PB#116: Management of Intrapartum Fetal Heart Rate Tracings Flashcards
Definition of FHR baseline
Mean FHR rounded to increments of 5 bpm over 10 min segment, excluding periodic/episodic changes, periods of marked variability, and/or segments of baseline that differ by >25 bpm
Minimum time requirement for FHT to be considered a baseline
2 mins in any 10 min segment, or else baseline for that period is indeterminate (in which case one may refer to prior 10 min window for determining baseline)
Normal baseline
110-160 bpm
Fetal tachycardia
> 160 bpm
Fetal bradycardia
<110 bpm
Definition of FHR variability
Fluctuations in baseline FHR that are irregular in amplitude and frequency, visually quantitated as amplitude of peak-to-trough in bpm
Absent variability
Undetectable amplitude range
Minimal variability
Amplitude range detectable but <5 bpm
Moderate variability
Amplitude range 6-25 bpm
Marked variability
Amplitude range >25 bpm
Definition of accels
Visually apparent abrupt increase (onset to peak <30 secs) in FHR
Criteria for accels at 32+wga; criteria for accels at <32wga
Peak >15 bpm above baseline, w/ duration of >15 secs but <2 mins from onset to return; peak >10 bpm above baseline, w/ duration of >10 secs but <2 mins from onset to return
Definition of prolonged accel
Lasting >2 mins but <10 mins in duration
What is it considered if an accel lasts >10 mins?
Baseline change
Definition of early decels
Visually apparent usually symmetrical gradual decrease and return of FHR associated w/ ctx, wherein onset to nadir is >30 secs, and nadir of decel occurs at same time as ctx peak
Timing of onset/nadir/recovery of early decel as it relates to ctx (in most cases)
Coincident w/ beginning/peak/ending of ctx, respectively
Definition of late decels
Visually apparent usually symmetrical gradual decrease and return of FHR associated w/ ctx, wherein onset to nadir is >30 secs, and nadir of decel occurring after peak of ctx
Timing of onset/nadir/recovery of late decel as it relates to ctx (in most cases)
Occur after beginning/peak/ending of ctx, respectively
Definition of variable decels
Visually apparent abrupt decrease in FHR, wherein onset to nadir is <30 secs, decrease is >15 bpm, and lasts >15 secs but <2 mins in duration
Are onset/depth/duration of variable decels consistent across ctxs?
No, they commonly vary w/ successive ctxs
How is decrease in FHR calculated when evaluating decels?
From onset to nadir
Definition of prolonged decels
Visually apparent decrease in FHR, wherein decrease is >15 bpm, and lasts >2 mins but <10 mins in duration
What is it considered if a decel lasts >10 mins?
Baseline change
Definition of sinusoidal pattern
Visually apparent, smooth, sine wave-like undulating pattern in FHR baseline w/ cycle frequency of 3-5 per min, which persists for >20 mins
Definition of normal contractility
5 or fewer ctxs in 10 mins averaged over 30 min period
Definition of tachysystole
> 5 ctxs in 10 mins averaged over 30 min period
How should tachysystole always be qualified?
In the presence/absence of decels
Criteria for Cat 1 FHTs
Include all of the following: normal baseline, mod variability, absent late/variable decels, present/absent early decels, present/absent accels
General classification, acid-base status prediction, and recommended monitoring for Cat 1 FHTs
Normal, strongly predictive of normal fetal acid-base status at time of obs, can be monitored in routine manner (no specific action required)
How often should FHT be reviewed in a pt w/o complications in first stage of labor, in second stage of labor?
q30mins, q15mins
When is management necessary for FHT that is Cat I?
Only if evolution to Cat II or Cat III
Criteria for Cat 2 FHTs
Brady not accompanied by absent variability; tachy; min variability; absent variability w/o recurrent decels; marked variability; absence of induced accels after fetal stim; recurrent variable decels accompanied by min/mod variability; prolonged decel; recurrent late decels w/ mod variability; variable decels w/ other characteristics (ie slow return to baseline, overshoots, “shoulders”)
General classification, recommended monitoring, potential considerations for Cat 2 FHTs
Indeterminate, require evaluation and continued surveillance/reevaluation, may require ancillary testing of fetal wellbeing and/or intrauterine resuscitative measures
Features of a Cat II FHT that are reassuring and highly predictive of normal fetal acid-base status (2)
Accels (either spontaneous or elicited by scalp/vibroacoustic stim), mod variability
Definition of intermittent variable decels
Variable decels occurring w/ <50% of ctxs
Most common FHT abnormality during labor
Intermittent variable decels
Are intermittent variable decels associated w/ abnormal perinatal outcomes?
Most often not
Definition of recurrent variable decels
Variable decels occurring w/ >50% of ctxs
Feature of recurrent variable decels that is more indicative of impending fetal acidemia
Decels that progress to greater depth and longer duration
FHT features w/ recurrent variable decels that require evaluation (5)
Frequency, depth, duration, ctx pattern, other FHT characteristics (ie variability)
Features of FHT tracings w/ recurrent variable decels that suggest that fetus is not currently acidemic (2)
Mod variability, spontaneous/induced accels
Goal of management of recurrent variable decels
Relieving cord compression
Initial maneuver used in management of recurrent variable decels
Maternal repositioning
Intervention shown to decrease recurrence of variable decels and rate of C/S for suspected fetal distress
Amnioinfusion
Poss FHT manifestations of cord compression (2)
Recurrent variable decels, prolonged decels/brady
Poss interventions to alleviate cord compression (3)
Maternal repositioning, amnioinfusion, elevation of presenting fetal part while preparations are made for C/S (if cord prolapse noted)
What are recurrent late decels thought to reflect?
Transient/Chronic uteroplacental insufficiency
Common causes of uteroplacental insufficiency (3)
Maternal hypotension (ie post-epidural), tachysystole, maternal hypoxia
Management options of recurrent late decels (4)
Maternal lateral positioning, IVF bolus, O2 administration, eval for tachysystole
Poss FHT manifestations of fetal hypoxia and uteroplacental insufficiency (3)
Recurrent late decels, prolonged decels/brady, min/absent variability
General principle of management of Cat II FHT w/ recurrent late decels?
Intrauterine resuscitation and reevaluation to determine whether adequate improvement in fetal status has occurred
What FHT features are suggestive of fetal acidemia (and need for expedited delivery) in setting of recurrent late decels?
Min variability and absent accels despite intrauterine resuscitative measures
When does an FHT w/ recurrent variable decels become Cat III?
If variability becomes absent
Poss underlying causes for fetal tachy (5)
Infection, drugs, maternal medical disorders, OB conditions, fetal tachyarrhythmias
Common infections leading to fetal tachy (3)
IAI, pyelo, other maternal infections
Common drugs leading to fetal tachy (3)
Terb, cocaine, other stimulants
Maternal medical disorder that can lead to fetal tachy
Hyperthyroidism
OB conditions that can manifest as fetal tachy (2)
Abruption, fetal bleeding
Common FHT features of an underlying fetal tachyarrhythmia
FHT >200
Is tachy predictive for fetal hypoxemia/acidemia?
Poorly predictive in isolation (unless accompanied by min/absent variability and/or recurrent decels)
Common causes of prolonged decels/brady (6)
Maternal hypotension (ie post-epidural), cord prolapse/occlusion, rapid fetal descent, tachysystole, abruption, uterine rupture
Rare fetal causeses of brady (2)
Congenital heart abnormalities, myocardial conduction defects (ie those associated w/ maternal collagen vascular disease)
When does onset of brady associated w/ congenital heart block typically begin?
2nd tri (extremely unlikely to have new onset intrapartum brady 2/2 congenital heart block)
When is prompt delivery recommended in setting of brady/prolonged decels?
If brady/prolonged decels do not resolve and/or presence of min/absent variability
Common poss causes of min variability (3)
Meds, fetal sleep cycle, fetal acidemia
Common meds that may cause min variability (2)
Opioids, mag sulfate
When does min variability typically improve to mod variability following opioid administration?
Within 1-2h
Length of most fetal sleep cycles; max length of fetal sleep cycle
20 mins; 60 mins
Management of min variability suspected to be 2/2 decreased fetal oxygenation (3)
Maternal repositioning, supp O2, IVF bolus
Next step if initial resuscitation measures do not improve min variability and there are no accels
Digital scalp/vibroacoustic stim
Poss indication of continued min variability in absence of accels that cannot be explained/resolved w/ resuscitation
Fetal acidemia
When does tachy require eval/tx?
For pts in spontaneous labor w/ associated recurrent decels
General intervention for laboring pts receiving pit w/ tachysystole
Reduction of uterine activity (to minimize risk of evolving fetal hypoxemia/acidemia)
Management of tachysystole in presence of Cat I FHT in setting of IOL/AOL
Decrease in pit
Management of tachysystole in present of Cat II/III FHT (2)
Decrease/stop pit, intrauterine resuscitation
Next step if tachysystole-induced FHT abnormalities do not resolve w/ initial maneuvers
Tocolytic meds (ie terb)
Intervention options for uterine hyperactivity (2)
Discontinuation of pit/cervical ripening agents, administration of tocolytic meds (ie terb)
Criteria for Cat III FHTs
Include either: absent variability + recurrent late decels/recurrent variable decels/brady, or sinusoidal pattern
General classification, acid-base status prediction, and recommended monitoring for Cat III FHTs
Abnormal, associated w/ abnormal fetal acid-base status at time of obs, require prompt evaluation
Fetal risks associated w/ Cat III FHTs (3)
Neonatal encephalopathy, CP, neonatal acidosis
How strong is predictive value of Cat III FHTs for abnormal neurological outcomes?
Poor
How quickly should delivery occur after decision is made for OVD in setting of Cat III FHT?
As expeditiously as feasible
How should one determine mode of delivery in setting of Cat III FHT?
Based on consideration of maternal and fetal risks/benefits
Logistical considerations in preparation for OVD in setting of Cat III FHT (7)
Provision of informed consent (verbal or written as feasible), surgical team assembly (including surgeon/scrub tech/anesthesia), assessment of pt transit time/location, confirmation of IV access, review of lab results (ie CBC, T&S) and assessment of need for availability of blood products, assessment of need for preop Foley catheter placement, assembly of personnel for neonatal resuscitation