uterine cx, nadir at peak of cx
2. Fetal head compression -> altered cerebral blood flow -> vagal reflex and cardiac slowing
Describe late deceleration
- Symmetric, gradual, nadir after peak of cx
2. Uteroplacental insufficiency results in decreased maternal/fetal O2 transfer
Describe variable deceleration
- abrupt decrease in FHR
2. Umbilical cord compression resulting in baroreceptor stimulation
Describe prolonged deceleration
Decrease in FHR >/= 15 bpm below BL and lasting >/= 2 min but <10 min
What are causes of prolonged decelerations?
- Uterine tachysystole or hypertonus
- Abruptio placenta
- Acute maternal hypotension
- Uterine rupture
- Maternal hypoxia (seizure of respiratory depression)
- Umbilical cord accidents
- Terminal fetal conditions
- Ruptured vasa previa
- Rapid fetal descent
- Vagal stimulation or maternal valsalva
What are causes of fetal tachycardia?
- Maternal or fetal infection (chorio, pyelo)
- Progressive disruption of fetal oxygenation (hypoxia, metabolic acidosis)(e.g. fetal bleeding)
- Fetal anemia
- Maternal hyperthyroidism
- Fetal tachyarrhythmias (sinus tach, SVT)
- Medications/Drugs - Sympathomimetics (terbutaline, ritodrine, albuterol), Parasympatholytic (atropine, phenothiazines), Other (caffeine, theophylline, cocaine, methamphetamine)
What does a sinusoidal FHR pattern look like?
Visually apparent, smooth, sine-wave like undulating pattern
What is sinusoidal heart rate associated with?
- True SHR pattern
- severe fetal anemia (massive FMH, tts, ruptured vasa previa, Rh isoimmunization)
- severe hypoxia/acidosis/asphyxia - Physiologic states/drug-induced
- rhythmic movements of fetal mouth or sucking
- fetal non-REM sleep
- effect of certain drugs particularly narcotics
What in-utero resuscitation can you do for indeterminate and abnormal tracings?
- Maternal position change
- IV fluid bolus of approx 500 mL nonglucose containing solution
- Correct maternal hypotension
- DC Oxytocin; remove cervidil
- Amnioinfusion (1st stage)
- Alteration in maternal pushing efforts (2nd stage)
- Oxygen 10L/min nonrebreather
- Medications (SQ terbutaline; IVP ephedrine)
When should you do repositioning?
- FHR pattern suggests
- decreased fetal oxygenation
- decreased uteroplacental perfusion
- umbilical cord compression - Maternal status suggests hypotension
- Uterine activity is excessive
When should you give an IV fluid bolus?
- FHR pattern suggests
- decreased fetal oxygenation
- decreased uteroplacental perfusion - Maternal status suggests
- hypotension
- dehydration - Uterine activity is excessive
How many half-lives does it take to reach steady state plasma conc of exogenous oxytocin?
3-4 half lives
Where should you start and increase for oxytocin?
Start at 1 mU/min, increase by 1-2 mU/min no more frequently than every 30-60 min based on maternal-fetal response
When do you use amnioinfusion?
- Recurrent variable decelerations during first stage labor that have not resolved with position change
What should you NOT use amnioinfusion for?
Late decels, active pushing phase of labor and meconium
What factors contribute to the fetus being less likely to tolerate continued pushing with recurrent decels?
- Minimal variability
- First stage decels
- Rising FHR baseline into abnormal range
- Infectious process
When should you administer oxygen?
When usual resuscitation measures haven’t resolved indeterminate/abnormal FHR patterns:
- lateral positioning
- discontinuation of oxytocin
- IV fluid bolus of approw 500 mL nonglucose containing solution
- Correction of maternal hypotension
- Amnioinfusion
- Modification of pushing efforts
If the fetus has moderate variability and/or accelerations what has been ruled out?
Hypoxemia (O2 not indicated)
When should you get umbilical cord gases?
- Abnormal FHR tracing
- CS for fetal compromise
- Maternal thyroid disease
- Severe growth restriction
- Low 5-min apgar
- intrapartum fever
- Multifetal gestations
Values for umbilical artery cord gas: Non acidemic
pH >/= 7.10
PCO2 <60
HCO3 >22
BE > - 12
Values for umbilical artery cord gas: Respiratory acidemia
pH <7.10 (decreased)
PCO2 >60 (increased)
HCO3 >22 (normal)
BE >-12 (normal)
Values for umbilical artery cord gas: Metabolic acidemia
pH <7.10 (decreased)
PCO2 <60 (normal)
HCO3 <22 (decreased)
BE = -12 (decreased)
Values for umbilical artery cord gas: Mixed
pH <7.10 (decreased)
PCO2 >60 (increased)
HCO3 <22 (decreased)
BE = -12 (decreased)
When should you consider intrapartum uterine rupture?
- FHR abnormality
- Most common sign (70% cases)
- Recurrent variable, late, prolonged decels -> fetal bradycardia - Continue EFM
- Loss of fetal station
- New intense maternal pain (often masked with epidural)
- vaginal bleeding (not consistent finding)
What is the influence on FHR of narcotics?
Decreased variability.
Decreased accelerations
What is the influence on FHR of butorphanol (stadol)?
Transient sinusoidal (pseudo-sinusoidal)
What is the influence on FHR of cocaine?
Decreased variability
What is the influence on FHR of magnesium sulfate?
Decreased variability
What is the influence on FHR of betamethasone?
Decreased variability
What is the influence on FHR of terbutaline?
Increased baseline FHR
What is the influence on FHR of zidovidine?
No change
Ultrasound transducer (doppler)
- send and receive US waves through the mother’s abdomen when the waves are reflected the frequency slightly changes
Tocodynamometer (TOCO)
Pressure-sensing device on abdomen detects changes in uterine wall shape
Fetal scalp electrode (FSE)
Converts FECG to FHR by measuring consecutive R-to-R wave intervals
Intrauterine pressure catheter (IUPC)
Converts pressure placed on the catheter tip during a contraction into mmHg
What can sustained SVT cause?
Non-immune hydrops
Nonstress test = Reactive
> /= 2 accelerations in 20-minutes with or without perception of FM by woman
Nonstress test = Nonreactive
Lacks sufficient FHR accelerations over 40-minute period; requires further testing.
Biophysical profile: reassuring
- NST reactive
- Fetal breathing movements: >/= 1 episodes of rhythmic fetal breathing >/= 30 sec in 30 min
- Fetal movement: >/= descrete body/limb movements in 30 min
- Fetal tone: >/= active ext/flexion of fetal extremity or hand in 30 min
- Amniotic fluid volume: Pocket of fluid >/= 2 cm in 2 perpendicular places OR single deepest vertical pocket >2cm
Biophysical profile: scoring
- Composite score 8-10 is normal
- Score of 6 is equivocal - decision to re-test within 12-24 hrs or proceed with delivery must be made within context of GA
- SCore of 4 or less is abnormal
What are the acute fetal variables in response to hypoxia?
Loss of fetal breathing movements, loss of FHR accelerations -> decreased fetal movement 0> loss of fetal tone
Contraction stress test: Positive
Recurrent late decelerations even if contx frequency is <3 contx in 10 min