Anesthesia for Cesarean Section

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Anesthesia for Cesarean Section

• Michelle Gros, FRCPC
• Feb 13, 2008

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Cesarean Section

• Cesarean section rate in Canada in 2005 was 23.7
  (CIH)
• Cesarean section rate in US now exceeds 24
• Incidence of anesthesia-related maternal
  mortality is declining
• Anesthesia remains responsible for 3-12 of all
  maternal deaths
• Majority during general anesthesia (failed
  intubation, failed ventilation and oxygenation,
  and or aspiration)
• Associated factors include obesity, hypertensive
  disorders of pregnancy, and emergently performed
  procedures

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Cesarean Section

• Review of anesthetic technique used for all
  c-sections performed at Brigham and Womens
  hospital between 1990 and 1995
• GA ? from 7.2 in 1990 to 3.6 in 1995
• Are we getting enough experience in GAs for
  c-sections?

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Preparation for Anesthesia - Meds

• Minimize drugs prior to delivery of infant
• If necessary, midazolam 0.5 1 mg or fentanyl
  25-50 ug IV
• Small doses minimal fetal and neonatal
  depression
• Disadvantage of benzos ?
• Anticholinergics decreases secretions
• Atropine crosses placenta - ? FHR and ?
  variability
• Glycopyrrolate does not cross placenta
• Aspiration prophylaxis

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Preparation for Anesthesia - Meds

• CJA 2006 53(1) 79-85.
• RCT of 60 women
• Either 1 ug/kg fent and 0.02 mg/kg midaz IV, OR
  an equal volume IV NS at time of skin prep for
  spinal
• No between group differences of neonatal outcome
  variables (Apgar, neurobehavioural scores,
  continuous oxygen saturation)
• Mothers had no difference in recall of the birth

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Preparation for Anesthesia IV Fluids

• Prior to regional 15-20 mL/kg RL or NS
• 30 mins prior
• Rout et al. 1993 incidence of hypotension ?
  from 71 to 55 if prehydrated
• Message
• Additional means are necessary
• In urgent situation not necessary to wait for
  fluid bolus
• ? hypotension means improved uteroplacental
  perfusion
• ?crystalloid vs. colloid

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Preparation for Anesthesia IV Fluids

• CJA 2000 47 607-610.
• Crystalloid preload no longer magic bullet
• Study found 1 L crystalloid preload was of no
  value in preventing hypotension
• Both speed and volume of preloading unimportant
• Still reasonable to give modest preload prior to
  spinal
• Patients are often relatively dehydrated
• BUT no need to delay emergency surgery in order
  to preload

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Preparation for Anesthesia IV Fluids

• Siddik showed 500 mL pentaspan more effective
  than 1 L NS in reducing hypotension (40 vs. 80)
• NV also reduced in colloid group
• Neonatal outcome unaffected
• Riley et al showed less hypotension in colloid
  group (45 vs. 85) but no difference in nausea
  scores or neonatal outcome

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Preparation for Anesthesia IV Fluids

• French et al showed less hypotension in colloid
  group (12.5 vs. 47.5), again no differences in
  neonatal outcome
• Karinen et al failed to find any differences in
  hypotension when colloid was used

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Preparation for Anesthesia IV Fluids

• Disadvantages to Colloid?
• Expensive
• Anaphylactoid reactions
• Coagulation effects

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Preparation for Anesthesia IV Fluids

• Is type, amount, timing of fluids that important?
• Also consider
• Effective LUD - 15? often not enough
• Aggressive use of vasopressors
• Low dose spinal anesthesia

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Preparation for Anesthesia Maternal Position

• Avoid aortocaval compression
• Results in ? uteroplacental perfusion by 3
  mechanisms
• ? venous return ? ? C.O. and BP
• Obstruction of uterine venous drainage ?s
  uterine venous pressure and ? uterine artery
  perfusion pressure
• Compression of aorta or common iliac arteries ? ?
  uterine artery perfusion pressure

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Preparation for Anesthesia Monitors

• Standard monitors
• /- art, CVP
• FHR
• Before, during, after administration of
  anesthesia
• Evaluates effects of maternal position,
  anesthesia, hypotension, and other drugs on the
  fetus

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General Considerations

• ? Support person
• ? Oxygen

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General Considerations - Oxygen

• For elective c-section, current evidence suggests
  that supplementary oxygen is unnecessary
• For emergency section further data are required
• Improvement of fetal oxygenation should be
  primary objective this achieved in short-term
  by using very high FiO2
• BUT, possibility of reperfusion injury with free
  radicals

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Prevention of Maternal Complications - Aspiration

• ALL patients should receive aspiration
  prophylaxis, regardless of planned anesthetic for
  c-section
• Large survey from Sweden
• Incidence of aspiration 15 per 10,000 cases of
  GA for c-sxn
• 3X greater than in nonobstetric surgery

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Preventing Aspiration Pharmacologic Tx

• Non-particulate antacid eg. 0.3 M sodium citrate
• H2-receptor antagonist
• ? gastric pH, BUT does NOT alter pH of existing
  gastric contents
• Rout et al 1993 IV ranitidine 50 mg po Na
  citrate ? resulted in greater ? in gastric pH
  than Na citrate alone (provided gt30 mins from
  time of administration to intubation)

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Preventing Aspiration Pharmacologic Tx

• Proton pump inhibitor eg. losec
• ? gastric acidity
• One study found it less effective than ranitidine
• Metoclopramide
• Accelerates gastric emptying
• ? Reliability of emptying stomach before c-sxn
• ? lower esophageal sphincter tone
• Antiemetic effect

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Prevention of Maternal Complications - Hypotension

• In obstetric patients - ? in SBP gt 25 OR, any
  SBP lt 100 mmHg
• Measures of prevention
• Fluids
• LUD
• Prophylactic vasopressors (ephedrine,
  phenylephrine)

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Prevention of Maternal Complications - Hypotension

• Lee et al., CJA 2002 systematic review of RCTs
  of ephedrine vs. phenylephrine for tx of
  hypotension during spinal for c-sxn
• No difference for prevention and treatment of
  maternal hypotension
• Maternal bradycardia more likely to occur with
  phenylephrine than with ephedrine
• No difference in the incidence of fetal acidosis
  (umbilical artery pH lt 7.2)

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Prevention of Maternal Complications - Hypotension

• Chestnut says
• They still mostly use ephedrine
• Phenylephrine preferred in patients who may not
  tolerate tachycardia eg. MS

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Prevention of Maternal Complications - Hypotension

• Varying reports of efficacy of prophylactic
  ephedrine
• Some advocate 25 50 mg IM before spinal, or
  5-10 mg IV immediately after intrathecal
  injection
• Chestnut dont give prophylactic ephedrine
  unless pt has a low baseline BP (ie. SBP lt105
  mmHg before spinal)

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Prevention of Maternal Complications - Failures

• Failed spinal
• 1 of cases

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Prevention of Maternal Complications - Failures

• Failed spinal
• 1 of cases
• If delivery not urgent 2nd spinal

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Prevention of Maternal Complications - Failures

• Failed spinal
• 1 of cases
• If delivery not urgent 2nd spinal
• Failed epidural
• 2-6 of cases

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Prevention of Maternal Complications - Failures

• Failed spinal
• 1 of cases
• If delivery not urgent 2nd spinal
• Failed epidural
• 2-6 of cases
• Repeat epidural
• Watch for local toxicity
• Pt impatient

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Prevention of Maternal Complications - Failures

• Failed spinal
• 1 of cases
• If delivery not urgent 2nd spinal
• Failed epidural
• 2-6 of cases
• Repeat epidural
• Watch for local toxicity
• Pt impatient
• Spinal
• Collection of local falsely think this is CSF
• High spinal

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Prevention of Maternal Complications - Failures

• Chestnut
• 5 planned epidurals converted to spinals
• High spinals in 3 of 27 (11)

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Indications for Cesarean Section

• Repeat
• Scheduled
• Failed attempt at vaginal delivery
• Dystocia
• Abnormal presentation
• Transverse lie
• Breech
• Multiple gestation

• Fetal stress/distress
• Deteriorating maternal medical illness
• Preeclampsia
• Heart disease
• Pulmonary disease
• Hemorrhage
• Placenta previa
• Placental abruption

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Choice of Technique
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Choice of Technique

• Indication for c-sxn
• Urgency of procedure
• Health of mother and fetus
• Desires of mother

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Spinal

• Pros
• Simple
• Rapid onset
• Dense blockade
• Negligible maternal risk of systemic local
  toxicity
• Minimal transfer of drug to infant
• Negligible risk of local anesthetic depression of
  infant

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Spinal

• Cons
• Rapid onset of sympathetic blockade abrupt,
  severe hypotension
• Limited duration
• Recovery time may be prolonged (if procedure
  shorter than anticipated)

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Epidural

• Popularity increasing
• LA ? nerve roots (dural cuffs) by absorption
  through arachnoid villi that penetrate dura
• ? spread of anesthesia is volume dependent

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Epidural

• Pros
• Titrated dosing and slower onset ? ? risk of
  severe hypotension and reduced uteroplacental
  perfusion
• Duration of surgery not an issue
• Less intense motor blockade ? good for pts with
  multiple gestation or pulmonary disease
• Lower extremity muscle pump may remain intact ?
  may ? incidence of thromboembolic disease

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Epidural

• Cons
• Slower onset
• Risk of systemic local toxicity
• Greater placental transfer of drug than with
  spinal
• BUT does not affect neonatal neurobehaviour and
  of little clinical significance when appropriate
  doses used
• Risk of high spinal

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Combined Spinal Epidural (CSE)

• Initially described in 1981 (epidural catheter at
  L1-2 and spinal at L3-4)

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Combined Spinal Epidural (CSE)

• Pros
• Rapid onset and density of spinal anesthesia
  combined with versatility of epidural anesthesia
• Cons
• Potential for high spinal
• Inability to test epidural catheter
• Only 1 published report of presumed unintentional
  insertion of epidural catheter through dural
  puncture site

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Spinal Anesthesia for C - Section

• Metoclopramide 10 mg IV
• Clear antacid orally
• Intravascular volume expansion with RL or NS
  (15-20 mL/kg)
• Application of monitors
• Supplemental oxygen by face mask or nasal prongs
• Prophylactic intramuscular ephedrine (25-50 mg)
  in patients with a baseline SBP lt 105 mmHg

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Spinal Anesthesia for C - Section

• Lumbar puncture at L3-4
• Right lateral or sitting position
• 25-gauge Sprotte or Whitacre needle
• Bupivacaine 12 mg (heavy)
• Morphine 0.1-0.25 mg for postoperative analgesia
• Left uterine displacement
• Aggressive treatment of hypotension
• Exaggerated LUD
• IV fluids
• Ephedrine and/or low dose phenylephrine

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Drugs Used for Spinal Anesthesia for Cesarean
Section
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Epidural Anesthesia for C-Section

• Maxeran 10 mg IV
• Clear antacid po
• IV expansion with RL or NS (15-20 mL/kg)
• Application of monitors
• Supplemental oxygen
• Epidural catheter at L2-3 or L3-4
• LUD
• Test dose

• Therapeutic dose
• 5 ml boluses of 2 lido with epi
• 5ml boluses of 0.5 bupivacaine, 0.5
  ropivacaine, or 3 2-chloroprocaine (lidocaine or
  2-chloroprocaine q 1-2 mins, bupiv or ropiv q 2-5
  mins)
• Aggressive tx of hypotension

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Drugs Used for Epidural Anesthesia for Cesarean
Section
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Aids with Regional

• 40-50 N2O
• Low-dose ketamine (0.25 mg/kg)
• Fentanyl 50-100 ug IV
• Remifentanil
• Metoclopramide, ondansetron, or droperidol may be
  given to treat nausea
• Small dose of a benzodiazepine to treat anxiety
  and/or restlessness

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Local Anesthetic?

• Int. J Ob Anesth. 2006 15 106-114.
• Prospective, single blind study
• Compared plain 0.5 bupivacaine (20 mL) with 2
  lidocaine (20 mL) 100 ug epi 100 ug fentanyl
  for extending previous low-dose epidural
  analgesia for emergency c-sxn in 68 pts

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Local Anesthetic?

• Sig. longer prep time for mixture (3.0 vs. 1.25
  min)
• Median onset time for block to T7 was 13.8 min
  for mixture and 17.5 min for plain bupivacaine
• Difference not statistically different, and was
  offset by the longer prep time
• Need for other intra-op supplementation was not
  significantly different between the groups
• Lidocaine is cheaper and less toxic than
  alternatives

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Local Dose How Low Can We Go?

• Int J Ob Anesth, 2006 15 273-278.
• Randomized to receive either intrathecal
  hyperbaric bupivacaine 3.75 mg or 9 mg, plus 25
  ug fentanyl, 100 ug morphine, and 1.5 lidocaine
  epidurally 3 mL
• Max sensory block achieved in low-dose group was
  significantly lower than that in conventional
  group (T4 vs. T2)
• Longer time to reach maximum sensory level in low
  dose group (8.6 min vs. 6.8 min)

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Local Dose How Low Can We Go?

• Low-dose group had less motor block, faster
  sensory regression to T10 and faster motor
  recovery
• No significant difference in need for epidural
  supplementation before or after delivery of baby
• Low-dose group less hypotension (14 vs. 73)
  with less ephedrine usage

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Spinal Bupivacaine Dosed According to Patient
Height

• Barash p 1149
• Spinal bupivacaine 0.75 dosed according to
  patient height
• 150-160 cm 8 mg
• 160-182 cm 10 mg
• gt182 cm 12 mg
• Onset of action 2-4 mins
• Duration of action 120-180 mins

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Addition of Fentanyl to Spinal

• Acta Anesth Scand, 2006 50 364-367.
• Tested effect of intrathecal fentanyl added to
  hyperbaric bupivacaine on maternal spirometry in
  40 pts
• 2 groups
• 2 mL hyperbaric bupivacaine 0.5 0.4 mL saline
• 2 mL hyperbaric bupivacaine 0.5 0.4 mL
  fentanyl (20 ug)
• Performed spirometry on arrival to OR and 15 mins
  after subarachnoid blockade

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Addition of Fentanyl to Spinal

• Subarachnoid block with bupivacaine
  significantly ? peak expiratory flow rates
• No changes in VC or FVC
• Addition of intrathecal fentanyl
• Improved quality of blockade (T1.5 vs. T4)
• Did not lead to a deterioration in resp function
  compared with intrathecal bupivacaine alone

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Addition of Fentanyl to Spinal

• Int. J Ob. Anesth. 1997 6 43-48.
• Double-blind placebo-controlled study
• Compared periop pain relief with fentanyl,
  morphine, or combination
• In addition to bupivacaine group A received 1
  mL NS, group B 25 ug fent, group C 100 ug
  morph, group D 25 ug fent 100 ug morph
• Quality of intraop analgesia similar in all
  groups receiving opioid
• Opioid use increased side effects
• Postop analgesia with fentanyl inferior to
  morphine

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Dose of Intrathecal Morphine?

• No good conclusive study
• Many varied practices
• Anesth 1999 90 437-44.
• Dose-finding study for intrathecal morphine
• No difference in PCA morphine use between 0.1 and
  0.5 mg groups
• Pruritis ? in direct proportion to dose
• No difference in NV between groups
• Conclusion no need to use more than 0.1 mg

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Epidural Morphine for Post-op Pain Control

• Anesth Analg. 2007 105(1) 176-83.
• Compared 4 mg epidural morphine with 10 mg
  extended release epidural morphine
• Found superior and prolonged post-c-section
  analgesia (especially 24-48 hours post-op)

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Risk Factors for Failure of Epidural Analgesia
for C-Section

• Acta Anesth Scand, 2006 50 1014-1018.
• Prospectively studied women undergoing c-sxn with
  a functioning epidural in place
• All pts received same epidural protocol
• 16 mL 2 lido, 1 mL bicarb, and 100 ug fentanyl
  given for c-sxn
• Failed epidural analgesia was defined as need to
  convert to GA

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Risk Factors for Failure of Epidural Analgesia
for C-Section

• Of 101 pts, 20 (19.8) required conversion to GA
• Failed epidural inversely correlated with pts
  age
• Directly correlated with
• Pre-pregnancy weight
• Weight at end of pregnancy
• BMI
• Gestational week
• Number of top-ups
• VAS 2 hour before c-sxn

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Risk Factors for Failure of Epidural Analgesia
for C-Section

• Therefore, younger, more obese pts at a higher
  gestational week, requiring more top-ups during
  labour, having a higher VAS in the 2 hours before
  c-sxn are at risk of inability to extend labour
  epidural analgesia to epidural analgesia for c-sxn

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Indications for General Anesthesia for Cesarean
Section
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Indications for General Anesthesia for Cesarean
Section

• Dire fetal distress in absence of pre-existing
  epidural
• Acute maternal hypovolemia
• Significant coagulopathy
• Inadequate regional anesthesia
• Maternal refusal of regional anesthesia

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General Anesthesia for Cesarean Section

• Ranitidine and/or metoclopramide IV
• Clear antacid po
• LUD
• Application of monitors
• Denitrogenation (100 O2)
• Cricoid pressure
• IV induction
• Pentothal, propofol, ketamine, or etomidate
• Succinylcholine (roc if sux contraindicated)

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General Anesthesia for Cesarean Section

• Intubation with 6.0-7.0 mm cuffed ETT
• 30-50 N2O in O2, and low conc of volatile (0.5
  MAC)
• After delivery
• Increased conc of N2O with low conc. Volatile
• Opioid
• IV hypnotic agent (eg. benzo, barbiturate,
  propofol) if needed
• Muscle relaxant (sux boluses or infusion, roc,
  cisatracurium)
• Extubation awake with intact airway reflexes

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General Anesthesia Traditional RSI Necessary?

• Int. J Ob Anesth. 2006 15 227-232
• The effects on the fetus of anesthetics and
  opioid analgesics are innocuous and reversible
• Dose-dependent neonatal respiratory depression is
  predictable and readily treatable by a neonatal
  pediatrician
• Choice of drug regimen for pt with cardiac or
  cerebrovascular disease should not be restricted
  on account of concern for the fetus
• Opioids should not be withheld in hypertensive
  disorders, when prevention of a dangerous
  hypertensive response to laryngoscopy and
  tracheal intubation is paramount

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General Anesthesia

• Adequate denitrogenation
• ? FRC
• ? O2 consumption
• Baraka compared head-up and supine positions
  for denitrogenation in pregnant and non-pregnant
  pts
• Head-up position prolonged interval between onset
  of apnea and desaturation (SpO2lt95) in
  non-pregnant pts, BUT NOT in pregnant pts

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General Anesthesia Induction Agents

• Goals
• Preserve maternal BP, CO, and uterine blood flow
• Minimize fetal and neonatal depression
• Ensure maternal hypnosis and amnesia

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General Anesthesia Induction Agents

• Thiopental
• Extensive published data
• Safe in obstetric pts
• 4 mg/kg
• Rapidly crosses placenta
• Detected in umbilical venous blood within 30 secs
• Equilibration in fetus rapid and occurs by time
  of delivery
• With doses 4 mg/kg peak concs in fetal brain
  rarely exceed threshold for depression

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General Anesthesia Unconscious mother and awake
neonate?

• Preferential uptake by fetal liver (1st organ
  perfused by blood from umbilical vein)
• Higher relative water content of fetal brain
• Rapid redistribution of drug into maternal
  tissues ? rapid reduction in maternal fetal
  conc gradient
• Non-homogeneity of blood flow to intervillous
  space
• Progressive dilution in fetal circulation

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General Anesthesia Propofol

• Rapid, smooth induction of anesthesia
• Attenuates cardiovascular response to
  laryngoscopy and intubation more effectively than
  pentothal
• Does not adversely affect umbilical cord blood
  gas measurements at delivery
• Rapidly crosses placenta
• Rapidly cleared from neonatal circulation
• Detected low concs in breast milk
• Propofol and pentothol ? similar Apgar and
  neurobehavioural scores

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General Anesthesia Ketamine

• 1 mg/kg
• Rapid onset
• Analgesia, hypnosis, and reliably provides
  amnesia
• Good in asthma or modest hypovolemia
• 1 mg/kg does NOT ? uterine tone (larger doses do)
• Rapidly crosses placenta
• Similar umbilical cord blood gas and Apgar scores
  with ketamine or pentothal

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General Anesthesia Succinylcholine

• 1-1.5 mg/kg
• Muscle relaxant of choice for most patients
• Highly ionized and water soluble, ? only small
  amounts cross placenta
• Maternal administration rarely affects neonatal
  neuromuscular function
• One study only doses gt 300 mg result in
  significant placental transfer
• Pseudocholinesterase activity ? 30 in pregnancy,
  BUT recovery is not prolonged
• ? volume of distribution offsets the effect of ?
  activity

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General Anesthesia Rocuronium

• 1 mg/kg
• Only very small amounts cross placenta
• Apgar and neurobehavioural scores not affected

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General Anesthesia Maternal Awareness

• Desire to minimize neonatal depression must be
  balanced against risk of awareness
• If another agent not given ? incidence of
  awareness ? in direct proportion to I-D interval
• 50 N2O/O2 alone ? 12-26 awareness
• Awareness ? ? catecholamines ? uterine artery
  vasoconstriction and ? oxygen delivery to fetus

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General Anesthesia Maternal Awareness

• Common Approaches
• 50/50 N2O/O2 with 0.5 MAC inhalational agent
• ? awareness to lt1
• Pregnancy ? anesthetic requirements by 30-40
• No adverse affect on neonatal condition
• No ? maternal blood loss
• Discontinue volatile only if there is uterine
  atony that is unresponsive to oxytocin

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General Anesthesia Oxygen

• Piggott et al, BJA 1990 100 O2 ? higher
  umbilical venous blood pO2 and higher 1 minute
  Apgar scores, compared to 50 O2
• 100 O2 ? higher conc of iso, without maternal
  awareness or excessive bleeding
• Supports 100 O2 and higher volatile in cases of
  fetal distress
• Lawes et al, BJA 1988 elective c-sxn no
  difference in neonatal oxygenation or outcome
  between 33 and 50 O2

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Cesarean Section Under Local

• Potential indications
• patient with severe coagulopathy, known difficult
  airway and requires emergency c-sxn
• No anesthesia provider immediately available and
  severe fetal distress
• Can begin surgery and deliver infant
• Temporary hemostasis achieved until anesthetist
  arrives, then induce GA to complete the surgery

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Cesarean Section Under Local

• Need
• Midline abdominal incision
• Minimal use of retractors
• Do not exteriorize the uterus

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Local Infiltration Anesthesia for Cesarean Section

• Professional support person with patient
• Infiltration with lidocaine 0.5 (total dose lt
  500mg)
• Intracutaneous injection in midline from
  umbilicus to symphysis pubis
• Subcutaneous injection
• Incision down to rectus fascia
• Rectus fascia blockade
• Parietal peritoneum infiltration and incision
• Visceral peritoneum infiltration and incision
• Paracervical injection
• Uterine incision and delivery
• GA with ETT for uterine repair and closure, if
  needed

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Cesarean Section Under Local

• Disadvantages
• Patient discomfort
• Potential for systemic toxicity and anesthesia
  may not be available to assist with resuscitation
• Requires time
• Does not provide satisfactory operating
  conditions for complications, eg. uterine atony,
  uterine laceration

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Once Infant Delivered

• Once umbilical cord clamped oxytocin given
• 10-20 U oxytocin in 1000 mL crystalloid and run
  at 40-80 mU/min
• Bolus IV oxytocin may cause maternal hypotension
  and tachycardia and should be avoided

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Once Infant Delivered

• If atony does not repond to oxytocin
• Methylergonovine 0.2 mg IM
• 15-methylprostaglandin F2-alpha 250 ug IM or IMM
• Ergots
• Severe hypertension
• PGF2a
• NV, diarrhea, fever, tachypnea, tachycardia,
  hypertension, bronchoconstriction
• Avoid in asthmatics

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Once Infant Delivered

• Exteriorize Uterus What to watch for
• Pain
• Nausea
• Hemodynamic changes
• Risk of VAE

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Effects of Anesthesia on Fetus and Neonate

• No significant difference in umbilical cord blood
  gas between general or regional anesthesia for
  elective or emergency c-sxn
• Goals
• Effective LUD
• Ensure adequate maternal oxygenation
• Avoid maternal hyperventilation
• Avoid excessive doses of anesthetic agents
• Treat hypotension promptly

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Effects of Anesthesia on Fetus and Neonate

• Crawford found uterine incision to delivery
  (U-D) interval is more important than I-D
  interval
• A U-D interval gt3 mins associated with ?
  incidence of low umbilical cord blood pH and
  Apgar scores, regardless of anesthetic technique