Anesthesia for the Obstetrical
Patient
Fred
Rotenberg, MD
Dept of Anesthesiology
Rhode
Island Hospital
Grand
Rounds February 27, 2008
Anesthesia for the Obstetrical Patient
The
Pregnant Patient for Nonobstetric Surgery
LABOR
DELIVERY
OBSTETRICAL
EMERGENCIES
SPINAL
HEADACHES AND BLOOD PATCHES
Alterations in Maternal Physiology
Respiratory
Increased
O2 consumption
Decreased
FRC and pCO2 (increased MV)
Cardiovascular
Increased
blood volume and CO
Dilutional
anemia
Possible
aorto-caval compression (when supine)
GI
Reduced
gastroesophogeal tone
Reduced
anesthetic requirements (both GA & regional)
Anesthesia for the pregnant patient undergoing
non-obstetric surgery
THE OBVIOUS
AVOID
MATERNAL HYPOXIA AND HYPOTENSION
THE NOT SO OBVIOUS
Prevention
/ Treatment of preterm labor
Probably
NOT related to anesthetic management
Due
to SURGERY and/or underlying pathology
Tocolytics
(indocin or MAGNESIUM, hi dose volatile anesthetics)
Teratogenic
effects of anesthetics
Benzodiazepenes?
Nitrous oxide?
NO
GOOD EVIDENCE re: risk in humans
THE NOT SO OBVIOUS - continued
Dose
dependent effect of general anesthetics on fetal or newborn animals -
Apoptotic
neurodegeneration
Persistent
memory/learning impairments
Therefore:
USE AS LITTLE GENERAL ANESTHETIC (iv and volatile) as possible
Things we can (& should) do:
If
possible delay surgery til 2nd trimester
Less
risk of teratogenicity, miscarriage, than
1
st trimester
preterm
labor more likely in 3rd trimester
Left
uterine displacement after 24th week
Consider
aspiration prophylaxis; midazolam (reduce maternal stress ->improve fetal
blood flow)
Consider
Fetal monitoring (but no good data)
Consult
with obstetrician
ANESTHETIC CHOICES
GA-preoxygenate,
rapid sequence induction, slow reversal of relaxants, +/- N2O
Loss
of beat to beat FHR variability is normal;
Fetal
bradycardia is not!
Regional
anesthesia-minimal effects on fetus (assuming normal BP)
Cut
neuraxial dose of local anesthetic by 1/3rd compared to non-pregnant
patient
NO
evidence showing better outcome
POST – OP
Continue
fetal monitoring
Because
of risk of thromboembolism:
Early
mobilization
Consider
anticoagulants
Post
op analgesia (regional is good at this)
LABOR ANALGESIA
Intravenous
Neuraxial:
Epidural
Spinal
Combined Spinal-Epidural
Goals of Labor Analgesia
Adequate
Analgesia
Allow
the mother to participate in birthing experience
Minimal
effect on the fetus
Minimal
effect on the progress of labor
Neuraxial Blockade
A
well conducted block provides the most effective and least depressant analgesic
Spinal
opiate (single shot) – fast onset, limited duration
Continuous
Epidural – slower onset, but duration is adjustable. Potential motor block.
Combined
Spinal Epidural – best of both
Arguments for epidural for Labor
Relative
risk of maternal mortality during C-section was 16x greater with GA compared to
regional anesthetic
Epidural
for labor is now used in ~2.4m of the 4m total births in the US per year
Arguments against epidural for Labor
p Incidence
of epidural infection ~ 1/145k
p Incidence
of Epidural bleed ~ 1/150-170k
p Incidence
of persistent neurological injury ~ 1/237k (transient neurologic injury ~
1/5,500)
p Still
about 20% of pts w/ labor epidural require conversion to GA for C-section
Disadvantages of epidural analgesia for labor
p Slows
labor by approximately one hour
p Questionable
effect on Cesarean Section delivery rate
p Increases
use of instruments during vaginal delivery
p Increased
incidence of maternal fever (and subsequent fever workup of mom and child)
Effect of Early Neuraxial Analgesia on C-Section Rate
p Many
older studies show no clear difference in section rate comparing neuraxial and
parenteral opiate analgesia.
p Wong
et al. NEJM 2005
p Prospective
p demonstrates
no increase in C-section rate comparing early vs later epidural
opiate administration.
Epidural analgesia increases rate of instrument assisted
deliveries
p Rate
of instrument assisted vaginal deliveries is at least doubled by epidural
analgesia
p Etiology
of this effect?
n Motor
block from neuraxial local anesthetic
n Epidural
analgesia is associated with increased rate of occiput posterior presentation
(does this painful presentation promote increased demand for epidural
analgesia?)
n The
presence of a block might lower obstetrician’s threshold for using instruments
LABOR EPIDURAL
p Continuous
combined dilute local anesthetic plus opiate.
p Better
pain relief when combined; less motor block. Less instrumented deliveries.
Minimal absorbtion by Mom or baby.
p Eg:
Bupivicaine 0.0625% plus 2ug/ml fentanyl (+/- epinephrine) @ 10-12 ml/hr.
Notes on epidural cath placement
p Sterile
technique
p Loss
of resistance to fluid (not air)
p Prevent
intrathecal placement (0.5-3% incidence)
p Prevent
intravenous placement (3-15% incidence) (use Arrow Flex-Tip; inject 10 ml
dilute local through needle prior to cath placement).
p Aspiration
of blood or csf is quite reliable
Notes on epidural cath placement – 2
p Epinephrine
test dose is not sensitive for intravenous location.*
p Local
anesthetic (eg 45mg of Lido w/ epi) as test for intrathecal placement is
somewhat better.
n Wait
5 min after test to see motor changes.
n Seek
subjective change in pt’s ability to feel normal contraction of muscles
controlling micturation.
n Rapid
profound analgesia suggests intrathecal dose.
Notes on epidural cath placement – 3
p Safety
is determined by the above careful placement AND
p DOSE
FRACTIONATION – give 3ml every 1-2 minutes.
p “patience
is wisdom and wisdom is patience”
Notes on epidural cath placement -4
p For
a “wet tap” consider:
p Thread
the epidural cath intrathecally and use it for continuous spinal. (Then leave it
in place for 24 hrs to reduce the risk of spinal HA.)
p Spinal
catheter dosing: Bupiv 0.1% plus sufentanil 0.5ug/ml. Start with 3 ml bolus; infuse a basal rate of
2 ml/hr; allow PCEA boluses of 1 ml q 30min prn.
Combined Spinal – Epidural Analgesia
p Most
beneficial in early or late labor (especially the multiparous patient)
p #27
spinal needle through epidural needle – followed by epidural catheter insertion
p Almost
immediate pain relief with spinal opiate (fentanyl 10-25ug or sufentanil
2.5-10ug)
p 2-3
hour duration of analgesia with the spinal opiate
p Patient
may ambulate
Combined Spinal – Epidural Analgesia
p In
early labor (<4 cm dilation) CSE promotes more rapid cervical dilation than
IV hydromorphone.
p Also,
high concentrations of local anesthetic slow labor.
Combined Spinal – Epidural Analgesia
p For
severe pain in the late stages of labor may need to add local anesthetic to
spinal mixture.
p Rx
– Sufentanil 2.5-5ug plus bupivicaine 2.5 mg ->
p Rapid
profound analgesia without significant motor block.
p Longer
duration of analgesia than opiate alone.
Problems with Intrathecal Opiates
p Pruritus
– usually mild and short lived
p Nausea
and vomiting – best treatment?
p Hypotension
– Rx ephedrine.
p Urinary
retention
p Uterine
hyperstimulation and fetal bradycardia? (studies show no increased risk)
p Maternal
respiratory depression – monitor for at least 20 minutes post injection
Technical Problems with CSE
p Post
dural puncture headache
p (Incidence
is 1% or less)
p Subarachnoid
migration of epidural catheter?
p Risk
is remote – especially with separate port in epidural needle for spinal needle.
p Still
– use small incremental epidural doses
Patient Controlled Epidural Analgesia
p May
minimize drug doses, less motor block, but may provide inferior analgesia –
should we add a basal infusion rate (6-9ml/hr)?
p Must
set limits to bolus doses. (4-6ml q 5-10min; max 4-6doses/hr)
p Although
less demands on anesthesia personnel, must still make periodic assessments.
Continuous Spinal Analgesia?
p Microcatheters
– are they associated with cauda equina syndrome?
p 28g
microcatheters seem safe (Arkoosh et al
2003) but are still not FDA approved.
p Clearly
increased risk of headache with larger catheters, but advantage of controlled
incremental dosing (cf epidural) may justify its use.
Anesthesia for delivery – Vaginal
p Epidural
“Perineal dose” for imminent delivery (10-12 ml of 0.062%bupiv + 50-100ug of
fentanyl) to allow the pt to push
p For
forceps delivery or episiotomy repair: epidural 8-12 ml of 2% lido.
Anesthesia for delivery (Cesarian)
p GETA
p Spinal
p Epidural
p CSE
Regional anesthesia for C-section
p Supplementation
of Indwelling Epidural:
p 10-15ml
of 1% lido or 0.125% bupiv, ropiviacaine or levobupivicaine.
p Spinal
(fast onset, dense block)
Spinal
p Fast
onset; profound anesthesia; avoid airway risks associated with GA
p Recipe:Bupivicaine
6-12mg + 0.1mg MS
or 20ug
fentanyl (setup in 5 min; 2-4 hr duration)
p Acute
Hypotension prevention–> 1000-1500ml crystalloid immediately before spinal;
left uterine displacement.
p Tx
of hypotension: Ephedrine (10mg) +/- phenylephrine
Post Dural Puncture Headache
p Caused
by decreased ICP, cerebral vasodilation
p Dx:
Postural component and cervical muscle spasm
p Not
always self limited, not always benign
n Abducens
N. palsy (visual problems)
n Auditory
disturbances
n Subdural
hematoma / hygroma
blood patch
p Autologous
blood patch is warranted –
n Risk
is small
n Effective
p Avoid
in coagulopathy or febrile patient
p Keep
pt recumbent for 2 hrs after patch
p Pts
should avoid heavy lifting or Valsalva
p Rx:
stool softener and/or cough suppressant
p Prophylactic
blood patch is not warranted (blood patch is less effective if done in 1st
24 hours)
ASA Guidelines
p Fetal
Heart Rate monitoring before and after labor epidural
p For
elective cases, clear liquids acceptable up to 2 hrs preop; no solids for 6-8
hrs.
p Timely
administration of non-particulate antacids, H2 blockers and/or metoclopramide.
p Pencil
point spinal needles should be used rather than cutting needles to reduce PDP
headache
ASA Guidelines – 2
p For
urgent delivery GA is faster than SAB which is faster than epidural
p GA
is associated with lower APGAR scores
p Phenylephrine
for maternal hypotension may cause less fetal acidosis than ephedrine
infusions.
p Cell
saver should be considered for massive hemorrhage
ASA Guidelines – 3
p Labor/delivery
units should be equipped with difficult airway, fluid resuscitation and ACLS
equipment
p For
maternal cardiopulmonary arrest (>4 min) consider emergent operative delivery
of the fetus in addition to maternal resuscitation
p Uterine
displacement improves maternal venous return and should be routinely utilized
Anesthetic Management for Obstetrical Emergencies
“Nonreassuring” Fetal Heart Rate (ie “Fetal Distress”)
p FHR
deceleration related to uteroplacental insufficiency.
p Prolonged
/ repeated deceleration of FHR may lead to fetal acidosis.
p Lack
of fetal heart rate variability may be due to fetal hypoxemia.
“Nonreassuring” Fetal Heart Rate (ie “Fetal Distress”)
p Profound
variable or late decelerations – especially if associated with decreased FHR
variability dictates consideration of immediate delivery.
p Fetal
pulse oximetry, used in conjunction with FHR monitoring decreases emergent
C-section rate related to “nonreassuring” FHR.
Image
PLACENTAL ABRUPTION
p Premature separation of normally implanted
placenta
p May occur pre- or intrapartum (incidence ~
1:80 deliveries)
p Associated with maternal hypertension,
heavy EtOH use or cocaine use.
p Leads to maternal blood loss, neonatal
neurologic damage or asphyxia
PLACENTAL ABRUPTION
p May
lead to consumptive coagulopathy and progress to DIC.
p For
suspected abruption – type and crossmatch blood; send H/H, plt count,
fibrinogen and FSP’s
p For
severe abruption consider immediate C-section under GA.
p Consider
oxytocin and other uterotonic drugs and aggressive transfusion.
PLACENTA PREVIA
p Abnormal
implantation of placenta close to or over the cervical os.
p Incidence:
1:200-250 deliveries (more common in multipara, prior C-section or previous
placenta previa).
p Common
cause of 3rd trimester bleeding
p For
ongoing bleeding may require C-section
image
UTERINE RUPTURE
p Often
related to previous uterine scar from previous C-section
p Sx:
Vaginal bleeding, severe uterine pain, shoulder pain, disappearance of FH
tones, hypotension.
p Requires
urgent delivery and abdominal exploration.
VBAC
p In
a prospective study between 1999-2002 ~18k women attempted VBAC; ~16k had
elective repeat C-section
p Symptomatic
uterine rupture occurred in 124 (0.7%) of VBAC women
p Hypoxic-ischemic
encephalopathy occurred in 12 infants in VBAC cases; none in elective section
p Lower
incidence of maternal complications in elective section
POST PARTUM HEMORRHAGE
p Retained
placenta
n Occurs
in about 1% of deliveries
n Requires
manual exploration of uterus
n 1
MAC of GA provides uterine relaxation
n NTG
(100 ug) also provides uterine relaxation
POST PARTUM HEMORRHAGE – 2
p Uterine
Atony
p Seen
following 2-5% of deliveries
p Associated
with over distention of uterus, retained placenta, excessive oxytocin use
during labor, and operative interventions.
p Rx:
Fluids, uterine massage and uterotonics.
Image]
THE END
p THANKS
FOR YOUR ATTENTION!
