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Anesthesia for cesarean section

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Title: Anesthesia for cesarean section


1
Anesthesia for cesarean section
  • Tom Archer, MD, MBA
  • UCSD Anesthesia

2
A unique psychosocial surgery
3
Outline
  • C-section a unique psychosocial surgery
  • How the OB anesthetist should behave.
  • Evolution of techniques
  • Neuraxial block physiology and management
  • GA physiology and management.
  • Management of common problems

4
C-section a unique psychosocial surgery
  • Psychological / interpersonal aspects
  • Unique surgery, happy event gone awry.
  • Strike a balance between happy event and risky
    surgery.
  • Most patients are awake and want to be.
  • Team approach (patient, family, nursing, OB,
    anesthesia)
  • Support person present in OR.
  • Family members in the labor room (face them).
  • Discretion about medical info JW, drug use,
    previous abortions, etc.

5
Anticipate and be available
  • Know every patient on the floor. Introduce
    yourself early.
  • Be accessible to OBs and nurses.
  • Get informed early about potential problems
    (airway, obesity, coagulopathy JW, congenital
    heart disease)
  • Remember the basics (IV access, airway)

6
Anticipate and be available
  • We need a certain knowledge of OB to know what is
    going to happen. Try to think one or two steps
    ahead.
  • Placenta isnt out yet in room 7
  • The lady in 6 has a pretty bad tear.
  • Strip review in 3, please.
  • We cant get an IV on the lady in 4.
  • Can you give us a whiff of anesthesia in 8? We
    dont need much.

7
Evolution of technique
  • Last 30 years decreasing use of GA, now about 5
    of cases. Was 20-30 in 70s at UCSD.
  • Epidural was all the rage in 70s and 80s.
  • SAB (or epidural) are now preferred anesthetics.

8
Anesthesia for C/S basic interventions
  • Happy event (sort of)
  • Gastric acid neutralization
  • Left uterine displacement
  • Fluid loading
  • Supplemental oxygen
  • Support person in room (regional only)

9
Anesthesia for C/S Complications
  • Sympathectomy / hypotension
  • Nausea
  • Bradycardia
  • High spinal / respiratory paralysis
  • Aspiration
  • Difficult intubation
  • Local anesthetic toxicity
  • Failed regional anesthesia
  • Persistent neurological deficit

10
C/S red flags
  • I dont feel so goodI think Im going to throw
    up (Hypotension until proven otherwise).
  • Doc, I feel like Im not getting enough to
    breathe
  • The floppy arm sign.
  • The shaking head sign.

11
Spinal-- advantages
  • Uniquely appropriate in C/S (happy event).
  • Really amazing when you think about it.
  • Awake and smiling.
  • Arms and hands are normal.
  • Major surgery inside the abdomen.
  • Quick, solid, simple, reliable, pretty safe.
  • LA narcotic gives great block.
  • Can give long-acting analgesia (intrathecal MS)

12
Regional anesthesia for c/s in Turkey (SOAP
outreach)
13
Spinal-- disadvantages
  • Fixed duration (unless continuous spinal).
  • Rapid onset of sympathectomy or high block.
  • Small chance of PDPH.

14
SAB absolute contraindications
  • Patient refusal
  • Uncorrected hypovolemia
  • Clinical coagulopathy
  • Infection at site of injection

15
SAB obsolete contraindication
  • Severe pre-eclampsia
  • Not associated with increased chance of severe
    hypotension with neuraxial block.
  • Show me the literature if you disagree.

16
SAB relative contraindications
  • Spinal cord, LE nerve disease.
  • Spinal deformity, instrumentation
  • Back problems / fear of block
  • Laboratory coagulopathy
  • Bacteremia

17
SAB relative contraindications
  • Potential for hypovolemia
  • Stenotic cardiac valve lesions (?)
  • Pulmonary hypertension (?)

18
Basic C/S monitoring
  • Talk with the patient!
  • Does her face display anxiety?
  • Take a deep breath!
  • Have her squeeze your fingers
  • What is her hand temperature?
  • Are the hand veins dilated?
  • Do your hands feel normal or do they feel a
    little numb?

19
SAB / epidural cause sympathectomy
  • Dilation of capacitance vessels (70-80 of blood
    volume)
  • May cause drop in CO
  • Dilation of resistance arterioles (0.1-0.4 mm
    diameter).
  • Drop in SVR

20
SAB / epidural cause sympathectomy
www.cvphysiology.com/Blood20Pressure/BP019.htm
21
SAB / epidural cause sympathectomy
www.cvphysiology.com/Blood20Pressure/BP019.htm
22
38 y.o. female, repeat c/s, 420 , gestational
hypertension, continuous spinal fall in SVR,
rise in CO with onset of block. Increased SVR
with phenylephrine.
23
When is sympathectomy (low SVR) bad?
  • BP CO x SVR
  • Whenever you cant increase CO!
  • Uncorrected hypovolemia
  • IVC compression
  • Stenotic valve lesions
  • Pulmonary hypertension

24
Pulmonary capillaries
LV dilation / hypertrophy
Tricuspid
Aortic stenosis
Mitral
Pulmonic
Aortic stenosis at rest? Cardiac output not
sufficient to cause critically high LV
intracavitary pressure / LV failure.
Resistance arterioles
25
Pulmonary capillaries (edema)
LV failure / ischemia
Tricuspid
Aortic Stenosis
Pulmonic
Mitral
Aortic stenosis with SAB increased cardiac
output / arteriolar vasodilation Decreased SVR?
Fall in systemic BP and / or increase in LV
intracavitary pressure? ischemia or LV failure.
Resistance arterioles decreased SVR
26
38 y.o. female, repeat c/s, 420, continuous SAB.
Delivery with increased CO at 17, oxytocin 3 U
bolus at 18, phenylephrine at 19
27
When is sympathectomy (low SVR) bad?
  • With bolus of other vasodilator (oxytocin)

28
Oxytocin 10 u bolus
29
When is sympathectomy (low SVR) bad?
  • When drop in SVR could exacerbate R gt L shunt.
  • ASD
  • VSD
  • PDA

30
Decompensated patient with REAL R?L shunt.
LA
LV
Decreased SVR? desaturation
Ao
PA
Increased pulmonary vascular resistance?
desaturation
RA
RV
Decompensated patient with ASD, VSD or PDA--
Decreased SVR or increased pulmonary vascular
resistance ? increased R?L shunt and increased
arterial desaturation.
31
Compensated patient with POTENTIAL R?L shunt.
LA
LV
High SVR, Minimal R?L shunt
Ao
PA
RA
RV
Low pulmonary vascular resistance
Normal, compensated patient with ASD, VSD or
PDA-- high SVR and low pulmonary vascular
resistance? minimal R?L shunt.
32
JW with previa / accreta for c-hyst. GA.
Induction at 7, 8, intubation before 9, incision
after 9. Note rise in SVR and fall in CO with GA.
33
How to prevent a sympathectomy from being a
problem
  • Keep the SVR up with a vasopressor like
    phenylephrine.

34
Preventing or treating hypotension from
sympathectomy augment venous return (CO).
  • Trendelenburg (empty capacitance vessels into
    central thoracic veins)
  • LUD (get pressure off vena cava)
  • Fluid loading (fill capacitance vessels)
  • Crystalloid
  • Hetastarch
  • Arteriolar constrictors (inc SVR)
  • Ephedrine, phenylephrine
  • Venous constrictors (inc venous return)
  • Ephedrine, phenylephrine

35
Hypotension with SAB or epidural
  • Pre-load does not prevent reliably.
  • 500 mL hetastarch better than 1500 mL
    crystalloid.
  • First symptom is nausea or I dont feel so
    good.

36
Hypotension
  • Use phenylephrine (neosynephrine) if tachycardia.
  • Use ephedrine if bradycardia.
  • Use atropine if severe bradycardia.
  • Glycopyrolate works slowly.

37
Sympathectomy
www.sympathectomy.co.uk/ETS.php
38
Sympathectomy
39
Endoscopic transthoracic sympathectomy
Virtually all patients immediately develop warm,
dry hands and leave the hospital the same day as
surgery.
www.sd-neurosurgeon.com/.../hyperhidrosis.html
40
Hyperhydrosis Rxd with T3 sympathectomy
41
Horners syndrome
42
Horners syndrome
43
Bradycardia
  • With hypotension High block of
    cardioaccelerator fibers (T1-T5).
  • Also can be reflex bradycardia with hypertension
    from phenylephrine

44
Inc SVR and BP with bradycardia from neo 50 mcgm
at 4. Brady occurs after SVR and BP changes.
45
Left Uterine Displacement (LUD)
46
Colman-Brochu S 2004
47
http//www.manbit.com/OA/f28-1.htm
48
http//www.manbit.com/OA/f28-1.htm
Manbit images
49
Chestnut chap. 2
50
www.siumed.edu/dking2/erg/images/placenta.jpg fro
m Google images
51
)
Normal placental function fetal and maternal
circulations separated by thin membrane
(syncytiotrophoblast).
Umbilical artery (UA)
Umbilical vein (UV)
Fetus
Lakes of maternal blood
Fetal capillaries in chorionic villi
Precariously oxygenated environment
Mom
Uterine arteries
Uterine veins
Archer TL 2006 unpublished
52
Ohms Law of the placenta O2 delivery
Placental blood flow (P1 P2) / R Aorto-caval
compression decreases P1 (aorto) and increases
P2 (caval) Therefore, aorto-caval compression
decreases O2 delivery to fetus.
R placental resistance (fixed in short term)
P1 uterine artery pressure
Placenta blood flow (O2 delivery) (P1 P2) / R
P2 uterine vein pressure
Archer TL 2006
53
Spine 20012611721178
54
Spine 20012611721178
55
Abdominal compression in non-pregnant subjects
compresses the IVC. Which leads to epidural vein
engorgement.
Spine 20012611721178
56
Hyperventilation and abdominal pressure shrink
the volume of the lumbar thecal sac via
engorgement of epidural veins and
vasoconstriction of cerebral vessels (CSF shift).
At rest
Abdominal compression and hyperventilation
Spine 20012611721178
57
Clinical bottom line of decreased lumbar CSF
volume in pregnancy
  • Decrease local anesthetic dose by 30, compared
    to non-pregnant dose.

58
Corrolary Loss of resistance may not be felt if
patient is holding her breath (crying or
straining).
  • You can be fooled into thinking you have not
    reached the epidural space, when you have!

59
Thecal sac at L4-5 more triangular than at
L3-4?
Naji M, Anaesthesia, 2009, 64, pages 3942
60
Triangular thecal sac at L4-5 may explain dry CSF
tap after epidural localization for CSE.
61
General anesthesia-- advantages
  • Fast
  • Reliable (if you get the tube in).
  • Doesnt cause sympathectomy
  • Duration is flexible
  • Patient is not awake (to experience problems).
  • Can be given despite coagulopathy

62
General anesthesia-- disadvantages
  • Patient not awake for birth.
  • Unprotected airway.
  • Possible cant intubate, cant ventilate
    scenario.
  • Nausea, post-op pain, sore throat.

63
Functional residual capacity (FRC) is our air
tank for apnea.
www.picture-newsletter.com/scuba-diving/scuba...
from Google images
64
Pregnant Mom has a smaller air tank.
Non-pregnant woman
www.pyramydair.com/blog/images/scuba-web.jpg
65
GA for C/S
  • Thorough pre-oxygenation
  • Cricoid pressure
  • Small tube (6.0-7.0)
  • RSI
  • 50 N2O until delivery 0.5 MAC volatile.
  • 60-70 N2O after delivery midazolam narcotic.
  • Small dose non-depolarizing NMB, if needed.

66
General anesthesia-- advantages
  • SVR is maintained high (no need to increase CO)
  • Hypovolemia
  • Stenotic cardiac valve lesion
  • Pulmonary hypertension
  • Potential RgtL shunt

67
JW with previa / accreta for c-hyst. GA.
Induction at 7, 8, intubation before 9, incision
after 9. Note rise in SVR and fall in CO with GA.
68
Managing common problems
69
High block patient cant breathe
  • Move to anesthesia mask and circle system early.
    Dont fuss around assessing the patient!
  • Reassure patient, tell them this happens, and
    tell them you will help them breathe.
  • You usually dont have to intubate.
  • Sometimes patients will panic and shake head back
    and forth to get the mask off of their face.
  • Assume accompanying hypotension. Give ephedrine
    or neo as you reach for the mask.

70
High block patient cant breathe
  • If patient becomes unresponsive, you probably
    should intubate BUT VENTILATE FIRST AND DONT
    PANIC.
  • Assistant can give cricoid pressure but
    VENTILATE, above all!
  • May not need relaxant to intubate.
  • Respiratory paralysis usually does not last long
    (5-15 minutes).

71
Failed regional anesthesia
  • Be honest with yourself recognize failure.
  • Move on to plan B.

72
Aspiration
  • 16 y.o. WF, Crystal, Hx substance abuse, C/S
    for failure to progress.
  • Epidural, patchy block, supplemented with
    ketamine, fentanyl, diazepam.
  • I was vigilant with breath sounds (precordial
    stethoscope era).
  • Baby OK. Mother OK in PACU at 4PM.

73
Aspiration
  • Called at home next AM Pt SOB, transferred to
    ICU and intubated.
  • I go to hospital, review nurses notes.
  • Nauseated during the night, got MS several doses.
    Lying flat during the night.
  • SOB at 4AM. Aspiration? When? My fault?
  • Died 10 days later of progressive ARDS, hypoxia.

74
Aspiration
  • Not only during GA!
  • Use triple Rx freely (on everybody?)
  • Beware with
  • High spinal
  • Heavy supplementation for bad block
  • Never turn your back on a spinal.

75
STAT C/S
  • Often a flail.
  • Weve got to go. NOW!
  • Egos and emotions run high.
  • Does the patient know what is happening?
  • Talk to patient. Informed consent.
  • Dont endanger the mother to save the baby.
  • Know when and how to say no to the OB.
  • Stay calm.
  • Cover the basics (HP, IV access, airway,
    informed consent, patient asleep before incision.)

76
Summary
  • Regional anesthesia is elegant and uniquely
    suited to C-section.
  • GA still has its place, and its dangers.
  • Early warning, good communications and equanimity
    under pressure promote good outcomes.

77
The End
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