1/25 Ch. 14. INTRAPARTUM ASSESSMENT 부산백병원 산부인과 R1 손영실

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Ch. 14.

INTRAPARTUM ASSESSMENT

부산백병원 산부인과부산백병원 산부인과

R1 R1 손영실손영실

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# Intrapartum Fetal Assessment

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INDEX

1. Internal Electronic Fetal Hearth Rate1. Internal Electronic Fetal Hearth Rate

MonitoringMonitoring

2. External (Indirect) Electronic Fetal 2. External (Indirect) Electronic Fetal Heart RateHeart Rate

MonitoringMonitoring

3. Fetal Heart Rate Pattern3. Fetal Heart Rate Pattern

- Baseline Fetal Heart Activity- Baseline Fetal Heart Activity

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◎ ◎ Continuous graph paper of fetal heart rateContinuous graph paper of fetal heart rate - Potentially diagnostic in assessing pathophysiological- Potentially diagnostic in assessing pathophysiological events affecting the fetusevents affecting the fetus

① ① Electronic fetal heart rate monitoring provided accurateElectronic fetal heart rate monitoring provided accurate informationinformation ② ② The information was of value in diagnosing fetalThe information was of value in diagnosing fetal distressdistress ③ ③ It would be possible to intervene to prevent fetal deathIt would be possible to intervene to prevent fetal death or morbidityor morbidity ④ ④ Continuous electronic fetal heart rate monitoring wasContinuous electronic fetal heart rate monitoring was superior to intermittent methodssuperior to intermittent methods

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◎ ◎ Measured by attaching a bipolar spiral electrodeMeasured by attaching a bipolar spiral electrode directly to the fetusdirectly to the fetus - the wire electrode penetrate the fetal scalp and the- the wire electrode penetrate the fetal scalp and the second pole is the metal wing on the electrodesecond pole is the metal wing on the electrode - vaginal body fluids create a saline electrical bridges- vaginal body fluids create a saline electrical bridges that completes the circuits and permits measurementthat completes the circuits and permits measurement of the voltage differences between two polesof the voltage differences between two poles

◎ ◎ The electrical fetal cardiac signal – P wave, QRSThe electrical fetal cardiac signal – P wave, QRS complex, and T wave – is amplified and fed into acomplex, and T wave – is amplified and fed into a cardiotachometer for heart rate calculationcardiotachometer for heart rate calculation

INTERNAL ELECTRONIC FETAL HEART RATE MONITORING

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◎ ◎ Electrical cardiac complexes detected by Electrical cardiac complexes detected by electrodeselectrodes

include those generated by motherinclude those generated by mother - maternal ECG signal is approximately five - maternal ECG signal is approximately five

times strongertimes stronger than fetal ECGthan fetal ECG - but, its amplitude is diminished when it is - but, its amplitude is diminished when it is

recordedrecorded through fetal scalp electrodethrough fetal scalp electrode ① ① In a live fetusIn a live fetus - this low maternal ECG signal is detected but - this low maternal ECG signal is detected but

maskedmasked by the fetal ECGby the fetal ECG ② ② If the fetus is deadIf the fetus is dead - the weaker maternal signal will be amplified - the weaker maternal signal will be amplified

by theby the automatic gain control circuitry in the fetal automatic gain control circuitry in the fetal

monitormonitor and displayed as “fetal” heart rateand displayed as “fetal” heart rate


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Standard fetal monitor tracing of heart rate using fetal scalp electrode shown at top. Bottom two tracings represent cardiac electrical complexes detected from fetal scalp and maternal chest wall electrodes. Spiking of the fetal rate in the monitor tracing is due to the premature atrial contractions. (F=fetus; M=mother; PAC=fetal premature atrial contraction.)

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Placental abruption: The fetal scalp electrode detected heart rate first of the dying fetus. After fetal death, the maternal ECG complex is detected and recorded.

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◎ ◎ External detectors to External detectors to monitormonitor

fetal heart and uterine fetal heart and uterine actionaction

⇒ ⇒ the necessity for the necessity for membranemembrane

rupture and uterine rupture and uterine invasioninvasion

may be avoidedmay be avoided

◎ ◎ FHR (fetal heart rate)FHR (fetal heart rate) ⇒ ⇒ detected through thedetected through the maternal abdominal maternal abdominal

wallwall using the ultrasound using the ultrasound

DopplerDoppler principleprinciple

EXTERNAL (INDIRECT) ELECTRONIC FETAL HEART RATE MONITORING

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◎ ◎ Consist of the unitConsist of the unit ① ① transducer - emits ultrasoundtransducer - emits ultrasound ② ② sensor - detect a shift in frequency of the reflectedsensor - detect a shift in frequency of the reflected soundsound

• • transducertransducer ⇒ ⇒ placed on the maternal abdomen at a site where fetalplaced on the maternal abdomen at a site where fetal heart action is best detectedheart action is best detected • • coupling gel must be appliedcoupling gel must be applied (∵ air conducts ultrasound poorly)(∵ air conducts ultrasound poorly) • • the device is held in position by a beltthe device is held in position by a belt • • care should be taken that maternal aortic ulsations are notcare should be taken that maternal aortic ulsations are not confused with fetal cardiac motionconfused with fetal cardiac motion

EXTERNAL (INDIRECT) ELECTRONIC FETAL HEART RATE MONITORING

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◎ ◎ Scaling factors (by the workshop)Scaling factors (by the workshop) - 30 bpm per vertical cm (range, 30 to 240 bpm)- 30 bpm per vertical cm (range, 30 to 240 bpm) - 3 cm/min chart recorder paper speed- 3 cm/min chart recorder paper speed

# Baseline fetal heart activity# Baseline fetal heart activity 1) Rate1) Rate • • with increasing fetal maturationwith increasing fetal maturation → → the heart rate decreasesthe heart rate decreases • • baseline FHR decreasedbaseline FHR decreased an average of 24 bpm (between 16 weeks and term)an average of 24 bpm (between 16 weeks and term) approximately 1 bpm/weekapproximately 1 bpm/week • • 16 weeks : 160 bpm16 weeks : 160 bpm 40 weeks : 150 bpm40 weeks : 150 bpm

FETAL HEART RATE PATTERNS

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• • during 3rd trimester, normal mean FHR is between 120during 3rd trimester, normal mean FHR is between 120 and 160 bpmand 160 bpm baseline FHR less than 110 bpmbaseline FHR less than 110 bpm ⇒ ⇒ bradycardiabradycardia baseline FHR greater than 160 bpmbaseline FHR greater than 160 bpm ⇒ ⇒ tachycardiatachycardia

sympathetic systemsympathetic system ⇒ ⇒ accelerator influenceaccelerator influence parasympathetic systemparasympathetic system ⇒ ⇒ decelerator factor mediated via vagal slowingdecelerator factor mediated via vagal slowing of heart rateof heart rate


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A. BradycardiaA. Bradycardia

• • mild bradycardiamild bradycardia : 100 ~ 119 bpm: 100 ~ 119 bpm - observed in 2% of monitored pregnancies, averaged- observed in 2% of monitored pregnancies, averaged about 50 minutes in durationabout 50 minutes in duration - attributed to head compression from occiput posterior- attributed to head compression from occiput posterior or transverse positions, particularly during 2nd stageor transverse positions, particularly during 2nd stage laborlabor • • moderate bradycardiamoderate bradycardia : 80 ~ 100 bpm: 80 ~ 100 bpm • • severe bradycardiasevere bradycardia : less than 80 bpm: less than 80 bpm


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• • other causeother cause : congenital heart block and serious fetal: congenital heart block and serious fetal compromisecompromise


Fetal bradycardia measured with a scalp electrode in a pregnancy complicated by placental abruption and subsequent fetal death.

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B. TachycardiaB. Tachycardia

• • mild : 161 ~ 180 bpmmild : 161 ~ 180 bpm severe : 181 bpm or moresevere : 181 bpm or more • • causecause maternal fever from amnionitis (m/c)maternal fever from amnionitis (m/c) fetal compromisefetal compromise cardiac arrhythmiascardiac arrhythmias parasympathetic (atropine) or sympathomimeticparasympathetic (atropine) or sympathomimetic (terbutaline) drugs(terbutaline) drugs • • fetal compromise with tachycardiafetal compromise with tachycardia ⇒ ⇒ concomitant heart rate deceleration (key point)concomitant heart rate deceleration (key point)


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2) Beat-to-beat variability2) Beat-to-beat variability • • an important index of cardiovascular functionan important index of cardiovascular function • • regulated largely by the autonomic nervous systemregulated largely by the autonomic nervous system

A. Short-term variabilityA. Short-term variability • • instantaneous change in FHR from one beat to the nextinstantaneous change in FHR from one beat to the next • • time interval between cardiac systolestime interval between cardiac systoles


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B. Long-term variabilityB. Long-term variability • • the oscillatory changes that occur during the coursethe oscillatory changes that occur during the course

of 1 minuteof 1 minute

- result in waviness of the baseline- result in waviness of the baseline

- normal frequency : 3 ~ 5 cycle/min- normal frequency : 3 ~ 5 cycle/min


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• • physiological and pathological processesphysiological and pathological processes

(affect or interfere with beat-to-beat variability)(affect or interfere with beat-to-beat variability)

① ① fetal breathingfetal breathing

② ② fetal body movementsfetal body movements

③ ③ advancing gestationadvancing gestation

- after 30 wks,- after 30 wks,

fetal inactivityfetal inactivity

→ → diminished variabilitydiminished variability

activityactivity

→ → variability increasedvariability increased


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④ ④ maternal acidemiamaternal acidemia

- cause decreased fetal beat-to-beat variability- cause decreased fetal beat-to-beat variability

⑤ ⑤ analgesic drugs given during laboranalgesic drugs given during labor

- diminished variabilitydiminished variability

(narcotics, barbiturates, phenothiazines,(narcotics, barbiturates, phenothiazines,

tranquilizer)tranquilizer)

- MgSO- MgSO44

: decrease variability only in the third hour of: decrease variability only in the third hour of

the infusionthe infusion

: be deemed clinically insignificant: be deemed clinically insignificant

: blunted the frequency of acceleration: blunted the frequency of acceleration


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Grades of baseline fetal heart rate variability. (1) Undetectable, absent variability; (2) minimal≤5 bpm variability; (3) moderate (normal), 6 to 25 bpm variability; (4) marked, ＞ 25 bpm variability; (5) sinusoidal pattern.

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3) Cardiac arrhythmia3) Cardiac arrhythmia ◎ ◎ first suspected signsfirst suspected signs - baseline bradycardia- baseline bradycardia - tachycardiatachycardia - abrupt baseline spiking (m/c)- abrupt baseline spiking (m/c)


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4) Sinusoidal heart rates4) Sinusoidal heart rates ◎ ◎ true sinusoidal patterntrue sinusoidal pattern - observed with serious fetal anemia- observed with serious fetal anemia • • from D-isoimmunizationfrom D-isoimmunization • • ruptured vasa previaruptured vasa previa • • fetomaternal hemorrhagefetomaternal hemorrhage • • twin to twin transfusiontwin to twin transfusion ◎ ◎ insignificant sinusoidal patterninsignificant sinusoidal pattern • • administration of meperidine, morphine, alphaprodine,administration of meperidine, morphine, alphaprodine, and butorphanoland butorphanol • • amnionitis, fetal distress, and umbilical cordamnionitis, fetal distress, and umbilical cord occlusionocclusion


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◎ ◎ definitiondefinition

① ① stable baseline heart rate of 120 ~ 160 bpm withstable baseline heart rate of 120 ~ 160 bpm with

regular oscillationsregular oscillations

② ② amplitude of 5 ~ 15 bpm (rarely greater)amplitude of 5 ~ 15 bpm (rarely greater)

③ ③ frequency of 2 ~ 5 cycles/min long-term variabilityfrequency of 2 ~ 5 cycles/min long-term variability

④ ④ fixed or flat short-term variabilityfixed or flat short-term variability

⑤ ⑤ oscillation of the sinusoidal waveform above oroscillation of the sinusoidal waveform above or

below a baselinebelow a baseline

⑥ ⑥ absence of accelerationsabsence of accelerations


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◎ ◎ pathophysiology of sinusoidal patterns is unclearpathophysiology of sinusoidal patterns is unclear


Sinusoidal fetal heart rate pattern associated with maternal intravenous meperidine administration. Sine waves are occurring at a rate of 6 cycles/min.

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감사합니다감사합니다 ..

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1/25 Ch. 14. INTRAPARTUM ASSESSMENT 부산백병원 산부인과 R1 손영실