Obstetrics Anesthesia Guide

Obstetrics Anesthesia
By Dr. Mahmoud Abdelkhalek

Physiological changes of pregnancy
 Physiologic and anatomic changes develop across many organ
systems during pregnancy and the postpartum period
 The Metabolic, hormonal and physical changes all have impact on
anesthetic management
 To the anesthesiologist, the most important changes are those that
affect the respiratory and circulatory systems.

Respiratory system
 There is an increased risk of difficult or failed intubation in the
parturient
 This is primarily due mucosal vascular engorgement which leads to
airway edema and friability.
 Laryngoscopy can be further impeded by the presence of large
breasts
 Increased risk of pulmonary aspiration of stomach contents due to:
– Upward displacement of the stomach
– Decreased gastric motility and increased gastric secretions
– Incompetent gastro-esophageal junction

Respiratory system
 In fact, airway complications (difficult intubation, aspiration) are the
most common anesthetic cause of maternal mortality
 The best means of avoiding this outcome is to avoid general
anesthesia (by using a regional technique)
 If a general anesthetic is required, NPO status for eight hours is
preferred although not achievable in an emergency situation
 Pretreatment of all parturients with a non-particulate antacid (30 cc
sodium citrate p.o.) as well as with a histamine blocker (ranitidine 50
mg IV) is important
 Finally, a rapid sequence induction with cricoid pressure is mandatory

Respiratory system
 With the apnea that occurs at induction of anesthesia, the parturient
becomes hypoxic much more rapidly than the non-pregnant patient
due to 2 main reasons:
– Oxygen requirement has increased by 20% by term
– Decrease of FRC, which serves as an “oxygen reserve” by 20%
due to upward displacement of the diaphragm
 Minute ventilation increases to 150% of baseline leading to a
decrease in PaCO2 (32 mmHg)
 The concomitant rightward shift in the oxyhemoglobin dissociation
curve allows increased fetal transfer of O2

CVS
 Blood volume increases by 40% during pregnancy in preparation for
the anticipated 500-1000 cc average blood loss during vaginal or
Caesarian delivery, respectively
 The increase of intravascular volume may not be tolerated by
parturients with concomitant cardiovascular disease, such as mitral
stenosis
 When the pregnant patient is in the supine position, the heavy gravid
uterus compresses the major vessels in the abdomen leading to
maternal hypotension and fetal distress (supine hypotensive
syndrome)
 Left lateral tilt, usually achieved with a pillow under the woman’s
right hip, is an important positioning maneuver

Stages of normal labour
 The 1st stage of labour
– Cervix effaces then cervical dilatation begins
– Rate of cervical dilatation:
 Primigravida: 1 cm/ hour
 Multigravida: 2 cm/ hour
– Routine observations:
 Fetal HR every 15 minutes
 Maternal pulse and BP every 30 minutes
 Temperature 4-hourly
 Urine analysis at each emptying of bladder

 The 2nd stage of labour
– Commences at full dilatation of the cervix and terminates at the
delivery of the baby
– If prolonged more than 1 hour the fetus may become acidotic
– At the delivery of anterior shoulder, IM oxytocin is given to hasten
the delivery of the placenta and to stimulate the uterine
contraction

 The 3rd stage of labour
– The complete delivery of the placenta& membranes& contraction
of the uterus
– Placental blood flow (15% of CO) redistribute to maternal
circulation and may precipitate heart failure immediately
postpartum in women with cardiac disease

Analgesia for labour
 The three most commonly used types of analgesic agents in labour
are:
1. Inhaled N2O (Entonox®)
2. Opioids
3. Regional techniques
 N2O/O2 (Entonox®) is the most commonly used inhalational agent
and may be slightly more efficacious than pethidine, but complete
analgesia is never attained

 Worldwide, pethidine remains one of the most popular opioids for
labour analgesia
 Drawbacks:
– Has a long half-life in the fetus (18–23hr)
– Known to reduce fetal heart rate variability in labour
– Associated with changes in neonatal neurobehaviour, including an
effect on breastfeeding
 When regional analgesia is contraindicated, fentanyl or remifentanil
PCA may be more beneficial

 Uterine pain is transmitted in sensory
fibres, which accompany sympathetic
nerves and end in the dorsal horns of
T10–L1
 Vaginal pain is transmitted via the
S2–S4 nerve roots (the pudendal
nerve)
 Neuraxial techniques; spinal,
combined spinal/epidural (CSE)&
epidural; can be expected to provide
effective analgesia in over 85% of
women
 Remember that acceptable analgesia
for women in labour does not mean a
complete absence of sensation

 However, neuraxial analgesia was associated with:
– Hypotension
– Increased oxytocin use
– An increased incidence of maternal pyrexia
– A 40% increase in the incidence of instrumental deliveries,
although techniques, such as using low concentrations of LA, can
reduce this effect
 Fetal umbilical pH was marginally improved with epidural analgesia

Regional labour analgesia
 Indications
– Maternal request
– Expectation of operative delivery (e.g. multiple pregnancy,
malpresentation)
– Obstetric disease (e.g. pre-eclampsia)
– Maternal disease: in particular, conditions in which sympathetic
stimulation may cause deterioration in maternal or fetal condition
– Specific CVS disease (e.g. regurgitant valvular lesions)
– Severe respiratory disease (e.g. cystic fibrosis)
– Conditions in which GA may be life-threatening (e.g. morbid obesity)

Regional labour analgesia
 Contraindications
– Allergy (true allergy to amide LAs is rare)
– Local infection
– Uncorrected hypovolemia
– Raised ICP
– Coagulopathy:
 Spinal analgesia is probably safer than epidural analgesia
 Tests of coagulation and the platelet count should be within 6hr of
the time of the procedure
 Especially with pre-eclampsia, it is also important to consider the rate
at which the platelet count is falling

Relative contraindications
 Expectation of significant hemorrhage
 Untreated systemic infection (risk of ‘seeding’ infection into the
epidural space)
 Specific cardiac disease (e.g. severe valvular stenosis, Eisenmenger’s
syndrome, peripartum cardiomyopathy (rapid changes in BP, preload,
and afterload of the heart)
 ‘Bad backs’ and previous back surgery do not contraindicate regional
analgesia/anesthesia, but scarring of the epidural space may limit the
effectiveness of epidural analgesia and increase the risk of
inadvertent dural puncture. Intrathecal techniques can be expected
to work normally

Consent
 Information about labour analgesia should always be available
antenatally
 Most UK anesthetists do not take written consent before inserting an
epidural for labour analgesia, but ‘appropriate’ explanation must be
given
 The explanation and, in particular, the possible hazards discussed
must be documented, as many women do not accurately recall
information given in labour
 Preferably an information leaflet for mothers including the incidence
of a variety of potential complications, including neurological injury

Epidural analgesia for labour
 Competent assistant should be available
 Scrupulous attention to sterile technique is required. A mask, hat,
gown, and gloves should be worn
 Establish IV access
 Fluid preload may help with subsequent hypotension
 Position in either a full lateral or sitting position
– Finding the midline in the obese may be easier in the sitting position
– Accidental dural puncture may be slightly lower in the lateral position
 Fetal HR should be recorded before and during the establishment of
analgesia

 Skin sterilization with 0.5% chlorhexidine is common in the UK:
– most sterilizing solutions, including chlorhexidine, are neurotoxic, so
great care must be taken to avoid contamination of the neuraxial
equipment or the anesthetist’s gloves
– It is recommended that chlorhexidine is never on the sterile work
surface, and it is sensible to complete skin sterilization before the
neuraxial equipment is unwrapped
– Chlorhexidine must be allowed to dry before the skin is touched
 Locate the epidural space:
– Loss of resistance to saline may have slight advantages in both the
reduced incidence of accidental dural puncture and reduced incidence of
‘missed segments’, compared with loss of resistance to air
– The incidence of puncturing a blood vessel with the epidural catheter is
reduced if 10mL of saline is flushed into the epidural space before the
catheter is inserted

 Always insert the catheter as gently as possible
 Introduce 4–5cm of the catheter into the epidural space:
– Longer has an increased incidence of unilateral block, and shorter
increases the chance that the catheter pulls out of the space
– Multihole catheters have a lower incidence of unsatisfactory blocks
 Check for blood/CSF:
– If blood is aspirated, see if the catheter can be withdrawn further (leave
a minimum of 3cm in the space)
– If blood is still present, remove the catheter, and reinsert

 Give an appropriate test dose
– Using 0.5% bupivacaine significantly increases motor block
– Using 1:200 000 adrenaline to detect IV placement of a catheter has
both high false positive and false negative rates
– Many anesthetists will use 8–15mL of 0.1% bupivacaine with a dilute
opioid (2 micrograms/mL fentanyl) as both the test and main doses
– This will exclude intrathecal placement but may not exclude intravascular
placement
– However, the complete absence of a detectable block after a normal
labour analgesia loading dose is a warning sign of possible IV cannulation
– Remember every dose is a ‘test dose’!

 If required, give further LA to establish analgesia:
– There should be no need to use concentrations >0.25% bupivacaine
 Measure maternal BP every 5min for at least 20min after every bolus
dose of LA
 Once the epidural is functioning, it can be maintained by one of three
methods:
1. Intermittent top-ups of LA administered by a PCEA
2. A continuous infusion of LA (5–12mL/hr of 0.0625–0.1%
bupivacaine with 2 micrograms/mL fentanyl)
3. Intermittent top-ups of LA administered by midwives

Combined spinal/epidural analgesia for labour
 A combination of low-dose subarachnoid LA and/or opioid, together
with subsequent top-ups of weak epidural LA, produces a rapid onset
of analgesia with minimal motor block
 An epidural technique alone can produce a similar degree of
analgesia and motor block but may take 10–15min longer to establish
 Indications for CSEs include establishing rapid analgesia in women
who are unable to cope with labour pain, re-establishing analgesia for
women who have had a failed epidural, and preservation of leg
strength for women who want to walk in labour
 In some centres, CSEs are used routinely because of the rapid speed
of onset, the reliable initial analgesia, together with some evidence of
improved epidural analgesia after the initial spinal analgesia has
receded

 CSE can be performed as a needle-through-needle technique or as
separate injections in the same, or in different, intervertebral spaces:
 Either:
– Locate the epidural space at the L3/4 interspace or below with a Tuohy
needle (The level of the iliac crests usually corresponds to the spinous
process of L4 (Tuffier’s line), although there is variation between
individuals)
– Pass a 25–27G pencil-point needle through the Tuohy needle to locate
the subarachnoid space
– Inject the subarachnoid solution (e.g. 0.5–1.0mL of 0.25% bupivacaine
with 5–25 micrograms of fentanyl or the equivalent dose in mg)
– Without rotating the epidural needle, insert an epidural catheter

 Or:
– Perform the spinal at L3/4 or below with a 25–27G pencil-point needle
– Inject the spinal solution
– Insert an epidural catheter at a different interspace
– This technique is particularly helpful when women are unable to stay still
because of pain
– The spinal is usually quick and relatively easy, and, once analgesia has
been established, an epidural can be performed with a more cooperative
patient after 15min, once the analgesia from the spinal solution is
established,
– check the degree of motor and sensory block, and then administer an
epidural test dose
– Further management of the epidural is the same as for epidural analgesia
alone

‘Walking’ epidurals
 Effective analgesia with minimal motor block of the lower limbs can be
readily produced with low doses of an epidural or intrathecal LA, usually in
combination with an opioid, e.g. subarachnoid injection of 1–2.5mg of
bupivacaine with 10–25micrograms of fentanyl or an epidural bolus of 15–
20mL of 0.1% bupivacaine with 2 micrograms/mL fentanyl, and subsequent
epidural
 Top-ups of 15mL of the same solution, as required
 In some centres, women with minimal motor blockade are encouraged to
mobilize
 The possible advantages of these techniques include:
– Minimal motor block associated with these techniques increases maternal
satisfaction scores
– Intrathecal, as opposed to epidural, techniques produce a more rapid
onset of analgesia

The poorly functioning epidural
 Look for the pattern of failure (Table 33.3)
 Remember that a full bladder may cause breakthrough pain, ask the
midwife if a full bladder is likely
 Carefully assess the spread of the block
 It is important to be confident that the epidural could be topped up
for a Caesarean section, if required
 Therefore, if in doubt, re-site the epidural

The poorly functioning epidural

Complications of epidural analgesia
 Hypotension:
– In the absence of fetal distress, a fall in systolic BP of 20% or to
100mmHg (whichever is higher) is acceptable
– However, uterine blood flow is not autoregulated, and prolonged
or severe hypotension will cause fetal compromise
– IV fluid loading is not routinely required but patients should not
be hypovolemic before instituting regional analgesia
– When hypotension or fetal distress is detected, it should be
treated quickly
– Avoid aortocaval occlusion—make sure that the patient is in the
full lateral position. (Remember that, in the lateral position, BP
should be measured in the dependent arm—there is often a
10mmHg difference between the upper and lower limbs)

Complications of epidural analgesia
– Give an IV fluid bolus of crystalloid solution and, if the fetus is
distressed, mask O2 supplementation
– Give 6mg IV ephedrine, and repeat as necessary
– If the fetus is distressed, call the obstetricians
– Remember that brachial artery pressure may not reflect uterine
artery blood flow
– If fetal distress is detected and is chronologically related to a
regional anesthetic procedure, treat as above, even in the
absence of overt hypotension

Subdural block
 Subdural block occurs when the epidural catheter is misplaced
between the dura mater and arachnoid mater
 In obstetric practice, the incidence of clinically recognized subdural
block is <1:1000 epidurals
 However, subdural blocks may be clinically indistinguishable from
epidural blocks
 Definitive diagnosis is radiological

Subdural block
 The classical characteristics of a subdural block are:
– A slow onset (20–30min) of a block that is inappropriately
extensive for the volume of LA injected
– The block may extend to the cervical dermatomes, and Horner’s
syndrome may develop
– The block is often patchy and asymmetrical
– Sparing of motor fibres to the lower limbs may occur
– A total spinal may occur with top-up doses. This is probably due
to an increase in volume, causing the arachnoid mater to rupture
– If a subdural is suspected, re-site the epidural catheter

Total spinal
 The incidence of unexpected high or total spinal is variously reported
to be 1:1500 to 1:4500 epidurals
 Symptoms are of a rapidly rising block
 Initially, difficulty in coughing may be noted (which is commonly seen
during regional anesthesia for a Caesarean section), then loss of
hand and arm strength, followed by difficulty with talking, breathing,
and swallowing
 Make sure that the equipment for ventilatory and CVS support are
immediately available
 Respiratory paralysis, CVS depression, unconsciousness, and finally
fixed dilated pupils may ensue

Management of total spinal
 Maintain airway and ventilation; avoid aortocaval compression, and
provide CVS support
 Even if consciousness is not lost, intubation may be required to
protect the airway
 Careful maternal and fetal monitoring is essential and, if appropriate,
delivery of the fetus
 In the absence of fetal distress, a Caesarean section is not an
immediate requirement
 Ventilation is usually necessary for 1–2hr

Accidental intravenous injection of local anesthetic
 ‘Every dose is a test dose.’ The maxim is to avoid injecting any single
large bolus of local LA intravascularly
 The risk can be minimized by:
– Meticulous attention to the technique during placement
– Always check for blood in the catheter
– Always being alert to symptoms of IV injection with every dose of LA,
even when previous doses have been uncomplicated
– Dividing all large doses of LA into aliquots
– Using appropriate LA’s
– If neurological or cardiovascular symptoms occur stop injecting the LA
– Treat according to BLS and ALS protocols
– Administer 20% lipid emulsion

Neurological damage
 Neurological damage does occur after childbirth, but establishing
cause and effect is difficult
 Neurological sequelae following delivery under GA is as common as
delivery under regional anesthesia, suggesting that obstetric causes
of neurological problems are probably commoner than any effects
from the regional technique
 Prolonged neurological deficit after epidural anesthesia occurs in
~1:10 000 to 1:15 000
 Major neurological damage probably occurs in <1:80 000 neuraxial
procedures in the obstetric population

Dural puncture
 When loss of CSF is greater than production, as might occur through
a dural tear, CSF pressure falls, and the brain sinks, stretching the
meninges
 This stretching is thought to cause headache
 Compensatory vasodilatation of intracranial vessels may further
worsen symptoms
 The incidence of dural puncture should be <1% of epidurals
 Symptoms may not develop for several days
 If untreated, headaches are not only unpleasant, but also can very
rarely be life-threatening, usually as a result of intracranial
hemorrhage or coning of the brainstem
 Management of an accidental dural puncture can be divided into
immediate and late

Management of dural puncture:
Immediate management
 The initial aim is to achieve effective analgesia without causing
further complication
 Either:
– If a dural puncture occurs, pass the ‘epidural’ catheter into the
subarachnoid space
– Label the catheter clearly as an intrathecal catheter, and only
allow anesthetists to perform top-ups
– Give intermittent top-ups through the catheter (1.0–2.5mg of
bupivacaine ± 5–25 micrograms of fentanyl)
– Tachyphylaxis may occur with prolonged labour

Management of dural puncture
– Advantages:
 The analgesia produced is likely to be excellent
 There is no possibility of performing another dural puncture on reinsertion of
the epidural
 The unpredictable spread of the epidural solution through the dural tear is
eliminated
 The need for an epidural blood patch (although not the incidence of
 PDPH) may be reduced
– Disadvantages:
 There is a theoretical risk of introducing infection
 The catheter may be mistaken for an epidural catheter

 Or:
– Remove the epidural catheter
– Reinsert the epidural at a different interspace—usually one interspace
higher
– If the reason for the dural puncture was difficult anatomy, a senior
colleague should take over
– Run the epidural as normal, but beware of intrathecal spread of LA
– Be particularly cautious if the epidural catheter is topped up with a large
dose of anesthetic for a Caesarean section
– All top-ups should be given by an anesthetist
 With either technique, the patient should be informed, at the earliest
opportunity, that a dural puncture has occurred and of the likely sequelae
 Labour itself may be allowed to continue normally. Arrange daily post-natal
follow-up

Late management
 Following a dural puncture with a 16G Tuohy needle, the incidence of
PDPH is ~90%
 In only 40% of dural punctures CSF is recognized flowing from the
Tuohy needle
 In >30% of individuals who develop PDPH, a dural puncture was not
recognized in labour
 Headaches in the post-natal period are common
 The key differentiating factor between a ‘normal’ post-natal headache
and PDPH is the positional nature of the latter

 Common features of PDPH include:
– Typically, the onset is 24–48hr post-dural puncture, if untreated,
they are said to last 7–10d, but the evidence is poor
– Characteristically, PDPH is worse on standing. Headache is often
absent after overnight bed rest but returns after mobilizing
– The headache is usually fronto-occipital and may be associated
with neck stiffness
– The headache may be relieved by tight abdominal compression—
while abdominal binders are no longer used as a treatment, this
can be a useful diagnostic tool

– Photophobia and difficulty in accommodation are common
– Hearing loss, tinnitus, and 6th nerve palsy with diplopia are
possible
– If these signs develop, women should be encouraged to have a
blood patch sooner rather than later, as these signs are an
indication of a more severe headache, and the risk of more
serious complications—seizures, subdural hematoma, and cerebral
herniation—may be increased
– Nausea in up to 60% of women
 Treatment is either to alleviate symptoms, while waiting for the dural tear
to heal itself, or to seal the puncture
 Epidural blood patching is the only commonly used method of sealing dural
tears, although neurosurgical closure has been reported

Symptomatic treatment
 While waiting for the dural puncture to seal itself, simple analgesics
(paracetamol and NSAIDs) are the mainstays of symptomatic
treatment. They should always be offered, even though they are
unlikely to completely relieve severe PDPH
 Adequate fluid intake should be encouraged, although there is no
evidence that hydration reduces the incidence of PDPH
 Caffeine/ theophyllines act by reducing intracranial vasodilatation,
which is partially responsible for the headache. IV aminophylline has
been shown to reduce the incidence of headache. However, concern
has been expressed that the incidence of seizures following dural
puncture may be increased in the presence of caffeine
 Definitive treatment is with epidural blood patching

Epidural blood patch
 Epidural blood patch performed around 48hr post-partum has a 60–
90% cure rate at the 1st attempt
 The proposed mechanism of action is 2-fold:
– Blood injected into the epidural space compresses the dural sac
and raises the ICP. This produces an almost instantaneous
improvement in pain
– The injected blood forms a clot over the site of the dural tear, and
this seals the CSF leak

 Blood injected into the epidural space predominantly spreads
cephalad, so blood patches should be performed at the same or lower
interspace as the dural puncture
 Consent must be obtained
 Two operators are required. One should be an experienced
‘epiduralist’; the other is required to take blood in a sterile manner
 The patient should have a period of bed rest before performing the
patch to reduce the CSF volume in the epidural space
 Aseptic technique must be meticulous both at the epidural site and
the site of blood letting (usually the antecubital fossa)

 An epidural should be performed at the same or a lower vertebral
interspace as the dural puncture, with the woman in the lateral
position to minimize CSF pressure in the lumbar dural sac
 Once the epidural space has been identified, 20mL of blood is
obtained
 Inject the blood slowly through the epidural needle, until either a
maximum of 20mL has been given or pain develops (commonly in the
back or legs). If pain occurs, pause, and, if the pain resolves, try
continuing with a slow injection. If the pain does not resolve or
recurs, then stop
 To allow the clot to form, maintain bed rest for at least 2hr, and then
allow slow mobilization

 As far as possible, the patient should avoid straining, lifting, or
excessive bending for 48hr, although there are obvious limitations
when a woman has a newborn infant to care for
 Follow-up is still required. Every woman should have clear
instructions to contact the anesthetists again if symptoms recur, even
after discharge home
 Serious complications of blood patching are rare. However, backache
is common, with 35% of women experiencing some discomfort 48hr
post-epidural blood patch and 16% of women having prolonged backache
(mean duration 27d)
Other reported complications include repeated dural puncture, neurological
deficits, epileptiform fits, and cranial nerve damage
Suggestions that labour epidurals after blood patching may be less effective
have not been confirmed

Cesarean section (CS)
 With all Caesarean sections, it is vital that the obstetrician clearly
communicates the degree of urgency to all staff. The four-point
classification in Table is a modification of a system originally
proposed by Lucas

Cesarean section (CS)
 For all emergency Cesarean sections, the patient must be transferred
to theatre as rapidly as possible. Fetal monitoring should be
continued until abdominal skin preparation starts
 For category 1 (emergency) sections, the objective should be to
deliver the fetus as quickly as possible, while not compromising
maternal safety
 It is the obstetrician’s responsibility to call the urgency of the
Cesarean section, but it is the anesthetist’s responsibility to choose a
method of anesthesia that is safe

Regional anesthesia for Cesarean section
 While, in many centres, GA is commonly used for category 1 sections,
do not be pressured into choosing a form of anesthetic that is
inappropriate for the mother
 Categories 2–4 Caesarean sections are usually performed under
regional anesthesia
 Remember that the classification of urgency should be continuously
reviewed. Category 1 sections can become category 2, and vice versa

Regional anesthesia for Cesarean section:
Advantages of regional anesthesia
 Minimal risk of aspiration and lower risk of anaphylaxis
 The neonate is more alert, which promotes early bonding and
breastfeeding
 Fewer drugs are administered, with less ‘hangover’ than after GA
 Better post-operative analgesia and earlier mobilization
 Mothers who are nervous about having a Cesarean section under regional
anesthesia should be given a clear explanation of the advantages and
disadvantages of regional anesthesia and GA but should never be coerced into
having a regional technique

 There are three techniques for neuraxial anesthesia—epidural, spinal,
and CSE
 Epidural anesthesia is most commonly used for women who already
have labour epidural analgesia
 Spinal anesthesia is the most popular technique for an elective
Caesarean section, although, in some centres, CSE’s are preferred
 The speed of onset of sympathectomy that occurs with spinal
anesthesia (as opposed to epidural) results in a greater fall in
maternal cardiac output and BP and may be associated with a more
acidotic neonate at delivery
 This can be minimized by using a prophylactic phenylephrine infusion
and careful positioning of the mother

 When there is particular concern about the speed of onset of a block,
a CSE approach can be used, injecting only a small dose of
intrathecal LA and extending the block, if required, using the epidural
catheter
 Spinal anesthesia generally provides a better quality of analgesia than
epidural anesthesia
 Whatever technique is chosen, a careful history and an appropriate
examination should be performed. This should include checking:
– Blood group and antibody screen. Routine cross-matching of blood is not
required, unless hemorrhage is expected or if antibodies that interfere
with cross-matching are present
– Ultrasound reports to establish the position of the placenta. A low-lying
anterior placenta puts a woman at risk of major hemorrhage, particularly
if associated with a scar from a previous Caesarean section

 An explanation of the technique must be offered. Although a
Cesarean section under regional anesthesia becomes routine for the
anesthetist, it can be an intimidating prospect for the mother
 Reassurance and support are important. However, the possibility of
complications must also be mentioned, including the possibility of
intraoperative discomfort and its management
 Pain during regional anesthesia remains a leading obstetric anesthetic
cause of maternal litigation
 Document all complications that are discussed

Cesarean section: epidural
 Indications for a Caesarean section under epidural anesthesia
include:
– Women who already have epidural analgesia established for
labour
– Specific maternal disease (e.g. cardiac disease) where rapid
changes in SVR might be problematic

Cesarean section: epidural
 Table shows advantages and disadvantages of epidural for CS

Cesarean section: spinal
 Spinal anesthesia is the most commonly used technique for elective
Cesarean sections
 It is rapid in onset, produces a dense block, and, with intrathecal
opioids, can produce long-acting post-operative analgesia.
 However, hypotension is much commoner than with epidural
anesthesia

Hypotension
 Preventing maternal hypotension, rather than treating BP after
hypotension has occurred, is associated with better fetal outcome
and less maternal nausea
 There are two principal methods of treating hypotension—pressor
agents and fluid

Hypotension: Pressor agents
 A simple regime is to use a syringe driver with a solution of 100 micrograms/mL of
phenylephrine (i.e. make up 10mg in 100mL of saline, and decant 20mL into a syringe)
 Start infusing at 30mL/hr, as the spinal solution is injected
 Titrate to response, adjusting the rate of infusion up or down in increments of 10mL/hr
 During the infusion, expect the HR to gradually slow, so give anticholinergic agents, as
required
 Reduce and stop the infusion post-delivery
 Be careful with this technique in hypertensive individuals. Start at a lower infusion rate
 Metaraminol can be used as an alternative to phenylephrine.
Using prophylactic pressor agents is beneficial for both mother and fetus. Ephedrine was
used to treat hypotension in obstetric neuraxial anesthesia for many years. However, in
the last decade, it has been established that treatment to normotension with
phenylephrine is associated with better fetal umbilical pH than when ephedrine is used,
although the difference is marginal. If phenylephrine is used, bolus doses of 50–100
micrograms can cause profound reflex bradycardias, so, if possible, use a phenylephrine
infusion instead

Hypotension: Fluid
 However, crystalloid preloading is very ineffective at preventing
hypotension
 In addition, in women with severe pre-eclampsia, large preloads are
harmful, as the rise in filling pressures and the reduced colloid
osmotic pressure will predispose to pulmonary edema
 Using colloids as a preload is more effective, but colloids may be
associated with significant problems such as anaphylaxis
 There is evidence that co-loading with crystalloid (giving fluid as the
block is establishing) is more effective than preloading
A fluid preload was a traditional part of the anesthetic technique for regional anesthesia
It had two functions:
 To maintain the intravascular volume in a patient who is likely to lose 500–1000mL of
blood
 To reduce the incidence of hypotension associated with regional anesthesia

Hypotension: Fluid
 A co-load should be:
– Timely (given immediately before or during the onset of the
regional technique to minimize redistribution)
– Limited to 10–15mL/kg of crystalloid. Larger volumes should be
avoided, as they offer little advantage and may be harmful
– More fluid should only be given as clinically indicated
– Emergency Caesarean section should not be delayed to allow a
fluid preload to be administered

Cesarean section: general anesthesia
 Maternal request
 Urgent surgery (in experienced hands and with a team that is familiar
with rapid regional anesthesia, a spinal can be performed almost as
rapidly as a GA)
 Regional anesthesia contraindicated (e.g. coagulopathy, maternal
hypovolemia)
 Failed regional anesthesia
 Additional surgery planned at the same time as a Caesarean section
• Elective GA is now uncommon in the UK
• The majority of complications relate to the airway
• Failed intubation is much more frequent in obstetric than non-obstetric anesthesia
• All obstetric theatres should have equipment to help with the difficult airway, and all
obstetric anesthetists should be familiar with a failed intubation drill
Indications for GA include:

Effect of general anesthesia on the fetus
 Lower fetal 1min and 5min Apgar scores are commoner when GA is
used for Cesarean section
 Most anesthetic agents, except for muscle relaxants, rapidly cross the
placenta
 Opioids administered before delivery may cause fetal depression.
Which can be rapidly reversed with naloxone (e.g. 200 micrograms
IM or 10 micrograms/kg IV)
 If there is a specific indication for opioids before delivery, they should
be given, and the neonatologist informed
 Hypotension, hypoxia, hypocapnia, and excessive maternal
catecholamine secretion may all be harmful to the fetus

Failed intubation
 Failed intubation is ten times commoner in the obstetric population
(~1:300, compared to 1:3000)
 Causes of failed intubation include obesity, increased fatty tissue,
pharyngeal/laryngeal edema, large tongue, large breasts, incorrect
cricoid pressure, complete dentition, and the experience and training
of anesthetic staff
 When intubation fails, but mask ventilation succeeds, a decision on
whether to continue with the Caesarean section must be made. A
suggested grading system is shown in Box

Failed intubation
 For grade 1 cases, surgery should continue, and for grade 5 the
mother should be woken. The action between these extremes must
take account of additional factors, including the ease of maintaining
the airway, the likely difficulty of performing a regional anesthetic,
and the experience of the anesthetist
 Once a failed intubation has occurred and an airway has been
established, while waiting for the muscle relaxant to wear off, reapply
fetal monitoring as this may give useful additional information to
guide management
 If the surgery continues, decisions will have to be made on whether
to use 1st- or 2nd-generation laryngeal masks and whether to use
muscle paralysis (if yes, then rocuronium with an availability of
sugammadex may be useful)
 Ask the obstetricians to avoid fundal pressure at delivery, if possible,
because fundal pressure can increase intragastric pressure to >70
mmHg

Antacid prophylaxis
Aspiration of particulate matter, blood, or bile is associated with worse
outcome than aspiration of gastric fluid. Fluid aspiration is commonly
associated with chemical pneumonitis, and the severity of this is, in turn,
dependent on the volume and acidity of the aspirated fluid. Use of antacids
and prokinetic agents can elevate the gastric pH and reduce the intragastric
volume. A suggested regime is as follows
Elective surgery
• Ranitidine 150mg orally, 2hr and 12hr before surgery
• Metoclopramide 10mg orally, 2hr before surgery
• A total of 30mL of 0.3M sodium citrate immediately before induction of GA. (Gastric pH
>2.5 is maintained for only 30min after 30mL of 0.3M sodium citrate. If a GA is required
after this, a further dose of citrate is required)
Emergency surgery (if prophylaxis has not already been given)
• Ranitidine 50mg by slow IV injection immediately before surgery (PPIs
are an alternative). Remember this will not alter the risk of aspiration during induction
but may offer benefit by the time of extubation
• Metoclopramide 10mg IV injection immediately before surgery
• A total of 30mL of 0.3M sodium citrate orally immediately before induction of GA

Obstetrics Anesthesia Guide

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