Obstetrics for Anaesthestists

Miss Julia Montgomery 15th September 2009

Overview

• Fetal monitoring - CTGs and Fetal Blood Sampling • Placenta praevia / accreta • Abruptio placentae • Uterine atony • Ruptured uterus • Vasa Praevia

Cardiotocograph CTG

• Continuous print out of fetal heart rate and contractions • Abdominal ultrasound • detects cardiac movements and hence heart rate • FSE (clip applied to the fetal scalp) • detects the R-R wave of the fetal ECG • STAN (PR interval)

Normal heart rate Baseline variability Accelerations Decelerations

Features of a CTG

110-160 bpm >5 bpm Reduced variability - hypoxia/fetal anaemia >15 bpm lasting 15s early late variable Occur with contractions Nadir of the deceleration occurs well after the peak of the contraction No relationship with contractions vary in shape as well

Significance of Decelerations

early late variable Normal vagal response Intracranial pressure increases with contractions either head compression or cord compression Suggestive of fetal hypoxia May mean cord compression - acc before and after the deceleration may indicate that the fetus is coping well May indicate hypoxia

Meconium stained liquor

Present in 15% of term labours Present in 40% of labours at 42 weeks Mechanism: •vagal stimulation causing gut contraction & anal sphincter relaxation •Maybe associated with hypoxia •If CTG normal ignore (let paediatrician know)

Fetal Blood Sampling

• Why?

– CTG is highly sensitive eg if normal, baby OK – But poorly specific eg if abnormal only a few babies are hypoxia • Use of CTG only leads to a 4 fold increase in Caesareans Sections for fetal distress • Need to check the CTG findings with FBS

Fetal Blood Sampling

• Tiny stab on the fetal scalp • Blood collected via a glass pipette • pH and base excess result • Contraindications – Infection such as HIV, Hepatitis B & Group B streptococci – Fetal bleeding disorder – Prematurity less than 32 weeks

Fetal Blood sampling

pH reflects the status of the baby at that moment of time Base excess reflects a change over a longer period of time pH > 7.25

pH 7.20-7.25

pH <7.20

<-6 mEq/L normal borderline abnormal -6.1-7.9 mEq/L >-8mEq/L No action Repeat in 30 mins Deliver baby normal borderline

Case 1

Case 9

Case 5

Case 8

Fetal bradycardia

• Turn off syntocinon • VE to exclude cord compression and assess cervical dilation • Turn on left • Fluid bolus • More than 3 minutes then immediate delivery • Can re-assess in theatre if fetal heart recovers

Prevalence of Placenta Previa

• Occurs in 1/200 pregnancies that reach 3 rd trimester • Placenta located in the lower segment of the uterus (ie after 24 weeks) • Low-lying placenta seen in 50% of ultrasound scans at 16 20 weeks – 90% will have normal implantation when scan repeated at >30 weeks – Repeat scan at 36 weeks

Risk Factors for Placenta Praevia

• Previous caesarean delivery • Previous uterine instrumentation/surgery • High parity • Advanced maternal age • Smoking • Multiple gestation

Morbidity with Placenta Praevia

• Maternal haemorrhage – Delivery of baby through placenta – Failure of contraction of placental bed – Excessive uterine bleeding – DIC • Operative delivery complications • Transfusion • Prematurity (bleeding in early pregnancy) • Placenta accreta, increta, or percreta

Placental Implantation

Abruptio placentae

Epidemiology of Abruption • Occurs in 1-2% of pregnancies • Risk factors – Hypertensive diseases of pregnancy – Smoking or substance abuse (e.g. cocaine) – Trauma – Over distention of the uterus (twins/polyhydramnios) – History of previous abruption – Unexplained elevation of MSAFP – Placental insufficiency – Maternal thrombophilia/metabolic abnormalities

Bleeding from Abruption

• Externalized hemorrhage • Bloody amniotic fluid • Retroplacental clot – 20% occult – “uteroplacental apoplexy” or “Couvelaire” uterus • Look for consumptive coagulopathy

Patient History - Abruption

• Pain = hallmark symptom painful bleeding – Varies from mild cramping to severe pain – Back pain – think posterior abruption • Bleeding – May not reflect amount of blood loss – Differentiate from exuberant bloody show • Trauma (RTA) • Other risk factors (e.g. hypertension)

Physical Exam - Abruption • Signs of circulatory instability – Mild tachycardia normal – Signs and symptoms of shock • Maternal abdomen – Tender uterus – Continuous pain – Hard uterus – “woody feel” – Fetal death/abnormal CTG

Abruption & DIC

• 20% of abruptions will have DIC • Release of Fibrin Split Products causing uterine atony & bleeding • Release of thromboplastin causing fibrinogen conversion to fibrin (in all organs) • • • Stimulation of extrinsic pathway (fall in Factors 1,11,V, V11 and platelets) • Also secondary fibrinolysis by plasminogen   PT, PTT and FDPs fibrinogen and platelets

Abruptio treatment

• Cyroprecipate (more fibrinogen than FFP) • FFP • Packed RBCs • ? platelets • ? Factor V11a • Uterine atony: – Syntocinon (50iu in 500mls), ergometrine, – Misprostol ( PG1 1000 ug pr) or haemobate (PGF2alpha) 250ug im every 15mins max dose 2gm)

Uterine Atony

• Drugs • Aortic compression • Balloon tamponade • B-Lynch suture • Ligation of uterine arteries (not v helpful) • Ligation of internal iliacs • Embolisation of internal iliacs • Hysterectomy

B-Lynch Brace suture

Epidemiology of Uterine Rupture

• Occult dehiscence vs. symptomatic rupture • 0.03 – 0.08% of all women • 0.3 – 2.5% of women with uterine scar • Previous caesarean incision most common reason for scar disruption (any uterine incision) • Previous uterine curettage or perforation, • Oxytocin usage • Use of prostaglandin pessary • Trauma

Morbidity with Uterine Rupture

• Maternal – Hemorrhage – Bladder rupture – Hysterectomy – Maternal death • Fetal – Respiratory distress – Hypoxia – Acidaemia – Neonatal death

Uterine Rupture

• Sudden deterioration of FHR pattern is most frequent finding • Vaginal bleeding • Constant lower abdominal pain • Treatment – emergency caesarean delivery – can repair scar – maybe hysterectomy

Vasa Praevia

• Rarest cause of haemorrhage • Onset with membrane rupture • Blood loss is fetal, with 50% mortality • Seen with placenta praevia, velamentous insertion of the cord or succenturiate lobe • Antepartum diagnosis – Color doppler ultrasound

Diagnostic Tests – Vasa Praevia

• Apt test – based on colorimetric response of fetal hemoglobin (HbF) to alkali • Wright stain of vaginal blood – for nucleated RBCs • Kleihauer-Betke test – response to acid – can quantify amount of fetal blood in maternal circulation – used to determine fetal-maternal haemorrhage – used to quantify amount of Anti-D to be given

Management – Vasa Praevia

• Immediate caesarean delivery if fetal heart rate is non-reassuring • Administer normal saline ? Maternal blood 10 – 20 cc/kg bolus to newborn, if found to be in shock after delivery