Anesthesia for cesarean section

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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.
• Management of common problems
         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
• 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 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
• 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

•   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
•   Sympathectomy / hypotension
•   Nausea
•   Bradycardia
•   High spinal / respiratory paralysis
•   Aspiration
•   Difficult intubation
•   Local anesthetic toxicity
•   Failed regional anesthesia
•   Persistent neurological deficit
              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
• 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)
Regional anesthesia for c/s
in Turkey (SOAP outreach)
      Spinal-- disadvantages

• Fixed duration (unless continuous spinal).

• Rapid onset of sympathectomy or high
  block.

• Small chance of PDPH.
                SAB–
      absolute contraindications
• Patient refusal

• Uncorrected hypovolemia

• Clinical coagulopathy

• Infection at site of injection
               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
• Spinal cord, LE nerve disease.

• Spinal deformity, instrumentation

• Back problems / fear of block

• Laboratory coagulopathy

• Bacteremia
                 SAB–
       relative contraindications


• Potential for hypovolemia

• Stenotic cardiac valve lesions (?)

• Pulmonary hypertension (?)
         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
• 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
                sympathectomy




www.cvphysiology.com/Blood%20Pressure/BP019.htm
              SAB / epidural cause
                sympathectomy




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

• BP = CO x SVR

• Whenever you can’t increase CO!
  – Uncorrected hypovolemia
  – IVC compression
  – Stenotic valve lesions
  – Pulmonary hypertension
                           Pulmonary                  LV dilation / hypertrophy
                           capillaries
Tricuspid
                                                                    Aortic
                                                                    stenosis

                 Pulmonic                    Mitral



            Aortic stenosis at rest
            Cardiac output not sufficient to cause
            critically high LV intracavitary pressure /
            LV failure.




                     Resistance arterioles
                           Pulmonary            LV failure /
                           capillaries          ischemia
                            (edema)
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
  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) bad?



• With bolus of other vasodilator (oxytocin)
Oxytocin 10 u bolus
      When is sympathectomy
         (low SVR) bad?


• When drop in SVR could exacerbate R > L
  shunt.
  – ASD
  – VSD
  – PDA
   Decompensated patient with REAL RL shunt.




                 LA           LV
                                                         Ao         Decreased
                                                                    SVR
                                                                    desaturation
                                                        PA
                 RA             RV                             Increased
                                                               pulmonary
                                                               vascular
                                                               resistance
                                                               desaturation



Decompensated patient with ASD, VSD or PDA-- Decreased SVR or
increased pulmonary vascular resistance  increased RL shunt and
increased arterial desaturation.
    Compensated patient with POTENTIAL RL shunt.




                    LA           LV                                   High SVR,
                                                           Ao
                                                                      Minimal
                                                                      RL shunt
                                                          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.
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



• Keep the SVR up with a vasopressor like
  phenylephrine.
        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
 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
• Use phenylephrine (neosynephrine) if tachycardia.

• Use ephedrine if bradycardia.

• Use atropine if severe bradycardia.

• Glycopyrolate works slowly.
www.sympathecto
my.co.uk/ETS.php
                   Sympathectomy
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
Hyperhydrosis Rx’d with
  T3 sympathectomy
Horner’s syndrome
Horner’s syndrome
              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.
Left Uterine Displacement
           (LUD)
Colman-Brochu S 2004
http://www.manbit.com/OA/f28-1.htm
 http://www.manbit.com/OA/f28-1.htm
Manbit images
Chestnut chap. 2
www.siumed.edu/~dking2/erg/images/placenta.jpg
from Google images
                                                )
    Normal placental function: fetal and maternal circulations separated by thin
    membrane (syncytiotrophoblast).




             Umbilical vein (UV)                      Umbilical artery (UA)

                                        Fetus

Fetal capillaries                                                             “Lakes” of
in chorionic villi                                                            maternal blood




                       Precariously oxygenated environment




                                         Mom
 Uterine veins                                                                  Uterine arteries

                         Archer TL 2006 unpublished
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
                       Placenta blood flow                        artery pressure
                          (O2 delivery) =
                             (P1 – P2) / R
P2 = uterine vein pressure
                                                      Archer TL 2006
    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

• Patient not awake for birth.

• Unprotected airway.

• Possible “can’t intubate, can’t ventilate”
  scenario.

• Nausea, post-op pain, sore throat.
Functional residual capacity (FRC) is our “air tank” for apnea.




 www.picture-newsletter.com/scuba-diving/scuba... from Google images
Pregnant Mom has a smaller “air tank”.

                                         Non-pregnant
                                         woman




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


• SVR is maintained high (no need to
  increase CO)

  – Hypovolemia
  – Stenotic cardiac valve lesion
  – Pulmonary hypertension
  – Potential R>L shunt
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.
Managing common problems
  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 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

• Be honest with yourself– recognize failure.

• Move on to plan B.
                  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.
                     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.
                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”

•   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.)
    A stat C/S, once upon a time…
•   Fetal decels
•   Rush to the OR
•   Anesthesiologist is sure he can get the tube in fast
•   He skips the pre-O2.
•   He can’t intubate or ventilate
•   Patient arrests.
•   Code blue called, staff intubates.
•   Post op seizures, hypoxic encepalopathy.
•   Patient recovers after several days.
                 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.
The End

				
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