Anaesthesia in OBG

Advantages of Regional Anaesthesia

Lower maternal mortality
Patient awareness
Post operative analgesia
Reduced incidence of DVT
Less neonatal depression
Reduced blood loss
Quicker return of GI function
Improved maternal bonding
Mother can participate in birth

Contraindications

Maternal refusal
Coagulopathy
Infection at injection site
uncorrected hypovolaemia
Raised ICP
Maternal haemorrhage and instability

0.5% Bupivacaie 2.2-2.5ml with Fentanyl 10-20mcg- post op analgesia plus reduce need for local anaesthesia
Co-load with 500ml of fluids or colloids to reduce hypotension after induction.
Treat hypo with phenylephrine


Advantages epidural over spinal anaesthesia

Ability to titrate the level of the block
Reduces the risk of profound and sudden hypotension
Unlimited duration of action if the catheter is used postoperatively for analgesia
Good for pre-eclamptic

Disadvantage of epidural

Inadvertent IV or subarachnoid injection
Increased time to surgical anaesthesia
Increased risk of post dural puncture headache if the dura breached and
Failed block/ inadequate block
Not all sensations will be blocked, especially during delivery of the baby. Can feel touch and movement but not pain


First test for light touch and then cold.
Sympathetic block is 2 segments higher than sensory block

Block from T4 (peritoneum) to T12
Advantages of combined spinal epidural

Rapid onset
All advantages of epidural



Regional Anaesthesia

Baseline maternal tachycardia indicates relative hypovolaemia and impending hypotenison
Give prophylactiv phenylephrine 100mcg per minute
Treat bradycardia with atropine
Dyspnoea and ineffective cough if extends to thoracic segments000 oxygenation with fae mask
Must check upper limb power to exclude possibility of an impending total spinal.
Itch- neuraxial opioid
Shivering- 20-25mg Pethidine or 25-50mcg Clonidine IV


Complications

Total spinal block
IV injection of LA
Headache
Obstetric palsy-- obturator nerve, femoral nerve and common peroneal nerve
Spinal or epidural abscess- permanent paralysis

Safest time for surgery
 Early to mid 2nd trimester
- lower risk of preterm
- uterus still small


24-34 weeks- corticosteroids

15 degrees left lateral tilt to prevent aortocaval compression

Induction of labour reduces variability
Vasoactive and chronotropic modifying agets cross the placenta and can produce changes in fetal heart rate in accordance with their vasoactive effect


Progesterone supplementation is recommeded when the corpus luteum is removed prior to 7-9 weeks of gestation
Progesterone 50-100mg vaginal suppositivery every 8-12 hours or a daily IM injection of 1mL (50mg) progesterone in oil


Problems with general anaesthesia

• Failed intubation- significant upper airway edema and vascular engorgement in pregnancy 

• Aspiration of gastric contents- difficult intubation, lower esophageal sphincter tone, labour pain and opiates delay gastric emptying. Prophylaxis: abstain from solid food for at least 6 hours prior to surgery, 8 hours for fried or fatty foods, clear liquids 2hours. Antacid, histamine receptor blocker and metoclopramide. Sodium citrate keeps pH >3.0 for 30 minutes. Cricoid pressure application at the time of rapid sequence induction of endotracheal intubation prevents aspiration of gastric contents until the airway has ben protected with a cuffed endotracheal tube

• Hypoxia- vasodilation due to decreased sympathetic tone during endotracheal itubation and direct cardiodepressant effect of inhalational anaesthetic agents-- hypotension--- decreased uterine blood flow. Controlled hypotension is dangerous for the fetus and should be avoided.
• Anaesthetic drug:
• Propofol
• THiopental- decrease dose
• Halothane, Isoflurane and enflurane- tocolytic effect, decreases uterine tone and inhibit labour during the procedure
• Inhaled NOx- no effect on uterine tone, maternal haemodynamic status nor fetal heart rate variability
• mechanical ventilation effect
• High progesterone in pregancy- respiratory alkalosis with an average pH of 7.44
• PaCO2 of 32mmHg
• HCO3 of 20mmHg
• SInce fetal and maternal PaCO2 correlate, maternal respiratory acidosis may lead to myocardial depression, hypotension and clinically significant vasoconstriction which csn compromise fetal oxygenation