Anesthesia for the Obstetrical Patient

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Anesthesia for the Obstetrical Patient

• Fred Rotenberg, MD
• Dept. of Anesthesiology
• Rhode Island Hospital
• Grand Rounds February 27, 2008

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Anesthesia for the Obstetrical Patient

• The Pregnant Patient for Nonobstetric Surgery
• LABOR
• DELIVERY
• OBSTETRICAL EMERGENCIES
• SPINAL HEADACHES AND BLOOD PATCHES

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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)

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Anesthesia for the pregnant patient undergoing
non-obstetric surgery
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THE OBVIOUS

• AVOID MATERNAL HYPOXIA AND HYPOTENSION

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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

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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

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Things we can ( should) do

• If possible delay surgery til 2nd trimester
• Less risk of teratogenicity, miscarriage, than
• 1st trimester
• preterm labor more likely in 3rd trimester
• Left uterine displacement after 24th week
• Consider aspiration prophylaxis midazolam
  (reduce maternal stress -gtimprove fetal blood
  flow)
• Consider Fetal monitoring (but no good data)
• Consult with obstetrician

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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

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POST - OP

• Continue fetal monitoring
• Because of risk of thromboembolism
• Early mobilization
• Consider anticoagulants
• Post op analgesia (regional is good at this)

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LABOR ANALGESIA

• Intravenous
• Neuraxial
• Epidural
• Spinal
• Combined Spinal-Epidural

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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

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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

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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

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Arguments against epidural for Labor

• Incidence of epidural infection 1/145k
• Incidence of Epidural bleed 1/150-170k
• Incidence of persistent neurological injury
  1/237k (transient neurologic injury 1/5,500)
• Still about 20 of pts w/ labor epidural require
  conversion to GA for C-section

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Disadvantages of epidural analgesia for labor

• Slows labor by approximately one hour
• Questionable effect on Cesarean Section delivery
  rate
• Increases use of instruments during vaginal
  delivery
• Increased incidence of maternal fever (and
  subsequent fever workup of mom and child)

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Effect of Early Neuraxial Analgesia on C-Section
Rate

• Many older studies show no clear difference in
  section rate comparing neuraxial and parenteral
  opiate analgesia.
• Wong et al. NEJM 2005
• Prospective
• demonstrates no increase in C-section rate
  comparing early vs later epidural opiate
  administration.

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Epidural analgesia increases rate of instrument
assisted deliveries

• Rate of instrument assisted vaginal deliveries is
  at least doubled by epidural analgesia
• Etiology of this effect?
• Motor block from neuraxial local anesthetic
• Epidural analgesia is associated with increased
  rate of occiput posterior presentation (does this
  painful presentation promote increased demand for
  epidural analgesia?)
• The presence of a block might lower
  obstetricians threshold for using instruments

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LABOR EPIDURAL

• Continuous combined dilute local anesthetic plus
  opiate.
• Better pain relief when combined less motor
  block. Less instrumented deliveries. Minimal
  absorbtion by Mom or baby.
• Eg Bupivicaine 0.0625 plus 2ug/ml fentanyl (/-
  epinephrine) _at_ 10-12 ml/hr.

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Notes on epidural cath placement

• Sterile technique
• Loss of resistance to fluid (not air)
• Prevent intrathecal placement (0.5-3 incidence)
• Prevent intravenous placement (3-15 incidence)
  (use Arrow Flex-Tip inject 10 ml dilute local
  through needle prior to cath placement).
• Aspiration of blood or csf is quite reliable

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Notes on epidural cath placement - 2

• Epinephrine test dose is not sensitive for
  intravenous location.
• Local anesthetic (eg 45mg of Lido w/ epi) as test
  for intrathecal placement is somewhat better.
• Wait 5 min after test to see motor changes.
• Seek subjective change in pts ability to feel
  normal contraction of muscles controlling
  micturation.
• Rapid profound analgesia suggests intrathecal
  dose.

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Notes on epidural cath placement - 3

• Safety is determined by the above careful
  placement AND
• DOSE FRACTIONATION give 3ml every 1-2 minutes.
• patience is wisdom and wisdom is patience

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Notes on epidural cath placement -4

• For a wet tap consider
• 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.)
• 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.

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Combined Spinal Epidural Analgesia

• Most beneficial in early or late labor
  (especially the multiparous patient)
• 27 spinal needle through epidural needle
  followed by epidural catheter insertion
• Almost immediate pain relief with spinal opiate
  (fentanyl 10-25ug or sufentanil 2.5-10ug)
• 2-3 hour duration of analgesia with the spinal
  opiate
• Patient may ambulate

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Combined Spinal Epidural Analgesia

• In early labor (lt4 cm dilation) CSE promotes more
  rapid cervical dilation than IV hydromorphone.
• Also, high concentrations of local anesthetic
  slow labor.

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Combined Spinal Epidural Analgesia

• For severe pain in the late stages of labor may
  need to add local anesthetic to spinal mixture.
• Rx Sufentanil 2.5-5ug plus bupivicaine 2.5 mg
  -gt
• Rapid profound analgesia without significant
  motor block.
• Longer duration of analgesia than opiate alone.

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Problems with Intrathecal Opiates

• Pruritus usually mild and short lived
• Nausea and vomiting best treatment?
• Hypotension Rx ephedrine.
• Urinary retention
• Uterine hyperstimulation and fetal bradycardia?
  (studies show no increased risk)
• Maternal respiratory depression monitor for at
  least 20 minutes post injection

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Technical Problems with CSE

• Post dural puncture headache
• (Incidence is 1 or less)
• Subarachnoid migration of epidural catheter?
• Risk is remote especially with separate port in
  epidural needle for spinal needle.
• Still use small incremental epidural doses

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Patient Controlled Epidural Analgesia

• May minimize drug doses, less motor block, but
  may provide inferior analgesia should we add a
  basal infusion rate (6-9ml/hr)?
• Must set limits to bolus doses. (4-6ml q 5-10min
  max 4-6doses/hr)
• Although less demands on anesthesia personnel,
  must still make periodic assessments.

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Continuous Spinal Analgesia?

• Microcatheters are they associated with cauda
  equina syndrome?
• 28g microcatheters seem safe (Arkoosh et al
  2003) but are still not FDA approved.
• Clearly increased risk of headache with larger
  catheters, but advantage of controlled
  incremental dosing (cf epidural) may justify its
  use.

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Anesthesia for delivery Vaginal

• Epidural Perineal dose for imminent delivery
  (10-12 ml of 0.062bupiv 50-100ug of fentanyl)
  to allow the pt to push
• For forceps delivery or episiotomy repair
  epidural 8-12 ml of 2 lido.

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Anesthesia for delivery (Cesarian)

• GETA
• Spinal
• Epidural
• CSE

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Regional anesthesia for C-section

• Supplementation of Indwelling Epidural
• 10-15ml of 1 lido or 0.125 bupiv, ropiviacaine
  or levobupivicaine.
• Spinal (fast onset, dense block)

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Spinal

• Fast onset profound anesthesia avoid airway
  risks associated with GA
• RecipeBupivicaine 6-12mg 0.1mg MS
• or 20ug fentanyl (setup in 5 min 2-4 hr
  duration)
• Acute Hypotension preventiongt 1000-1500ml
  crystalloid immediately before spinal left
  uterine displacement.
• Tx of hypotension Ephedrine (10mg) /-
  phenylephrine

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Post Dural Puncture Headache

• Caused by decreased ICP, cerebral vasodilation
• Dx Postural component and cervical muscle spasm
• Not always self limited, not always benign
• Abducens N. palsy (visual problems)
• Auditory disturbances
• Subdural hematoma / hygroma

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blood patch

• Autologous blood patch is warranted
• Risk is small
• Effective
• Avoid in coagulopathy or febrile patient
• Keep pt recumbent for 2 hrs after patch
• Pts should avoid heavy lifting or Valsalva
• Rx stool softener and/or cough suppressant
• Prophylactic blood patch is not warranted (blood
  patch is less effective if done in 1st 24 hours)

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ASA Guidelines

• Fetal Heart Rate monitoring before and after
  labor epidural
• For elective cases, clear liquids acceptable up
  to 2 hrs preop no solids for 6-8 hrs.
• Timely administration of non-particulate
  antacids, H2 blockers and/or metoclopramide.
• Pencil point spinal needles should be used rather
  than cutting needles to reduce PDP headache

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ASA Guidelines - 2

• For urgent delivery GA is faster than SAB which
  is faster than epidural
• GA is associated with lower APGAR scores
• Phenylephrine for maternal hypotension may cause
  less fetal acidosis than ephedrine infusions.
• Cell saver should be considered for massive
  hemorrhage

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ASA Guidelines - 3

• Labor/delivery units should be equipped with
  difficult airway, fluid resuscitation and ACLS
  equipment
• For maternal cardiopulmonary arrest (gt4 min)
  consider emergent operative delivery of the fetus
  in addition to maternal resuscitation
• Uterine displacement improves maternal venous
  return and should be routinely utilized

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Anesthetic Management for Obstetrical Emergencies
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Nonreassuring Fetal Heart Rate (ie Fetal
Distress)

• FHR deceleration related to uteroplacental
  insufficiency.
• Prolonged / repeated deceleration of FHR may lead
  to fetal acidosis.
• Lack of fetal heart rate variability may be due
  to fetal hypoxemia.

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Nonreassuring Fetal Heart Rate (ie Fetal
Distress)

• Profound variable or late decelerations
  especially if associated with decreased FHR
  variability dictates consideration of immediate
  delivery.
• Fetal pulse oximetry, used in conjunction with
  FHR monitoring decreases emergent C-section rate
  related to nonreassuring FHR.

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PLACENTAL ABRUPTION

• Premature separation of normally implanted
  placenta
• May occur pre- or intrapartum (incidence 180
  deliveries)
• Associated with maternal hypertension, heavy EtOH
  use or cocaine use.
• Leads to maternal blood loss, neonatal neurologic
  damage or asphyxia

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PLACENTAL ABRUPTION

• May lead to consumptive coagulopathy and progress
  to DIC.
• For suspected abruption type and crossmatch
  blood send H/H, plt count, fibrinogen and FSPs
• For severe abruption consider immediate C-section
  under GA.
• Consider oxytocin and other uterotonic drugs and
  aggressive transfusion.

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PLACENTA PREVIA

• Abnormal implantation of placenta close to or
  over the cervical os.
• Incidence 1200-250 deliveries (more common in
  multipara, prior C-section or previous placenta
  previa).
• Common cause of 3rd trimester bleeding
• For ongoing bleeding may require C-section

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UTERINE RUPTURE

• Often related to previous uterine scar from
  previous C-section
• Sx Vaginal bleeding, severe uterine pain,
  shoulder pain, disappearance of FH tones,
  hypotension.
• Requires urgent delivery and abdominal
  exploration.

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VBAC

• In a prospective study between 1999-2002 18k
  women attempted VBAC 16k had elective repeat
  C-section
• Symptomatic uterine rupture occurred in 124
  (0.7) of VBAC women
• Hypoxic-ischemic encephalopathy occurred in 12
  infants in VBAC cases none in elective section
• Lower incidence of maternal complications in
  elective section

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POST PARTUM HEMORRHAGE

• Retained placenta
• Occurs in about 1 of deliveries
• Requires manual exploration of uterus
• 1 MAC of GA provides uterine relaxation
• NTG (100 ug) also provides uterine relaxation

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POST PARTUM HEMORRHAGE - 2

• Uterine Atony
• Seen following 2-5 of deliveries
• Associated with over distention of uterus,
  retained placenta, excessive oxytocin use during
  labor, and operative interventions.
• Rx Fluids, uterine massage and uterotonics.

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THE END

• THANKS FOR YOUR ATTENTION!