This document provides information on obstetric analgesia techniques for labor pain. It discusses: - The physiology of labor pain and its effects on the mother and fetus. Labor pain stimulates the release of hormones that can affect uterine contraction and fetal oxygen levels. - Various pharmacological and non-pharmacological techniques for pain management, including systemic opioids, inhalational gases, regional nerve blocks, and spinal analgesia using local anesthetics and opioids. - The advantages and disadvantages of different techniques. Neuraxial blocks like epidurals provide the most effective pain relief with few side effects on the mother or fetus, while minimizing depressant effects seen with systemic opioids.

1. OBSTETRIC ANALGESIA
Department of Anaesthesiology & Critical Care
Regional Institute of Medical Sciences, Imphal
Presented by
Dr. Subrat Kumar Nayak
3rd Year Post Graduate Resident
Moderator: Dr. N. Anita Devi

2. Labor pain is one of the most intense pains
that a woman can experience, and it is
typically worse than a pain associated with
a deep laceration.
60% of primiparous women described the
pain of uterine contractions as being
“unbearable, intolerable, extremely severe,
or excruciating.”

3. Comparison of pain scores using the McGill
Pain Questionnaire

5. Physiology of labor Pain
• 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
1st stage
of labor
Mostly
visceral
• 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
2nd stage
of labor
Mostly
somatic

7. Pain Pathways during Labor

8. Site of Origin Cause Pathway Site of Pain
Uterus and cervix Contraction and distension
of uterus and dilatation of
cervix
Afférent T10 – L1
Post. Rami T10 – L1
Upper abdomen to
groin, mid back and
inner upper thighs
(referred pain)
Peri-uterine
tissue (mainly
posterior)
Pressure often associated
with occipito posterior
position and flat sacrum
Lumbo sacral plexus
L5- S1
Mid and lower back
and back of thighs
(referred pain)
Lower birth canal Distension of vagina and
perineum in second stage
Somatic roots S2- S4 Vulva, Vagina and
Perineum
Bladder Over distension Sympathetic T11-L2
Parasympathetic S2-S4
Usually suprapubic
Myometrium and
uterine visceral
peritonium
Abruption
Scar dehiscence
T10-L1 Referred Pain to site
of pathology
Pain in labor – location and neural pathways

9. Obstetric Course
• Neural stimulation through pain pathways results in
the release of substances that either drive (oxytocin)
or brake (epinephrine) uterine activity and cervical
dilation;
• effect of analgesia on the course of labor can vary
between individuals.
Effects of labor pain on mother

10. Cardiac and Respiratory Effects
• The intermittent pain of uterine contractions also
stimulates respiration and results in periods of
intermittent hyperventilation.
• In the absence of supplemental oxygen
administration, compensatory periods of
hypoventilation between contractions result in
transient periods of maternal hypoxemia and, in some
cases, fetal hypoxemia.

11. Psychological Effects
• Small proportion of women can be psychologically
harmed by either providing or withholding
analgesia
• Both individual and environmental influences upon
this meaning.

12. Labor pain affects multiple systems that
determine utero-placental perfusion:
uterine contraction frequency and intensity, by the
effect of pain on the release of oxytocin and
epinephrine;
uterine artery vasoconstriction, by the effect of pain
on the release of norepinephrine and epinephrine;
and
maternal oxyhemoglobin desaturation, which may
result from intermittent hyperventilation followed by
hypoventilation
Effects of labor pain on fetus

13. The ideal labor analgesic technique
is safe for both the mother and the infant
does not interfere with the progress of labor and delivery
provides flexibility in response to changing conditions
provides consistent pain relief
has a long enough duration of action
minimizes undesirable side effects (e.g., motor block)
minimizes ongoing demands on the anesthesia provider’s time

14. Techniques for Labor Analgesia
Non
pharmacological
Psycho
prophylaxis as is
Lamaze, Doula
Transcutaneous
electrical nerve
stimulation TENS
Acupuncture
Hydrotherapy
Pharmacological
Systemic
Inhalational
Regional

15. Non pharmacological techniques
Psycho prophylaxis
• These methods focus on teaching the mother
conditional reflexes to overcome pain and fear of
childbirth.
• Includes human support, breathing techniques,
relaxation techniques and others…
Acupuncture
• Generally two local points and two distal points on the
arms or on the legs are selected.
• Best when started 4 weeks before the expected time
of delivery.
• Needles are placed once a week using the specific
points

16. Hydrotherapy
• Hydrotherapy involve a simple shower or tub bath,
or it include the use of a whirlpool or large tub
specially equipped for pregnant patients.
• Benefits of hydrotherapy includes reduced pain &
anxiety, decreased BP & increased efficiency of
uterine relaxation.
TENS
• Very popular in Europe, easy to apply and frequently
effective.
• 4 electrodes are placed one on either side of the spine
in the lower thoracic region (T 10) and one on either
side of the spine in the sacral area.
• The patient may control level of intensity of stimuli, and
can switch it off.

17. Pharmacological Techniques
Systemic opioids
Inhalational
Regional

18. Systemic Opioids
Advantages
• Easy administration
• Inexpensive
• No needles
• Avoids complications of
regional block
• Does not require skilled
personnel
• Few serious maternal
complications
• Perceived as “natural”
Disadvantages
• Placental transfer
• Inadequate pain relief
• Maternal sedation
• Nausea, vomiting, gastric stasis
• Fetal heart rate effects:Loss of
beat-to-beat variability,
Sinusoidal rhythm
• Dose-related maternal /
neonatal depression
• Newborn neurobehavioral
depression

19. Potential Fetal/Neonatal Effects
Low 1 and 5
min Apgar
scores
Respiratory
acidosis
Naloxone/
ventilatory
assistance may
be needed
Neurobehavioral
depression - dose
dependent
Occasionally,
prolonged
observation in
NICU needed

20. Modalities for systemic opioids
• Dose : 50-100 mg IM or 25-50 mg IV
• onset: 45mins for IM , 5mins for IV
• optimal time: Given early (>4hrs from expected
labor) for IM and within 1 hour from labor for IV
Meperidine
• 50-100µg/hr, peaks @ 3-5minsFentanyl
• ½life 6mins, 0.5microgms/kgRemifentanil
• may also be usedNalbuphine
• Loading dose of 50 – 100 ug
• No background infusion
• Carefully controlled bolus dose (around 10ug) and lockout
periods (10mins) with a 4 hour limit of 300mg
Some centers advocate the use of IV-PCA fentanyl pumps or accufusers
during labor with special considerations including :

21. Dexmedetomidine
Recently , intravenous infusion of
Dexmedetomidine is being used in combination
with remifentanil infusion for labor analgesia.
• Opioid sparing effect
• Adequate level of sedation
• Minimal haemodynamic side effects.
• Very low incidence of nausea and vomiting
Advantages

22. Ketamine
Ketamine has been used in subanesthetic doses (0.5 to
1 mg/kg or 10 mg every 2 to 5 minutes to a total of 1 mg/kg in
30 minutes) during labor.
ketamine in a dose of 25 to 50 mg can be used to supplement
an incomplete neuraxial blockade for cesarean section.
• Its cause hypertension, tachycardia & emergence
reactions.
• High doses (>2 mg/kg) can produce psychomimetic effects
and increased uterine tone, which may cause low Apgar
scores and abnormalities in neonatal muscle tone.
Disadvantages

23. Inhalational Analgesia
Entonox
(50% N20/50% O2)
Advantages:
• Easy to administer (no
needles or PDPH)
• “Satisfactory”
analgesia variable
• Minimal neonatal
depression
Disadvantages:
• Decreased uterine
contractility (except N2O)
• Rapid induction of
anesthesia in pregnancy
• Risk of unconsciousness and
aspiration
• Difficulties with scavenging
in labor rooms

24. Regional blocks

25. Nerve Blocks
First stage
Paracervical
block
Lumbar
sympathetic
block
second stage
Pudendal
nerve block

26. Paracervical Block
Nerve plexus lies lateral & posterior to the junction of uterus & cervix, at the
base of broad ligament.
Patient position: Lithotomy with left uterine displacement
Timing: First stage of labor, before the cervix is dilated 8 cm.
Equipments: 12-14cm 22G needle/ Kobak needle with Iowa trumpet.
Lignocaine without adrenalin is the most preferred drug. Bupivacaine is
NOT recommended for this block.
Onset usually within 5 minute, failure rate between 5-13%

27. Technique: Index & middle finger of right hand introduce the needle into the lateral
fornix for the right side & vice-versa in the left, with lateral diversion, the after aspiration
deposit 10ml LA just beneath the epithelium.
Site of drug deposition: Two 10ml at 3 & 9 o’clock cervical position
3-5ml LA at four sites ( 4,5,7,8 o’clock position)
Six different injections, 3ml each
Contralateral injection should be given after 5 min or two uterine contraction.
Complications include broad ligament hematoma, sciatic nerve block, parametritis,
subgluteal & retropsoal abscess, neuropathy and LAST

28. Lumbar Block
interrupts the transmission of pain impulses from the cervix
and lower uterine segment to the spinal cord.
provides analgesia during the first stage of labor
It provides analgesia comparable to that provided by
paracervical block but with less risk of fetal bradycardia.
Modest hypotension occurs in 5% to 15% of patients..

29. Technique
• Patient in the sitting position
• 10-cm, 22-gauge needle is used to identify the transverse process
on one side of the second lumbar vertebra. The needle is then
withdrawn, redirected, and advanced another 5 cm so that the tip
of the needle is at the anterolateral surface of the vertebral
column, just anterior to the medial attachment of the psoas
muscle.
• Two increments of 5ml LA solution on each side of vertebral
column after careful negative aspiration.

30. Pudendal Block
Pudendal nerve(S2-4) represents the primary source of sensory
innervation for the lower vagina, vulva, and perineum
Effective in relieving second stage labor pain
Technique: Transvaginal (More popular)
Maternal complications are uncommon, but can be Laceration of
the vaginal mucosa, Vaginal and ischiorectal hematoma, Retropsoal
and subgluteal abscess & LAST.
The primary fetal complications result from fetal trauma and/or
direct fetal injection of local anesthetic.

31. Technique: Transvaginal (More popular)
• A needle and needle guide is introduced into the vagina with the
left hand for the left side of the pelvis and with the right hand for
the right side. The needle is introduced through the vaginal
mucosa and sacrospinous ligament, just medial and posterior to
the ischial spine. The pudendal artery lies in close proximity to the
pudendal nerve; thus the one must aspirate before and during
the injection of LA.

32. Local TechniquesParacervicalblock
• Local bilateral
injection near the
cervix
• Given during 1st
stage of labor
• Disadvantage
• fetal bradycardia
• Lidocaine toxicity
PudendalBlock
• Causes perineal
anesthesia
• Useful in 2nd stage
of labor

33. Neuraxial Blocks
Techniques
• Spinal
• Epidural
• Combined
Drugs
•Opioids
•Local anesthetics
•Both
Mode
• Single shot
• Continuous
infusion

34. Neuraxial BlocksAdvantages
Most effective & Least
depressant
Great versatility in strength
& Duration
Reduces maternal
Catecholamines
Improved Uteroplacental
perfusion
Low dose LA – NO Effect on Uterine
activity
Low dose opioids – NO neonatal
depression

35. Neuraxial Blocks
• Uterine
perfusion
maintained
• Doesn’t affect
Apgar scores,
acid-base status
• Neurobehavioral
effects absent
• LA toxicity -
extremely rare
Specific
Fetal
Advantages
• Blunts Haemodynamic
response in :
• Hypertensive
disorders
• Cardiac disease
• Asthma
• Diabetics
• Avoids depressant
effects of opioids in :
• Prolonged labor
• Prematurity
• Multiple gestation
• Breach delivery
Specific
Maternal
Advantages

36. Contraindications to neuraxial blocks
ABSOLUTE
• Patients refusal
• Inability to cooperate
• Increased
intracranial pressure
• Infection at the site
• Frank coagulopathy
• Hypovolemic shock
RELATIVE
• Systemic infection
• Preexisting
neurological
deficiency
• Mild coagulation
abnormalities
• Relative hypovolemia
• Poor communication

37. Spinal Analgesia
Involves intrathecal injection of opiods, Local anesthetics
or more commonly a mixture of both.
Has the benefit of having the most rapid onset of
analgesia.
The most commonly used modality for labor, the “saddle
block” provides profound perineal analgesia with minimal
hemodynamic side effects.

38. Choice Of Local Anesthetic
Rapid onset with
minimal motor
block
Minimal risk of
maternal
toxicity
Negligible effects
on uterine activity
and uteroplacental
perfusion
Limited
uteroplacental
transfer
Long duration of
action

39. Local Anesthetic agents
• Rapid onset
• Dense motor block
• Risk for cumulative toxicity
Lignocaine
• Good sensory block
• Minimal motor block
• No adverse effects on labor
Bupivacaine
(0.0625%)
• Lower toxicity
• Less motor block
• Less potent
Ropivacaine
• Lower toxicity than BupivacaineLevobupivacaine

40. Intrathecal opioids
Inadequate analgesics if used alone
Synergize with local anesthetics
Speed onset of analgesia
Improve quality of analgesia
Permit use of very dilute LA solutions
Help relieve persistent perineal pain and unblocked segments

41. Side effects of Intrathecal opioids
Nausea, Vomiting
Pruritis
Sedation
At very high doses can cause respiratory depression
and fetal bradycardia
• Using the least effective doses
• Mixing opioids with local anesthetics
These side effects can be controlled via

42. Opioids & Lactation
Analgesic Category Milk: plasma ratio Newborn tolerance
Butorphanol 3 1.9 (oral) 0.7
(intramuscular)
No reports of adverse effects
Codeine 3 2.5 Possible accumulation
Fentanyl 3 > 1 Well tolerated
Heroin 3 > 1 Possible addiction
Hydromorphone — No data No data
Meperidine 3 1.4 Prolonged half-life
Methadone 3 0.83 CAUTION: Withdrawal symptoms
possible with abrupt cessation
Morphine 3 0.23–5.07 Possible accumulation
Nalbuphine — No data No data
Oxycodone — 3.4 Periodic sleeplessness; failure to
feed
Oxymorphone — No data No data
Pentazocine — Minimal excretion No data
Propoxyphene 3 0.50 Poor muscle tone reported

43. “The American Academy of Pediatrics Committee
on Drugs lists butorphanol, codeine, fentanyl,
methadone, and morphine as maternally
administered opioids that typically are compatible
with breast-feeding.”-
American Academy of Pediatrics
Committee on Drugs: The transfer of drugs and other chemicals into
human milk. Pediatrics 2001; 108:776-789

44. Choice of Intrathecal opioids
• Both have rapid onset and few side effects.
• Sufentanil is slightly more effective
• No significant fetal drug accumulation
• No serious adverse neonatal effects
Fentanyl &
Sufentanyl

45. Continuous Spinal Analgesia
Used by some centers in Europe,
however it is restricted by FDA
regulations in the US.
Uses 28 or 32-G catheters for 22
or 26-G spinal needles.
Risks include development of
Cauda Equina Syndrome,
hypotension and nerve injury.

46. Epidural AnalgesiaIntermittentBolus
•Analgesia is
reestablished with
bolus injection of 8
to 12 ml of LA/Opioid
solution.
•Pain relief is
constantly
interrupted by
regression of
analgesia.
•The spread and
quality of analgesia
may change with
repeated lumbar
epidural injections.
Continuousinfusion
•Prolonged infusion
might lead to
Significant motor
blockade. Therefore
dose requires
titration.
•Strict monitoring is
required as migration
of catheter into
subarachnoid,
subdural or
intravenous space
are likely to go
unnoticed.
PatientcontrolledEpidural
Analgesia
•May be utilized with or
without an ongoing
background infusion rate.
•A meta-analysis of five studies
reported in the ASA Practice
Guidelines for Obstetric
Anesthesia concluded that a
background infusion provides
better analgesia than pure
PCEA without a background
infusion.
•There is no evidence that the
higher local anesthetic dose
associated with a background
infusion increases motor
blockade or has adverse
effects on obstetric outcome
when low-concentration
infusion solutions are used.
Common Applications

47. Suggested infusion rates for Epidural analgesia
Intermittent bolus injections
• 5 to 10 ml of Bupivacaine (0.125%-0.375%) every 1 to 2 hours
Continuous infusion
• Bupivacaine 0.0625%-0.25%,8 -15 ml/hr
• Ropivacaine: 0.125%-0.25%, 6 -12 ml/hr
• Fentanyl 1-2 µg/ml
• Sufentanyl 0.2-0.5µg/ml
Epidural opioids

48. Ambulatory Neuraxial
Analgesia “Walking epidural”
Applied to any
neuraxial analgesic
technique that allows
safe ambulation.
It was first coined to
describe low-dose
CSE opioid analgesia
because motor
function was
maintained and the
ability to walk was
not impaired.

49. •Faster onset with intense analgesia.
•Additional flexibility due to presence
of epidural.
•Very low failure rate.
•Minimal motor block if only opioid
used for spinal.
•Less need for supplemental boluses.
Combined spinal Epidural
Needle through needle Back eye

50. Causes of inadequate epidural analgesia
Catheter
migration
Inadequate
dose
Blocked
catheter
Subdural
placement
Uterine
Rupture
Second stage
of labor

51. Complications of Epidural analgesia
Hypotension
Inadequate analgesia
Extensive motor blockade
Respiratory depression
Faulty placement
Back pain

52. How to avoid epidural disasters
• Maintain constant verbal contact.
• Nurse in lateral position as much as possible.
• Assure continuous maternal and fetal monitoring throughout
placing and handling epidural infusions.
• Always aspirate before each injection.
• Treat every injection as a test dose.
• Always observe for passive return through the catheter.
• Do not inject more than 4 ml of LA at a time.
• If in doubts, repeat test dose. Still in doubts? Replace it
• After all, be mentally prepare to treat :
1. Convulsions
2. Total spinal
3. Cardiovascular collapse and arrest

53. Adjunctive Peripheral Nerve Blocks
• Rectus sheath block
• Bilateral ilioinguinal & iliohypograstic nerve
block
• Bilateral transversus abdominis plane block

54. NSAID
• They reduce opioid consumption by the
patient.
• NSAIDs reduce the inflammatory pain.
• Acetaminophen, Ibuprofen, Aspirin,
Ketorolac & Diclofenac are designated as
Category 3 drug by AAP, so they are well
tolerated.

55. References
Miller’s Anaesthesia, 8th edn.
Barash’s Clinical Anaesthesia, 7th edn.
Chestnut’s Obstetrics Anaesthesia, 4th edn.
Wall PD, Melzack OC: Text book of pain.