Obstetrics Simplified - Diaa
Relief of Pain in Labour
- During first stage: pain arises from the uterus, cervix and upper
vagina passes through the Frankenhäuser’s ganglion to the hypogastric
and then the pre-aortic plexuses to enter the spinal cord at T10-12
and L1. The pain is due to increased intrauterine pressure with each
contraction to 25 mmHg or more and due to cervical dilatation. The highest
degree of pain felt during the transitional period between the first
and second stage.
- During second stage: pain arises from the vagina and perineum is
transmitted through the pudendal nerves to enter the spinal cord at
These are safe for the mother and foetus but it needs long time to be
effective and of varying degrees.
- Breathing and relaxation exercises: increases the oxygen supply
to the contracting myometium so ischaemia is reduced and pain is minimised.
- Diazepam: 5-10 mg IM / 4 hours during the first stage. Complications:
it may cause neonatal hypothermia, hypotonia and respiratory depression.
- Promazine HCL (Sparine): 50 mg IM potentiate the analgesic effect
of pethidine and has a good antiemetic action.
- Narcotic analgesics: given during the active phase of cervical dilatation
and postpartum after caesarean section.
- Pethidine: 50-150 mg IM. Maximum analgesic effect is achieved
after 45 minutes and lasts for 3-4 hours. It has sedative, analgesic
and antispasmodic effect. It should not be given 2 hours before
delivery to avoid foetal respiratory depression.
- Morphine. 10-15 mg IM. It has more potent analgesic effect but
more depression to the foetal respiratory centre so it should not
be given 4 hours before delivery.
- The antidote of narcotic analgesics is Naloxone 5 mg/ kg body
weight into the umbilical vein.
- Inhalational analgesics:
- Inhaled during contractions by the mother herself so when she
becomes drowsy her hand catching the inhaled analgesic falls away
and she recovers immediately.
- Nitrous oxide (50%) + Oxygen (50%) (Entonox).
- Trichloroethylene (Trilene 0.5% in air): inhaled through Cyprane
- Methoxyflurane (Penthrane 0.35% in air): inhaled through Cardiff
- General anaesthesia:
- Injectable agents:
- Thiopentone (Intraval 0.5-1 gm): IV induces short acting
general anaesthesia suitable for instrumental vaginal delivery
and repair of episiotomy or perineal tear.
- Ketamine (Ketalar): 2 mg/kg body weight IV. Its action lasts
5-10 minutes, indicated as thiopentone. Hallucination and unpleasant
dreams may occur.
- Inhalation agent:
- Nitrous oxide (80%) + Oxygen (20%):
- It is of benefit in shocked patient as it does not lower
the blood pressure but it is inflammable.
- Halothane (Fluothane 0.5%):
- It produces muscle relaxation suitable for intrauterine
manipulations as internal podalic version but it may lead
to atonic postpartum haemorrhage.
- Regional and Local Anaesthesia:
- Epidural block:
- Relief of pain in the first stage.
- Extension of analgesia to the lower birth canal during
the second stage .
- Caesarean section.
- Lumbar block:
- Using the Tuohy needle with catheter the lignocaine
(Xylocaine) 1% or bupivacaine (Marcaine) 0.5% is injected
into the extradural space between L3 and L4 vertebrae.
- Sacral (caudal) block:
- The anaesthetic agent is injected through the sacral
hiatus. It abolishes the perineal reflex leading to prolonged
second stage and hence increased incidence of instrumental
- Spinal block:
- Lignocaine 1% or bupivacaine 0.5% is injected into the subarachnoid
- It is useful for vaginal operative procedures and caesarean
section but never as a long term analgesia during labour.
- Advantage over epidural anaesthesia is that procedure is
easier and blockade can be rapidly achieved with a smaller dose
of local anaesthetic.
- Paracervical block:
- Lignocaine 1% is injected into the paracervical tissues
through the lateral vaginal fornices.
- Its action lasts for about 2 hours.
- It is effective in relieving pain during the first stage
of labour but foetal bradycardia is a common complication.
- Pudendal nerve block:
- 10 ml of lignocaine 1% is injected in the region of the
ischial spine on each side either from inside through the vaginal
mucosa or from outside through the perineal skin with a guiding
finger in the vagina in both procedures.
- It may be supplemented by local infiltration anaesthesia
into the fourchette, perineum and adjacent vagina.
- It is safe, simple and can be used for spontaneous and instrumental
delivery and repair of episiotomy.
- Local (perineal) infiltration anaesthesia:
- 10 ml of lignocaine 1% is injected into the episiotomy line
including the lower vagina, fourchette, perineal muscles and
- It is suitable for episiotomy incision and repair as well
as repair of perineal lacerations by injection around it.
- It is the safest and simplest technique but time should
be allowed to establish analgesia.
Complications of General Anaesthesia
- Depression of the respiratory centre and asphyxia.
- Uterine atony leading to postpartum haemorrhage.
- Respiratory complications:
- Pulmonary collapse.
- Mendelson’s syndrome:
- It is inhalation of the acidic gastric juice during anaesthesia.
- Manifestations may appear immediately or after 1-3 hours in
the form of:
- initial bronchospasm,
- systemic hypotension,
- pulmonary hypertension,
- death supervenes within very short time.
- The patient should be fasting at least 6 hours before anaesthesia.
- Preoperative oral antacids e.g. magnesium trisilicate 15 ml / 3hours.
- Preoperative histamine-2 antagonist e.g. cimetidine or raniditine
- During induction: occlude the oesophagus by cricoid pressure and
guard the trachea by cuffed endotracheal tube.
- During recovery: remove the tube in lateral position with the head
lower down and only when the patient is conscious.
- Endotracheal intubation.
- Upper airway aspiration.
- Oxygen under positive pressure.
- Hydrocortisone 200 mg IV to minimise the inflammatory reaction.
- Tracheostomy may be considered in severe cases.
Complications of Epidural Anaesthesia
- Hypotension: because block of the sympathetic nerve supply to the
lower part of the body leads to peripheral vasodilatation.
- Accidental dural puncture: There is a 50% possibility of a low pressure
headache which lasts for few days from leakage of cerebrospinal fluid
into the epidural space.
- Ringer - lactate solution infused into the epidural space.
- Bed rest for 4 days.
- Blood patch: if the previous methods failed, 10-20 ml from
patient’s own blood is injected into her epidural space.
- Subarachnoid injection: The usual dose needed for spinal (subarachnoid)
block is far less than that required for epidural block so if accidentally
injected into the subarachnoid space it may result in paralysis of the
- Endotracheal intubation + oxygen.
- Rapid fluid infusion to combat hypotension.
- Ephedrine hydrochloride 5-10 mg for hypotension.
- Artificial ventilation is continued with nitrous oxide 50%
+ oxygen 50%.
- Increased incidence of forceps delivery: as the maternal perineal
reflex and urge to push is blocked leading to prolonged second stage.
- Neurological complications:
- Patches of numbness on the outer side of the thighs or legs
for few days.
- Fracture of the catheter:
- Fragments are left in situ as it causes no problems.
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Edited by Aldo Campana,