Non stress test gynaecology presentation

Obstetrics

1. Non Stress Test N S T

2. External (indirect) electronic monitoring of FHR Based on ultrasound Doppler principle Unit consists of Transducer – emits ultrasound Sensor – detects shift in frequency of reflected sound Require coupling gel – air conducts ultrasound waves poorly Correct positioning – can differentiate fetal cardiac motion from maternal arterial pulsations Reflected ultra sound signals are analyzed through a micro processor, that compares incoming signals with most recent previous signal – autocorrelation

3. FHR Patterns

4. NICHD – propose standardized definitions for interpretation of FHR pattern during labor. - modified in 2008  adopted by ACOG 30 bpm per vertical cm (Range – 30 to 240bpm) and 3 cm per min chart recorder paper speed

5. Baseline Fetal Heart Activity Rate With an increase in fetal maturation – FHR decreases, continues post natally Decline an average of 24 bpm b/w 16 wk to term Due maturation of parasympathetic (vagal) heart control Avg FHR – result of tonic balance b/w symp and parasymp influences on pacemaker cells – under the control of arterial chemoreceptors[ prolonged hypoxia with rising blood lactate level & severe metabolic acidemia  fall FHR

6. Bradycardia T3 – normal FHR 120 to 160 bpm 100 to 119 bpm in the absence of other changes – not represent fetal compromise 80 to 120 bpm with good variability – reassuring < 80 bpm – non reassuring Causes Congenital heart block Serious fetal compromise – placental abruption/hypoxia/sepsis Maternal hypoglycemia /hypothermia Drugs to mother-pethidine,antihypertensive,mgso4 Severe pyelonephritis

7. Tachycardia Causes Maternal fever Fetal compromise- hypoxia,infection Cardiac arrhythmia Drugs to mother-sympathomimetic[ isoxsuprine,ritodrine ], parasymp inhibiting[atropine] Maternal hypotension Anemia-maternal/fetal

8. Beat to Beat variability Important index of cardio vascular function Regulated by ANS Short term variability – instantaneous change from 1 beat to the next – measure of time interval b/w cardiac systoles – most reliably determined by scalp electrode Long term variability – oscillatory changes during 1min & result in the waviness of the baseline – normal frequency 3 to 5 cycles per min

9. Increased variability – fetal breathing and body movements – advancing gestation Up to 30 wks - similar baseline characteristics in fetal rest and activity After 30 wks – fetal inactivity  diminished variability – fetal activity  enhance Baseline FHR becomes less variable as rate rises Decreased variability – causes Analgesics CNS depressant drugs (transient variation) – Narcotics, barbiturates, phenothiazine's, tranquilizers, general anaesthetics Corticosteroids MgSO4 – without adverse neonatal effects Severe maternal acidemia – DKA  Depression of fetal brainstem or the heart itself creates loss of variability

10. Diminished BBV with fetal compromise – due to acidemia (not hypoxia) A bsent variability – within the normal baseline rate range and without deceleration  previous fetal insult resulted in neurological damage Sinusoidal heart rate Seen in Fetal intracranial hemorrhage Severe fetal asphyxia Severe fetal anemia – anti D alloimmunization , feto maternal hemorrhage, TTTS, fetal parvo viral inf , vasaprevia with bleeding Narcotics – sine frequency of 6 cycles per min Chorioamnionitis Fetal distress Umbilical cord occlusion

11. Features of sinusoidal pattern Stable baseline FHR of 120 to 160 bpm with regular oscillations Amplitude of 5 to 15 bpm Long term variability frequency of 2 to 5 cycles per min Fixed or flat short term variability Oscillations of sinusoidal waveform above or below a baseline Absent acceleration Intrapartum sine wave like baseline variation with periods of acceleration – pseudo sinusoidal Mild – epidural Intermediate – transient episodes of fetal hypoxia caused by umbilical cord compression

12. Periodic FHR changes Accelerations Represent intact neurohormonal cardio vascular control mechanisms linked to fetal behavioral states Always reassuring – no acidemia Seen in Fetal movement Stimulation by uterine contraction Umbilical cord occlusion Fetal stimulation during pelvic examination Scalp blood sampling Acoustic stimulation

13. Early Deceleration Head compression  Dural stimulation  vagal nerve activation  early deceleration Degree of deceleration is proportional to contraction strength Rarely falls below 100 to 110 bpm or 20 to 30 bpm below baseline Common during active labor Not associated with fetal hypoxia or acidemia Late Deceleration Utero placental insufficiency Magnitude is not more than 30 to 40 bpm below baseline (typically 10 to 20 bpm) Seen in Maternal Hypotension – epidural Uterine hyper activity – oxytocin stimulation Chronic placental dysfunction – maternal disease (HTN, DM, collagen vascular disorders) Placental abruption – acute late deceleration

14. Variable Deceleration Cord compression 2 types Type A – seen in complete occlusion Type B – due to differing degrees of partial occlusion – Acceleration before and after – Vein occlusion  reduce fetal blood return  trigger baroreceptor mediated acceleration – With increase in intrauterine pressure  complete cord occlusion  obstruction of umbilical artery flow  fetal systemic HTN  baroreceptor mediated deceleration – vagal response due to chemo/ baro receptor activity Recurrent variable deceleration with minimal to moderate BBV are indeterminate whereas those with absent variability are abnormal

15. Other FHR patterns (associated with umbilical cord compression) Saltatory baseline HR – rapidly recurring couplets of acceleration & deceleration – seen in post term pregnancies Lambda – acceleration followed by a variable deceleration with no acceleration at the end of deceleration – seen in early labor – Result from mild cord compression or stretch Overshoot - variable deceleration followed by acceleration

16. Prolonged deceleration Causes Cervical examination Uterine Hyperactivity Cord Entanglement Maternal Supine Hypotension Epidural / Spinal / Paracervical analgesia Maternal hypo perfusion / Hypoxia from any cause Placental abruption Umbilical cord knots / prolapse Maternal Seizure Application of fetal scalp electrode Impending birth or maternal valsalva maneuver Placenta is effective in resuscitating the fetus if the original insult does not recur immediately Fetus may die during prolonged decelerations

17. Normal NST More than or equal to 2 accelerations peaking at 15 bpm or more above baseline, each lasting 15 secs or more within 20 mins of test Acceleration with or without fetal movements – 40 mins tracing (fetal sleep cycle) Long duration NST – Not move up to 75 mins  reactive within 80 mins/ non reactive for 120 mins (very ill) Absence of acceleration in 80 min recording – uteroplacental pathology IUGR Oligohydramnios Fetal acidemia Meconium Placental infarction Interval b/w testing – 7 days Twice weekly – post term pregnancy , multi fetal gestation , pregest DM, IUGR, GHTN Daily – severe PE Repetitive deceleration – 3 in 20 mins OR accompany more than 50% of contractions in 20 mins  Fetal distress

18. False normal NST – fetal death within 7 days (post term pregnancy) Mean interval b/w testing and death - 4 days (1 to 7 days) Causes of fetal death Intrauterine infection Abnormal cord position Malformation Placental abruption FHR patterns during second stage of labor Decelerations are common due to both cord and fetal head compression If prolonged  still birth and neonatal death If total no. of decelerations < 70 bpm increased, persistent baseline brady / tachy – decreased APGAR

19. 3 tier FHR interpretation system Category 1 – normal Baseline rate – 110 to 160 bpm Baseline FHR variability – moderate Late or variable decelerations- absent Early decelerations – present / absent Accelerations – present / absent Category 2 – Indeterminate Baseline rate Bradycardia not accompanied by absent baseline variability Tachycardia Baseline FHR variability Minimal baseline variability Absent variability not accompanied by recurrent decelerations Marked baseline variability

20. Accelerations Absence of induced accelerations after fetal stimulation Periodic / Episodic decelerations Recurrent variable decelerations with minimal or moderate baseline variability Prolonged deceleration Recurrent late decelerations with moderate baseline variability Variable decelerations with other characteristics – slow return to baseline, overshoot, shoulders Category 3 – Abnormal Include either Absent baseline FHR variability & any of the following Recurrent late decelerations Recurrent variable decelerations Bradycardia Sinusoidal pattern

21. Resuscitative measures for Category II or III Tracings FHR abnormality Interventions Recurrent late decelerations Prolonged decelerations or Brady Minimal/Absent FHR variability Lateral decubitus positioning, administer maternal oxygen, IV fluid bolus, reduce uterine contraction frequency Tachysystole with category II or III tracing Discontinue oxytocin or PG, give tocolytics – MgSO4, Terbutaline Recurrent variable decelerations Prolonged decelerations or brady Reposition mother, amnioinfusion , with cord prolapse – manually elevate the presenting part while preparing for immediate delivery

22. Thank You