nesthesia and analgesia in obstetrics

2.  Relief of pain during labor and delivery is an essential part
in good obstetric care.
 Choice of anesthesia depends upon the patient’s conditions
and the associate disorders. Anesthetic complications may
cause maternal death.
 Anesthesia following full meal may cause maternal death
due to vomiting and aspiration of gastric contents.
 Maternal risk factors for anesthesia are: Short stature,
short neck, marked obesity, severe preeclampsia, bleeding
disorders, placenta previa, medical disorders, like cardiac,
respiratory and neurological disease.

3.  Anatomical and Physiological considerations
 Nerve supply of the genital Tract: Uterus is under both
nervous and hormonal control.
 Hypothalamus controls the uterine activity through the reticular
formation which balances the effects of the two autonomic
divisions.
 Motor nerve supply: The uterus receives both sympathetic and
parasympathetic nerve fibers.
 The sympathetic nerve fibers arise from lower thoracic and upper
lumbar segments of the spinal cord.
 The parasympathetic fibers arise from sacral 2, 3 and 4 segments
of the spinal cord.

4.  The preganglionic fibers of the sympathetic nerves arising from the
spinal cord pass through the ganglia of the sympathetic trunk to
aorticorenal plexus where they synapse.
 The aorticorenal plexus continues as the superior hypogastric plexus or
presacral nerve and passes over the bifurcation of aorta and divides
into right and left hypogastric nerves.
 Each hypogastric nerve joins the pelvic parasympathetic nerve of the
corresponding side and forms the pelvic plexus (right and left) or
inferior hypogastric plexus.
 The pelvic plexus then continues along the course of the uterine artery
as paracervical plexus on each side of the cervix.

5.  Sensory pathway: Sensory stimuli from the uterine body are
transmitted through the pelvic, superior hypogastric and aorticorenal
plexus to the 10th, 11th and 12th dorsal and the first lumbar segments of
the spinal cord.
 Sensory stimuli from cervix pass through the pelvic plexus along the
pelvic parasympathetic nerves to sacral segments 2, 3 and 4 of the
spinal cord.
 Sensory stimuli from upper vagina pass to 2, 3 and 4 sacral
parasympathetic segments and from lower vagina pass through the
pudendal nerve.
 The perineum receives both motor and sensory innervation from sacral
roots 2, 3 and 4 through the pudendal nerve.
 The branches of ilioinguinal and genital branch of genitofemoral
nerves supply the labia majora and also carry the impulses from the
perineum.

6.  Nervous control of uterine activity: Regarding
motor innervation of the uterus, the sympathetic
nerves rather than the parasympathetic have the
influences over the uterine activity.

8.  Hormonal Control :It is generally agreed that intact nerve
supply is not essential for the initiation and progress of
labor.
 Total spinal block does not inhibit uterine activity,
provided blood pressure is not allowed to fall, and normal
vaginal delivery can occur in the paraplegic patient.
 Oxytocin, a hormone derived from posterior pituitary
maintains the uterine activity during labor. Progesterone is
the pregnancy–stabilizing hormone. Labor commences
when it is withdrawn.
 Adrenaline with its beta activity inhibits the contraction of
uterus, while its alpha activity excites it.

10. Analgesia during labour and delivery:
 Pain during labor results from a combination of uterine contractions and
cervical dilatation.
 During cesarean delivery incision is usually made around the T12 dermatome
anesthesia is required from the level of T4 to block the peritoneal discomfort.
Labor pain is experienced by most women with satisfaction at the end of a
successful labor.
 Antenatal (mother craft) classes, sympathetic care and encouraging
environment during labor can reduce the need of analgesia. Drugs have an
important part to play in the relief of labor pain but it must not be supposed
that they are of greater importance than proper preparation and training for
childbirth. The intensity of labor pain depends on the intensity and duration
of uterine contractions, degree of dilatation of cervix, distension of perineal
tissue, parity and the pain threshold of the subject.
 The most distressing time during the whole labor is just prior to full
dilatation of the cervix.

11.  The ideal procedure should produce efficient relief of pain
but should neither depress the respiration of the fetus nor
depress the uterine activity causing prolonged labor.
 The drug must be nontoxic and safe for both mother and
fetus.
 But it is regretted that no such agent is available at present
that fulfills all these conditions.
 Every case of labor does not require analgesia and only
sympathetic explanation may be all that is required.

12. Sedatives and Analgesics
 The following factors are important to control the dose of
sedative and analgesics:
(1) Pain threshold: The threshold of pain varies from patient to
patient. Some patients experience severe pain though the uterine
contractions are relatively weak. In such cases, it is preferable to
control the pain adequately.
(2) Parity: The multiparous women need less analgesia due to
added relaxation of the birth canal and rapid
delivery.
(3) Maturity of the fetus—Minimal doses of drugs are indicated
while the fetus is thought to be premature to avoid neonatal
asphyxia.

13.  For the purpose of selecting a general analgesic drug,
labor has been divided arbitrarily into two phases.
 The first phase corresponds up to 8 cm dilatation of the
cervix in primigravidae and 6 cm in case of multipara.
 The second phase corresponds to dilatation of the cervix
beyond the above limits up to delivery.
 The first phase is controlled by sedatives and analgesics,
and the second phase is controlled by inhalation agents.
 The idea is to avoid the risk of delivery of a depressed baby.

14.  Opioid analgesics—Pethidine: is generally used in the early first stage of labor
and indicated when the discomfort of labor merges into regular, frequent and
painful contractions. The initial dose is 100 mg (1.5 mg/kg body weight) IM and
repeated as the effect of the first dose begins to wane, without waiting for the
reestablishment of labor pain.
 The side effects of pethidine to the mother are nausea, vomiting, delayed gastric
emptying. Ranitidine should be given to inhibit gastric acid production, and
emetic effect is counteracted by metoclopramide (10 mg IM).
 Pethidine crosses the placenta and accumulates in fetal tissues. Pethidine
reduces baseline variability, depresses respiration and suckling of the newborn
when administered before delivery.

15.  Meperidine: Compared to morphine, analgesic effect is one tenth,
but respiratory depression effect is less. It is used 25–50 mg (1–3
mg/kg IM) or a PCA pump 15 mg every 10 minutes. Repeated use or
PCA in labor, infants may need naloxone at delivery. Maximum
placental transfer and neonatal depression occur 2–3 hours of use.
 Fentanyl is a short acting synthetic opioid and is equipotent to
pethidine. It has less neonatal effects and less maternal nausea and
vomiting. It needs frequent dosing. It can be used as PCA.
 Phenothiazines: Promethazine (phenergan) is commonly used in
labor in combination with an opioid. It does not cause major
neonatal depression.
 Promethazine is a weak antiemetic drug and causes sedation in
the mother.

16.  Inhalation Methods
 Premixed nitrous oxide and oxygen: Cylinders contain
50% nitrous oxide and 50% oxygen mixture.
 Entonox apparatus has been approved for use by midwives.
This agent is used in the second phase (from 8 cm
dilatation of cervix to delivery). It can be self administered.
Entonox is most commonly used inhalation agent during
labor in the UK.
 Hyperventilation, dizziness, hypocapnia are the side
effects. The woman is to take slow and deep breaths before
the contractions and to stop when the contractions are
over. The woman should be monitored with pulse oximetry.

17.  Regional (neuraxial) anesthesia
 When complete relief of pain is needed throughout
labor, epidural analgesia is the safest and simplest
method for procuring it.
 It provides sensory as well as various degrees of motor
blockade over a region of the body.
 But anesthetists/obstetricians have to be trained
properly to make use of this very valuable method in
normal and abnormal labor.

18. Continuous lumbar epidural block:
A lumbar puncture is made between L2 and L3 with the epidural
needle (Tuohy needle).
 With the patient on her left side, the back of the patient is cleansed
with antiseptics before injection. When the epidural space is ensured,
a plastic catheter is passed through the epidural needle for continuous
epidural analgesia.
 A local anesthetic agent (0.5% bupivacaine) is injected into the
epidural space.
 Full dose is given after a test dose when there is no toxicity.
 For complete analgesia a block from T10 to the S5 dermatomes is
needed.

19.  For cesarean delivery a block from T4 to S1 is needed. Repeated doses
(top ups) of 4–5 mL of 0.5% bupivacaine or 1% lignocaine are used to
maintain analgesia.
 Epidural analgesia, as a general rule should be given when labor is well
established.
 Maternal hydration should be adequate with normal saline or
Hartmann’s solution (crystalloid) infusion prior commencing the
blockade.
 The patient’s blood pressure, pulse and the fetal heart rate should be
recorded at 15 minutes interval following the induction of analgesia
and hypotension, if occurs, should be treated immediately.
 The woman is kept in semilateral position to avoid aortocaval
compression.

20.  Epidural analgesia is especially beneficial in cases like
pregnancy-induced hypertension, breech
presentation, twin pregnancy and preterm labor.
Previous cesarean section is not a contraindication.
 Epidural analgesia when used there is no change in
duration of first stage of labor. But second stage of
labor appears to be prolonged by 15–30 minutes.
 This might lead to frequent need of instrumental
delivery like forceps or ventouse.

21.  Paracervical nerve block: Is useful for pain relief
during the first stage of labor. Following the usual
antiseptic safe guards, a long needle (15 cm or more) is
passed into the lateral fornix, at the 3 and 9 o’clock
positions.

22.  Five to ten milliliter of 1% lignocaine are injected at the site of the cervix and the procedure is repeated on
the other side. This dose is quite sufficient to relieve pain for about an hour or two, and injections can be
given more than once if necessary.
 Bupivacaine is avoided due to its cardiotoxicity. Paracervical block should not be used where placental
insufficiency is present .
 Although paracervical block may be used from 5 cm dilatation of the cervix, it is most useful toward the
end of the first stage of labor to remove the desire to bear down earlier.
 Paracervical block can only relieve the pain of uterine contraction and the perineal discomfort is removed
by pudendal nerve block. Fetal bradycardia is a known complication. This is due to decreased placental
perfusion resulting from uterine artery vasoconstriction or its direct depressant effect on the fetus
following transplacentalmtransfer. This method is not commonly used.

24. Pudendal nerve block:
 It is a safe and simple method ofanalgesia during delivery.
 Pudendal nerve block does not relieve the pain of labor but affords perineal
analgesia and relaxation.
 Pudendal nerve block is mostly used for forceps and vaginal breech delivery.
 Simultaneous perineal and vulval infiltration is needed to block the perineal branch
of the posterior cutaneous nerve of the thigh and the labial branches of the
ilioinguinal and genitofemoral nerves (vide supra). This method of analgesia is
associated with less danger, both for mother and baby than general anesthesia.
 Technique: The pudendal nerve may be blocked by either the transvaginal or the
transperineal route.

25.  Transvaginal route:
Transvaginal route is commonly preferred:
 A 20 mL syringe, one 15 cm (6”) 22 gauge spinal needle and about 20 mL of 1% lignocaine
hydrochloride are required.
 The index and middle fingers of one hand are introduced into the vagina, the finger tips are
placed on the tip of the ischial spine of one side.
 The needle is passed along the groove of the fingers and guided to pierce the vaginal wall on
the apex of ischial spine and thereafter to push a little to pierce the sacrospinous ligament just
above the ischial spine tip.
 After aspirating to exclude blood, about 10 mL of the solution is injected. The similar procedure
is adopted to block the nerve of the other side by changing the hands

26. Methods of labial-perineal block for episiotomy
during outlet forceps/ventouse operati on

27. Methods of transvaginal pudendal block anesthesia. Note the relation of the
pudendal nerve to the ischial spine in the inset

28. Complications:
 Hematoma formation, infection and rarely
intravascular injection or allergic reaction. Toxicity
may affect: (A) CNS: excitation, ringing in the ears and
convulsions. (B) Cardiovascular: tachycardia,
hypotension, arrythmias, even cardiac arrest.

29.  Spinal anesthesia: Spinal anesthesia is obtained by injection of
local anesthetic agent into the subarachnoid space. It has less
procedure time and high success rate. Spinal anesthesia can be
employed to alleviate the pain of delivery and during the third stage of
labor.
 For normal delivery or for outlet forceps with episiotomy, ventouse
delivery, block should extend from T10 (umbilicus) to S1.
 For cesarean delivery level of sensory block should be up to T4
dermatome. Hyperbaric bupivacaine (5–10 mg) or lignocaine (25–50
mg) is used.
 Addition of fentanyl (to enhance the onset of block) or morphine (to
improve pain control) may be done. Brief or minimal spinal anesthesia
is far safer than prolonged spinal anesthesia.

30. The advantages of spinal anesthesia
 are: (a) less fetal hypoxia unless there is
hypotension and (b) minimal blood loss. The
technique is not difficult and no inhalation anesthesia
is required, but postspinal headache occurs in 5–10%
of patients.

31.  Spinal anesthesia can be obtained by injecting the drug into the subarachnoid
space of the third or fourth lumbar interspace with the patient lying on her side
with a slight head uptilt.
 The blood pressure and respiratory rate should be recorded every 3 minutes for
the first 10 minutes and every 5 minutes thereafter.
 Oxygen should be given for respiratory depression and hypotension.
Sometimes vasopressor drugs may be required if a marked fall in blood
pressure occurs.
 It is used during vaginal delivery, forceps, ventouse and cesarean delivery.

32.  Combined spinal-epidural analgesia (CSE):
 An introducer needle is first placed in the epidural space.
 A small gauge spinal needle is introduced through the epidural
needle into the subarachnoid space (needle through needle
technique). A single bolus of 1 mL 0.25% bupivacaine with 25 μg
fentanyl is injected into the subarachnoid space.
 The spinal needle is then withdrawn. An epidural catheter is
thus sited for repeated doses of anesthetic drug. The
 method gives rapid and effective analgesia during labor and
cesarean delivery. It allows women to move (walking
 epidural) during labor.

33.  Side eff ects of Spinal anesthesia
 Hypotension due to blocking of sympathetic bers leading to vasodilatation
and low cardiac output
 Respiratory depression may occur due to paralysis of respiratory muscles
including diaphragm (C3–C5)
 Failed block, chemical meningitis, epidural abscess
 Total spinal—due to excessive dose or improper positioning
 Postspinal headache—due to low or high CSF pressure and leakage of CSF
 Meningitis due to faulty asepsis
 Transient or permanent paralysis
 Toxic reaction of local anesthetic drugs
 Paralysis and nerve injury
 Nausea and vomiting are not uncommon and Urinary retention (bladder
dysfunction)

34.  Infiltration analgesia
 Perineal infiltration:
 For episiotomy—Perineal infiltration anesthesia is extensively
used prior to episiotomy.
 A 10 mL syringe, with a fine needle and about 8–10 mL 1%
lignocaine hydrochloride (Xylocaine) are required.
 The perineum on the proposed episiotomy site is infiltrated in a
fanwise manner starting from the middle of the fourchette.
 Each time prior to infiltration, aspiration to exclude blood is
mandatory. Episiotomy is to be done about 2–5 minutes
following infiltration.

35.  For outlet forceps or ventouse—(Perineal and labial
infiltration):
 The combined perineal and labial infiltration is effective in outlet
forceps operation or ventouse traction. A 20 mL syringe, a long fine
needle and about 20 mL of 1% lignocaine hydrochloride are required.
 The needle is inserted just posterior to the introitus. About 10 ml of
the solution is infiltrated in a fanwise manner on both sides of the
midline (as for episiotomy). The needle is then directed anteriorly
along each side of the vulva as far as the anterior-third to block the
genital branch of the genitofemoral and ilioinguinal nerve.
 Five milliliter is required to block each side.

36.  Local abdominal for cesarean delivery:
 This method is rarely used where regional block is patchy
or inadequate.
 The skin is infiltrated along the line of incision with
diluted solution of lignocaine (2%) with normal saline.
 The subcutaneous fatty layer, muscle, rectus sheath layers
are infiltrated as the layers are seen during operation.
 The operation should be done slowly for the drug to
become effective.

37.  Patient controlled analgesia (PCA):
 Narcotics are administered by mother herself from a
pump at continuous or intermittent demand rate
through intravenous route.
 This offers better pain control than high doses given at
a long interval by the midwife. Maternal satisfaction is
high with this method. Drugs commonly used are
fentanyl, meperidine or remifentanil.

38.  PSYCHOPROPHYLA XIS (Syn: Natural childbirth):
 It is psychological method of antenatal preparation
designed to prevent or at least to minimize pain and difficulty
during labor. For most women, labor is a time of apprehension,
fear and agony. As a result of suitable antenatal preparation,
majority of women have labor that is easy and painless.
 Relaxation and motivation can reduce the fear and apprehension
to a great extent. Patient is taught about the physiology of
pregnancy and labor in antenatal (mothercraft) classes.
Relaxation exercises are practiced. Husband or the partner is also
involved in the management. His presence in labor would
encourage the bearing down efforts.
 Need of analgesia would be less.

39.  Transcutaneous electric nerve stimulation
(TENS):
 It is a noninvasive procedure and is preferred by many
women during labor. Electrodes are placed over the
level of T10 – L1 and S2 – 4.
 Current strength can be adjusted according to pain. It
works by inhibiting transmitter release through
interneuron level. However, no change in pain score
was observed when TENS was switched on.

40.  GENERAL ANESTHESIA FOR CESAREAN SECTION
 The following are the important considerations of general anesthesia for
cesarean section:
 Cesarean section may have to be done either as an elective or emergency procedure
 Ryle’s tube aspiration of gastric contents is to be done, especially when the stomach
contains food materials
 A large number of drugs pass through the placental barrier and may depress the baby
 Uterine contractility may be diminished by volatile anesthetic agents like ether,
halothane
 Halothane, isoflurane cause cardiac depression, hepatic necrosis and hypotension
 Hypoxia and hypercapnia may occur
 Time interval from uterine incision to delivery is related directly to fetal acidosis and
hypoxia
 Longer the exposure to general anesthetic before delivery the more depressed is the
Apgar score.

41. Preoperative preparations: These safety measures should be taken to
prevent complications of general anesthesia.
 Preoperative medication with sedatives or narcotics is not required as they
cause respiratory depression of the fetus.
 Fasting of about 6 hours is preferable for an elective surgery.
 High-risk women in labor should preferably not be allowed to eat.
 Ryel’s tube aspiration of gastric contents is to be done when the stomach
contains food materials.
 H2-blocker (Ranitidine 150 mg orally) should be given night before (elective
procedure). H2 receptor
 blocking agent and metoclopramide is to be given IM especially to women
with high risks (obesity).
 Non-particulate antacid (0.3 molar sodium citrate 30 ml) is given orally before
transferring the patient to theater to neutralize the existing gastric acid.

42.  While on the theater table, left lateral tilt of the woman maintained with a
wedge on the back.
 This is To avoid autocaval compression as it is detrimental to both mother and
fetus.
 Metoclopramide (10 mg IV) is given after minimum 3 minutes of
preoxygenation to decrease gastric volume and to increase the tone of lower
esophageal sphincter.
 Intubation with adequate cricoid pressure following induction should be
done.
 Uterine incision — Delivery (U-D) interval is more predictive of
neonatal status (Apgar score).
 Prolonged U-D interval of more than 3 minutes results in lower Apgar scores
and neonatal acidosis.
 Awake extubation should be a routine.

43.  Preoxygenation with 100% oxygen is administered by tight mask fit for
more than 3 minutes.
 Induction of anesthesia is done with the injection of thiopentone
sodium 200–250 mg (4 mg/kg) as a 2.5% solution intravenously.
 Muscle relaxants: Succinylcholine is commonly used immediately after
the induction drug to facilitate intubation.
 It is a short acting muscle relaxant with rapid onset of action.
 Intubation: An assistant is asked to apply cricoid pressure as soon as
the consciousness is lost.
 Intubation is done with a cuffed endotracheal tube and the cuff is
inflated. Presence of obesity, severe edema, neck abnormalities, short
stature or airway abnormalities make intubation difficult.

44.  Anesthesia is maintained with 50% nitrous oxide, 50%
oxygen and a trace (0.5%) of halothane.
 Relaxation is maintained with nondepolarizing
muscle relaxant (vecuronium bromide 4 mg or
atracurium 25 mg). After delivery of the baby, the
nitrous oxide concentration should be increased to
70% and narcotics are injected intravenously to
supplement anesthesia.

45.  Complications of general anesthesia:
 Aspiration of gastric contents (Mendelson’s syndrome) is a serious and
life threatening one. Delayed gastric emptying due to high level of
serum progesterone, decreased motilin and maternal apprehension
during labor is the predisposing factor. The complication is due to
aspiration of gastric acid contents (pH < 2.5) with the development of
chemical pneumonitis, lung damage, atelectasis and
bronchopneumonia.
 Right lower lobe is commonly involved as the aspirated food material
reach the lung parenchyma through the right bronchus. Clinical
presentation: tachycardia, tachypnea, bronchospasm, rhonchi, rales,
cyanosis, decreased PaO2 and hypotension. X-ray chest reveals right
lower lobe involvement.

46.  Management: Immediate suctioning of oropharynx and
nasopharynx is done to remove the inhaled fluid.
 Bronchoscopy may be needed if there is any large particulate
matter. Continuous positive pressure ventilation to maintain
arterial oxygen saturation of 95% is done. Pulse oximeter is a
useful guide. Antibiotics are administered
 when infection is evident. Role of corticosteroid is doubtful.
 Other complications of general anesthesia are: (i) Failure in
intubation and ventilation, (ii) Nausea, vomiting and sore
throat.

48.  Medication administration. Nurses are primarily
involved in the administration of medications across
settings.
 Nurses can also be involved in both the dispensing and
preparation of medications (in a similar role to
pharmacists), such as crushing pills and drawing up a
measured amount for injections.
 If the nurse fails to follow the orders, she or he will be
liable for malpractice if the patient is injured.
The nurse may also be liable for negligently following
otherwise proper orders, like injecting a medication into
muscle instead of a vein or injecting the wrong patient.

49. Rights of Medication Administration
1. Right patient
 Check the name on the order and the patient.
 Use 2 identifiers.
 Ask patient to identify himself/herself.
 When available, use technology (for example, bar-code system).
2. Right medication
 Check the medication label.
 Check the order.
3. Right dose
 Check the order.
 Confirm appropriateness of the dose using a current drug reference.
 If necessary, calculate the dose and have another nurse calculate the dose as well.
4. Right route
 Again, check the order and appropriateness of the route ordered.
 Confirm that the patient can take or receive the medication by the ordered route.

50. 5. Right time
 Check the frequency of the ordered medication.
 Double-check that you are giving the ordered dose at the correct time.
 Confirm when the last dose was given.
6. Right documentation
 Document administration AFTER giving the ordered medication.
 Chart the time, route, and any other specific information as necessary. For example, the site of
an injection or any laboratory value or vital sign that needed to be checked before giving the
drug.
7. Right reason
 Confirm the rationale for the ordered medication. What is the patient’s history? Why is
he/she taking this medication?
 Revisit the reasons for long-term medication use.
8. Right response
 Make sure that the drug led to the desired effect. If an antihypertensive was given, has his/her
blood pressure improved? Does the patient verbalize improvement in depression while on an
antidepressant?
 Be sure to document your monitoring of the patient and any other nursing interventions that
are applicable.

51. Thank you