2. Objectives
Overview of maternal physiology
Analgesia for labor and delivery
Regional anesthesia
Anesthesia concerns in the parturient
Study MCQs with explanations
3. Physiological Changes-CVS
Almost all the changes seen are due to high
levels of progesterone and include:
35% Total Blood Volume
heart rate 15 beats/min
40% CO
30% SV
15% SVR
500ml/min blood flow to uterus
venous return from legs
AORTOCAVAL COMPRESSION (mechanical)
4. Impact of CVS changes
Patients with pre-existing cardiac disease may decompensate either
during labor or immediately post delivery. This corresponds to the
time of maximal CO
Approx 400 – 600ml blood loss occurs at delivery
Supine hypotensive syndrome
6. Physiological Changes - Resp
oxygen consumption ~ 20% (100% in labor) due to
increased metabolic rate
minute ventilation ~ 50% (due to increased tidal volume)
arterial pCO2
FRC causing a decrease in oxygen reserves
7. Impact of Resp. changes
Uptake of inhalational agents is faster
Decreased FRC and increased oxygen consumption
increase the risk of hyoxia with apnea
Preoxygenation prior to GA less effective
8. Physiological Changes- Airway
Venous engorgement of airway mucosa
Edema of airway mucosa
Worsening of Mallampati score in labor
9. Impact of Airway Changes
Trauma to upper airway with suctioning, intubation
Increased incidence of difficult/failed intubation x10
Require smaller ETT
10. Physiological Changes-CNS
Decrease in MAC by 25 – 40%
Decreased dose of Local Anesthetic requirement for
regional techniques
More rapid onset of neural blockade
11. Impact of CNS Changes
Decreased inhalation anesthetic agent requirements
Decreased dose of local anesthetic for same effect
Increased risk of local anesthetic toxicity
13. Impact of GIT Changes
Increased risk of aspiration
All parturients are a “full stomach”
Aspiration prophylaxis recommended for C/S
0.3M Sodium citrate 30 mls po
Ranitidine 50mg iv
Metoclopramide 10mg iv
14. Analgesia for labor and delivery
Where is the pain coming from?
Is pain bad in labor?
Analgesic options
16. Is pain bad in labor?
Psychological stress can cause:
increased levels of catecholamines
hyperventilation
These may result in decreased uterine blood flow leading to
hypoxia and acidosis in the fetus
17. Factors affecting pain
perception in labor
Mental preparation
Family support
Medical support
Cultural expectations
Underlying mental status
Parity
Size and presentation of the fetus
Maternal pelvic anatomy
Duration of labor
Medications
18. Analgesia for labor and delivery
Non-medication
Inhalational
Parenteral
Regional
19. Analgesia- Non medication
options
Breathing exercises
Autohypnosis
Acupuncture
White Noise/ Music
Massage/ walking
TENS
Water bath
20. Inhalation Medications
Nitronox: 50:50 mixture of oxygen and
nitrous oxide
Low dose Isoflurane in oxygen
Advantages: on demand delivery,
relatively safe
Disadvantages: variable efficacy,
nausea, drowsiness, neonatal
depression
21. Parenteral Medications
Narcotics: meperidine, morphine
fentanyl
Advantages: relatively good analgesia
Disadvantages: nausea, vomiting,
sedation, neonatal depression (max. 2
hours after meperidine dose), short
duration of action
22. Regional techniques
Epidural, spinal, combined spinal-epidural
Advantages: excellent pain control, minimal
impact on progress of labor with low doses,
less drug transfer to fetus, improved uterine
blood flow, decrease in birth trauma e.g.
use of forceps, minimal neonatal depression
Disadvantages: invasive technique, side
effects (hypotension, headache, itching,
nausea, urinary retention, limited mobility),
nerve damage, infection
23. Anesthesia in the parturient
General considerations of the parturient undergoing surgery
Obstetric surgery
24. General considerations
Altered physiology as mentioned
Risks to the fetus:
Effect of the disease process/therapies
Possible teratogenicity of anesthetic agents
Intraoperative effects on uteroplacental blood flow
Increased risk of preterm labor/ risk of abortion
25. Maternal considerations
Altered physiology
Altered response to anesthesia
Decrease in MAC
Increased sensitivity to neuraxial agents
Decreased plasma cholinesterase
Decreased protein binding (more free drug)
Limited drug information in parturients
26. Fetal Considerations
Teratogenicity:
Limited information due to impracticality of conducting trials
with sufficient power
Guidelines based on a) effects on reproduction in animals; b)
epidemiological surveys of OR personnel; c) studies of
pregnancy outcomes in parturient undergoing ante partum
surgery
27. Nitrous oxide has been shown to have
a teratogenic effect in rats during the
first trimester
No anesthetic agent is a proven
teratogen in humans
Anesthetic agents deemed safe
include: thiopental,morphine,
meperidine,fentanyl, succinylcholine,
NDMRs
Limiting nitrous oxide use but only if
hypotension secondary to volatiles
can be avoided
28. Anesthetic management in the parturient should be directed
to:
Avoidance of hypoxemia
Avoidance of hypotension
Avoidance of acidosis
Maintain PaCO2 in the normal range for the parturient
Minimize effects of aortocaval compression
30. Preparation
Premeds: antacid (sodium citrate)
IV access and fluid bolus within 30
minutes of operating (avoid glucose
containing fluids)
Left lateral tilt with wedge under right
pelvis
Routine Monitors: ECG, NIBP, pulse
oximeter, fetal monitoring
Additional monitors for GAs: ETCO2,
nerve stimulator, temp probe
31. Preventing complications
Aspiration prophylaxis
Detailed airway assessment
Fluid resuscitation/left lateral tilt to prevent hypotension
Safe practice for placement of neuraxial blocks
32. Anesthetic techniques
Local infiltration by surgeon
Regional anesthesia: spinal, epidural, combined spinal-
epidural
General anesthesia
33. Local Infiltration
Rarely performed
Patient usually in extremis
Surgery must be done via midline incision, gentle retraction,
no exteriorization of the uterus
Usually done to supplement a regional technique if local
anesthetic toxicity not a concern
34. Regional: Spinal Anesthesia
Simple to perform
Rapid onset
Single shot technique
Profound neural block
Technique of choice for uncomplicated elective caesarean
sections and in many emergency caesarean sections
36. Regional: Epidural Anesthesia
More technically challenging
Slower onset
Used when already placed for labor analgesia
Useful in parturient where a slow, controlled onset of block
is needed
Allows prolongation of block should surgery be complicated
38. Regional: Combined spinal-
epidural
Used when require the speed and density of a spinal
anesthetic with the flexibility of prolonging the block by
supplemental increments of local anesthesia via the
epidural catheter
Complications: as mentioned for spinals and epidurals
39. General Anesthesia
Used when
Patient refuses regional technique
Regional technique is contraindicated
Emergency C/S when there is inadequate/absent regional
analgesia and to delay will cause undue risk to the fetus /
mother
40. General Anesthesia
Complications:
Failed intubation
Failed ventilation causing death or neurological injury
Awareness
Aspiration pneumonia
41. Anesthesia: Effects on the
fetus
Avoid hypotension, hypoxia, acidosis,
hyperventilation
Limit time between uterine incision
and delivery to less than 3 minutes
Infants exposed to GA have lower
Apgar at one minute but no difference
at 5 mins
No significant alteration in
neurobehavioral scores with regional
techniques
42. MCQ 1. Epidural Anesthesia in
Obstetric Practice. Which of the
following is false.
A. Commonly causes itching
B. Can be used to control blood pressure in pre-eclampsia
C. Causes uterine relaxation
D. Causes urinary retention
E. Contributes to the effects of aortocaval compression
43. MCQ 1. Epidural Anesthesia in
Obstetric Practice…
A. Commonly causes itching
B. Can be used to control blood pressure in pre-eclampsia
C. Causes uterine relaxation
D. Causes urinary retention
E. Contributes to the effects of aortocaval compression
44. Itching is one of the most common side-effects of opioids
when delivered in the epidural space. Their use allows for a
decreased concentration of local anesthetic whilst
maintaining excellent analgesia. Patients have better motor
function and retain the ability to push.
45. MCQ 2. All of the following are
false concerning general
anesthesia in the parturient,
EXCEPT:
A. General anesthesia reduces gastric pH
B. MAC is decreased
C. It is contra-indicated in patients with a bleeding diathesis
D. Is a major cause of overall maternal mortality
E. Succinylcholine crosses the placenta
46. MCQ 2. All of the following are
false concerning general
anesthesia in the parturient,
EXCEPT:
A. General anesthesia reduces gastric pH
B. MAC is decreased
C. It is contra-indicated in patients with a bleeding diathesis
D. Is a major cause of overall maternal mortality
E. Succinylcholine crosses the placenta
47. General anesthetics have no effect on gastric pH.
It is the method of choice in patients with a bleeding diathesis since
regional anesthesia is contra-indicated.
Although of concern to Anesthesiologists general anesthesia is not a
major cause of maternal mortality.
Succinylcholine is unable to cross the placenta and effect the fetus.
48. MCQ 3. The following are all true
concerning the nerve supply of the
uterus , EXCEPT:
A. Sensation from the upper segment
travels with the sympathetic nerves to
T11-T12
B. Sensation from the birth canal is
via the pudendal nerve
C. Lower segment innervation is via
S2-4
D. Motor function occurs via
sympathetic and parasympathetic
nerves
E. An intact nerve supply is essential
to initiate normal labor
49. MCQ 3. The following are all true
concerning the nerve supply of the
uterus , EXCEPT:
A. Sensation from the upper segment
travels with the sympathetic nerves to
T11-T12
B. Sensation from the birth canal is
via the pudendal nerve
C. Lower segment innervation is via
S2-4
D. Motor function occurs via
sympathetic and parasympathetic
nerves
E. An intact nerve supply is essential
to initiate normal labor
50. Normal labor occurs in patients with a transected spinal
cord.
51. MCQ 4: Physiological changes
seen in the last trimester include all
EXCEPT
A. Resting PaCO2 is decreased
B. Hematocrit is decreased
C. Blood volume is increased
D. Gastric secretion is increased
E. Total peripheral resistance is decreased
52. MCQ 4: Physiological changes
seen in the last trimester include all
EXCEPT
A. Resting PaCO2 is decreased
B. Hematocrit is decreased
C. Blood volume is increased
D. Gastric secretion is increased
E. Total peripheral resistance is decreased
53. Gastric acid production does not increase. There is an
increased risk of aspiration due to delayed gastric emptying
and a decrease in lower esophageal sphincter tone.
54. MCQ 5: All of the following are
suitable for aspiration prophylaxis
prior to caesarean section,
EXCEPT:
A. Metoclopramide
B. Glycopyrollate
C. Sodium citrate
D. Clear fluids 4 hours pre-op
E. Ranitidine
55. MCQ 5: All of the following are
suitable for aspiration prophylaxis
prior to caesarean section,
EXCEPT:
A. Metoclopramide
B. Glycopyrollate
C. Sodium citrate
D. Clear fluids 4 hours pre-op
E. Ranitidine
56. Metoclopramide acts as a pro-kinetic to
empty the stomach of any gastric contents.
Sodium citrate is a non-particulate antacid
used to neutralize gastric contents.
Ranitidine is an H2 antagonist used to
prevent gastric acid secretion.
Allowing clear fluids up to 4 hours prior to
suregry has been shown to decrease the
gastric content volume so decreasing the
risk of aspiration.
Glycopyrollate is an anti-sialogogue used for
preoperative preparation when an awake
intubation is anticipated.
57. MCQ 6: All are suitable techniques
for pain relief in labor EXCEPT:
A. Transcutaneous electrical nerve stimulation
B. White noise
C. Epidural bupivacaine
D. Intrathecal narcotics
E. 70% Nitrous oxide in Oxygen
58. MCQ 6: All are suitable techniques
for pain relief in labor EXCEPT:
A. Transcutaneous electrical nerve stimulation
B. White noise
C. Epidural bupivacaine
D. Intrathecal narcotics
E. 70% Nitrous oxide in Oxygen
59. The concentration of nitrous oxide in oxygen when used for
analgesia is 50%. Higher concentrations can result in loss
of consciousness.
60. MCQ 7: Which of the following is a
contraindication to epidural
analgesia in labor:
A. Previous caesarean section
B. Fetal distress
C. INR 1.6
D. Maternal exhaustion
E. Maternal multiple sclerosis
61. MCQ 7: Which of the following is a
contraindication to epidural
analgesia in labor:
A. Previous caesarean section
B. Fetal distress
C. INR 1.6
D. Maternal exhaustion
E. Maternal multiple sclerosis
62. Epidural analgesia is not contraindicated in
patients who have had a prior C/S. The pain
caused as a result of uterine rupture is not
effectively masked by epidural analgesia.
Fetal distress can be reduced by epidural
analgesia so long as hypotension is avoided
Maternal exhaustion is an indication for
epidural analgesia.
Maternal multiple sclerosis is not a
contraindication to epidural analgesia as
long as the concentration of local anesthetic
is reduced
Coagulopathy is an absolute
contraindication to epidural analgesia
63. MCQ 8 : Likely complications of
epidural opioids include all of the
following, EXCEPT:
A. Itching
B. Urinary retention
C. Hypotension
D. Respiratory depression
E. Nausea
64. MCQ 8 : Likely complications of
epidural opioids include all of the
following, EXCEPT:
A. Itching
B. Urinary retention
C. Hypotension
D. Respiratory depression
E. Nausea