TOPICS IN OB ANESTHESIA
Educational Objectives
| The goals of this program are to educate the clinician on new developments in obstetric anesthesia, improve anesthetic
management of chorioamnionitis and dural puncture, and review the use of intralipid therapy. After hearing and assimilating
this program, the clinician will be better able to:
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 | 1. Discuss the use of vasopressors for preventing hypotension in the obstetric patient.
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| 2. Examine the use of spinal anesthesia in preeclampsia, compare combined spinal-epidural analgesia with continuous
lumbar epidural analgesia, and explain the impact of early epidurals on the progress of labor.
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| 3. Develop an appropriate analgesic and anesthetic plan for the parturient with chorioamnionitis.
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| 4. Create a strategy for dealing with a dural puncture that occurs during epidural placement.
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| 5. Review the use of lipid emulsion for the treatment of local anesthetic cardiac toxicity.
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Faculty Disclosure
In adherence to ACCME Standards for Commercial Support, Audio-Digest requires all faculty and members of the planning
committee to disclose relevant financial relationships within the past 12 months that might create any personal conflicts of interest.
Any identified conflicts were resolved to ensure that this educational activity promotes quality in health care and not a
proprietary business or commercial interest. For this program, the faculty and planning committee reported nothing to disclose.
Acknowledgements
Dr. Hawkins spoke in Chicago, IL, at the 21st Annual Conference, Challenges for Clinicians, held November 30 to
December 2, 2007, and sponsored by the University of Chicago Pritzker School of Medicine, Department of Anesthesia
and Critical Care; Dr. Kopp, in Scottsdale, AZ, at the Mayo Clinic Symposium on Anesthesia and Perioperative
Medicine, held February 21-24, 2007, and sponsored by Mayo Medical School College of Medicine. The Audio-Digest
Foundation thanks the speakers and the sponsors for their cooperation in the production of this program.
| WHAT’S NEW IN OBSTETRIC ANESTHESIA —Joy L. Hawkins, MD, Professor of Anesthesiology, and Director, Obstetric
Anesthesia, University of Colorado School of Medicine, Denver
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| Choice of vasopressor: previously thought that ephedrine only drug safe for treating hypotension in pregnant patient;
however, phenylephrine shown to produce best outcome for mother and baby when treating hypotension due to spinal anesthesia;
studies—study showed combination of ephedrine and phenylephrine resulted in less hypotension, less need for
supplemental ephedrine, and higher umbilical artery pH values; another study showed that α-agonist (compared to ephedrine)
provided better control of blood pressure (BP), higher umbilical pH, and similar umbilical artery pulsatility; another
study found that giving phenylephrine alone produced least amount of nausea and vomiting and best fetal pH; adding ephedrine
offered no advantage; further study looked at avoiding use of high doses of α-agonists and whether BP should be allowed
to fall 20% before treating; 75 women randomized to receive enough phenylephrine to keep BP at 80%, 90%, or
100% of baseline; patients whose BP kept at 100% of baseline had fewest episodes of hypotension, highest fetal umbilical
pH values, and fewest episodes of maternal nausea and vomiting; this occurred despite receiving highest doses of phenylephrine;
editorial—1) ephedrine may adversely affect fetus by increasing metabolic rate, 2) using α-agonist does not cause
vasoconstriction, it returns maternal physiology to normal, and 3) maternal sensitivity to vasoconstrictors decreased in
pregnancy (may also protect fetus); meta-analysis—cord pH lowest using spinal anesthesia, compared to epidural and
general anesthesia (GA); base deficit significantly higher with spinal anesthesia
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| Preload: adequate preload does not prevent maternal hypotension after regional anesthesia (RA) for cesarean delivery;
studies—women undergoing emergency cesarean delivery randomized to 20 mL/kg preload or no preload before spinal anesthesia;
had similar episodes of hypotension; women randomized to 10, 20, or 30 mL/kg preload had similar incidence of
hypotension and ephedrine use; however, colloid osmotic pressure decreased; review of spinal anesthesia for cesarean delivery
found no intervention eliminated need to treat hypotension; however, incidence reduced by administering intravenous
(IV) fluids, ephedrine or phenylephrine use, and lower-limb compression
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| Spinal anesthesia in preeclampsia: spinal anesthesia for cesarean delivery safe and appropriate for severe preeclampsia;
studies—showed no difference in incidence of vasopressor use or hypotension when comparing spinal to epidural
anesthesia; another looked at women with severe preeclampsia (BP ≥160/110 mm Hg), compared to healthy women;
severely preeclamptic patients had significantly less hypotension than healthy women, despite receiving less fluid prophylactically
and larger doses of spinal bupivacaine; same researchers compared patients with preeclampsia to patients with
preterm pregnancy; found preeclamptic patient had significantly less hypotension and required less ephedrine than parturient
with preterm pregnancy; randomized trial compared spinal and epidural anesthesia; found clinically insignificant
differences (eg, hypotension more frequent with spinal, but duration short; more ephedrine used with spinal, but hypotension
easily treated); neonatal outcomes similar
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| Combined spinal-epidural (CSE) analgesia in preeclampsia: CSE analgesia more successful than continuous
lumbar epidural (CLE) analgesia; complications after CSE or CLE similar; studies—compared to CLE, CSE failed less
often, provided inadequate analgesia less often, less likely to need replacement, and less likely to require wet tap; another
study compared 1100 parturients who received CSE to 1100 who received CLE; no difference in complications
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| Progress of labor: little evidence that regional analgesia for labor negatively affects delivery outcome in spontaneously
laboring patient; studies—in one year, use of epidural analgesia for labor increased from 1% incidence to 84%; no
change in overall rates of cesarean or forceps delivery seen; duration of second stage of labor increased by 25 min; in another
study, patients randomized to IV patient-controlled analgesia (PCA) fentanyl for labor analgesia, or epidural; again,
no difference in rates of cesarean or forceps delivery; epidural group had longer second-stage labor (23 min), but pain and
satisfaction score improved; more maternal nausea and sedation, and more need for newborn naloxone, seen in IV PCA
group; nulliparous women randomized to IV meperidine (Demerol) or epidural analgesia; patients in epidural group had
no greater incidence of cesarean delivery but did experience increased oxytocin use, slightly longer second stage of labor,
and more fevers; based on systematic review, concluded that 1) epidural infusion with low-concentration local anesthetics
unlikely to increase rate of cesarean delivery, 2) although risk for instrumented vaginal delivery increased, operator
bias cannot be excluded, and 3) epidural analgesia associated with longer second stage of labor (≈15 min) and increased
oxytocin requirement (importance unclear)
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| Early analgesia: neuraxial analgesia does not adversely affect progress of labor in woman with severe pain in early labor;
choice of neuraxial technique may be important; Wong—≈800 nulliparous women, <4 cm dilated, randomized to
receive CSE or IV hydromorphone (Dilaudid) for analgesia; pain scores lower after intrathecal fentanyl; rates of cesarean
delivery no different; time to complete dilation (duration of first stage of labor) 90 min shorter with neuraxial block (intrathecal
fentanyl); newborn outcome worse after Dilaudid; second study of women whose labor induced showed similar
conclusions; no difference in rates of cesarean or forceps delivery; no difference in length of labor; pain scores lower, and
nausea and vomiting less, in those receiving neuraxial anesthesia; newborn outcomes similar; study of 450 term, nulliparous
women compared early epidural (<3 cm dilation) to late epidural (>4 cm dilation); mean dilation different; rates of
cesarean delivery no different; labor shorter in early group; women preferred early epidural analgesia
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| Epidurals and fevers: women who have labor epidural more likely to have increase in core temperature; not associated
with increased rates of infection in mother or neonate; unclear whether elevated maternal temperature causes fetal or
newborn complications; American Academy of Pediatrics stated women and doctors should discuss possible consequences
of fever resulting from epidural use when deciding which method of pain relief to use during labor; epidurals associated
with fever due to selection bias, loss of cooling mechanism below sympathectomy, no hyperventilation with
contractions, and increased shivering; unclear whether CLE increases inflammatory mediators or whether parenteral opioids
suppress febrile responses; studies—incidence of maximum temperature increased twenty-fold after epidural analgesia
became available (83% usage); in another study, hyperthermia found to increase susceptibility to fetal brain injury
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| Supplemental O2: when given during RA for cesarean delivery, probably does not benefit fetus or neonate; may actually
harm fetus; studies—mothers randomized to room air, nasal cannula, or face mask; no difference in umbilical cord
gases (modest but insignificant increase in O2 ); free-radical activity increased in mother and neonate; hyperoxia known
to reduce cerebral blood flow in newborn; depletion of antioxidants from free-radical activity could weaken newborn’s
ability to withstand ischemic insult; meta-analysis comparing resuscitation with 100% O2 or room air in ≈1300 newborns
found benefit to using room air (risk for death significantly lower); guidelines recommend not using 100% O2 initially for
resuscitation of newborn
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| Surgery in pregnancy: unknown which anesthetic “best” for surgery in pregnancy to protect fetal brain from neurotoxicity;
anesthetic drugs may cause developing neurons to commit suicide; studies—7-day-old rats (human equivalent, 0-6
mo of age) received 6 hr of GA with common drugs; animals had memory/learning impairments and cell death in specific
areas of brain; questions about whether adverse effects attributable to anesthetic or result of factors anesthesia provider
would not see clinically (eg, high doses over long periods, acidosis, starvation, hypoxia); study of patients requiring adnexal
mass surgery during pregnancy compared GA and RA techniques; found incidence of preterm labor 5 times higher
in women who had RA
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| FEVER, WET TAPS, AND INTRALIPID THERAPY —Sandra L. Kopp, MD, Assistant Professor of Anesthesiology,
Mayo Medical School, Rochester, MN
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Chorioamnionitis
| Case study: 21-yr-old woman, gravida 1, para 0; presents at 39 wk gestation with spontaneous rupture of membranes ≈4
hr earlier; patient uncomfortable and requesting epidural; negative history; healthy; normal pregnancy; physical examination
indicates oral temperature of 101.6°F, white blood cell (WBC) count 27,000, maternal and fetal heart rates normal;
obstetrician unsure of uterine tenderness (due to painful contractions)
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| Clinically evident: in 1% to 5% of deliveries (8%-12% of those bacteremic; usually caused by normal vaginal flora); risk
factors include young age, nulliparity, extended duration of labor, extended rupture of membranes, multiple vaginal examinations,
internal monitors, and preexisting infection of genital tract
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| Maternal signs and symptoms: fever (>30.0°C); elevated WBC count; tachycardia; uterine tenderness, purulent or
foul-smelling amniotic fluid
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| Effects on labor and delivery: increased risk for dysfunctional labor (75% require oxytocin; 30% to 40% require cesarean
delivery)
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| Maternal morbidity: hemorrhage, infection, sepsis, and death
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| Fetal effects: tachycardia and/or decreased variability; lower Apgar scores; higher incidence of neonatal sepsis work-up;
5% to 10% have pneumonia or bacteremia
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| Antibiotics: therapy should be initiated as soon as diagnosis made; decreases incidence of sepsis and bacteremia in neonate;
decreases duration of maternal fever; typically ampicillin or penicillin plus gentamicin (add anaerobic coverage [eg,
metronidazole (eg, Flagyl)] for cesarean delivery); initiation of antibiotics before neuraxial block recommended, but not
uniformly mandated
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| Safety of spinal and epidural anesthesia: study of 531 patients with neuraxial anesthesia; all placentas positive for
chorioamnionitis; 13 of 146 blood cultures positive; 23% received antibiotics before block, 48% after block, and 29% received
no antibiotics; epidural in place for >24 hr in 46 of 260 women with fever; study found no neuraxial abscess or
meningitis
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| Neuraxial block: benefits—alleviates pain and anxiety; less hyperventilation and decreased O2 consumption; lower
catecholamine levels; avoids maternal and fetal risks for GA; risks—epidural abscess; acute bacterial meningitis; dehydration
common in febrile patient
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Dural Puncture
| In parturients: incidence of dural puncture 0% to 2.6%, related to operator inexperience, and increased with sleep deprivation
(even with experienced practitioner); incidence of postdural puncture headache (PDPH), 76% to 85%
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| Conservative treatment: bed rest, analgesics, and hydration—may temporize pain for short time, but have not been
shown to decrease incidence of PDPH or to lower risk of requiring epidural blood patch (EBP); caffeine—increases cerebrovascular
resistance; IV caffeine (large doses) 85% effective; oral caffeine (300 mg) showed no difference in 24 hr and no
difference in need for EBP; sumatriptan—binds serotonin receptors and causes vasoconstriction; methylergonovine
(Methergine)—orally, 0.25 mg tid for 48 hr (spinal only); 24 of 25 patients with PDPH improved in 24 hr; only one patient
required EBP; epidural saline—increases pressure and decreases cerebrospinal fluid (CSF) leak; temporary relief until saline
absorbed; ineffective after dural puncture with epidural needle
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| Intrathecal catheter: seals hole; may cause inflammatory reaction (decreases CSF leak); when pulled immediately after
delivery, no difference in incidence or severity; if continued for ≥24 hr, with or without continuous intrathecal analgesia,
incidence of PDPH likely decreased; Ayad looked at 115 women who had dural puncture with epidural needle;
found those who had subarachnoid catheter in place for 24 hr had lower incidence of PDPH and need for EBP; study of
continuous intrathecal analgesia after dural puncture found similar results
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| Complications: neurologic (cauda equina syndrome; persistent paresthesias); infection (abscess; aseptic meningitis); cerebral
hemorrhage; CSF leak through open catheter; drugs (maldistribution may cause local anesthetic toxicity; careful
management necessary); caregiver unfamiliarity
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| Invasive treatment: EBP—compression of thecal space and elevation of subarachnoid pressure; clot then prevents further
CSF leak; blood spreads 7 to 14 spinal segments (mean spread, 6 upward and 3 downward); complications include
back pain, radicular pain, infection, and subarachnoid blood (causing arachnoiditis and meningitis)
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| Timing of EBP: studies show greater success with waiting 24 to 48 hr after headache; success rate 75% to 93% after first
EBP, 97% after second EBP
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| Prophylactic EBP: study of 64 parturients; 17-gauge epidural needle; EBP through epidural or not; no difference in rate
of PDPH or need for subsequent therapeutic EBP; shortened headache duration; exposes patients to risk for EBP
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| Survey of United Kingdom practice: 85% of maternity units have plan in case of dural puncture; 28% place catheter
intrathecally; 41% reposition catheter at different level; 31% allow either option; in 1993, 99% of catheters repositioned
at different level; 26% treated with EBP as soon as diagnosed; 71% treated after failure of conservative measures
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Intralipid Therapy
| Local anesthetic toxicity: risk for systemic toxic reaction; incidence of epidural toxicity, 1.2 to 11 per 10,000; peripheral
nerve blocks, 7.5 to 20 per 10,000; difficult to estimate risk for cardiovascular toxicity; <10% of patients with systemic
toxic reaction have cardiovascular reaction
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| Lipid emulsion to treat bupivacaine-induced cardiac toxicity: mechanism of action—provides lipid sink and
extracts bupivacaine out of plasma; metabolic benefit; dosing recommendations—bolus dose of 1 mL/kg over 1 min (repeat
every 3-5 min to maximum of 3 mL/kg) in 20% intralipid solution; followed by infusion of 0.25 mL/kg per min until
stable
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| Case report: 58-yr-old man; rotator cuff repair; interscalene nerve block; received 0.5% bupivacaine, 20 mL, plus 1.5% mepivacaine,
20 mL; 5-mL increments with negative aspiration; 30 sec after block, patient became incoherent, followed by
tonic-clonic seizure; propofol, 50 mg, administered and seizure stopped; 90 sec later, patient had another seizure followed by
asystole; cardiopulmonary resuscitation (CPR) started; patient intubated and given epinephrine (3 mg), atropine (2 mg), amiodarone
(300 mg), and vasopressin (40 U); defibrillated multiple times; 20 min of CPR; arrangements made for
cardiopulmonary bypass; instead, patient given 100 mL of 20% intralipid, and within seconds had single sinus beat; patient
then given epinephrine (1 mg) and atropine (1 mg), and CPR continued; 15 sec later, patient had sinus rhythm of 90 bpm; patient
extubated 2 hr later; awake, responsive, and had upper extremity block; problems also seen with ropivacaine
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Suggested Reading
Aya AG et al: Spinal anesthesia-induced hypotension: a risk comparison between patients with severe preeclampsia and
healthy women undergoing preterm cesarean delivery. Anesth Analg 101:869, 2005; Ayad S et al: Subarachnoid catheter
placement after wet tap for analgesia in labor: influence on the risk of headache in obstetric patients. Reg Anesth Pain Med
28:512, 2003; Goodman EJ et al: Safety of spinal and epidural anesthesia in parturients with chorioamnionitis. Reg
Anesth 21:436, 1996; Mercier FJ et al: Phenylephrine added to prophylactic ephedrine infusion during spinal anesthesia
for elective cesarean section. Anesthesiology 95:668, 2001; Ngan Kee WD et al: Comparison of metaraminol and
ephedrine infusions for maintaining arterial pressure during spinal anesthesia for elective cesarean section. Anesthesiology
95:307, 2001; Ohel G et al: Early versus late initiation of epidural analgesia in labor: does it increase the risk of cesarean
section? A randomized trial. Am J Obstet Gynecol 194:600, 2006; Turnbull DK et al: Post-dural puncture headache:
pathogenesis, prevention and treatment. Br J Anaesth 91:718, 2003; Visalyaputra S et al: Spinal versus epidural anesthesia
for cesarean delivery in severe preeclampsia: a prospective randomized, multicenter study. Anesth Analg 101:862,
2005; Viscomi CM et al: Maternal fever, neonatal sepsis evaluation, and epidural labor analgesia. Reg Anesth Pain
Med 25:549, 2000; Wallace DH et al: Randomized comparison of general and regional anesthesia for cesarean delivery
in pregnancies complicated by severe preeclampsia. Obstet Gynecol 86:193, 1995; Weinberg GL et al: Lipid infusion
accelerates removal of bupivacaine and recovery from bupivacaine toxicity in the isolated rat heart. Reg Anesth Pain Med
31:296, 2006; Wong CA et al: The risk of cesarean delivery with neuraxial analgesia given early versus late in labor. N
Engl J Med 352:655, 2005.
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