Transcript Anesthesia for cesarean section

Anesthesia for
cesarean section
Tom Archer, MD, MBA
UCSD Anesthesia
A unique psychosocial surgery
Outline
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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.
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“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
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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
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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
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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
capillaries
LV dilation / hypertrophy
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
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
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
Decreased
SVR
desaturation
Ao
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 artery (UA)
Umbilical vein (UV)
Fetus
“Lakes” of
maternal blood
Fetal capillaries
in chorionic villi
Precariously oxygenated environment
Uterine veins
Mom
Archer TL 2006 unpublished
Uterine arteries
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
(O2 delivery) =
artery pressure
(P1 – P2) / R
P2 = uterine vein pressure
Archer TL 2006
General anesthesia-- advantages
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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/scubaweb.jpg
GA for C/S—
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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”
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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…
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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