This document discusses the history and physiology of labor analgesia. It provides an overview of the controversy around pain relief during labor and outlines both non-pharmacological and pharmacological options. Regional techniques like epidural analgesia are highlighted as the most effective methods with minimal effects on the fetus when used properly. The goals of labor analgesia and factors to consider when selecting drugs and techniques are also summarized.

2. Analgesia for Labor and Delivery
 ALWAYS controversial !
 “Birth is a natural process”
 Women should suffer!!
 Concerns for mother’s safety
 Concerns for baby
 Concerns for effects on labor

3.  Garden of Eden
History
Original Sin
God punished Eve: “In sorrow thou shalt bring forth children.”
Genesis 3:16
Formed the basis of 1800 years of opposition to pain relief in
labor.
 1591
Lady Euframe MacAlyane of Edinburgh, Scotland: was Burned
at the Stake because asking for labor analgesia.

4. HISTORY
 1847 – James Young Simpson; ETHER
 1853 – John Snow ; CHLOROFORM
- Queen Victoria, 8th child

5. Chloroform a’ la reine
“The inhalation lasted fifty-three minutes.
The chloroform was given on a
handkerchief in fifteen minim doses; the
Queen expressed herself as greatly
relieved by the administration.”

6. Chloroform a’ la reine
“Dr Snow gave me the blessed
chloroform and the effect was soothing,
quieting and delightful beyond measure”

7. History contd..
 1855
Religious acceptance
Archbishop of Canterbury's (leader of
the Anglican/Episcopal Church) daughter received
chloroform for labor pains. He refused to criticize.
 1860-1940 : Dark ages of obstetric anesthesia

8. History
 August Bier ,……………..,
Virginia Apgar ,…
 1900 :
Oskar Kreis , used spinal anesthesia for
childbirth for the first time

9.  1933 : John Cleland – pain pathways
 1943 : Hingson – Continuous caudal
 1949 : Flowers - Continuous lumbar epid.

10. DEFINITION OF PAIN
 ISAP - AS AN UNPLEASANT SENSORY
AND EMOTINAL EXPERIENCE
ASSOCIATED WITH ACTUAL
POTENTIAL TISSUE DAMAGE (OR)
DESCRIBED IN TERMS OF SUCH
DAMAGE.

11. TERMINOLOGY
NOCICEPTION:DETECTION,TRANSDUCTION,AND
TRANSMISSION OF NOXIOUS STIMULI
NOCICEPTORS:FREE NERVE ENDINGS ACTIVATED
BY NOXIOUS STIMULI.
PHYSIOLOGIC PAIN:NOXIOUS STIMULI ACTIVATING
|
NOCICEPTORS ACCOMPANIED BY WITHDRAWAL
PATHOLOGIC PAIN: NON NOXIOUS STIMULI
PRODUCING PAIN

12. PHYSIOLOGY OF PAIN
 PATHWAYS
 MEDIATORS
 PERCEPTION

13. PATHWAYS
 PERIPHERAL AFFERENT(FIRSTORDER NEURON)
|
DORSAL ROOT GANGLION
|
DORSAL HORN(SECOND ORDER)
|
CONTRALATERAL HEMISPHERE
|
SPINOTHALAMIC TRACT
|
THALAMUS

14. MECHANISMS
PERIPHERAL
CENTRAL

15. PERIPHERAL MECHANISMS
NOCICEPTORS:
1.NON MYELINATED(c-fibers)
2.MYELINATED(A-DELTA)
 POLYMODAL.
 A-DELTA- SHARP,HEAT,PRESSURE
 C-FIBERS-DULL BURNING PAIN.
 PATHOLOGICAL PAIN-A-BETA.

16. CHEMICAL MEDIATORS
 BRADYKININ
 HISTAMINE
 EICOSANOIDS
 SUBSTANCE-P
 5-HT
 ATP
 H2 ION
 OPIOID PEPTIDES

17. CENTRAL MECHANISMS
 NOCICEPTIVE AFFERENTS
DORSAL ROOT
GANGLION
DORSALHORN
C&SOME A-DELTA SUPERFICIAL LAMINA(1&2)
SOME A-FIBERS —LAMINA - 5
30% -C-FIBERS
—DOUBLE BACK THROUGH
VENTRAL ROOT
1&5 -------THALAMUS
LAMINA 2—SUBSTANTIA GELATINOSA (INHIBITORY)
“THE GATE CONTROL THEORY OF PAIN”

18. MODULATORS AT SPINAL
CORD
 OPIOID PEPTIDES
 BIOGENIC AMINES
 OTHERS

19. SUPRASPINAL MODULATION
 PERIAQUEDUCTAL GREY(PAG) MATTER
 DESCENDING INHIBITORY PATH
 LOSS OF RESPONSE TO NOXIOUS STIMULI
 RESPONSE TO STIMULI-3 WAYS
 “ON CELLS” FACILITATE NOCICEPTIVE
TRANSMISSION
 “OFF CELLS” INHIBITS TRANSMISSION
 “NEUTRAL CELLS”NO CHANGE IN FIRING

20. Grading Of Pains

22. PAIN PATHWAYS
 1st stage of labor – mostly visceral
 Dilation of the cervix and distention of the
lower uterine segment
 Dull, aching and poorly localized
 Slow conducting, C fibers, T10 to L1
 2nd stage of labor – mostly somatic
 Distention of the pelvic floor, vagina and
perineum
 Sharp, severe and well localized
 Rapidly conducting, A-delta fibers,S2 to S4

25. Labor Pain & Stages of Labor
Eltzschig, Leiberman, Camann, NEJM 348; 319:2003

26. Effects of labor pain
 Maternal hyperventillation
 Hypocarbia – Uteroplacental vasoconstriction
- ODC to left
 ↑O2 consumption
 ↑Cardiac output, ↑BP
 ↑Maternal plasma catecholamines
Fetal acidosis and hypoxia

29. Ill effects Of Pain?
 High risk parturient – Pre-eclampsia
- Cardiac disease
- Asthma
 Marginal uteroplacental circulation
 Prolonged labor

31. Labor Analgesia
Non-Pharmacological
Pharmacological

32. Non-Pharmacological
 Psycho prophylaxis – Lamaze, Doula
 TENS
 Acupuncture
 Hydrotherapy
 Intradermal water inj.

33. ACUPUNTURE
 Generally two local points and two distal points on the
arms or on the legs are selected.
Begin Acupuncture 4 weeks before the expected time of
delivery.
Needles are placed once a week using the specific points.
 Points
LI.4 Hegu, SP.6 Saninjiao, Extra Neima
PC 6 (Neiguan), Du.20,Du.2,Du6, GB.21,
He.7(shenmen)

34. TENS
 Beneficial in patients with moderate to severe
contraction pains in an otherwise reasonably
normal labor.
 Very popular in Europe.
 Easy to apply, non-toxic 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 up to 3 levels of
intensity
of stimuli, and she can switch it off if she
wishes.

35. Pharmacological
Systemic
Medications
Inhalational
Regional Blocks

36. Factors Determining Fetal Drug Levels
 Lipid solubility
 Molecular size
 Total dose of drug
 Concentration gradient
 Maternal metabolism and excretion
 Degree of ionization
 pKa of drug, maternal and fetal pH
 Protein binding - mother and fetus
 Uterine blood flow
 Time for equilibrium to occur

37. Systemic Opioids in Labor
Advantages:
 Easy administration
 Inexpensive
 No needles
 Avoids complications of regional block
 Does not require skilled personnel
 Few serious maternal complications
 Perceived as “natural”

38. Systemic Opioids - 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

39. 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

40.  Mepridine: 50-100mg IM / 25-50mgIV
onset: 45mins
/ 5mins
neonatal depr: 3hrs
/ 20 mins
optimal time: >4hrs
/ <1hr
 Fentanyl: 50-100µg/hr, peaks @ 3-5mins
 Remifentanil : ½life 6mins, 0.5mirogms/kg
 Butraphanol, Nalbhuphine, Phenothiazines

41. IV-PCA Fentanyl during Labor
 Loading dose -50-100µg
 No background infusion
 10-12.5µg bolus
 8-10 min lockout
 4 hour limit - 300 mcg
 Pulse oximeter when large doses

42. Inhalation Analgesia
Entonox (N2O:O2 = 50:50), %,
Advantages:
 Easy to administer (no
needles or PDPH)
 “Satisfactory” analgesia
variable
 Minimal neonatal depression

44. Inhalational Analgesia
 Isoflurane ( 0/2%)
 Enflurane (0/2%)
 Desflurane (0/2%)
LIMITED USE
Drowsiness ,Unpleasant smell, High cost,
Accidental overdose

45. Inhalation Analgesia
Disadvantages:
 Decreased uterine contractility (except N2O)
 Rapid induction of anesthesia in pregnancy
 Risk of unconsciousness and aspiration
 Difficulties with scavenging in labor rooms

46. Regional blocks

47. Paracervical Block
 Local bilateral injection near the cervix
 Given during 1st stage of labor
 Lasts about 2 hours
 Disadvantage
 fetal bradycardia
 Lidocaine toxicity

48. Pudendal Block
 Perineal anaesthesia
 Second stage of labor

49. Neuraxial Blocks - advantages




Most effective & Least depressant
Great versatility – Extent & Duration
Reduces maternal Catechols
↑Intervillous blood flow



Improved Uteroplacental perfusion
Low dose LA – NO Effect on Uterine activity
Low dose opioids – NO neonatal depression

50. Regional Analgesia - Neonatal Effects
 Uterine perfusion maintained
 FHR changes:
 baseline variability

periodic decelerations (due to↓ maternal catechols?)
 Apgar scores, acid-base status - unaffected
 Neurobehavioral effects absent
 LA toxicity - extremely rare
 Profound hypotension - possible fetal compromise

51. Indications
PAIN EXPERIENCED BY A WOMAN IN LABOR
 ACOG and ASA stated
“ in the absence of a medical contraindication,
maternal request is a sufficient medical
indication for pain relief…”
 Points of controversy
 When?
 Who?
 How?

52. Particularly beneficial
 Hypertensive disorders
 Cardiac disease
Blunts Haemodynamic
response
 Asthma
 Diabetes
 Prolonged lobor/ Oxytocin augmentation
Depressant
 Prematurity
effects of
opioids
 Multiple gestation
avoided
 Vaginal breech delivery

53. Maternal catecholamines decrease during labor
after lumbar epidural analgesia.
Am J Obstet Gynecol 1983;147:13-5.

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

55. GOALS OF LABOR ANALGESIA
 Dramatically reduce pain of labor
 Should allow parturients to participate in birthing
experience
 Minimal motor block to allow ambulation
 Minimal effects on fetus
 Minimal effects on progress of labor

56. How to Achieve Goals:
 What you put in:
Drugs, concentrations, combinations
 How you deliver it:
Intermittent boluses, Continuous, PCEA
 How much you give:
Low Vs. High infusion rates

57. Neuraxial Blocks



Epidural alone
Combined epidural and spinal
Spinal alone
 Local anaesthetics(LA) alone
 Opioids and LA
 Opioids alone

58. Neuraxial Blocks
 Spinal opioids alone: very high risk pts
 Epidural opioids alone: High doses
 Spinal LA alone: Saddle block, 6mg bupivacaine
Epidural LA alone
Epidural LA + Opioid ± Adjuvants
Combined Spinal & epidural – LA+Opioid
± Adjuvants
 Continuous spinal – LA ± Opioids




59. 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

60. Choice of Epidural LA
 Lignocaine: Rapid onset, Dense motor block, Risk of
cummulative toxicity, UV/MV ratio – 0.6
 Chlorprocaine:Rapid onset, Low toxicity, Dense block,
Antagonises bupivacaine &poioids
 Bupivacaine( 0.0625%): Good sensory, Minimal motor
block, 2hrs, No adverse effects on labor, UV/MV – 0.3
 Ropivacaine: Lower toxicity, ?Less motor block, Less
potent
 Levobupivacaine: Lower toxicity

61. Epinephrine Use in Labor
 May transiently slow labor
 Increases motor block, Improves analgesia
 Epinephrine test dose often avoided in labor
 Low specificity - maternal heart rate very variable
 Low sensitivity - ↓ response to sympathomimetics
 Increases motor block - prevents ambulation
 Potential for ↓ UBF with repeated doses
 Very dilute agents - “whole first dose is test dose.”

62. Epidural Opioids in Labor
 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

63. Effect of low conc LA + opioid
(Comet Study UK , Lancet 2001;358:19)
50
%
Patients
40
*
*
*
30
20
10
0
"Traditional"
Bupivacaine
0.25%
Low-dose
Infusion
Bupiv 2.5 mg
+ Fent 25 mcg
Bupivacaine
0.1% + fentanyl
Spontaneous
Instrumental
C/Section

64. Which Epidural Opioid ?
Fentanyl and Sufentanil
 Rapid onset, few side effects
 Sufentanil slightly more effective
 No significant fetal drug accumulation
 No serious adverse neonatal effects

65. Light or “Ultra-light Analgesic
Techniques
Bupivacaine
Ropivacaine
+ OPIOID
Levobupivacaine

66. Epidural analgesia
Opioid: Fentanyl 1-2 µg/ml,
Sufentanyl 0.20.5µg/ml
Continuous infusion
 Bupivacaine 0.0625%-0.25%,8 -15 ml/hr
 Ropivacaine: 0.125%-0.25%, 6 -12 ml/hr
Intermittent bolus injections
 Bupivacaine: 0.125%-0.375%, 5-10 ml,
duration:1-2 hr

67. Continous Epidural

68. Continuous epidural infusion
“A larger volume of a more dilute agent is more
effective for labor analgesia than a smaller
volume of higher concentration”
 Good pain releif
 Less motor block
 Increased maternal hamodynamic stability
 Safe drug concentrations
 No change in neonatal outcome

69. PCEA





Good analgesia
Patient autonomy
Less anaesthetist interventions
Cost effective
Lower total dose
Bupivacaine 0.125% + Fentanyl 2µg/ml – 6ml basal
infusion, 3ml bolus, 10min lockout interval, max
24ml/hr

70. From Gambling DR et al. Comparison of patient-controlled epidural
analgesia and conventional intermittent top up injections during labor.
Anesth Analg 1990;70:256-61.

71. Combined spinal-epidural
 Faster onset - intense analgesia
 Additional flexibility - epidural
 Very low failure rate
 Minimal motor block if only opioid used for spinal
 Less need for supplemental boluses
 IT opioids: Fentanyl 5-25 μg, sufentanil 5-10 μg
Early labor : opioid ± 0.125 mg bupivacaine;
Advanced labor: opioid ± 2-2.5 mg bupivacaine

72. COMBINED SPINAL EPIDURAL
Needle” through “Needle”
“ Back “ eye”
 Needle” through “Needle” technique is the best
 Can be placed in lateral or sitting position
 Walking Epidural possible

73. Onset of Analgesia: CSE vs.
Epidural
Collis et al. Lancet 1995;345:1413
100
CSE
Epidural
75
VAPS
(0-100)
50
25
0
Baseline
5
10
Time (minutes)
15
20

74. Combined spinal-epidural
 Not recommended - morbidly obese, difficult airway
or non-reassuring fetal heart rate
 Two interspace techniques
 Needle through needle
-PDPH: 1% or less, small bore atraumatic needles.
-Subarchanoid migration of epidural catheter - No added
risk with CSE

75. Continuous Spinal Analgesia
 28 or 32-G catheters for 22 or 26-G spinal needles
 Bupivacaine 2.5mg+25µg fentanyl,
1-2ml/hr of bupivacaine 0.125% + 2µg/ml fentanyl
 Cauda Equina Syndrome
 Restricted by FDA in 1992
 Ongoing multi-institutional study – 28-G catheters
sufentanil ± bupivacaine
 Appears safe

76. Side effects of IT opioids
Nausea, Vomitting
Pruritis
Sedation
At very high doses - Resp depression
- Fetal bradycardia
 Stratergy to ↓ side effect - Add LA
- Lowest dose opioid





77. We are All Ready…Now What?
Obstetrician is consulted
Pre-anesthetic evaluation
Pt’s informed consent
Fetal well-being assessed and reassured
(obstetrician?, midwife?, yourself?)
 Stage of labor/ Cervical dilatation
 Resuscitation equipment and drugs are
immediately available
 Aspiration prophylaxis





78. Conduct of Labour analgesia








Baseline BP, HR, FHR
IV access, Preload 500 -1000ml
Perform epidural / CSE
Pregnancy – Physiologic changes
Left lateral / sitting
R/O intrathecal/ IV placement
3-5cm catheter inside space
4ml of the drug

79. Conduct of Labour analgesia
 Monitoring:
 BP every 1 to 2 min , 20 min
 Continuous maternal HR during induction
(pulseoximetry)
 Continuous FHR monitoring
 Continual verbal communication




After 5mins, 4-8ml of drug » T10-L1 block
Alternatively continuous infusion /PCEA
Assess progression of labor
Treat every bolus as test dose

80. Conduct of Labor analgesia





Nursed in lateral position
Second stage of labor – S2 -4
Head end elevation, 4-8ml drug bolus
Intermittent techniques – 10-15ml drug
Prolonged for instrumental delivery /
C.section

81. Inadequate analgesia






Inadequate dose
Patency of catheter
Subdural placement
Second stage of labor
Catheter migration
Uterine rupture

82. Complications
 Hypotension: preloading, LUD, O2, fluid, ephedrine
 Inadequate analgesia:
 Unintentional intravascular placement:
slow injection of dilute conc – less risk
ligonocaine – light headedness, perioral numbness, seizures.
Bupivacaine – Ventricular arrythmia, cardiac arrest
 Unintentional intrathecal placement:
Hypotension, total spinal, PDPH
 Subdural placement :patchy block, high level

83. Fetal
Heart
Rate

84. Management of FHR Changes
 Left uterine displacement
 Maternal position change
 O2 administration
 STOP OXYTOCIN!
 Fetal scalp stimulation
 Nitroglycerin: 400 µg sublingual X 2 (or more)
 Terbutaline 0.25 mg, subcutaneous
 Treat hypotension
 Ephedrine -  epinephrine level;  UBF

85. Controversial areas
 Maternal pyrexia:
↑0.1 C/hr, No infection, No neonatal sepsis
 Progress of Labor:
?only minimally prolongs
 Rate of C/S: Not increased
 Epidural test dose:
? Adrenaline, ?isoprotenerol
Careful aspiration

86. Avoiding Epidural Disasters







Maintain constant verbal contact
Always aspirate before each injection
Observe for passive return through the catheter
Do not inject more than 4 ml of LA at a time
Observe the patient at least 1.5-2 min between boluses
If in doubts, repeat test dose. Still in doubts? Replace it
i
After all, be mentally prepare to treat
1. Convulsions
2. Total spinal
3. Cardiovascular collapse and arrest

87. Conclusions
 Individualize technique to patient’s goals and
stage of labor
 Optimize management for spontaneous delivery
 Provide safe, cost-effective analgesia

88. The Ideal Labor Analgesic
 Good pain relief
 No autonomic block (no hypotension)
 No adverse maternal or neonatal effects
 No motor block
 No effect on labor and delivery:

No increase in C/S rate
 No increase in forceps/vacuum delivery
 Patient can ambulate
 Economical: cost and personnel