Anesthesia for the Obstetrical

Patient

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, than1st 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:EpiduralSpinal

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 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

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)

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.

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 obstetrician’s threshold for using instruments

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) @ 10-12 ml/hr.

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

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 pt’s ability to feel

normal contraction of muscles controlling micturation.

Rapid profound analgesia suggests intrathecal dose.

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”

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.

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

Combined Spinal – Epidural Analgesia In early labor (<4 cm dilation) CSE

promotes more rapid cervical dilation than IV hydromorphone.

Also, high concentrations of local anesthetic slow labor.

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 ->

Rapid profound analgesia without significant motor block.

Longer duration of analgesia than opiate alone.

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

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

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.

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.

Anesthesia for delivery – Vaginal Epidural “Perineal dose” for imminent

delivery (10-12 ml of 0.062%bupiv + 50-100ug of fentanyl) to allow the pt to push

For forceps delivery or episiotomy repair: epidural 8-12 ml of 2% lido.

Anesthesia for delivery (Cesarian) GETA Spinal Epidural CSE

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)

Spinal Fast onset; profound anesthesia; avoid

airway risks associated with GA Recipe:Bupivicaine 6-12mg + 0.1mg MS

or 20ug fentanyl (setup in 5 min; 2-4 hr duration)

Acute Hypotension prevention–> 1000-1500ml crystalloid immediately before spinal; left uterine displacement.

Tx of hypotension: Ephedrine (10mg) +/- phenylephrine

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

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)

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

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

ASA Guidelines - 3 Labor/delivery units should be equipped

with difficult airway, fluid resuscitation and ACLS equipment

For maternal cardiopulmonary arrest (>4 min) consider emergent operative delivery of the fetus in addition to maternal resuscitation

Uterine displacement improves maternal venous return and should be routinely utilized

Anesthetic Management for

Obstetrical Emergencies

“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.

“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.

PLACENTAL ABRUPTION Premature separation of normally

implanted placenta May occur pre- or intrapartum (incidence

~ 1:80 deliveries) Associated with maternal hypertension,

heavy EtOH use or cocaine use. Leads to maternal blood loss, neonatal

neurologic damage or asphyxia

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 FSP’s

For severe abruption consider immediate C-section under GA.

Consider oxytocin and other uterotonic drugs and aggressive transfusion.

PLACENTA PREVIA Abnormal implantation of placenta close to

or over the cervical os. Incidence: 1:200-250 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

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.

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

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

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.

THE END

THANKS FOR YOUR ATTENTION!