Anesthesia for the Obstetrical Patient

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 2^nd trimester
   Less risk of teratogenicity, miscarriage, than
1^st trimester
  preterm labor more likely in 3^rd trimester
  Left uterine displacement after 24^th 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 1/3^rd 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 1^st 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.
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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 3^rd trimester bleeding
p  For ongoing bleeding may require C-section
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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.
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THE END
p  THANKS FOR YOUR ATTENTION!

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