Obstetric analgesia and anesthesia

1. Obstetric analgesia and
anesthesia
Presenter: Kemboi Aaron
Facilitator: Prof. Were

2. Definition
• Analgesia: The loss or modulation of pain perception. (local, systemic)
• Anesthesia: the total loss of sensory perception (light tough, pain,
temperature, and her capacity for vasomotor control) , and may
include loss of consciousness.

3. History
Dr. John Snow born 15
March 1813 in York, England.
Queen Victoria was given
chloroform by John Snow for
the birth of her eighth child and
this did much to popularize the
use of pain relief in labor
• The first anesthetic used in obstetrics was chloroform and
ether in 1848
• Simpson 1847 used diethyl ether to anesthetize a parturient
with a deformed pelvis
• 1902- Morphine and Scopolamine were used to induce a
twilight sleep.
• 1924 Barbituates were added for sedation
• 1958 Dr. Lamaze and Read advocated “natural child birth”

4. Pain Pathways of Labor
• 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
• 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

5. ADVERSE CONSEQUENCES OF
LABOR PAIN
• Labor pain produces physiologic effects, including hyperventilation and
increased catecholamine levels. Such effects are usually well tolerated by
healthy parturients with normal pregnancies, but may be problematic for
parturients with medical comorbidities (eg, some cardiac lesions,
preeclampsia).
• Hyperventilation — Intermittent hyperventilation consistently
accompanies labor pain. The resultant hypocarbia can inhibit ventilatory
drive and, in the absence of supplemental oxygen, can cause maternal
and fetal hypoxemia.
• Neurohumoral effects — Neurohumoral responses to stress and pain
may adversely affect placental perfusion and fetal oxygenation, and may
be reversed by analgesia. Elevated plasma catecholamines increase
maternal peripheral vascular resistance and decrease uteroplacental
perfusion
• Labor pain can also cause psychological effects (eg, postpartum

6. THE AIMS OF OBSTETRIC ANALGESIA
• Dramatically reduce pain of labor
• Should allow parturient to participate in birthing experience
• Minimal motor block to allow ambulation
• Minimal effects on fetus
• Minimal effects on progress of labor

7. What analgesic options are available for labor?
• Types of Labor Analgesia
1. Non-pharmacological analgesia
2. Pharmacological
3. Regional Anesthesia/Analgesia
4. General Anesthesia

8. 1.) NONPHARMACOLOGICAL METHODS OF PAIN CONTROL
• Nonpharmacologic approaches to labor pain management do
not make pain disappear; instead, these approaches help
women better cope with the pain of labor and maintain a sense
of personal control over the birth process, thus reducing
suffering.
a) The gate control theory of pain asserts that non-painful input
closes the nerve "gates" to painful input, which prevents pain
sensation from traveling to the central nervous system. Specific
activities channeled during pain perception flood the gates. This
includes acupuncture, gentle massage, water immersion, sterile
water injections for back pain, transcutaneous electrical nerve
stimulation (TENS), and yoga.

9. b.) Psychoprophylaxis-
• Relaxation, concentration on breathing, and partner participation.
• Avoid emotional tension- Make a woman who is free from fear, and
develop confidence in the obstetrical staff that cares for her
• Lamaze technique is a breathing technique based on the idea that
controlled breathing can enhance relaxation and decrease the
perception of pain. Some of the important techniques for controlled
breathing include: slow, deep breathing. maintaining a rhythm
• Motivatation
• the presence of a supportive spouse

10. 2.) PHARMACOLOGIC OPTIONS FOR LABOR
ANALGESIA
• Pharmacologic approaches to manage childbirth pain can be
broadly classified as either systemic or locoregional.
• Locoregional analgesic techniques consist of neuraxial
techniques (ie, epidural, spinal, combined spinal-epidural, or
dural puncture epidural and pudendal and paracervical nerve
blocks .
• Systemic administration includes parenteral and inhalation
routes.

11. Systemic Analgesics in Labour
• Parenteral Opioids
• The following opioids have been used: Morphine, fentanyl, sufentanil,
meperidine, diamorphine.
• Opioids have the advantages of ease of administration, wide
availability, lower cost, and are less invasive than neuraxial
techniques, though substantial relief of labor pain is generally not
achieved.
• Frequent maternal side effects
• One opioid not better than another
• All cross the placenta, all associated with neonatal respiratory depression
and neurobehavioral changes
• All result in decrease in fetal heart rate (FHR) beat-to-beat variability

13. • Meperidine/pethidine
• 25-50 mg IV, 50-100 mg IM
• it is the most commonly prescribed opioid for labor pain relief worldwide.
• potential side effects in both the parturient and the neonate. Neonatal
effects are primarily related to accumulation of the very long acting
metabolite, normeperidine.
• It should be administered within one hour or more than four hours before
delivery as meperidine reaches a maximal concentration in the fetus from
two to three hours after maternal dosing.
• Readily crosses placenta Neonatal depression proportional to the total
amount of meperidine transferred to fetus before deliver

14. • Fentanyl
• doses of 50 to 100mcg intravenously every hour.
• Useful in obstetrics because of rapid onset, short duration,lack of active metabolites
• Its main disadantage is a short duration of action, which requires frequent dosing
or the use of a patient-controlled intravenous pump.
• Less maternal nausea,vomiting,sedation than meperidine.
• Morphine
• Infrequently administered during labour
• 2-5 mg IV/5-10 mg IM
• Rapidly crosses placenta, fetal effects depend upon dose and gestational age
• Decreased FHR variability
• Greater neonatal respiratory depression than meperidine

15. Agonist/Antagonist Opioids
• nalbuphine
• IV doses 2.5 to 10 mg IV every 2 to 4 hours, depending on the
level of analgesia and maternal sedation .
• There is a dose ceiling effect with regard to respiratory
depression in contrast to longer-acting opioids such
as morphine.
• Similar to other opioids, nalbuphine is associated with opioid
side effects in the mother and fetus; maternal dysphoria may be
particularly disconcerting.

16. • Narcotic Antagonists
• Naloxone is a narcotic antagonist capable of reversing respiratory
depression induced by opioid narcotics.
• It acts by displacing the narcotic from specific receptors in the central
nervous system.
• Withdrawal symptoms may be precipitated in recipients who are physically
dependent on narcotics. For this reason, naloxone is contraindicated in a
newborn of a narcotic-addicted mother.
• Naloxone, along with proper ventilation, may be given to reverse
respiratory depression in a newborn infant whose mother received
narcotics.

17. • Acetaminophen and nonsteroidal anti-inflammatory drugs
• The literature regarding the efficacy of nonopioid analgesics
(ie, acetaminophen and nonsteroidal anti-inflammatory drugs
[NSAIDs]) is limited. Ketorolac most used
• NSAIDs are avoided during labor because of their potential for
precipitating premature closure of the ductus arteriosus .
• We do not offer acetaminophen for labor analgesia because of
its limited efficacy.

18. • Sedatives and analgesic adjuncts
• Various agents have been used to minimize opioid side effects
or provide sedation, relief from anxiety, or analgesia during
labor.
• Nonopioid agents (eg, promethazine, a phenothiazine,
or hydroxyzine, an antihistamine) are often administered in
combination with an opioid to potentiate analgesia and
decrease nausea and nausea and vomiting. They are less
effective used alone than opioids, although they appear to
provide some relief

19. • Barbiturates
• hypnotics and anxiolytics, not analgesics.
• For early labour management of anxiety
• Pentobarbital 100-200 mg PO /IM
• Readily cross placenta
• Single dose early in labour rarely results in neonatal depression
Benzodiazepines (eg, midazolam and diazepam) are anxiolytics
that may be used for sedation during vaginal delivery.

20. • Ketamine
• is a phencyclidine derivative that produces a dissociative state and
analgesia.
• It is a potent amnestic, and has a rapid onset of action (less than
one minute after intravenous administration).
• Ketamine tends to preserve airway reflexes, but also increases
airway secretions, which may lead to laryngospasm. Its propensity to
produce psychotomimetic effects may be prevented with
coadministration of benzodiazepines.
• Ketamine will induce general anesthesia at doses of 1 mg/kg IV, but
lower doses (0.1 to 0.2 mg/kg IV titrated to effect) may be used to
provide analgesia for vaginal delivery or minor operative procedures,
such as manual uterine exploration.

21. Nitrous oxide
• Nitrous oxide inhalation analgesia (usually a blend of 50 percent nitrous oxide
and 50 percent oxygen gas) for labor pain.
• self-administers the anesthetic gas, as needed, using a hand-held face mask
over her nose and mouth or a mouthpiece. A demand valve on the portable gas
tank opens with inhalation and closes with exhalation. Correctly timing each
inhalation is important because analgesia takes up to 50 seconds to take effect .
Thus, peak analgesia will occur out of phase with uterine contractions if the gas is
administered with onset of contractions, which usually peak 30 seconds after they
begin and last one minute.
• nitrous oxide is eliminated quickly via the lungs, it does not accumulate in the
mother or fetus/neonate or cause newborn depression. Nitrous oxide does not
affect uterine contractile activity.
• Side effects of nitrous oxide include nausea in 5 to 40 percent of women and
vomiting in up to 15 percent Pulse oximetry should be used to monitor all
parturients who receive nitrous oxide. It should not be used in women with
oxygen saturation <95 percent or in patients with respiratory compromise, and
should be used with caution in combination with opioids because of the added
risk of respiratory depression.

22. Inhalation anesthetics
• Nitrous oxide
• Halothane:
• Isoflurane:
• Sevoflurane:
• •
• intubation
• • Halothane and isoflurane: uterine relaxation

23. Regional Analgesia Techniques for Labour and
Delivery
• Paracervical block
• Analgesia for first stage
• <6%of deliveries in USA
• Associated with fetal bradycardia
• Small volumes of dilute local anesthetic sufficient
• Pudendal nerve block
• Analgesia for second stage
• Ideally performed at beginning of second stage
• Inadequate analgesia for mid-forceps delivery, postpartum repair of cervix, and
manual uterine exploration
• Perineal infiltration of local anesthetics
• Anesthesia for episiotomy and perineal repair

24. Pudendal nerve block
• Pudendal block is typically used to alleviate pain from minor surgical
procedures involving the perineum and from events related to
delivery.
• Anatomy of pudendal nerve — The basis of the pudendal block is
that the lower vagina, perineum, and vulva obtain most of their
sensory and motor innervation from sacral nerve roots 2, 3, and 4 via
the pudendal nerve. The nerve crosses posterior to the sacrospinous
ligament in close approximation to where the ligament attaches to
the ischial spine.
• Infiltration of a local anesthetic around the trunk of the pudendal
nerve at the level of the ischial spine results in analgesia of these
areas (lower vagina, posterior perineum and vulva).

25. Pudendal nerve
block
• For pudendal block, use 1 percent
lidocaine without epinephrine.
• The end of the introducer is placed
against the vaginal mucosa just
beneath the tip of the ischial spine.
• To guard against intravascular
infusion, aspiration is attempted
before injections
• Within four to five minutes block is
achieved. Maximum anesthesia is
achieved after 10 to 20 minutes.
• Complications, although uncommon,
include hematoma formation,
infection, nerve injury, and maternal
and fetal drug toxicity

26. Paracervical block
• mainly used to reduce pain associated with cervical dilation or
manipulation (the first stage of labor. MVA, D&C, hysterescopy)
• Inject local anesthetic into the cervicovaginal junction in either a
four-point (at 2, 4, 8, and 10 o'clock) or two-point (at 4 and 8
o'clock only) fashion. A total dose of 10 to 20 mL of 1
percent lidocaine is injected approximately 10 mm into the
cervical stroma at the cervicovaginal junction.
• Because the pudendal nerves are not blocked, however,
additional analgesia is required for delivery.
• Post-block fetal bradycardia common complication.

27. Neuraxial analgesia for labor and delivery
• Neuraxial techniques (ie, epidural, combined spinal-epidural [CSE], dural puncture epidural
[DPE], single-shot spinal, and continuous spinal).
• Neuraxial analgesia blocks T10 to L1 for the first stage of labor and extend to S2 to S4 during the
late first stage and second stage of labor.
• The drugs used for neuraxial labor analgesia techniques usually include a combination of
dilute local anesthetic (LA) and an opioid. The goal should be to use the lowest effective
total dose of drugs to minimize motor block, avoid hypotension, minimize placental drug
transfer, and reduce the chance of LA toxicity. The combination of LA with opioid allows
the use of lower doses of each class of drug

28. Epidural
analgesia/anaesthes
ia
• Need prior IV hydration
• Continuous monitoring of the FHR and
contractions
• Used in SVDs
• Close BP monitoring after 1st dose and after
top off doses.
• An epidural needle is positioned below
the L2 to L3 lumbar interspace.
• Bupivicaine and Chlorprocaine have become
the agents of choice for epidural anesthesia
(IV of either can cause cardiac collapse and
death)
• An epidural catheter is threaded through
the needle into the epidural space;
• the needle is removed, and the catheter
is secured and connected to an infusion
pump system

29. Advantages of Epidural Labour Analgesia
• Continuous effective analgesia through labour
• Avoidance of systemic opioids, sedatives, inhalational agents which depress
both mother and fetus
• Fully conscious mother retains airway reflexes
• Mother remains awake, and can fully participate in birthing process
• Episiotomy and postpartum examination may be performed without
discomfort
• Should cesarean section be required, block can be rapidly extended
• Block may be utilized for postpartum tubal ligation

30. Indications for Epidural Labour Analgesia
• Pain relief
• Facilitates use of oxytocin augmentation of labour
• Trial of labour for any reason, especially women who have had prior
C-section
• High risk pregnancies:
• Diabetes, preeclampsia, preterm delivery, multiple gestation,
malpresentation, placenta previa, prolonged rupture of membranes*

31. Contraindication to Labour Epidural Analgesia
• Patient refusal
• Personnel, equipment, continuous obstetric care not available
• Infection near site or septicemia
• Coagulation abnormality (inherited, acquired, anticoagulant therapy,
Thrombocytopenia.
• Anatomic spinal abnormalities
• Raised intracranial pressure

32. Complications of spinal/epidural anaesthesia
• Hypotension
• Postdural puncture headache
• Pruritus
• Failed regional block (need for general endotracheal anesthesia)
• High spinal block
• Chemical meningitis or epidural abscess or hematoma
• Intravascular injection of local anesthetic

33. Epidural Effects on Labour and Mode of Delivery
• Motor blockade from epidural may prevent or inhibit maternal
expulsive efforts during second stage
• Epidural analgesia associated with a higher frequency of occiput
posterior position at delivery
• Presence of an epidural may decrease obstetrician’s threshold for
performing instrument-assisted deliveries- instrument-assisted
vaginal deliveries and epidural analgesia

34. Spinal Anesthesia
• used to alleviate the pain of delivery and cesarean delivery.
• 0.25~0.5% bupivacaine 2-5mg, with narcotic (fentanyl 25μg) are used
• Good relaxation of pelvic floor, lower birth canal and abdominal
muscle
• Short onset time
• duration time 50~70mins
• The dosage is small
• the complications (hypotension) are fewer

35. Combined Spinal-Epidural Anesthesia
• Most effective methods of analgesia in labour
• Opioids ± LA
• Rapid onset of intense analgesia.
• Ideal in late or rapidly progressing labour.
• Very low failure rate.
• Less need for supplemental boluses.

36. General Anesthesia
• Indicate for cesarean section delivery when regional techniques
cannot be used, Mother :unconscious, no pain, unpleasant memories,
Fetus: should not be injured with minimal depression and intact reflex
irritability.
• Goals of GA include hypnosis/unconsciousness, amnesia,
analgesia, and immobility or muscle relaxation as appropriate
for the procedure, as well as autonomic and sensory blockade
of responses to noxious surgical stimulation.

37. GA PROCEDURE
• Preparation for general anesthesia — Preoperative assessment, get
consent, explain procedure to the patient, intravenous (IV) access,
monitoring, and administration of premedications: anxiety(anxiolytics),
antisialogogue (atropine), analgesia, antiemetic, antiacid.
• Pre-oxygenate with 100% oxygen
• Induction of anesthesia- Rapid sequence induction and intubation (RSII) or Sellicks
Manourve
 Induction agents – Propofol (2 to 2.5 mg/kg IV) or etomidate (0.3 to 0.5 mg/kg IV) are the induction
agents of choice.
 Neuromuscular blocking agents – A neuromuscular blocking agent (NMBA) is usually administered
during induction as part of RSII. Generally, succinylcholine is the preferred agent as it has the quickest
onset and, in the case of difficult laryngoscopy, the quickest offset

38. Procedure of GA
Maintenance of general anesthesia — After induction and intubation,
administer high-dose volatile anesthetic (eg, sevoflurane, isoflurane,
desflurane) with high flows of oxygen to quickly obtain an adequate
end-tidal concentration of anesthetic (1.0 MAC) and minimize the
chance of awareness under anesthesia. Nitrous oxide may be
administered as well
Ventilation should be controlled or supported to achieve an end-tidal
CO2 of approximately 30 mmHg,
Emergence/reversal— Emergence from GA discontinue administration
of anesthetic and reversing residual NMBA effects using neostigmine
then Extubate.
Transport from the operating room to the post-anesthesia care unit
(PACU) is safely accomplished when the extubated patient continues to
maintain adequate oxygenation and ventilation du

39. THANK YOU
References:
1. https://www.uptodate.com
2. https://www.glowm.com/resources/glowm/cd/pages/v3/v3c090.html
3. Workshop on Labour Analgesia Dennis L. Wagner, M.D. Professor of Anesthesiology/Pain
Medicine Director, Pain Medicine Service Indiana University School of Medicine.