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Anesthesia for cesarean section. Tom Archer, MD, MBA UCSD Anesthesia. A unique psychosocial surgery. 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.

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anesthesia for cesarean section

Anesthesia for cesarean section

Tom Archer, MD, MBA

UCSD Anesthesia

outline
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
c section a unique psychosocial surgery
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.
anticipate and be available
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)
anticipate and be available1
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 isn’t out yet in room 7”
    • “The lady in 6 has a pretty bad tear.”
    • “Strip review in 3, please.”
    • “We can’t get an IV on the lady in 4.”
    • “Can you give us a whiff of anesthesia in 8? We don’t need much.”
evolution of technique
Evolution of technique
  • Last 30 years: decreasing use of GA, now about 5% of cases. Was 20-30% in 70’s at UCSD.
  • Epidural was “all the rage” in 70’s and 80’s.
  • SAB (or epidural) are now preferred anesthetics.
anesthesia for c s basic interventions
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)
anesthesia for c s complications
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
c s red flags
C/S red flags
  • “I don’t feel so good…I think I’m going to throw up…” (Hypotension until proven otherwise).
  • “Doc, I feel like I’m not getting enough to breathe…”
  • The “floppy arm sign.”
  • The “shaking head sign.”
spinal advantages
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)
spinal disadvantages
Spinal-- disadvantages
  • Fixed duration (unless continuous spinal).
  • Rapid onset of sympathectomy or high block.
  • Small chance of PDPH.
sab absolute contraindications
SAB– absolute contraindications
  • Patient refusal
  • Uncorrected hypovolemia
  • Clinical coagulopathy
  • Infection at site of injection
sab obsolete contraindication
SAB– obsolete contraindication
  • Severe pre-eclampsia—
  • Not associated with increased chance of severe hypotension with neuraxial block.
  • Show me the literature if you disagree.
sab relative contraindications
SAB– relative contraindications
  • Spinal cord, LE nerve disease.
  • Spinal deformity, instrumentation
  • Back problems / fear of block
  • Laboratory coagulopathy
  • Bacteremia
sab relative contraindications1
SAB– relative contraindications
  • Potential for hypovolemia
  • Stenotic cardiac valve lesions (?)
  • Pulmonary hypertension (?)
basic c s monitoring
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?”
sab epidural cause sympathectomy
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
sab epidural cause sympathectomy1
SAB / epidural cause sympathectomy

www.cvphysiology.com/Blood%20Pressure/BP019.htm

sab epidural cause sympathectomy2
SAB / epidural cause sympathectomy

www.cvphysiology.com/Blood%20Pressure/BP019.htm

slide22
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.
when is sympathectomy low svr bad
When is sympathectomy(low SVR) bad?
  • BP = CO x SVR
  • Whenever you can’t increase CO!
    • Uncorrected hypovolemia
    • IVC compression
    • Stenotic valve lesions
    • Pulmonary hypertension
slide24
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

slide25
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

slide26
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
when is sympathectomy low svr bad1
When is sympathectomy(low SVR) bad?
  • With bolus of other vasodilator (oxytocin)
when is sympathectomy low svr bad2
When is sympathectomy(low SVR) bad?
  • When drop in SVR could exacerbate R > L shunt.
    • ASD
    • VSD
    • PDA
slide30
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.

slide31
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.

slide32
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.
how to prevent a sympathectomy from being a problem
How to prevent a sympathectomy from being a problem
  • Keep the SVR up with a vasopressor like phenylephrine.
preventing or treating hypotension from sympathectomy augment venous return co
Preventing or treating hypotensionfrom 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
hypotension with sab or epidural
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 don’t feel so good.”
hypotension
Hypotension
  • Use phenylephrine (neosynephrine) if tachycardia.
  • Use ephedrine if bradycardia.
  • Use atropine if severe bradycardia.
  • Glycopyrolate works slowly.
endoscopic transthoracic sympathectomy
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

bradycardia
Bradycardia
  • With hypotension: High block of “cardioaccelerator fibers” (T1-T5).
  • Also can be reflex bradycardia with hypertension from phenylephrine
inc svr and bp with bradycardia from neo 50 mcgm at 4 brady occurs after svr and bp changes
Inc SVR and BP with bradycardia from neo 50 mcgm at 4. Brady occurs after SVR and BP changes.
slide51
)

Normal placental function: fetal and maternal circulations separated by thin membrane (syncytiotrophoblast).

Umbilicalartery (UA)

Umbilical vein (UV)

Fetus

“Lakes” of maternal blood

Fetal capillaries in chorionic villi

Precariously oxygenated environment

Mom

Uterine veins

Uterine arteries

Archer TL 2006 unpublished

slide52
Ohm’s 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

slide55
Abdominal compression in non-pregnant subjects compresses the IVC. Which leads to epidural vein engorgement.

Spine 2001;26:1172–1178

slide56
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 2001;26:1172–1178

clinical bottom line of decreased lumbar csf volume in pregnancy

Clinical bottom line of decreased lumbar CSF volume in pregnancy:

Decrease local anesthetic dose by 30%, compared to non-pregnant dose.

corrolary loss of resistance may not be felt if patient is holding her breath crying or straining

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!

slide59
Thecal sac at L4-5: more “triangular” than at L3-4?

Naji M, Anaesthesia, 2009, 64, pages 39–42

general anesthesia advantages
General anesthesia-- advantages
  • Fast
  • Reliable (if you get the tube in).
  • Doesn’t cause sympathectomy
  • Duration is flexible
  • Patient is not awake (to experience problems).
  • Can be given despite coagulopathy
general anesthesia disadvantages
General anesthesia-- disadvantages
  • Patient not awake for birth.
  • Unprotected airway.
  • Possible “can’t intubate, can’t ventilate” scenario.
  • Nausea, post-op pain, sore throat.
slide63
Functional residual capacity (FRC) is our “air tank” for apnea.

www.picture-newsletter.com/scuba-diving/scuba... from Google images

slide64
Pregnant Mom has a smaller “air tank”.

Non-pregnant woman

www.pyramydair.com/blog/images/scuba-web.jpg

ga for c s
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.
general anesthesia advantages1
General anesthesia-- advantages
  • SVR is maintained high (no need to increase CO)
    • Hypovolemia
    • Stenotic cardiac valve lesion
    • Pulmonary hypertension
    • Potential R>L shunt
slide67
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.
high block patient can t breathe
High block– patient can’t breathe
  • Move to anesthesia mask and circle system early. Don’t fuss around “assessing” the patient!
  • Reassure patient, tell them this happens, and tell them you will help them breathe.
  • You usually don’t 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.
high block patient can t breathe1
High block– patient can’t breathe
  • If patient becomes unresponsive, you probably should intubate– BUT VENTILATE FIRST AND DON’T 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).
failed regional anesthesia
Failed regional anesthesia
  • Be honest with yourself– recognize failure.
  • Move on to plan B.
aspiration
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.
aspiration1
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.
aspiration2
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.”
stat c s
“STAT C/S”
  • Often “a flail”.
  • “We’ve got to go. NOW!”
  • Egos and emotions run high.
  • Does the patient know what is happening?
  • Talk to patient. Informed consent.
  • Don’t endanger the mother to “save” the baby.
  • Know when and how to say “no” to the OB.
  • Stay calm.
  • Cover the basics (H&P, IV access, airway, informed consent, patient asleep before incision.)
summary
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.
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