Pain relief in labour

Question 1

Physiology of Pain in Labor

Answer 1

 1st stage of labor – mostly visceral
 Dilation of the cervix and distention of the lower uterine segment
 Dull, aching and poorly localized
 Slow conducting, visceral C fibers, enter spinal cord at T10 to L1
 Sensory fibres are T10 to L1 for both body and cervix. T11 and 12 are
stimulated during latent phase when pain is not severe,T10-L1 are stimulated
during active phase
 Pain during first stage is visceral and is therefore mediated by the T10 through
L1 segments of the spine, whereas during the later part of the first stage and
throughout the second stage and additional somatic component is present
mediated by the S1 through S4 segments of the spine.
 2nd stage of labor – mostly somatic
 Distention of the pelvic floor, vagina and perineum
 Sharp, severe and well localized
 Rapidly conducting A-delta fibers, enter spinal cord at S2 to S4

Question 2

Causes of pain in labour

Answer 2

 Dilation of the cervix and distention of the lower uterine segment
 Uterine contraction and distension cause ischaemia leading to accumulation of
pain-producing substances e.g., lactic acid, adenosine from ATP break down
 Distension of vagina and perineum
 Pressure on organs (e.g. bladder and rectum) or the lumbosacral plexus ; spasm in
skeletal muscles

Question 3

Pharmacological Types of Analgesia

Answer 3

a) Systemic narcotics
 Opiates, such as pethidine and diamorphine, fentanyl
b) Inhalation analgesia
Nitrous oxide (NO) in the form of Entonox
c) Regional analgesia
1. Epidural Analgesia
2. Spinal anaesthesia
3. Combined spinal–epidural (CSE) analgesia
d) Local infiltration
 Perineal Infiltration
 Paracervical block
 Pudendal nerve block

Question 3

Non Pharmacological Types of Analgesia

Answer 3

a) Relaxation and breathing exercises
b) Psychoanalgesic techniques
c) Under water delivery
d) Homeopathy
e) Acupuncture- alleviates labour pain and reduces use of both epidural analgesia and parenteral opioids
f) Hypnosis
g) Relaxation techniques
 Patterned breathing
 Attention focusing (imaginary)
 Movement and positioning
 Touch and massage
 Water therapy
h) Transcutaneous electrical nerve stimulation

Question 3

what constitutes the Ideal labour analgesic technique

Answer 3

 Is safe for both the mother and the infant
 Does not interfere with the progress of labor and delivery
 Is flexibility to changing conditions
 Provides consistent pain relief
 Has a long duration of action
 Minimizes undesirable side effects
 Minimizes ongoing demands on the anesthesia provider’s time

Question 4

Transcutaneous electrical nerve stimulation (TENS

Answer 4

works on the principle of blocking pain fibers in the
posterior ganglia of spinal cord by stimulation of small afferent fibers (‘gate’ theory).
 TENS is the use of electric current to stimulate nerves for therapeutic purposes
 Reduces pain by stimulating large myelinated nerve fibers to reduce input from small myelinated and non
myelinated fibers linked to peripheral pain receptors
 Low-intensity continous stimulation is applied to the dermatomes associated with pain
 It can provide good to moderate pain relief but success depends on time spent teaching
and supporting the mother before and during use

Question 5

Pethidine rationale

Answer 5

Pethidine (Aka Miperidine or Demerol) in combination with a phenothiazine (e.g Promethazine)
 Has a half-life of about 5 hours
 Mode of action: Attaches to specific opiod receptors located in the spine and supraspinal sites in
CNS. Opens Ca channels thus blocking transmission by neurons
 Dose: 50-100mg IM with Promethazine 25mg

Question 6

pethidine Side effect

Answer 6

 Nausea and vomiting (they should always been given with an anti-emetic);
 Maternal drowsiness and sedation;
 Delayed gastric emptying (increasing the risks of General anaesthesia if subsequently required);
 Short-term respiratory depression of the baby;
 Possible interference with breastfeeding
 May produce maternal and fetal tachycardia and can rarely cause oculogyric crisis ((refers to
spasms of extraocular muscles leading to tonic eye deviation (usually upward), with each spasm
lasting from seconds to several hours)

Question 7

how to treat respiratory depression due to opiod

Answer 7

 Ventilation
 Oxygenation
 Gentle stimulation
 Naloxone- Pure competitive antagonist at the opiod receptors
 Dose: 0.1-0.2mg /kg/dose or 0.25-0.5mls/kg of 0.4mg/ml given IV, SC or intraracheal

Question 7

Fentanyl rationale

Answer 7

Fentanyl- also called Fentanil
* Short acting and potent apioid analgesic
. Analgesia lasts 30-60 Minutes
* Mode of action is similar to pethidine.
* Dose: 50 microgrammes IM
 Provide sedation and a sense of euphoria
 Analgesic effect in labour is limited
 Primary mechanism of action is sedation

Question 8

Advantages of opiods

Answer 8

1. Ease of administration
2. Reasonably rapid analgesia
3. Antagonists available
4. Low incidence of serious side-effects

Question 9

 Disadvantages of opiods

Answer 9

1. Inadquate analgesia in up to 40% of patients
2. Nausea and vomitting common
3. Psychic disturbance common e.g confusion, inability to cooperate
4. Delayed gastric emptying
5. Neonatal respiratory depression

Question 10

Contraindications of opioid usage

Answer 10

1. Previuos idiosyncratic reactions
2. Current monoamine oxidase inhibitors

Question 11

Inhalation analgesia rationale

Answer 11

Nitrous oxide (NO) in the form of Entonox (an equal mixture of NO- 50% & O2 -50%)
 Nitrous oxide is administered in subanaesthetic concentrations
 Has a quick onset, a short duration of effect (1-2hrs), & is more effective than pethidine.
 Analgesia without loss of consciousness
 It may cause light-headedness and nausea.
 Not suitable for prolonged use from early labour because hyperventilation may result in hypocapnoea,
dizziness and ultimately tetany and fetal hypoxia.
 Most beneficial in late 1st stage of labour
 Crosses the placenta but is eliminated efficiently, no neonatal effects
 No effects on uterine contractions

Question 12

Epidural Analgesia rationale

Answer 12

 Epidural block is the most effective and least depressant (pharmacologic
option) allowing for an alert, participating mother.)
 Primary indication is the patient’s desire for pain relief
 Not ideal in early labour as epidural will limit mobility

Question 13

epidural Indications during labor

Answer 13

1. Prolonged labour,
2. Maternal hypertensive disorders,
3. Multiple gestation,
4. Certain maternal medical conditions- CVS and respiratory disease
5. A high risk of operative intervention- Instrumental delivery

Question 14

 Contraindications of epidural

Answer 14

 Contraindications of epidural
1. Coagulopathy
2. Sepsis at the site of needle placement
3. Patient’s refusal or inability to cooperate
4. Thrombocytopenia
5. Uncorrected maternal Hypovolemia
6. Increased intracranial pressure secondary to a mass lesion
7. Recent anticoagulant therapy
8. Lack of experienced personnel
9. Bony abnormalities of spinal column
10. Idiosyncratic reactions to local anaesthetic agents

Question 15

 Choice of epidural local anaesthetic

Answer 15

1. Lignocaine- rapid onset, dense motor block, risk of cumulative toxicity
   with repeated doses
2. Bupivacaine- good sensory block with minimal motor effect
    No adverse effect on labour with 0.0625% concentration
    Highly protein bound, fetal blood concentrations are lower than with other local anaesthetics

Question 16

 Complications of regional analgesia

Answer 16

1. spinal headache
2. Accidental dural puncture during- This results in a ‘spinal headache
3. Accidental total spinal anaesthesia
4. Tend to prolong 2nd stage of labour and there is a greater chance of instrumental delivery,
5. Drug toxicity- with accidental placement of a catheter within a blood vessel
6. Bladder dysfunction- if the bladder is allowed to overfill esp. after delivery
7. Backache during and after pregnancy
8. Hypotension
9. Short-term neonatal respiratory depression- epidural solutions may contain opioids
10. Motor paralysis-reduces maternal expulsive effort
11. Prolongation of second stage of labour
12. Toxic reactions to local anaesthetic agents

Question 17

Spinal anaesthesia indications

Answer 17

Used as the anaesthetic for;
a) Caesarean sections,
b) Trial of instrumental deliveries (in theatre),
c) Manual removal of retained placentae
d) Repair of difficult perineal and vaginal tears.
 Spinals are not used for routine analgesia in labour

Question 18

3. Combined spinal–epidural (CSE) analgesia rationale

Answer 18

 Produce a rapid onset of pain relief and provide long lasting analgesia.
 Because the initiating spinal dose is relatively low, and so is a viable option for pain relief in labour.

Question 19

Perineal Infiltration rationale

Answer 19

 Direct infiltration of 1% lignocaine is used for perineal & lower vaginal lacerations
 Advance the needle and inject and aspirate to avoid intravascular injection
 Dose of lignocaine is 3-4 mg/kg plain sol, and 7-8 mg/kg with added epinephrine
 1% solution = 10 mg/ml
 For 60 kg woman total dose should not exceed 200 mg or 20 ml
 After local infiltration one should wait 3 minutes before proceeding.
 Used in episiotomy, outlet forceps and vantouse traction

Question 20

Paracervical block rationale

Answer 20

 5 to 6 ml of a dilute solution of local anesthetic without epinephrine (e.g., 1% lidocaine) is injected into
the mucosa of the cervix at the 3- and 9- o’clock positions
 Fetal bradycardia that follows in 2 to 70 percent of applications
 Paracervical block should be used cautiously at all times and should not be
used at all in mothers with fetuses in either acute or chronic distress.

Question 21

 Mechanism of post paracervical block fetal bradycardia

Answer 21

 Local anesthetic injected close to the uterine artery passed to the fetus
 Uterine artery vasoconstriction secondary to a direct effect of local anesthetic on the uterine artery
 Local anesthetic injected directly into the uterine musculature increases uterine tone

Question 22

 Pudendal nerve block

Answer 22

 Minor regional block, effective and very safe  Using 20-gauge needle, inject 5 to 10 ml of local anesthetic below ischial spine- use 1% lidocaine  Satisfactory for all spontaneous vaginal deliveries and episiotomies, and for some outlet or low operative vaginal deliveries  Potential for local anesthetic toxicity is higher with pudendal block compared with perineal infiltration because of large vessels proximal to injection site  Aspiration before injection is particularly important  Used for forceps delivery & vaginal breech delivery. Does not block pain of labour